Doctoral Thesis: Characterising the Electrophysiological Properties of Cells in Health and Disease
July 2, 2025
Dr Krista Clarke is a post-doctoral researcher at the University of Surrey, and was co-funded by ME Research UK and the ME Association to assess the electrical properties of white blood cells in ME/CFS. Krista's thesis has now been published.
Abstract
Dielectrophoresis Myalgic Encephalomyelitis/ Chronic Fatigue Syndrome SARS-CoV-2 PBMC COVID-19 Chondrocyte Diagnosis
Biological cells possess intrinsic electrophysiological properties which are fundamental to cellular function. Changes in cell elctrophysiology can act as a biomarker, for example to indicate transition from healthy to diseased cell states, changes in cell function, or cell differentiation. This thesis presents three studies which used dielectrophoresis (DEPtech 3DEP) and ζ-potential analysis (two fast, label-free, high-throughput, non-invasive, and low-cost tools) to examine the electrophysiological properties of two cell types, peripheral blood mononuclear cells (PBMCs) and chondrocytes, for novel medical applications.
The first study investigated the electrophysiological properties of PBMCs in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS); a debilitating disease of unknown pathophysiology with no reliable, validated, and quantitative diagnostic test. The dielectric and ζ-potential response of PBMCs to 1.5-hour hyperosmotic challenge differentiated ME/CFS donors from healthy controls with 81.80% sensitivity and 85.70% specificity. This shows potential as a quantitative diagnostic biomarker
The second study examined whether the electrophysiological properties of PBMCs could act as a correlate of protection to SARS-CoV-2. Cytoplasmic conductivity in unchallenged PBMCs was significantly reduced in donors who had received three SARS-CoV-2 vaccine doses compared with unmatched COVID-19 naïve donors. Stimulation with the receptor binding domain of the SARS-CoV-2 spike protein resulted in significant differences in normalised values of membrane conductance in third-dose vaccinated donors, from COVID-19 naïve and second-dose donors.
The third study investigated chondrocytes, which are used extensively in cell-based cartilage-repair therapies. Chondrocytes rapidly dedifferentiate and become fibroblastic during monolayer cell culture – decreasing the success of reimplantation surgery. Significant changes in chondrocyte electrophysiological properties were observed over time in culture, laying the foundations for the identification of an electrophysiological biomarker that correlates with chondrocytic phenotype, to improve re-implantation outcome.
These studies demonstrate novel applications of dielectrophoresis and ζ-potential analysis – to quantitatively diagnose ME/CFS, identify changes in PBMCs following COVID-exposure, and changes in chondrocyte electrophysiology during dedifferentiation.
______________________________________________________________________
Original Investigation Infectious Diseases
Sex Differences in Long COVID
Dimpy P. Shah, MD, PhD1; Tanayott Thaweethai, PhD2,3; Elizabeth W. Karlson, MD, MS4; et al
JAMA Netw Open Published Online: January 22, 2025
2025;8;(1):e2455430. doi:10.1001/jamanetworkopen.2024.55430
Key Points
Question Does the risk of long COVID, or post-COVID condition, differ by sex?
Findings In this cohort study of 12 276 individuals, females had a significantly higher risk of long COVID compared with males after adjusting for sociodemographic and clinical risk factors. The sex-based difference in long COVID risk was age, pregnancy, and menopause dependent, with the highest risk among females aged 40 to 55 years.
Meaning These findings highlight the importance of evaluating differences in risk of long COVID after SARS-CoV-2 infection in males and females and of comparing biological mechanisms that may underlie sexually dimorphic long COVID trajectories.
Abstract
Importance A substantial number of individuals worldwide experience long COVID, or post-COVID condition. Other postviral and autoimmune conditions have a female predominance, but whether the same is true for long COVID, especially within different subgroups, is uncertain.
Objective To evaluate sex differences in the risk of developing long COVID among adults with SARS-CoV-2 infection.
Design, Setting, and Participants This cohort study used data from the National Institutes of Health (NIH) Researching COVID to Enhance Recovery (RECOVER)–Adult cohort, which consists of individuals enrolled in and prospectively followed up at 83 sites in 33 US states plus Washington, DC, and Puerto Rico. Data were examined from all participants enrolled between October 29, 2021, and July 5, 2024, who had a qualifying study visit 6 months or more after their initial SARS-CoV-2 infection.
Exposure Self-reported sex (male, female) assigned at birth.
Main Outcomes and Measures Development of long COVID, measured using a self-reported symptom-based questionnaire and scoring guideline at the first study visit that occurred at least 6 months after infection. Propensity score matching was used to estimate risk ratios (RRs) and risk differences (95% CIs). The full model included demographic and clinical characteristics and social determinants of health, and the reduced model included only age, race, and ethnicity.
Results Among 12 276 participants who had experienced SARS-CoV-2 infection (8969 [73%] female; mean [SD] age at infection, 46 [15] years), female sex was associated with higher risk of long COVID in the primary full (RR, 1.31; 95% CI, 1.06-1.62) and reduced (RR, 1.44; 95% CI, 1.17-1.77) models. This finding was observed across all age groups except 18 to 39 years (RR, 1.04; 95% CI, 0.72-1.49). Female sex was associated with significantly higher overall long COVID risk when the analysis was restricted to nonpregnant participants (RR, 1.50; 95%: CI, 1.27-1.77). Among participants aged 40 to 54 years, the risk ratio was 1.42 (95% CI, 0.99-2.03) in menopausal female participants and 1.45 (95% CI, 1.15-1.83) in nonmenopausal female participants compared with male participants.
Conclusions and Relevance In this prospective cohort study of the NIH RECOVER-Adult cohort, female sex was associated with an increased risk of long COVID compared with male sex, and this association was age, pregnancy, and menopausal status dependent. These findings highlight the need to identify biological mechanisms contributing to sex specificity to facilitate risk stratification, targeted drug development, and improved management of long COVID.
______________________________________________________________________
Review Infection 2025 Feb;53(1):1-13.
doi: 10.1007/s15010-024-02386-8. Epub 2024 Sep 6.
Towards an understanding of physical activity-induced post-exertional malaise: Insights into microvascular alterations and immunometabolic interactions in post-COVID condition and myalgic encephalomyelitis/chronic fatigue syndrome
Simon Haunhorst 1 2, Diana Dudziak 3, Carmen Scheibenbogen 4, Martina Seifert 4 5, Franziska Sotzny 4, Carsten Finke 6, Uta Behrends 7 8 9, Konrad Aden 10 11, Stefan Schreiber 11, Dirk Brockmann 12, Paul Burggraf 13, Wilhelm Bloch 14, Claudia Ellert 15 16, Anuradha Ramoji 17 18, Juergen Popp 17 18, Philipp Reuken 19, Martin Walter 20 21, Andreas Stallmach 19, Christian Puta 22 23 24
PMID: 39240417 PMCID: PMC11825644 DOI: 10.1007/s15010-024-02386-8
Abstract
Background: A considerable number of patients who contracted SARS-CoV-2 are affected by persistent multi-systemic symptoms, referred to as Post-COVID Condition (PCC). Post-exertional malaise (PEM) has been recognized as one of the most frequent manifestations of PCC and is a diagnostic criterion of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Yet, its underlying pathomechanisms remain poorly elucidated.
Purpose and methods: In this review, we describe current evidence indicating that key pathophysiological features of PCC and ME/CFS are involved in physical activity-induced PEM.
Results: Upon physical activity, affected patients exhibit a reduced systemic oxygen extraction and oxidative phosphorylation capacity. Accumulating evidence suggests that these are mediated by dysfunctions in mitochondrial capacities and microcirculation that are maintained by latent immune activation, conjointly impairing peripheral bioenergetics. Aggravating deficits in tissue perfusion and oxygen utilization during activities cause exertional intolerance that are frequently accompanied by tachycardia, dyspnea, early cessation of activity and elicit downstream metabolic effects. The accumulation of molecules such as lactate, reactive oxygen species or prostaglandins might trigger local and systemic immune activation. Subsequent intensification of bioenergetic inflexibilities, muscular ionic disturbances and modulation of central nervous system functions can lead to an exacerbation of existing pathologies and symptoms.
Keywords: ME/CFS; Physical activity; Post COVID condition; Post-exertional malaise; SARS-CoV-2.
______________________________________________________________________
Home | JAMA Pediatrics | New Online Original Investigation
Characterizing Long COVID Symptoms During Early Childhood
Rachel S. Gross, MD, MS1; Tanayott Thaweethai, PhD2,3; Amy L. Salisbury, PhD4; et al
Published Online: May 27, 2025
2025;179;(7):781-792. doi:10.1001/jamapediatrics.2025.1066
Key Points
Question Which prolonged symptoms in early childhood are associated with SARS-CoV-2 infection?
Findings In the Researching COVID to Enhance Recovery (RECOVER)–Pediatrics cohort study including 472 infants/toddlers and 539 preschool-aged children, prolonged symptoms were identified that were more common in young children with infection history than those without. Infants/toddlers (0-2 years) with infection history were more likely to experience trouble sleeping, fussiness, poor appetite, stuffy nose, and cough, and preschool-aged children (3-5 years) were more likely to experience dry cough and daytime tiredness/sleepiness or low energy; empirically derived indices for long COVID research were developed from these symptoms.
Meaning Results of this cohort study suggest that symptom patterns were distinguishable across infants/toddlers and preschool-aged children, and from previously studied older children and adults.
Abstract
Importance Recent studies have identified characteristic symptom patterns of long COVID (LC) in adults and children older than 5 years. However, LC remains poorly characterized in early childhood. This knowledge gap limits efforts to identify, care for, and prevent LC in this vulnerable population.
Objectives To identify symptoms that had the greatest difference in frequency comparing children with a history of SARS-CoV-2 infection to those without, to identify differences in the types of symptoms by age group (infants/toddlers [0-2 years] vs preschool-aged children [3-5 years]), and to derive an index that can be used in research studies to identify young children with LC.
Design, Setting, and Participants This was a multisite longitudinal cohort study with enrollment from over 30 US health care and community settings, including infants, toddlers, and preschool-aged children with and without SARS-CoV-2 infection history. Study data were analyzed from May to December 2024.
Exposure SARS-CoV-2 infection.
Main Outcomes and Measures LC and 41 symptoms among infants/toddlers and 75 symptoms among preschool-aged children.
Results The study included 472 infants/toddlers (mean [SD] age, 12 [9] months; 278 infected with SARS-CoV-2; 194 uninfected; 234 male [50%]; 73 Black or African American [16%]; 198 Hispanic, Latino, or Spanish [43%]; 242 White [52%]) and 539 preschool-aged children (mean [SD] age, 48 [10] months; 399 infected with SARS-CoV-2; 140 uninfected; 277 female [51%]; 70 Black or African American [13%]; 210 Hispanic, Latino, or Spanish [39%]; 287 White [54%]). The median (IQR) time between first infections and completion of symptom surveys was 318 (198-494) days for infants/toddlers and 520 (330-844) days for preschool-aged children. A research index was derived for each age group based on symptoms most associated with infection history. The index is calculated by summing scores assigned to each prolonged symptom that was present, where higher scores indicate greater magnitude of association with history of SARS-CoV-2 infection: poor appetite (5 points), trouble sleeping (3.5 points), wet cough (3.5 points), dry cough (3 points), and stuffy nose (0.5 points) for infants/toddlers, and daytime tiredness/sleepiness/low energy (6.5 points) and dry cough (3 points) for preschool-aged children. Among infants/toddlers with infection, 40 of 278 (14%) were classified as having probable LC by having an index of at least 4 points. Among preschool-aged children, 61 of 399 (15%) were classified as having probable LC by having an index of at least 3 points. Participants with higher indices often had poorer overall health, lower quality of life, and perceived delays in developmental milestones.
