A key consideration in ME/CFS research efforts is the complex and multisystemic nature of this disease, and we are happy to see the involvement of several NIH institutes in developing this plan. Because the causative factors driving the disease remain unknown, and because work from our team and others has indicated effects on neurology, metabolism, immunity, and more, it will be crucial that calls for proposals allow for open, unbiased, multifaceted, and systematic research. Broadening the scope of ME/CFS research will create opportunities for engaging researchers in other disciplines. Similarly, investigating numerous organ systems and biological pathways perturbed in ME/CFS may well reveal informative parallels to other diseases – for example, we and others have observed symptomatic, transcriptomic, and metabolic overlap between ME/CFS and neurodegenerative disorders like Parkinson's Disease. It is important not to limit research to single organs like the brain, and to integrate results from many different organs and molecular processes so that they can be understood at the systems level. Big data approaches and high-throughput, large-scale molecular profiling should therefore be prioritized. Such efforts hold promise to identify key genes or pathways underlying ME/CFS. Similarly, large-scale in vitro drug screening efforts would help point to a variety of molecules and molecular processes as therapeutic targets.
Understanding the molecular etiology of ME/CFS is another important opportunity. A long-standing belief in the field is that an infectious agent causes the disease, and that the pathogenicity of the as-yet-undiscovered organism is responsible for the severity of the illness. An equally plausible explanation is that a stressor such as trauma, infection, or genotoxic stress may trigger a series of events that lead to a hypometabolic state. This model is observed in children with congenital mitochondrial disorders, where the phenotype does not present itself until after a serious viral infection. This shift in thinking opens up the possibility that ME/CFS has strong genetic and environmental associations, which may also explain the extensive heterogeneity in its presentation, progression, and recovery across patients. The search for novel infectious agents should continue, but research efforts should also focus on understanding individual host susceptibility and response to infection. For example, it may not be a particular infectious agent that results in the disease, but rather a particular host state as a function of numerous biological and external factors that governs an individual’s susceptibility. This perspective mirrors the NIGMS-funded Glue Grant on Inflammation and Host Response to Injury, which used an integrated omics approach to define variable responses to infection and trauma. Characterizing host responses to infection and understanding the mechanisms of the long-term sequelae may reveal insights into ME/CFS that are relevant to numerous other diseases of infectious origin, such as Chronic Lyme Disease and Post-Ebola Syndrome (Mattia et al., 2016). Moreover, such precision medicine approaches would build a more comprehensive understanding of ME/CFS and offer richer opportunities for therapeutic intervention.
Another major challenge is our lack of understanding of the prevalence and landscape of ME/CFS, which is largely due to the difficulty in diagnosing the disease. The search for precise molecular biomarkers is a great opportunity afforded by this research program, which would be accelerated through multi-omics approaches in large patient cohorts. Current estimates of the prevalence of ME/CFS vary widely (800,000 to 2.5 million cases in the US) due to varying diagnostic and data collection methods. There is an opportunity here to improve these estimates based on modernized methods and community-defined standards, including criteria specified in the 2015 Institute of Medicine Report, and by considering questionnaire-based responses like the Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort in the United Kingdom (Collin et al., 2016).
Because of these complex scientific challenges, ME/CFS research presents an excellent opportunity for developing and piloting novel methods and technologies in discovering biomarkers, elucidating disease mechanisms, and revealing therapeutic possiblities. The methods we need to understand this complex disease may very well not exist yet. Engineering and technology development efforts towards highly sensitive, quantitative molecular profiling and/or measuring novel cellular properties, as well as novel computational analyses that integrate multiple datatypes to define disease mechanisms, should be encouraged. Again, it is highly likely that such efforts will prove useful in the study of other diseases, be they infectious, genetic, or complex in origin.
Beyond scientific considerations, we would like to note several programmatic considerations that we believe are key for rapid progress. Long-term studies of patients are absolutely essential. Such a mechanism has proven effective in the NIGMS Glue Grants described above. Moreover, maintaining an open structure in RFAs will allow scientists to develop and refine their hypotheses as research progresses, as appropriate for the unknown/uncertain nature of the field. As highlighted in several places above, the opportunities for collaborative efforts within and beyond the ME/CFS research community to understand and treat this disease are numerous. There are numerous experts spread across the world, each taking their own approaches based on their own expertise. We believe future funding programs should not only encourage, but establish frameworks for highly collaborative data sharing and strategizing that bring together researchers and clinicians. All data should be made publicly available as early as possible (even before publication), in both raw and accessible formats. This will not only facilitate collaboration (for example by encouraging biocomputing experts to engage with the data) and integrative analyses, but also empower patients to understand more about their disease and what progress is being made. As we have all seen, the ME/CFS patient community is extremely active, engaged, and eager for actionable results.
We thank you once again for the opportunity to provide input on this matter, and look forward to the new strategies for ME/CFS research efforts put forth by this working group.
Ronald W. Davis, Ph.D. Professor of Biochemistry and Genetics, Stanford University
Director, Stanford Chronic Fatigue Syndrome Research Center and Stanford Genome Technology Center
Director, Scientific Advisory Board, Open Medicine Foundation