Conclusions and Relevance This cohort study identified symptom patterns and derived research indices that were distinct between the 2 age groups and differed from those previously identified in older ages, demonstrating the need to characterize LC separately across age ranges.
______________________________________________________________________
Original Investigation Infectious Diseases
Sex Differences in Long COVID
Dimpy P. Shah, MD, PhD1; Tanayott Thaweethai, PhD2,3; Elizabeth W. Karlson, MD, MS4; et al
JAMA Netw Open Published Online: January 22, 2025
2025;8;(1):e2455430. doi:10.1001/jamanetworkopen.2024.55430
Question Does the risk of long COVID, or post-COVID condition, differ by sex?
Findings In this cohort study of 12 276 individuals, females had a significantly higher risk of long COVID compared with males after adjusting for sociodemographic and clinical risk factors. The sex-based difference in long COVID risk was age, pregnancy, and menopause dependent, with the highest risk among females aged 40 to 55 years.
Meaning These findings highlight the importance of evaluating differences in risk of long COVID after SARS-CoV-2 infection in males and females and of comparing biological mechanisms that may underlie sexually dimorphic long COVID trajectories.
Abstract
Importance A substantial number of individuals worldwide experience long COVID, or post-COVID condition. Other postviral and autoimmune conditions have a female predominance, but whether the same is true for long COVID, especially within different subgroups, is uncertain.
Objective To evaluate sex differences in the risk of developing long COVID among adults with SARS-CoV-2 infection.
Design, Setting, and Participants This cohort study used data from the National Institutes of Health (NIH) Researching COVID to Enhance Recovery (RECOVER)–Adult cohort, which consists of individuals enrolled in and prospectively followed up at 83 sites in 33 US states plus Washington, DC, and Puerto Rico. Data were examined from all participants enrolled between October 29, 2021, and July 5, 2024, who had a qualifying study visit 6 months or more after their initial SARS-CoV-2 infection.
Exposure Self-reported sex (male, female) assigned at birth.
Main Outcomes and Measures Development of long COVID, measured using a self-reported symptom-based questionnaire and scoring guideline at the first study visit that occurred at least 6 months after infection. Propensity score matching was used to estimate risk ratios (RRs) and risk differences (95% CIs). The full model included demographic and clinical characteristics and social determinants of health, and the reduced model included only age, race, and ethnicity.
Results Among 12 276 participants who had experienced SARS-CoV-2 infection (8969 [73%] female; mean [SD] age at infection, 46 [15] years), female sex was associated with higher risk of long COVID in the primary full (RR, 1.31; 95% CI, 1.06-1.62) and reduced (RR, 1.44; 95% CI, 1.17-1.77) models. This finding was observed across all age groups except 18 to 39 years (RR, 1.04; 95% CI, 0.72-1.49). Female sex was associated with significantly higher overall long COVID risk when the analysis was restricted to nonpregnant participants (RR, 1.50; 95%: CI, 1.27-1.77). Among participants aged 40 to 54 years, the risk ratio was 1.42 (95% CI, 0.99-2.03) in menopausal female participants and 1.45 (95% CI, 1.15-1.83) in nonmenopausal female participants compared with male participants.
Conclusions and Relevance In this prospective cohort study of the NIH RECOVER-Adult cohort, female sex was associated with an increased risk of long COVID compared with male sex, and this association was age, pregnancy, and menopausal status dependent. These findings highlight the need to identify biological mechanisms contributing to sex specificity to facilitate risk stratification, targeted drug development, and improved management of long COVID.
______________________________________________________________________
The Role of T-Cell Exhaustion as a Driver in the Development of Post-Acute Infection Syndromes: A Literature Review
Willem Gielen1, Mahican Gielen1, Nigel McCracken2, Peter Derek Christian Leutscher1
Abstract
This literature review summarizes recent studies on T cell exhaustion and its role in post-acute infection syndromes (PAIS), including Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) and Long COVID. It synthesizes the current evidence on how persistent immune dysfunction contributes to the chronic symptoms seen in these conditions. T cell exhaustion, marked by continuous antigen exposure, diminished effector function, and increased expression of inhibitory receptors such as PD-1, CTLA-4, TIM-3, and TIGIT, is increasingly recognized as a key factor in the pathogenesis of PAIS. Clinical and molecular studies have revealed altered T cell populations, impaired proliferative responses, and metabolic dysregulation in affected patients. Persistent viral antigens are implicated in maintaining this exhausted state, whereas neuroimmune interactions and autoimmune processes may further sustain symptomatology. Although this review did not employ a formal systematic methodology, it integrated findings from multiple studies to provide a comprehensive overview of the field. Challenges remain regarding standardized diagnostic criteria and biomarkers; however, advances in immune exhaustion markers present the potential for improved diagnosis and targeted treatments. Emerging therapeutic approaches include immune checkpoint modulation, metabolic interventions, antiviral therapy, and immunomodulation. Further research is needed to clarify the mechanisms, validate the biomarkers, and develop effective clinical interventions. Recognizing T cell exhaustion as a central mechanism offers a foundation for advancing our understanding and management of PAIS.
Correspondence: [email protected] — Qeios will forward to the authors
______________________________________________________________________
Patient-reported treatment outcomes in ME/CFS and long COVID
Martha Eckey, Peng Li, Braxton Morrison, +2 , and Wenzhong Xiao [email protected]Authors Info & Affiliations
Contributed by Ronald Davis; received December 24, 2024; accepted April 7, 2025; reviewed by Lucinda Bateman and Lewis E. Kazis
July 8, 2025 122 (28) e2426874122 https://doi.org/10.1073/pnas.2426874122
Significance
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and long COVID are debilitating conditions that currently lack FDA-approved treatments. This study analyzes patient-reported outcomes from over 3,900 individuals, identifying treatments perceived as beneficial and uncovering symptom-based patient subgroups with distinct responses to therapies. Notably, there is significant overlap in the symptom profiles and treatment responses between ME/CFS and long COVID, suggesting that they may share underlying mechanisms. These findings offer valuable real-world insights for patients and their healthcare providers and help identify promising candidates for clinical trials, addressing an urgent need for effective therapies in these chronic illnesses.
Abstract
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and long COVID are persistent multisystem illnesses affecting many patients. With no known effective FDA-approved treatments for either condition, patient-reported outcomes of treatments may prove helpful in identifying management strategies that can improve patient care and generate new avenues for research. Here, we present the results of an ME/CFS and long COVID treatment survey with responses from 3,925 patients. We assess the experiences of these patients with more than 150 treatments in conjunction with their demographics, symptoms, and comorbidities. Treatments with the greatest perceived benefits are identified. Patients with each condition who participated in the study shared similar symptom profiles, including all the core symptoms of ME/CFS, e.g., 89.7% of ME/CFS and 79.4% of long COVID reported postexertional malaise (PEM). Furthermore, treatment responses between these two patient groups were significantly correlated (R2 = 0.68). Patient subgroups, characterized by distinct symptom profiles and comorbidities, exhibited increased responses to specific treatments, e.g., a POTS-dominant cluster benefiting from autonomic modulators and a cognitive-dysfunction cluster from CNS stimulants. This study underscores the symptomatic and therapeutic similarities between ME/CFS and long COVID and highlights the commonalities and nuanced complexities of infection-associated chronic diseases and related conditions. While this study does not provide recommendations for specific therapies, in the absence of approved treatments, insights from patient-reported experiences provide urgently needed real-world evidence for developing targeted patient care therapies and future clinical trials.
______________________________________________________________________
Defective peripheral B cell tolerance leads to dysregulated B cell responses in Fibromyalgia Syndrome
Rachael Bashford-Rogers, Alexander Long, Antonio Choi Chiu, Orthi Onupom, and 8 more
This is a preprint; it has not been peer reviewed by a journal.
https://doi.org/10.21203/rs.3.rs-6836742/v1
This work is licensed under a CC BY 4.0 License
Abstract
Fibromyalgia syndrome (FMS) is a chronic pain disorder characterised by widespread musculoskeletal pain, fatigue, and cognitive dysfunction, with no definitive biomarkers or mechanism-based treatments. Emerging evidence suggests that immune dysregulation may contribute to the FMS pathogenesis, particularly involving B cells, which have been implicated in autoantibody production and neuronal sensitisation. However, whether peripheral B cell tolerance, a critical safeguard against autoimmunity, is compromised in FMS remains unknown. Here, we combined high-resolution B cell receptor (BCR) repertoire sequencing, deep immunophenotyping, and functional assays in a well-characterised FMS cohort to uncover profound defects in peripheral B cell tolerance. We reveal significant defects in peripheral B cell tolerance in FMS, including: (1) impaired naïve B cell anergy, marked by elevated CD21, CD22, and CD24 expression; (2) exaggerated proliferative responses and rapid CD24 downregulation upon stimulation; and (3) altered BCR selection patterns, with increased IGHV6-1/IGHJ6 usage, skewed class switching toward IGHA1, and enhanced clonal expansion. These features closely resemble immune pathology profiles observed in classical autoimmune diseases. These findings redefine FMS as a disorder of immune dysregulation, with defective B cell tolerance contributing to disease mechanisms. The convergence of interferon-driven B cell activation, clonal expansion, and autoantibody production suggests shared pathways with classical autoimmune diseases. Our study provides a foundation for mechanism-based diagnostics and targeted immunomodulatory therapies, offering new avenues for intervention in this debilitating condition.
______________________________________________________________________
Inflammation and Interferon Signatures in Peripheral B-Lymphocytes and Sera of Individuals With Fibromyalgia
Serena Fineschi 1 2, Joakim Klar 3, Kristin Ayoola Gustafsson 3, Kent Jonsson 2 4, Bo Karlsson 2, Niklas Dahl 3
Abstract
Fibromyalgia (FM) is an idiopathic chronic disease characterized by widespread musculoskeletal pain, hyperalgesia and allodynia, often accompanied by fatigue, cognitive dysfunction and other symptoms. Autoimmunity and neuroinflammatory mechanisms have been suggested to play important roles in the pathophysiology of FM supported by recently identified interferon signatures in affected individuals. However, the contribution of different components in the immune system, such as the B-lymphocytes, in the progression to FM are yet unknown. Furthermore, there is a great need for biomarkers that may improve diagnostics of FM. Herein, we investigated the gene expression profile in peripheral B-cells, as well as a panel of inflammatory serum proteins, in 30 FM patients and 23 healthy matched control individuals. RNA sequence analysis revealed 60 differentially expressed genes when comparing the two groups. The group of FM patients showed increased expression of twenty-five interferon-regulated genes, such as S100A8 and S100A9, VCAM, CD163, SERPINA1, ANXA1, and an increased interferon score. Furthermore, FM was associated with elevated levels of 19 inflammatory serum proteins, such as IL8, AXIN1, SIRT2 and STAMBP, that correlated with the FM severity score. Together, the results shows that FM is associated with an interferon signature in B-cells and increased levels of a set of inflammatory serum proteins. Our findings bring further support for immune activation in the pathogenesis of FM and highlight candidate biomarkers for diagnosis and intervention in the management of FM.
Keywords: B-lymphocytes; RNA sequencing; fatigue; fibromyalgia; fibromyalgia score; inflammation; inflammatory proteins; interferon signature.
______________________________________________________________________
Patient-reported treatment outcomes in ME/CFS and long COVID
Martha Eckey, Peng Li, Braxton Morrison, and Wenzhong Xiao [email protected]Authors Info & Affiliations
Contributed by Ronald Davis; received December 24, 2024; accepted April 7, 2025; reviewed by Lucinda Bateman and Lewis E. Kazis
July 8, 2025 122 (28) e2426874122 https://doi.org/10.1073/pnas.2426874122
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and long COVID are debilitating conditions that currently lack FDA-approved treatments. This study analyzes patient-reported outcomes from over 3,900 individuals, identifying treatments perceived as beneficial and uncovering symptom-based patient subgroups with distinct responses to therapies. Notably, there is significant overlap in the symptom profiles and treatment responses between ME/CFS and long COVID, suggesting that they may share underlying mechanisms. These findings offer valuable real-world insights for patients and their healthcare providers and help identify promising candidates for clinical trials, addressing an urgent need for effective therapies in these chronic illnesses.
Abstract
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and long COVID are persistent multisystem illnesses affecting many patients. With no known effective FDA-approved treatments for either condition, patient-reported outcomes of treatments may prove helpful in identifying management strategies that can improve patient care and generate new avenues for research. Here, we present the results of an ME/CFS and long COVID treatment survey with responses from 3,925 patients. We assess the experiences of these patients with more than 150 treatments in conjunction with their demographics, symptoms, and comorbidities. Treatments with the greatest perceived benefits are identified. Patients with each condition who participated in the study shared similar symptom profiles, including all the core symptoms of ME/CFS, e.g., 89.7% of ME/CFS and 79.4% of long COVID reported postexertional malaise (PEM). Furthermore, treatment responses between these two patient groups were significantly correlated (R2 = 0.68). Patient subgroups, characterized by distinct symptom profiles and comorbidities, exhibited increased responses to specific treatments, e.g., a POTS-dominant cluster benefiting from autonomic modulators and a cognitive-dysfunction cluster from CNS stimulants. This study underscores the symptomatic and therapeutic similarities between ME/CFS and long COVID and highlights the commonalities and nuanced complexities of infection-associated chronic diseases and related conditions. While this study does not provide recommendations for specific therapies, in the absence of approved treatments, insights from patient-reported experiences provide urgently needed real-world evidence for developing targeted patient care therapies and future clinical trials.
______________________________________________________________________
Long COVID Gene Variants: A Step Toward a Diagnostic Test?
Solarina Ho July 23, 2025
A large-scale global study has identified genetic variants that are risk factors for long COVID, a discovery that helps researchers better understand the biological systems involving the disease and one small, early step toward the elusive goal of developing a long COVID diagnostic test.
International researchers with the Long COVID Host Genetics Initiative used data from 33 independent studies and 19 countries across North America, Europe, the Middle East, and Asia to analyze the genomes of nearly 16,000 patients with long COVID, representing populations from six genetic ancestries. Nearly 1.9 million controls were included in the genome-wide association study, a research method that scans complete sets of DNA to identify genetic variations associated with a specific trait or disease.
Genetic variants found in the FOXP4 gene had a statistically significant risk linked to long COVID, the study, published in Nature Genetics, found. The FOXP4 gene is known to impact lung function, and its expression levels were higher in those with long COVID than in controls. In addition, the risk variants had a consistent effect across different ancestries.
The researchers also found a causal relationship between a SARS-CoV-2 infection and long COVID and an additional causal risk between infections severe enough to require hospitalization and long COVID. Researchers also analyzed possible connections between variants associated with long COVID and those linked to other diseases and conditions.
Scientists said the overall findings provided evidence that was consistent with long COVID research that suggests both individual genetic variants and environmental risk factors contribute to disease risk. The findings also provide genetic proof linking abnormal lung physiology and the development of long COVID, the authors concluded; however, they noted that long COVID symptoms are not only limited to lung function and may include fatigue and cognitive dysfunction as well.
The study’s co-author, Hanna Ollila, PhD, with the Institute for Molecular Medicine Finland, University of Helsinki, Helsinki, Finland, underscored that the newly discovered genetic variants were not predictive for clinical tests or personal disease risk.
“The findings from our study, and from genome-wide association studies in general, tell about biological mechanisms behind a disease. This can then help to understand the disease better. For example, is it a disease neuronal, immune, metabolic, and so on?” said Ollila, who is also a researcher with the Department of Anesthesia and Center for Genomic Medicine at Massachusetts General Hospital, Boston. There are still many steps between these types of discoveries and the development of a diagnostic test, she explained, since these types of genetic variants do not function like high-impact variants such as the BRCA mutations in breast cancer.
“In other words, they do not strongly predict whether someone will develop long COVID at the individual level,” Ollila said. “Instead, they highlight the biological systems involved in the disease. In this case, our findings point to immune pathways related to lung function.”
Ollila explained that genetics can guide diagnostic development by pointing to underlying mechanisms, which may then help identify biomarkers in blood or other tissues. These biomarkers could eventually contribute to diagnostic tools, but it is a process that takes time and collaboration and often depends on progress across several fields of research including imaging and clinical phenotyping.
Researchers hope that when larger sample sizes become available for bigger studies, the analyses and understanding of the correlations will become more precise, bringing more understanding and clarity on genetic risk factors, biological mechanisms, and biomarkers that could someday help with disease diagnosis.
“We are likely still several years away, and possibly even a decade or more, from having a clinically useful diagnostic test based on genetic or biological markers for long COVID,” said Ollila. “That said, progress is accelerating thanks to the growing number of well-characterized cohorts and international collaborations. While these genetic findings are not yet ready for clinical application, they are an important step toward understanding long COVID, its relationship with other diseases, and the disease mechanisms that modulate risk for long COVID.”
Andreas Goebel a,b,*PMCID: PMC12226001 PMID: 40612406
______________________________________________________________________
Either the majority or all patients with severe fibromyalgia syndrome harbour proalgetic serum-immunoglobulin G autoantibodies; their possible relevance for patients must now be established through clinical trials.
Keywords: Fibromyalgia syndrome, FMS, Autoimmunity, Passive transfer, immunoglobulin
Abstract
Assessments of serum-autoantibodies in fibromyalgia syndrome (FMS) date back to the 1980s and have yielded inconsistent results. Based on a new passive transfer paradigm, since 2021 causative involvement of immunoglobulin G–mediated autoimmunity in severe FMS has been demonstrated in several studies, which have included UK, Swedish, and Canadian patients. These findings open the path to the development of novel diagnostic and immune-therapeutic approaches. Autoantibody targets and downstream mechanisms and the molecular processes that translate infection-, toxicity-, or stress-triggers into the FMS immune response in genetically or otherwise vulnerable individuals require study. These results in FMS also suggest that other chronic pain conditions or nonpainful symptom-based disorders may similarly be caused by noninflammatory minimally destructive autoantibody-mediated autoimmunity, thus offering hope for large groups of patients.
1. Background
Abnormal serum autoantibody titres in fibromyalgia syndrome (FMS) have been investigated at least as far back as the 1980s when Dinerman et al.16 reported the possible existence of a FMS subgroup without rheumatological comorbidity but with seropositivity for antinuclear antibodies (ANAs). The authors suggested that this finding may indicate involvement of autoimmune mechanisms. Since then, small studies have identified raised titres of various autoantibodies, potentially indicating abnormal immune activation or autoimmunity, although other studies were negative, and no consistent patterns have emerged.1,4,5,7,10,13,17,20,28,29,31,33,37–41,45–47,49–51,57,60 This evidence indicates that FMS is sometimes associated with mildly raised titres of specific immunoglobulin G (IgG) autoantibodies; furthermore, antibody-positivity is occasionally associated with an retrospectively identified FMS subgroup. The underpinning conceptual framework for these studies has in most cases been that antibody-induced structural or inflammatory change in tissue will induce activation of nociceptive (damage-sensing) nerve fibres, causing pain.
2. Witebsky–Rose postulates
In 1957, Witebsky et al.58 outlined criteria that can be used to identify a disorder as autoimmune, modelled on the Koch's postulates for the identifications of infectious microbes. A revised version was published 35 years later by one of the original authors, Noel Rose, together with Constantin Bona48 reflecting on advanced understanding of autoimmune mechanisms. Rose and Bona proposed to categorise evidence for autoimmune involvement in disease into (1) direct proof, (2) indirect evidence, and (3) circumstantial evidence.
Very rare direct proof derives from human-to-human transfer of disease such as when a scientist self-injects with plasma from a sick patient, or when pathogenic IgG from a mother is transported across the blood–placental barrier into the unborn child's circulation during the third trimester. Any transfer of serum-IgG purified from patients to experimental animals, which causes the patient phenotype in the animals is considered an alternative form of direct evidence; the authors specifically highlighted the example of serum-IgG transfer from patients with pemphigus to neonatal mice causing typical skin blisters. Sometimes, direct evidence can also derive from in vitro techniques, such as when serum-antibodies purified from patients with paroxysmal cold hemoglobinemia lyse erythrocytes taken from suitable patients.
Methods producing indirect evidence include the immunisation of experimental animals with the pertinent autoantigen, ie, the molecular structure against which the autoimmune response is directed in the human. As with direct proof approaches, these indirect methods are considered successful if they trigger the development of the human phenotype in the animals. Examples for indirect evidence include classical experimental results in myasthenia gravis where immunisation of rabbits with acetylcholine receptors derived from eel causes profound muscle weakness.42 Such methods obviously require that the antigen is known.
Finally, circumstantial evidence involves a favourable patient response to immune suppression. Rose and Bona thought that any such evidence would not provide proof for autoimmune disease, however, should incentivise further research. Several novel immune treatment methods might, however, instead be classed as direct evidence if the Witebsky–Rose criteria were to be revised in the future. Immunoadsorption, which removes serum-antibodies by filtration,6 and treatment with FcRn receptor antagonists,14 a novel class of drugs which reduces serum-antibodies by increasing their metabolism, both specifically target antibodies rather than causing general immune suppression. Such novel treatment technologies have been shown effective in several autoantibody-associated disorders, including myasthenia gravis.27 They differ from immune-suppressive approaches with very broad immune modifying effects known at the time of publication of the Witebsky–Rose criteria.
______________________________________________________________________
Defective peripheral B cell tolerance leads to dysregulated B cell responses in Fibromyalgia Syndrome
Rachael Bashford-Rogers, Alexander Long, Antonio Choi Chiu, Orthi Onupom, and 8 more
This is a preprint; it has not been peer reviewed by a journal.
https://doi.org/10.21203/rs.3.rs-6836742/v1
This work is licensed under a CC BY 4.0 License
Abstract
Fibromyalgia syndrome (FMS) is a chronic pain disorder characterised by widespread musculoskeletal pain, fatigue, and cognitive dysfunction, with no definitive biomarkers or mechanism-based treatments. Emerging evidence suggests that immune dysregulation may contribute to the FMS pathogenesis, particularly involving B cells, which have been implicated in autoantibody production and neuronal sensitisation. However, whether peripheral B cell tolerance, a critical safeguard against autoimmunity, is compromised in FMS remains unknown. Here, we combined high-resolution B cell receptor (BCR) repertoire sequencing, deep immunophenotyping, and functional assays in a well-characterised FMS cohort to uncover profound defects in peripheral B cell tolerance. We reveal significant defects in peripheral B cell tolerance in FMS, including: (1) impaired naïve B cell anergy, marked by elevated CD21, CD22, and CD24 expression; (2) exaggerated proliferative responses and rapid CD24 downregulation upon stimulation; and (3) altered BCR selection patterns, with increased IGHV6-1/IGHJ6 usage, skewed class switching toward IGHA1, and enhanced clonal expansion. These features closely resemble immune pathology profiles observed in classical autoimmune diseases. These findings redefine FMS as a disorder of immune dysregulation, with defective B cell tolerance contributing to disease mechanisms. The convergence of interferon-driven B cell activation, clonal expansion, and autoantibody production suggests shared pathways with classical autoimmune diseases. Our study provides a foundation for mechanism-based diagnostics and targeted immunomodulatory therapies, offering new avenues for intervention in this debilitating condition.
______________________________________________________________________
The sensitising effect of IgG in fibromyalgia syndrome is mediated by Mrgprb2 in mast cells
Karla R. Sanchez, Jamie Burgess, Qin Zheng, Uazman Alam, Harvey Neiland, Richard Berwick,
David Andersson, Samantha Korver, Anne Marshall, Andreas Goebel, Xinzhong Dong
doi: https://doi.org/10.1101/2025.05.15.652596
This article is a preprint and has not been certified by peer review
Abstract
Fibromyalgia syndrome (FMS) is characterized by elevated levels of immunoglobulin G (IgG), altered bowel habits, and increased pain sensitivity, suggesting immune dysregulation, but the exact mechanism remains unclear. Here, we found that FMS-IgG binds to mast cells in a MRGPRX2/b2-dependent manner, leading to mast cell recruitment and IL-6 secretion. Transferring serum-IgG from FMS patients to mice induced FMS-like symptoms and increased skin mast cells, indicating that FMS-IgG acts through mast cell activation. The ablation of mice Mrgprb2 mast cells or deleting Mrgprb2 receptors prevented IgG-induced heightened sensitivity to mechanical and cold stimuli. Stimulating human LAD2 cells with FMS IgG elicited MRGPRX2-dependent IL-6 production. Consistent with mice findings, mast cell density and tryptase levels increased in human FMS skin samples compared to healthy controls. Taken together our results suggests that FMS IgG mediates hypersensitivity via activation of mast cells bearing the MRGPRX2 receptor and that these cells are a potential therapeutic target.
Competing Interest Statement
X.D. is the scientific founder of and consultant for Escient Pharmaceuticals, a pharmaceutical company developing drugs targeting Mrgprs. X.D. collaborates with GlaxoSmithKline (GSK) on Mrgpr-related projects unrelated to this manuscript. Other authors declare no competing interests.
Funder Information Declared
Howard Hughes Medical Institute, https://ror.org/006w34k90
Pain Relief Foundation, https://ror.org/0017mh436
Versus Arthritis, https://ror.org/02jkpm469, 22471
Copyright
The copyright holder for this preprint is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY 4.0 International license.
bioRxiv and medRxiv thank the following for their generous financial support:
The Chan Zuckerberg Initiative, Cold Spring Harbor Laboratory, the Sergey Brin Family Foundation, California Institute of Technology, Centre National de la Recherche Scientifique, Fred Hutchinson Cancer Center, Imperial College London, Massachusetts Institute of Technology, Stanford University, The University of Edinburgh, University of Washington, and Vrije Universiteit Amsterdam.
Posted May 16, 2025.
______________________________________________________________________
Sec. Infectious Diseases: Pathogenesis and Therapy
Volume 12 - 2025 | https://doi.org/10.3389/fmed.2025.1607353
Plasma cell targeting with the anti-CD38 antibody daratumumab in myalgic encephalomyelitis/chronic fatigue syndrome—a clinical pilot study
Øystein Fluge1,2*Ingrid Gurvin Rekeland1Kari Sørland1Kine Alme1Kristin Risa1Ove Bruland3Karl Johan Tronstad4Olav Mella1
1The Cancer Clinic, Haukeland University Hospital, Bergen,2Institute of Clinical Sciences, University of Bergen, Bergen, Norway
Background: Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) entails low quality of life for patients and massive societal costs. There is an urgent need for elucidation of disease mechanisms and for rational treatment. Our working hypothesis is that ME/CFS in a subgroup of patients is associated with functional autoantibodies emerging after an infection, and that plasma-cell depletion with transient reductions in serum immunoglobulins will have a beneficial effect on patients’ symptoms.
Infectious diseases: Mitochondrial function is impaired in long COVID patients
Jane Macnaughtan,K-Yin Chau, Ewen Brennan, Marco Toffoli, Antonella Spinazzola, Toby Hillman
Article: 2528167 | Received 25 Sep 2024, Accepted 28 Mar 2025, Published online: 12 Aug 2025
https://doi.org/10.1080/07853890.2025.2528167
Abstract
Background
The Long COVID syndrome is a major global health problem, affecting approximately 10–20% of individuals infected with SARS-CoV-2 virus with many remaining symptomatic beyond one year. Fatigue, reduced exercise tolerance and hyperlactataemia on minimal exertion have led to the suggestion of a bioenergetic defect. We hypothesised that mitochondrial dysfunction is a pathological feature in Long COVID cases and would correlate with clinical outcome.
Methods
This prospective, case-controlled, observational study recruited 27 participants with an established diagnosis of Long COVID syndrome from a single tertiary clinic together with 16 age-matched controls aged 25–65 years. Seahorse-based mitochondrial flux analysis and bioenergetics profile of isolated peripheral blood mononuclear cells (PBMCs) was performed and correlated with clinical phenotype.
Findings
Long COVID cases had an increased baseline and ATP-induced oxygen consumption rate with a significant attenuation in tetramethylrhodamine methyl ester perchlorate fluorescence response to oligomycin. Correlations were observed between mitochondrial function and autonomic health, quality of life and time from index infection. Sex-specific differences were also observed.
Interpretation
PBMCs from Long COVID subjects exhibit an exceptional and distinctive change in ATP synthase, as it contributes to the mitochondrial membrane potential rather than using it exclusively to generate ATP. The findings suggest that the enzyme runs both forward and reverse reactions, synthesising and hydrolysing ATP. The correlation of mitochondrial function with clinical phenotype in Long COVID may indicate a causal relationship and warrants further validation in larger scale studies.
Keywords:
ATP synthase, long COVID, mitochondrial dysfunction, peripheral blood mononuclear cells
______________________________________________________________________
University if Edinburgh
Initial findings from the DecodeME genome-wide association study of myalgic encephalomyelitis/chronic fatigue syndrome
DecodeME collaboration Research output: Working paper › Preprint
Abstract
Myalgic encephalomyelitis / chronic fatigue syndrome (ME/CFS) is a common, poorly understood disease that has no effective treatments, and has long been underserved by scientific research and national health systems. It is a sex-biased disease towards females that is often triggered by an infection, and its hallmark symptom is post-exertional malaise. People with ME/CFS often report their symptoms being disbelieved. The biological mechanisms causing ME/CFS remain unclear. We recruited 21,620 ME/CFS cases and performed genome-wide association studies (GWAS) for up to 15,579 cases and 259,909 population controls with European genetic ancestry. In these GWAS, we discovered eight loci that are significantly associated with ME/CFS, including three near BTN2A2, OLFM4, and RABGAP1L genes that act in the response to viral or bacterial infection. Four of the eight loci (RABGAP1L, FBXL4, OLFM4, CA10) were associated at p < 0.05 with cases ascertained using post-exertional malaise and fatigue in the UK Biobank and the Netherlands biobank Lifelines. We found no evidence of sex-bias among discovered associations, and replicated in males two genetic signals (ARFGEF2, CA10) discovered in females. The ME/CFS association near CA10 colocalises with a known association to multisite chronic pain. We found no evidence that the eight ME/CFS genetic signals share common causal genetic variants with depression or anxiety. Our findings suggest that both immunological and neurological processes are involved in the genetic risk of ME/CFS.
Original language
English
Publication status
Published - 6 Aug 2025
______________________________________________________________________
An integrative review on the orexin system and hypothalamic dysfunction in myalgic encephalomyelitis/chronic fatigue syndrome: implications for precision medicine
Noé López-Amador *
Pain Med:. 2025 Jul 8:pnaf089. doi: 10.1093/pm/pnaf089. Online ahead of print
Pain Relief by Targeting Nonrestorative Sleep in Fibromyalgia: A Phase 3 Randomized Trial of Bedtime Sublingual Cyclobenzaprine
Seth Lederman 1, Lesley M Arnold 2, Ben Vaughn 3, Jean M Engels 1, Mary Kelley 1, Gregory M Sullivan 1
PMID: 40627411 DOI: 10.1093/pm/pnaf089
Abstract
Objective: Fibromyalgia is the prototypic nociplastic chronic pain syndrome, characterized by widespread pain, nonrestorative sleep, and fatigue. We evaluated efficacy and safety of bedtime TNX-102 SL (sublingual cyclobenzaprine) 5.6 mg for treatment of fibromyalgia.
Methods: This phase 3, double-blind, multicenter, placebo-controlled trial randomized patients 1:1 to once-nightly TNX-102 SL 2.8 mg for 2 weeks, followed by 5.6 mg for 12 weeks, or to matching placebo (NCT05273749). The primary endpoint was change from baseline at week 14 in weekly average of daily diary pain intensity scores. Secondary endpoints included Patient Global Impression of Change, Fibromyalgia Impact Questionnaire (Revised) Symptoms and Function domains, Patient-Reported Outcomes Measurement Information System instruments for Sleep Disturbance and Fatigue, and daily diary sleep quality scores.
Results: Overall, 81.0% (n = 187/231) and 79.6% (n = 179/225) of patients receiving TNX-102 SL and placebo completed the trial, respectively. Treatment with TNX-102 SL vs placebo was associated with significantly greater reductions in the primary pain endpoint (P < 0.001; mean [SE], -1.8 [0.12] vs -1.2 [0.12]) and in each of the 6 secondary endpoints (P ≤ 0.001; all). The most common systemic treatment-emergent adverse events (TEAEs) with TNX-102 SL and placebo were COVID-19 (4.3% vs 3.1%, respectively), headache (3.0% vs 1.8%), and somnolence (3.0% vs 1.3%); the most common TEAEs overall were local administration-site reactions including oral hypoesthesia (23.4% vs 0.4%), product taste abnormal (11.3% vs 0.9%), and oral paresthesia (6.9% vs 0.9%), which were transient and self-limited.
Conclusion: Bedtime TNX-102 SL treatment was associated with significant improvements in fibromyalgia symptoms and function and was well tolerated.
Keywords: Fibromyalgia; clinical trial; cyclobenzaprine; nociplastic pain; sleep.
© The Author(s) 2025. Published by Oxford University Press on behalf of the American Academy of Pain Medicine.
PubMed Disclaimer
July 2, 2025
Dr Krista Clarke is a post-doctoral researcher at the University of Surrey, and was co-funded by ME Research UK and the ME Association to assess the electrical properties of white blood cells in ME/CFS. Krista's thesis has now been published.
Abstract
Dielectrophoresis Myalgic Encephalomyelitis/ Chronic Fatigue Syndrome SARS-CoV-2 PBMC COVID-19 Chondrocyte Diagnosis
Biological cells possess intrinsic electrophysiological properties which are fundamental to cellular function. Changes in cell elctrophysiology can act as a biomarker, for example to indicate transition from healthy to diseased cell states, changes in cell function, or cell differentiation. This thesis presents three studies which used dielectrophoresis (DEPtech 3DEP) and ζ-potential analysis (two fast, label-free, high-throughput, non-invasive, and low-cost tools) to examine the electrophysiological properties of two cell types, peripheral blood mononuclear cells (PBMCs) and chondrocytes, for novel medical applications.
The first study investigated the electrophysiological properties of PBMCs in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS); a debilitating disease of unknown pathophysiology with no reliable, validated, and quantitative diagnostic test. The dielectric and ζ-potential response of PBMCs to 1.5-hour hyperosmotic challenge differentiated ME/CFS donors from healthy controls with 81.80% sensitivity and 85.70% specificity. This shows potential as a quantitative diagnostic biomarker
The second study examined whether the electrophysiological properties of PBMCs could act as a correlate of protection to SARS-CoV-2. Cytoplasmic conductivity in unchallenged PBMCs was significantly reduced in donors who had received three SARS-CoV-2 vaccine doses compared with unmatched COVID-19 naïve donors. Stimulation with the receptor binding domain of the SARS-CoV-2 spike protein resulted in significant differences in normalised values of membrane conductance in third-dose vaccinated donors, from COVID-19 naïve and second-dose donors.
The third study investigated chondrocytes, which are used extensively in cell-based cartilage-repair therapies. Chondrocytes rapidly dedifferentiate and become fibroblastic during monolayer cell culture – decreasing the success of reimplantation surgery. Significant changes in chondrocyte electrophysiological properties were observed over time in culture, laying the foundations for the identification of an electrophysiological biomarker that correlates with chondrocytic phenotype, to improve re-implantation outcome.
These studies demonstrate novel applications of dielectrophoresis and ζ-potential analysis – to quantitatively diagnose ME/CFS, identify changes in PBMCs following COVID-exposure, and changes in chondrocyte electrophysiology during dedifferentiation.
______________________________________________________________________
Original Investigation Infectious Diseases
Sex Differences in Long COVID
Dimpy P. Shah, MD, PhD1; Tanayott Thaweethai, PhD2,3; Elizabeth W. Karlson, MD, MS4; et al
JAMA Netw Open Published Online: January 22, 2025
2025;8;(1):e2455430. doi:10.1001/jamanetworkopen.2024.55430
Key Points
Question Does the risk of long COVID, or post-COVID condition, differ by sex?
Findings In this cohort study of 12 276 individuals, females had a significantly higher risk of long COVID compared with males after adjusting for sociodemographic and clinical risk factors. The sex-based difference in long COVID risk was age, pregnancy, and menopause dependent, with the highest risk among females aged 40 to 55 years.
Meaning These findings highlight the importance of evaluating differences in risk of long COVID after SARS-CoV-2 infection in males and females and of comparing biological mechanisms that may underlie sexually dimorphic long COVID trajectories.
Abstract
Importance A substantial number of individuals worldwide experience long COVID, or post-COVID condition. Other postviral and autoimmune conditions have a female predominance, but whether the same is true for long COVID, especially within different subgroups, is uncertain.
Objective To evaluate sex differences in the risk of developing long COVID among adults with SARS-CoV-2 infection.
Design, Setting, and Participants This cohort study used data from the National Institutes of Health (NIH) Researching COVID to Enhance Recovery (RECOVER)–Adult cohort, which consists of individuals enrolled in and prospectively followed up at 83 sites in 33 US states plus Washington, DC, and Puerto Rico. Data were examined from all participants enrolled between October 29, 2021, and July 5, 2024, who had a qualifying study visit 6 months or more after their initial SARS-CoV-2 infection.
Exposure Self-reported sex (male, female) assigned at birth.
Main Outcomes and Measures Development of long COVID, measured using a self-reported symptom-based questionnaire and scoring guideline at the first study visit that occurred at least 6 months after infection. Propensity score matching was used to estimate risk ratios (RRs) and risk differences (95% CIs). The full model included demographic and clinical characteristics and social determinants of health, and the reduced model included only age, race, and ethnicity.
Results Among 12 276 participants who had experienced SARS-CoV-2 infection (8969 [73%] female; mean [SD] age at infection, 46 [15] years), female sex was associated with higher risk of long COVID in the primary full (RR, 1.31; 95% CI, 1.06-1.62) and reduced (RR, 1.44; 95% CI, 1.17-1.77) models. This finding was observed across all age groups except 18 to 39 years (RR, 1.04; 95% CI, 0.72-1.49). Female sex was associated with significantly higher overall long COVID risk when the analysis was restricted to nonpregnant participants (RR, 1.50; 95%: CI, 1.27-1.77). Among participants aged 40 to 54 years, the risk ratio was 1.42 (95% CI, 0.99-2.03) in menopausal female participants and 1.45 (95% CI, 1.15-1.83) in nonmenopausal female participants compared with male participants.
Conclusions and Relevance In this prospective cohort study of the NIH RECOVER-Adult cohort, female sex was associated with an increased risk of long COVID compared with male sex, and this association was age, pregnancy, and menopausal status dependent. These findings highlight the need to identify biological mechanisms contributing to sex specificity to facilitate risk stratification, targeted drug development, and improved management of long COVID.
______________________________________________________________________
Review Infection 2025 Feb;53(1):1-13.
doi: 10.1007/s15010-024-02386-8. Epub 2024 Sep 6.
Towards an understanding of physical activity-induced post-exertional malaise: Insights into microvascular alterations and immunometabolic interactions in post-COVID condition and myalgic encephalomyelitis/chronic fatigue syndrome
Simon Haunhorst 1 2, Diana Dudziak 3, Carmen Scheibenbogen 4, Martina Seifert 4 5, Franziska Sotzny 4, Carsten Finke 6, Uta Behrends 7 8 9, Konrad Aden 10 11, Stefan Schreiber 11, Dirk Brockmann 12, Paul Burggraf 13, Wilhelm Bloch 14, Claudia Ellert 15 16, Anuradha Ramoji 17 18, Juergen Popp 17 18, Philipp Reuken 19, Martin Walter 20 21, Andreas Stallmach 19, Christian Puta 22 23 24
PMID: 39240417 PMCID: PMC11825644 DOI: 10.1007/s15010-024-02386-8
Abstract
Background: A considerable number of patients who contracted SARS-CoV-2 are affected by persistent multi-systemic symptoms, referred to as Post-COVID Condition (PCC). Post-exertional malaise (PEM) has been recognized as one of the most frequent manifestations of PCC and is a diagnostic criterion of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Yet, its underlying pathomechanisms remain poorly elucidated.
Purpose and methods: In this review, we describe current evidence indicating that key pathophysiological features of PCC and ME/CFS are involved in physical activity-induced PEM.
Results: Upon physical activity, affected patients exhibit a reduced systemic oxygen extraction and oxidative phosphorylation capacity. Accumulating evidence suggests that these are mediated by dysfunctions in mitochondrial capacities and microcirculation that are maintained by latent immune activation, conjointly impairing peripheral bioenergetics. Aggravating deficits in tissue perfusion and oxygen utilization during activities cause exertional intolerance that are frequently accompanied by tachycardia, dyspnea, early cessation of activity and elicit downstream metabolic effects. The accumulation of molecules such as lactate, reactive oxygen species or prostaglandins might trigger local and systemic immune activation. Subsequent intensification of bioenergetic inflexibilities, muscular ionic disturbances and modulation of central nervous system functions can lead to an exacerbation of existing pathologies and symptoms.
Keywords: ME/CFS; Physical activity; Post COVID condition; Post-exertional malaise; SARS-CoV-2.
______________________________________________________________________
Home | JAMA Pediatrics | New Online Original Investigation
Characterizing Long COVID Symptoms During Early Childhood
Rachel S. Gross, MD, MS1; Tanayott Thaweethai, PhD2,3; Amy L. Salisbury, PhD4; et al
Published Online: May 27, 2025
2025;179;(7):781-792. doi:10.1001/jamapediatrics.2025.1066
Key Points
Question Which prolonged symptoms in early childhood are associated with SARS-CoV-2 infection?
Findings In the Researching COVID to Enhance Recovery (RECOVER)–Pediatrics cohort study including 472 infants/toddlers and 539 preschool-aged children, prolonged symptoms were identified that were more common in young children with infection history than those without. Infants/toddlers (0-2 years) with infection history were more likely to experience trouble sleeping, fussiness, poor appetite, stuffy nose, and cough, and preschool-aged children (3-5 years) were more likely to experience dry cough and daytime tiredness/sleepiness or low energy; empirically derived indices for long COVID research were developed from these symptoms.
Meaning Results of this cohort study suggest that symptom patterns were distinguishable across infants/toddlers and preschool-aged children, and from previously studied older children and adults.
Abstract
Importance Recent studies have identified characteristic symptom patterns of long COVID (LC) in adults and children older than 5 years. However, LC remains poorly characterized in early childhood. This knowledge gap limits efforts to identify, care for, and prevent LC in this vulnerable population.
Objectives To identify symptoms that had the greatest difference in frequency comparing children with a history of SARS-CoV-2 infection to those without, to identify differences in the types of symptoms by age group (infants/toddlers [0-2 years] vs preschool-aged children [3-5 years]), and to derive an index that can be used in research studies to identify young children with LC.
Design, Setting, and Participants This was a multisite longitudinal cohort study with enrollment from over 30 US health care and community settings, including infants, toddlers, and preschool-aged children with and without SARS-CoV-2 infection history. Study data were analyzed from May to December 2024.
Exposure SARS-CoV-2 infection.
Main Outcomes and Measures LC and 41 symptoms among infants/toddlers and 75 symptoms among preschool-aged children.
Results The study included 472 infants/toddlers (mean [SD] age, 12 [9] months; 278 infected with SARS-CoV-2; 194 uninfected; 234 male [50%]; 73 Black or African American [16%]; 198 Hispanic, Latino, or Spanish [43%]; 242 White [52%]) and 539 preschool-aged children (mean [SD] age, 48 [10] months; 399 infected with SARS-CoV-2; 140 uninfected; 277 female [51%]; 70 Black or African American [13%]; 210 Hispanic, Latino, or Spanish [39%]; 287 White [54%]). The median (IQR) time between first infections and completion of symptom surveys was 318 (198-494) days for infants/toddlers and 520 (330-844) days for preschool-aged children. A research index was derived for each age group based on symptoms most associated with infection history. The index is calculated by summing scores assigned to each prolonged symptom that was present, where higher scores indicate greater magnitude of association with history of SARS-CoV-2 infection: poor appetite (5 points), trouble sleeping (3.5 points), wet cough (3.5 points), dry cough (3 points), and stuffy nose (0.5 points) for infants/toddlers, and daytime tiredness/sleepiness/low energy (6.5 points) and dry cough (3 points) for preschool-aged children. Among infants/toddlers with infection, 40 of 278 (14%) were classified as having probable LC by having an index of at least 4 points. Among preschool-aged children, 61 of 399 (15%) were classified as having probable LC by having an index of at least 3 points. Participants with higher indices often had poorer overall health, lower quality of life, and perceived delays in developmental milestones.
Conclusions and Relevance This cohort study identified symptom patterns and derived research indices that were distinct between the 2 age groups and differed from those previously identified in older ages, demonstrating the need to characterize LC separately across age ranges.
______________________________________________________________________
Original Investigation Infectious Diseases
Sex Differences in Long COVID
Dimpy P. Shah, MD, PhD1; Tanayott Thaweethai, PhD2,3; Elizabeth W. Karlson, MD, MS4; et al
JAMA Netw Open Published Online: January 22, 2025
2025;8;(1):e2455430. doi:10.1001/jamanetworkopen.2024.55430
Question Does the risk of long COVID, or post-COVID condition, differ by sex?
Findings In this cohort study of 12 276 individuals, females had a significantly higher risk of long COVID compared with males after adjusting for sociodemographic and clinical risk factors. The sex-based difference in long COVID risk was age, pregnancy, and menopause dependent, with the highest risk among females aged 40 to 55 years.
Meaning These findings highlight the importance of evaluating differences in risk of long COVID after SARS-CoV-2 infection in males and females and of comparing biological mechanisms that may underlie sexually dimorphic long COVID trajectories.
Abstract
Importance A substantial number of individuals worldwide experience long COVID, or post-COVID condition. Other postviral and autoimmune conditions have a female predominance, but whether the same is true for long COVID, especially within different subgroups, is uncertain.
Objective To evaluate sex differences in the risk of developing long COVID among adults with SARS-CoV-2 infection.
Design, Setting, and Participants This cohort study used data from the National Institutes of Health (NIH) Researching COVID to Enhance Recovery (RECOVER)–Adult cohort, which consists of individuals enrolled in and prospectively followed up at 83 sites in 33 US states plus Washington, DC, and Puerto Rico. Data were examined from all participants enrolled between October 29, 2021, and July 5, 2024, who had a qualifying study visit 6 months or more after their initial SARS-CoV-2 infection.
Exposure Self-reported sex (male, female) assigned at birth.
Main Outcomes and Measures Development of long COVID, measured using a self-reported symptom-based questionnaire and scoring guideline at the first study visit that occurred at least 6 months after infection. Propensity score matching was used to estimate risk ratios (RRs) and risk differences (95% CIs). The full model included demographic and clinical characteristics and social determinants of health, and the reduced model included only age, race, and ethnicity.
Results Among 12 276 participants who had experienced SARS-CoV-2 infection (8969 [73%] female; mean [SD] age at infection, 46 [15] years), female sex was associated with higher risk of long COVID in the primary full (RR, 1.31; 95% CI, 1.06-1.62) and reduced (RR, 1.44; 95% CI, 1.17-1.77) models. This finding was observed across all age groups except 18 to 39 years (RR, 1.04; 95% CI, 0.72-1.49). Female sex was associated with significantly higher overall long COVID risk when the analysis was restricted to nonpregnant participants (RR, 1.50; 95%: CI, 1.27-1.77). Among participants aged 40 to 54 years, the risk ratio was 1.42 (95% CI, 0.99-2.03) in menopausal female participants and 1.45 (95% CI, 1.15-1.83) in nonmenopausal female participants compared with male participants.
Conclusions and Relevance In this prospective cohort study of the NIH RECOVER-Adult cohort, female sex was associated with an increased risk of long COVID compared with male sex, and this association was age, pregnancy, and menopausal status dependent. These findings highlight the need to identify biological mechanisms contributing to sex specificity to facilitate risk stratification, targeted drug development, and improved management of long COVID.
______________________________________________________________________
The Role of T-Cell Exhaustion as a Driver in the Development of Post-Acute Infection Syndromes: A Literature Review
Willem Gielen1, Mahican Gielen1, Nigel McCracken2, Peter Derek Christian Leutscher1
Abstract
This literature review summarizes recent studies on T cell exhaustion and its role in post-acute infection syndromes (PAIS), including Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) and Long COVID. It synthesizes the current evidence on how persistent immune dysfunction contributes to the chronic symptoms seen in these conditions. T cell exhaustion, marked by continuous antigen exposure, diminished effector function, and increased expression of inhibitory receptors such as PD-1, CTLA-4, TIM-3, and TIGIT, is increasingly recognized as a key factor in the pathogenesis of PAIS. Clinical and molecular studies have revealed altered T cell populations, impaired proliferative responses, and metabolic dysregulation in affected patients. Persistent viral antigens are implicated in maintaining this exhausted state, whereas neuroimmune interactions and autoimmune processes may further sustain symptomatology. Although this review did not employ a formal systematic methodology, it integrated findings from multiple studies to provide a comprehensive overview of the field. Challenges remain regarding standardized diagnostic criteria and biomarkers; however, advances in immune exhaustion markers present the potential for improved diagnosis and targeted treatments. Emerging therapeutic approaches include immune checkpoint modulation, metabolic interventions, antiviral therapy, and immunomodulation. Further research is needed to clarify the mechanisms, validate the biomarkers, and develop effective clinical interventions. Recognizing T cell exhaustion as a central mechanism offers a foundation for advancing our understanding and management of PAIS.
Correspondence: [email protected] — Qeios will forward to the authors
______________________________________________________________________
Patient-reported treatment outcomes in ME/CFS and long COVID
Martha Eckey, Peng Li, Braxton Morrison, +2 , and Wenzhong Xiao [email protected]Authors Info & Affiliations
Contributed by Ronald Davis; received December 24, 2024; accepted April 7, 2025; reviewed by Lucinda Bateman and Lewis E. Kazis
July 8, 2025 122 (28) e2426874122 https://doi.org/10.1073/pnas.2426874122
Significance
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and long COVID are debilitating conditions that currently lack FDA-approved treatments. This study analyzes patient-reported outcomes from over 3,900 individuals, identifying treatments perceived as beneficial and uncovering symptom-based patient subgroups with distinct responses to therapies. Notably, there is significant overlap in the symptom profiles and treatment responses between ME/CFS and long COVID, suggesting that they may share underlying mechanisms. These findings offer valuable real-world insights for patients and their healthcare providers and help identify promising candidates for clinical trials, addressing an urgent need for effective therapies in these chronic illnesses.
Abstract
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and long COVID are persistent multisystem illnesses affecting many patients. With no known effective FDA-approved treatments for either condition, patient-reported outcomes of treatments may prove helpful in identifying management strategies that can improve patient care and generate new avenues for research. Here, we present the results of an ME/CFS and long COVID treatment survey with responses from 3,925 patients. We assess the experiences of these patients with more than 150 treatments in conjunction with their demographics, symptoms, and comorbidities. Treatments with the greatest perceived benefits are identified. Patients with each condition who participated in the study shared similar symptom profiles, including all the core symptoms of ME/CFS, e.g., 89.7% of ME/CFS and 79.4% of long COVID reported postexertional malaise (PEM). Furthermore, treatment responses between these two patient groups were significantly correlated (R2 = 0.68). Patient subgroups, characterized by distinct symptom profiles and comorbidities, exhibited increased responses to specific treatments, e.g., a POTS-dominant cluster benefiting from autonomic modulators and a cognitive-dysfunction cluster from CNS stimulants. This study underscores the symptomatic and therapeutic similarities between ME/CFS and long COVID and highlights the commonalities and nuanced complexities of infection-associated chronic diseases and related conditions. While this study does not provide recommendations for specific therapies, in the absence of approved treatments, insights from patient-reported experiences provide urgently needed real-world evidence for developing targeted patient care therapies and future clinical trials.
______________________________________________________________________
Defective peripheral B cell tolerance leads to dysregulated B cell responses in Fibromyalgia Syndrome
Rachael Bashford-Rogers, Alexander Long, Antonio Choi Chiu, Orthi Onupom, and 8 more
This is a preprint; it has not been peer reviewed by a journal.
https://doi.org/10.21203/rs.3.rs-6836742/v1
This work is licensed under a CC BY 4.0 License
Abstract
Fibromyalgia syndrome (FMS) is a chronic pain disorder characterised by widespread musculoskeletal pain, fatigue, and cognitive dysfunction, with no definitive biomarkers or mechanism-based treatments. Emerging evidence suggests that immune dysregulation may contribute to the FMS pathogenesis, particularly involving B cells, which have been implicated in autoantibody production and neuronal sensitisation. However, whether peripheral B cell tolerance, a critical safeguard against autoimmunity, is compromised in FMS remains unknown. Here, we combined high-resolution B cell receptor (BCR) repertoire sequencing, deep immunophenotyping, and functional assays in a well-characterised FMS cohort to uncover profound defects in peripheral B cell tolerance. We reveal significant defects in peripheral B cell tolerance in FMS, including: (1) impaired naïve B cell anergy, marked by elevated CD21, CD22, and CD24 expression; (2) exaggerated proliferative responses and rapid CD24 downregulation upon stimulation; and (3) altered BCR selection patterns, with increased IGHV6-1/IGHJ6 usage, skewed class switching toward IGHA1, and enhanced clonal expansion. These features closely resemble immune pathology profiles observed in classical autoimmune diseases. These findings redefine FMS as a disorder of immune dysregulation, with defective B cell tolerance contributing to disease mechanisms. The convergence of interferon-driven B cell activation, clonal expansion, and autoantibody production suggests shared pathways with classical autoimmune diseases. Our study provides a foundation for mechanism-based diagnostics and targeted immunomodulatory therapies, offering new avenues for intervention in this debilitating condition.
______________________________________________________________________
Inflammation and Interferon Signatures in Peripheral B-Lymphocytes and Sera of Individuals With Fibromyalgia
Serena Fineschi 1 2, Joakim Klar 3, Kristin Ayoola Gustafsson 3, Kent Jonsson 2 4, Bo Karlsson 2, Niklas Dahl 3
Abstract
Fibromyalgia (FM) is an idiopathic chronic disease characterized by widespread musculoskeletal pain, hyperalgesia and allodynia, often accompanied by fatigue, cognitive dysfunction and other symptoms. Autoimmunity and neuroinflammatory mechanisms have been suggested to play important roles in the pathophysiology of FM supported by recently identified interferon signatures in affected individuals. However, the contribution of different components in the immune system, such as the B-lymphocytes, in the progression to FM are yet unknown. Furthermore, there is a great need for biomarkers that may improve diagnostics of FM. Herein, we investigated the gene expression profile in peripheral B-cells, as well as a panel of inflammatory serum proteins, in 30 FM patients and 23 healthy matched control individuals. RNA sequence analysis revealed 60 differentially expressed genes when comparing the two groups. The group of FM patients showed increased expression of twenty-five interferon-regulated genes, such as S100A8 and S100A9, VCAM, CD163, SERPINA1, ANXA1, and an increased interferon score. Furthermore, FM was associated with elevated levels of 19 inflammatory serum proteins, such as IL8, AXIN1, SIRT2 and STAMBP, that correlated with the FM severity score. Together, the results shows that FM is associated with an interferon signature in B-cells and increased levels of a set of inflammatory serum proteins. Our findings bring further support for immune activation in the pathogenesis of FM and highlight candidate biomarkers for diagnosis and intervention in the management of FM.
Keywords: B-lymphocytes; RNA sequencing; fatigue; fibromyalgia; fibromyalgia score; inflammation; inflammatory proteins; interferon signature.
______________________________________________________________________
Patient-reported treatment outcomes in ME/CFS and long COVID
Martha Eckey, Peng Li, Braxton Morrison, and Wenzhong Xiao [email protected]Authors Info & Affiliations
Contributed by Ronald Davis; received December 24, 2024; accepted April 7, 2025; reviewed by Lucinda Bateman and Lewis E. Kazis
July 8, 2025 122 (28) e2426874122 https://doi.org/10.1073/pnas.2426874122
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and long COVID are debilitating conditions that currently lack FDA-approved treatments. This study analyzes patient-reported outcomes from over 3,900 individuals, identifying treatments perceived as beneficial and uncovering symptom-based patient subgroups with distinct responses to therapies. Notably, there is significant overlap in the symptom profiles and treatment responses between ME/CFS and long COVID, suggesting that they may share underlying mechanisms. These findings offer valuable real-world insights for patients and their healthcare providers and help identify promising candidates for clinical trials, addressing an urgent need for effective therapies in these chronic illnesses.
Abstract
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and long COVID are persistent multisystem illnesses affecting many patients. With no known effective FDA-approved treatments for either condition, patient-reported outcomes of treatments may prove helpful in identifying management strategies that can improve patient care and generate new avenues for research. Here, we present the results of an ME/CFS and long COVID treatment survey with responses from 3,925 patients. We assess the experiences of these patients with more than 150 treatments in conjunction with their demographics, symptoms, and comorbidities. Treatments with the greatest perceived benefits are identified. Patients with each condition who participated in the study shared similar symptom profiles, including all the core symptoms of ME/CFS, e.g., 89.7% of ME/CFS and 79.4% of long COVID reported postexertional malaise (PEM). Furthermore, treatment responses between these two patient groups were significantly correlated (R2 = 0.68). Patient subgroups, characterized by distinct symptom profiles and comorbidities, exhibited increased responses to specific treatments, e.g., a POTS-dominant cluster benefiting from autonomic modulators and a cognitive-dysfunction cluster from CNS stimulants. This study underscores the symptomatic and therapeutic similarities between ME/CFS and long COVID and highlights the commonalities and nuanced complexities of infection-associated chronic diseases and related conditions. While this study does not provide recommendations for specific therapies, in the absence of approved treatments, insights from patient-reported experiences provide urgently needed real-world evidence for developing targeted patient care therapies and future clinical trials.
______________________________________________________________________
Long COVID Gene Variants: A Step Toward a Diagnostic Test?
Solarina Ho July 23, 2025
A large-scale global study has identified genetic variants that are risk factors for long COVID, a discovery that helps researchers better understand the biological systems involving the disease and one small, early step toward the elusive goal of developing a long COVID diagnostic test.
International researchers with the Long COVID Host Genetics Initiative used data from 33 independent studies and 19 countries across North America, Europe, the Middle East, and Asia to analyze the genomes of nearly 16,000 patients with long COVID, representing populations from six genetic ancestries. Nearly 1.9 million controls were included in the genome-wide association study, a research method that scans complete sets of DNA to identify genetic variations associated with a specific trait or disease.
Genetic variants found in the FOXP4 gene had a statistically significant risk linked to long COVID, the study, published in Nature Genetics, found. The FOXP4 gene is known to impact lung function, and its expression levels were higher in those with long COVID than in controls. In addition, the risk variants had a consistent effect across different ancestries.
The researchers also found a causal relationship between a SARS-CoV-2 infection and long COVID and an additional causal risk between infections severe enough to require hospitalization and long COVID. Researchers also analyzed possible connections between variants associated with long COVID and those linked to other diseases and conditions.
Scientists said the overall findings provided evidence that was consistent with long COVID research that suggests both individual genetic variants and environmental risk factors contribute to disease risk. The findings also provide genetic proof linking abnormal lung physiology and the development of long COVID, the authors concluded; however, they noted that long COVID symptoms are not only limited to lung function and may include fatigue and cognitive dysfunction as well.
The study’s co-author, Hanna Ollila, PhD, with the Institute for Molecular Medicine Finland, University of Helsinki, Helsinki, Finland, underscored that the newly discovered genetic variants were not predictive for clinical tests or personal disease risk.
“The findings from our study, and from genome-wide association studies in general, tell about biological mechanisms behind a disease. This can then help to understand the disease better. For example, is it a disease neuronal, immune, metabolic, and so on?” said Ollila, who is also a researcher with the Department of Anesthesia and Center for Genomic Medicine at Massachusetts General Hospital, Boston. There are still many steps between these types of discoveries and the development of a diagnostic test, she explained, since these types of genetic variants do not function like high-impact variants such as the BRCA mutations in breast cancer.
“In other words, they do not strongly predict whether someone will develop long COVID at the individual level,” Ollila said. “Instead, they highlight the biological systems involved in the disease. In this case, our findings point to immune pathways related to lung function.”
Ollila explained that genetics can guide diagnostic development by pointing to underlying mechanisms, which may then help identify biomarkers in blood or other tissues. These biomarkers could eventually contribute to diagnostic tools, but it is a process that takes time and collaboration and often depends on progress across several fields of research including imaging and clinical phenotyping.
Researchers hope that when larger sample sizes become available for bigger studies, the analyses and understanding of the correlations will become more precise, bringing more understanding and clarity on genetic risk factors, biological mechanisms, and biomarkers that could someday help with disease diagnosis.
“We are likely still several years away, and possibly even a decade or more, from having a clinically useful diagnostic test based on genetic or biological markers for long COVID,” said Ollila. “That said, progress is accelerating thanks to the growing number of well-characterized cohorts and international collaborations. While these genetic findings are not yet ready for clinical application, they are an important step toward understanding long COVID, its relationship with other diseases, and the disease mechanisms that modulate risk for long COVID.”
Andreas Goebel a,b,*PMCID: PMC12226001 PMID: 40612406
______________________________________________________________________
Either the majority or all patients with severe fibromyalgia syndrome harbour proalgetic serum-immunoglobulin G autoantibodies; their possible relevance for patients must now be established through clinical trials.
Keywords: Fibromyalgia syndrome, FMS, Autoimmunity, Passive transfer, immunoglobulin
Abstract
Assessments of serum-autoantibodies in fibromyalgia syndrome (FMS) date back to the 1980s and have yielded inconsistent results. Based on a new passive transfer paradigm, since 2021 causative involvement of immunoglobulin G–mediated autoimmunity in severe FMS has been demonstrated in several studies, which have included UK, Swedish, and Canadian patients. These findings open the path to the development of novel diagnostic and immune-therapeutic approaches. Autoantibody targets and downstream mechanisms and the molecular processes that translate infection-, toxicity-, or stress-triggers into the FMS immune response in genetically or otherwise vulnerable individuals require study. These results in FMS also suggest that other chronic pain conditions or nonpainful symptom-based disorders may similarly be caused by noninflammatory minimally destructive autoantibody-mediated autoimmunity, thus offering hope for large groups of patients.
1. Background
Abnormal serum autoantibody titres in fibromyalgia syndrome (FMS) have been investigated at least as far back as the 1980s when Dinerman et al.16 reported the possible existence of a FMS subgroup without rheumatological comorbidity but with seropositivity for antinuclear antibodies (ANAs). The authors suggested that this finding may indicate involvement of autoimmune mechanisms. Since then, small studies have identified raised titres of various autoantibodies, potentially indicating abnormal immune activation or autoimmunity, although other studies were negative, and no consistent patterns have emerged.1,4,5,7,10,13,17,20,28,29,31,33,37–41,45–47,49–51,57,60 This evidence indicates that FMS is sometimes associated with mildly raised titres of specific immunoglobulin G (IgG) autoantibodies; furthermore, antibody-positivity is occasionally associated with an retrospectively identified FMS subgroup. The underpinning conceptual framework for these studies has in most cases been that antibody-induced structural or inflammatory change in tissue will induce activation of nociceptive (damage-sensing) nerve fibres, causing pain.
2. Witebsky–Rose postulates
In 1957, Witebsky et al.58 outlined criteria that can be used to identify a disorder as autoimmune, modelled on the Koch's postulates for the identifications of infectious microbes. A revised version was published 35 years later by one of the original authors, Noel Rose, together with Constantin Bona48 reflecting on advanced understanding of autoimmune mechanisms. Rose and Bona proposed to categorise evidence for autoimmune involvement in disease into (1) direct proof, (2) indirect evidence, and (3) circumstantial evidence.
Very rare direct proof derives from human-to-human transfer of disease such as when a scientist self-injects with plasma from a sick patient, or when pathogenic IgG from a mother is transported across the blood–placental barrier into the unborn child's circulation during the third trimester. Any transfer of serum-IgG purified from patients to experimental animals, which causes the patient phenotype in the animals is considered an alternative form of direct evidence; the authors specifically highlighted the example of serum-IgG transfer from patients with pemphigus to neonatal mice causing typical skin blisters. Sometimes, direct evidence can also derive from in vitro techniques, such as when serum-antibodies purified from patients with paroxysmal cold hemoglobinemia lyse erythrocytes taken from suitable patients.
Methods producing indirect evidence include the immunisation of experimental animals with the pertinent autoantigen, ie, the molecular structure against which the autoimmune response is directed in the human. As with direct proof approaches, these indirect methods are considered successful if they trigger the development of the human phenotype in the animals. Examples for indirect evidence include classical experimental results in myasthenia gravis where immunisation of rabbits with acetylcholine receptors derived from eel causes profound muscle weakness.42 Such methods obviously require that the antigen is known.
Finally, circumstantial evidence involves a favourable patient response to immune suppression. Rose and Bona thought that any such evidence would not provide proof for autoimmune disease, however, should incentivise further research. Several novel immune treatment methods might, however, instead be classed as direct evidence if the Witebsky–Rose criteria were to be revised in the future. Immunoadsorption, which removes serum-antibodies by filtration,6 and treatment with FcRn receptor antagonists,14 a novel class of drugs which reduces serum-antibodies by increasing their metabolism, both specifically target antibodies rather than causing general immune suppression. Such novel treatment technologies have been shown effective in several autoantibody-associated disorders, including myasthenia gravis.27 They differ from immune-suppressive approaches with very broad immune modifying effects known at the time of publication of the Witebsky–Rose criteria.
______________________________________________________________________
Defective peripheral B cell tolerance leads to dysregulated B cell responses in Fibromyalgia Syndrome
Rachael Bashford-Rogers, Alexander Long, Antonio Choi Chiu, Orthi Onupom, and 8 more
This is a preprint; it has not been peer reviewed by a journal.
https://doi.org/10.21203/rs.3.rs-6836742/v1
This work is licensed under a CC BY 4.0 License
Abstract
Fibromyalgia syndrome (FMS) is a chronic pain disorder characterised by widespread musculoskeletal pain, fatigue, and cognitive dysfunction, with no definitive biomarkers or mechanism-based treatments. Emerging evidence suggests that immune dysregulation may contribute to the FMS pathogenesis, particularly involving B cells, which have been implicated in autoantibody production and neuronal sensitisation. However, whether peripheral B cell tolerance, a critical safeguard against autoimmunity, is compromised in FMS remains unknown. Here, we combined high-resolution B cell receptor (BCR) repertoire sequencing, deep immunophenotyping, and functional assays in a well-characterised FMS cohort to uncover profound defects in peripheral B cell tolerance. We reveal significant defects in peripheral B cell tolerance in FMS, including: (1) impaired naïve B cell anergy, marked by elevated CD21, CD22, and CD24 expression; (2) exaggerated proliferative responses and rapid CD24 downregulation upon stimulation; and (3) altered BCR selection patterns, with increased IGHV6-1/IGHJ6 usage, skewed class switching toward IGHA1, and enhanced clonal expansion. These features closely resemble immune pathology profiles observed in classical autoimmune diseases. These findings redefine FMS as a disorder of immune dysregulation, with defective B cell tolerance contributing to disease mechanisms. The convergence of interferon-driven B cell activation, clonal expansion, and autoantibody production suggests shared pathways with classical autoimmune diseases. Our study provides a foundation for mechanism-based diagnostics and targeted immunomodulatory therapies, offering new avenues for intervention in this debilitating condition.
______________________________________________________________________
The sensitising effect of IgG in fibromyalgia syndrome is mediated by Mrgprb2 in mast cells
Karla R. Sanchez, Jamie Burgess, Qin Zheng, Uazman Alam, Harvey Neiland, Richard Berwick,
David Andersson, Samantha Korver, Anne Marshall, Andreas Goebel, Xinzhong Dong
doi: https://doi.org/10.1101/2025.05.15.652596
This article is a preprint and has not been certified by peer review
Abstract
Fibromyalgia syndrome (FMS) is characterized by elevated levels of immunoglobulin G (IgG), altered bowel habits, and increased pain sensitivity, suggesting immune dysregulation, but the exact mechanism remains unclear. Here, we found that FMS-IgG binds to mast cells in a MRGPRX2/b2-dependent manner, leading to mast cell recruitment and IL-6 secretion. Transferring serum-IgG from FMS patients to mice induced FMS-like symptoms and increased skin mast cells, indicating that FMS-IgG acts through mast cell activation. The ablation of mice Mrgprb2 mast cells or deleting Mrgprb2 receptors prevented IgG-induced heightened sensitivity to mechanical and cold stimuli. Stimulating human LAD2 cells with FMS IgG elicited MRGPRX2-dependent IL-6 production. Consistent with mice findings, mast cell density and tryptase levels increased in human FMS skin samples compared to healthy controls. Taken together our results suggests that FMS IgG mediates hypersensitivity via activation of mast cells bearing the MRGPRX2 receptor and that these cells are a potential therapeutic target.
Competing Interest Statement
X.D. is the scientific founder of and consultant for Escient Pharmaceuticals, a pharmaceutical company developing drugs targeting Mrgprs. X.D. collaborates with GlaxoSmithKline (GSK) on Mrgpr-related projects unrelated to this manuscript. Other authors declare no competing interests.
Funder Information Declared
Howard Hughes Medical Institute, https://ror.org/006w34k90
Pain Relief Foundation, https://ror.org/0017mh436
Versus Arthritis, https://ror.org/02jkpm469, 22471
Copyright
The copyright holder for this preprint is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY 4.0 International license.
bioRxiv and medRxiv thank the following for their generous financial support:
The Chan Zuckerberg Initiative, Cold Spring Harbor Laboratory, the Sergey Brin Family Foundation, California Institute of Technology, Centre National de la Recherche Scientifique, Fred Hutchinson Cancer Center, Imperial College London, Massachusetts Institute of Technology, Stanford University, The University of Edinburgh, University of Washington, and Vrije Universiteit Amsterdam.
Posted May 16, 2025.
______________________________________________________________________
Sec. Infectious Diseases: Pathogenesis and Therapy
Volume 12 - 2025 | https://doi.org/10.3389/fmed.2025.1607353
Plasma cell targeting with the anti-CD38 antibody daratumumab in myalgic encephalomyelitis/chronic fatigue syndrome—a clinical pilot study
Øystein Fluge1,2*Ingrid Gurvin Rekeland1Kari Sørland1Kine Alme1Kristin Risa1Ove Bruland3Karl Johan Tronstad4Olav Mella1
1The Cancer Clinic, Haukeland University Hospital, Bergen,2Institute of Clinical Sciences, University of Bergen, Bergen, Norway
Background: Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) entails low quality of life for patients and massive societal costs. There is an urgent need for elucidation of disease mechanisms and for rational treatment. Our working hypothesis is that ME/CFS in a subgroup of patients is associated with functional autoantibodies emerging after an infection, and that plasma-cell depletion with transient reductions in serum immunoglobulins will have a beneficial effect on patients’ symptoms.
- Objective: To evaluate feasibility and toxicity of plasma-cell targeting treatment using the subcutaneous anti-CD38 antibody daratumumab (Darzalex®) in moderate to severe ME/CFS, and to assess the clinical course through 12–24 months follow-up after daratumumab intervention.
- Methods: We performed a prospective, open-label pilot trial (EudraCT 2022–000281-18). Ten female patients were enrolled. Following 12 weeks run-in, six patients received four daratumumab injections. The next four patients received four, followed by three additional injections from week 14.
- Results: All planned treatments were administered, and there were no serious adverse events. Four patients had no significant clinical changes. Six patients experienced marked improvement. For all 10 patients, mean SF-36 Physical Function (SF-36 PF) increased from 25.9 to 55.0 at 8–9 months (p = 0.002). DePaul Questionnaire-Short Form (DSQ-SF) symptom scores decreased from 72.3 to 43.1 (p = 0.002). In six responders, mean SF-36 PF increased from 32.2 to 78.3, and DSQ-SF score decreased from 71.1 to 24.3. Five of these six patients had major and sustained improvement with a mean SF-36 PF of 88 (range 80–95) toward end of follow-up. Mean steps per 24 h was 3,359 (range 1,493–6,277) at baseline. At 8–9 months, the mean number of steps was 5,862, and 7,392 in the six responders. All five patients with sustained improvement reached a mean step count above 10,000/24 h for some weeks, and above 15,000 on individual days. Relative reduction of serum IgG levels was 54% in six patients with clinical improvement, and 40% among four with no benefit. Low baseline NK-cell count in blood was significantly associated with lack of clinical response.
- Conclusion: Subcutaneous daratumumab in 10 ME/CFS patients was well tolerated. In six patients, treatment was associated with clinical improvement and concurrent transient reduction of serum IgG levels, indicating important pathomechanistic roles for long-lived plasma cells and functional autoantibodies. No definite conclusions should be drawn before a randomized study has been performed.
- Clinical trial registration: https://euclinicaltrials.eu, Identifier: 2022-000281-18.
Infectious diseases: Mitochondrial function is impaired in long COVID patients
Jane Macnaughtan,K-Yin Chau, Ewen Brennan, Marco Toffoli, Antonella Spinazzola, Toby Hillman
Article: 2528167 | Received 25 Sep 2024, Accepted 28 Mar 2025, Published online: 12 Aug 2025
https://doi.org/10.1080/07853890.2025.2528167
Abstract
Background
The Long COVID syndrome is a major global health problem, affecting approximately 10–20% of individuals infected with SARS-CoV-2 virus with many remaining symptomatic beyond one year. Fatigue, reduced exercise tolerance and hyperlactataemia on minimal exertion have led to the suggestion of a bioenergetic defect. We hypothesised that mitochondrial dysfunction is a pathological feature in Long COVID cases and would correlate with clinical outcome.
Methods
This prospective, case-controlled, observational study recruited 27 participants with an established diagnosis of Long COVID syndrome from a single tertiary clinic together with 16 age-matched controls aged 25–65 years. Seahorse-based mitochondrial flux analysis and bioenergetics profile of isolated peripheral blood mononuclear cells (PBMCs) was performed and correlated with clinical phenotype.
Findings
Long COVID cases had an increased baseline and ATP-induced oxygen consumption rate with a significant attenuation in tetramethylrhodamine methyl ester perchlorate fluorescence response to oligomycin. Correlations were observed between mitochondrial function and autonomic health, quality of life and time from index infection. Sex-specific differences were also observed.
Interpretation
PBMCs from Long COVID subjects exhibit an exceptional and distinctive change in ATP synthase, as it contributes to the mitochondrial membrane potential rather than using it exclusively to generate ATP. The findings suggest that the enzyme runs both forward and reverse reactions, synthesising and hydrolysing ATP. The correlation of mitochondrial function with clinical phenotype in Long COVID may indicate a causal relationship and warrants further validation in larger scale studies.
Keywords:
ATP synthase, long COVID, mitochondrial dysfunction, peripheral blood mononuclear cells
______________________________________________________________________
University if Edinburgh
Initial findings from the DecodeME genome-wide association study of myalgic encephalomyelitis/chronic fatigue syndrome
DecodeME collaboration Research output: Working paper › Preprint
Abstract
Myalgic encephalomyelitis / chronic fatigue syndrome (ME/CFS) is a common, poorly understood disease that has no effective treatments, and has long been underserved by scientific research and national health systems. It is a sex-biased disease towards females that is often triggered by an infection, and its hallmark symptom is post-exertional malaise. People with ME/CFS often report their symptoms being disbelieved. The biological mechanisms causing ME/CFS remain unclear. We recruited 21,620 ME/CFS cases and performed genome-wide association studies (GWAS) for up to 15,579 cases and 259,909 population controls with European genetic ancestry. In these GWAS, we discovered eight loci that are significantly associated with ME/CFS, including three near BTN2A2, OLFM4, and RABGAP1L genes that act in the response to viral or bacterial infection. Four of the eight loci (RABGAP1L, FBXL4, OLFM4, CA10) were associated at p < 0.05 with cases ascertained using post-exertional malaise and fatigue in the UK Biobank and the Netherlands biobank Lifelines. We found no evidence of sex-bias among discovered associations, and replicated in males two genetic signals (ARFGEF2, CA10) discovered in females. The ME/CFS association near CA10 colocalises with a known association to multisite chronic pain. We found no evidence that the eight ME/CFS genetic signals share common causal genetic variants with depression or anxiety. Our findings suggest that both immunological and neurological processes are involved in the genetic risk of ME/CFS.
Original language
English
Publication status
Published - 6 Aug 2025
______________________________________________________________________
An integrative review on the orexin system and hypothalamic dysfunction in myalgic encephalomyelitis/chronic fatigue syndrome: implications for precision medicine
Noé López-Amador *
- Explor Neuroprot Ther. 2025;5:1004112 DOl: https://doi.org/10.37349/ent.2025.1004112
- Received: May 26, 2025 Accepted: July 22, 2025 Published: August 13, 2025
- Academic Editor: Janez Mavri, National Institute of Chemistry, Slovenia
- Abstract
- Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating multisystem disorder affecting an estimated 0.4% to 2.5% of community populations. Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis and marked metabolic heterogeneity underscore its complex pathophysiology. The hypothalamic peptides hypocretin-1 and -2 (also known as orexin-A and orexin-B), synthesized by neurons in the lateral hypothalamus, regulate sleep-wake cycles, arousal, autonomic function, and energy homeostasis. This integrative review aimed to synthesize current evidence on hypothalamic orexinergic dysfunction in ME/CFS and assess its potential as a biomarker framework for stratification in precision medicine. The review followed Whittemore and Knafl’s five-stage methodology. Comprehensive searches were conducted across PubMed, Scopus, Web of Science, and OpenAlex up to April 2025, supplemented by manual screening of reference lists. Data extraction and synthesis were performed using constant comparison techniques to integrate quantitative outcomes with theoretical insights. Twenty-seven studies met the inclusion criteria, consistently reporting reduced orexin-A levels in individuals with ME/CFS and variable orexin-B responses indicative of biomarker potential. Neuroendocrine findings, including alterations in cortisol and adrenocorticotropic hormone levels, along with inflammatory profiles, confirmed the involvement of neuroimmune interactions. Multi-omics analyses further delineated distinct patient subtypes characterized by unique molecular signatures. Hypothalamic orexinergic dysfunction emerges as a central feature of ME/CFS, with orexin-B representing a promising candidate biomarker. The integration of orexin profiling with multi-omics data and machine learning strategies provides a viable pathway towards precision-medicine interventions for this heterogeneous condition.
Pain Med:. 2025 Jul 8:pnaf089. doi: 10.1093/pm/pnaf089. Online ahead of print
Pain Relief by Targeting Nonrestorative Sleep in Fibromyalgia: A Phase 3 Randomized Trial of Bedtime Sublingual Cyclobenzaprine
Seth Lederman 1, Lesley M Arnold 2, Ben Vaughn 3, Jean M Engels 1, Mary Kelley 1, Gregory M Sullivan 1
PMID: 40627411 DOI: 10.1093/pm/pnaf089
Abstract
Objective: Fibromyalgia is the prototypic nociplastic chronic pain syndrome, characterized by widespread pain, nonrestorative sleep, and fatigue. We evaluated efficacy and safety of bedtime TNX-102 SL (sublingual cyclobenzaprine) 5.6 mg for treatment of fibromyalgia.
Methods: This phase 3, double-blind, multicenter, placebo-controlled trial randomized patients 1:1 to once-nightly TNX-102 SL 2.8 mg for 2 weeks, followed by 5.6 mg for 12 weeks, or to matching placebo (NCT05273749). The primary endpoint was change from baseline at week 14 in weekly average of daily diary pain intensity scores. Secondary endpoints included Patient Global Impression of Change, Fibromyalgia Impact Questionnaire (Revised) Symptoms and Function domains, Patient-Reported Outcomes Measurement Information System instruments for Sleep Disturbance and Fatigue, and daily diary sleep quality scores.
Results: Overall, 81.0% (n = 187/231) and 79.6% (n = 179/225) of patients receiving TNX-102 SL and placebo completed the trial, respectively. Treatment with TNX-102 SL vs placebo was associated with significantly greater reductions in the primary pain endpoint (P < 0.001; mean [SE], -1.8 [0.12] vs -1.2 [0.12]) and in each of the 6 secondary endpoints (P ≤ 0.001; all). The most common systemic treatment-emergent adverse events (TEAEs) with TNX-102 SL and placebo were COVID-19 (4.3% vs 3.1%, respectively), headache (3.0% vs 1.8%), and somnolence (3.0% vs 1.3%); the most common TEAEs overall were local administration-site reactions including oral hypoesthesia (23.4% vs 0.4%), product taste abnormal (11.3% vs 0.9%), and oral paresthesia (6.9% vs 0.9%), which were transient and self-limited.
Conclusion: Bedtime TNX-102 SL treatment was associated with significant improvements in fibromyalgia symptoms and function and was well tolerated.
Keywords: Fibromyalgia; clinical trial; cyclobenzaprine; nociplastic pain; sleep.
© The Author(s) 2025. Published by Oxford University Press on behalf of the American Academy of Pain Medicine.
PubMed Disclaimer
RSS Feed