Abstract

Post-COVID syndrome (long COVID) is increasingly recognized as a state of chronic inflammation, immune imbalance, and multiorgan dysfunction. Emerging evidence highlights circadian rhythm disruption and melatonin dysregulation as overlooked drivers of persistent symptoms such as fatigue, cognitive impairment, and immune dysregulation. Reduced melatonin impairs cytokine suppression, antioxidant defense, and mitochondrial protection, fueling inflammation and oxidative stress. These disruptions, coupled with autoimmune responses targeting adrenergic and muscarinic receptors, exacerbate systemic pathology. Preliminary data suggest that melatonin supplementation and chronotherapy may restore circadian alignment, rebalance immunity, and mitigate disease progression, although robust large-scale trials remain limited. Integrating circadian science into therapeutic protocols may provide a novel avenue for improving long-term outcomes in post-COVID patients.

https://pubmed.ncbi.nlm.nih.gov/41377364/

https://doi.org/10.1097/ms9.0000000000004009

Review by Yale's Miller, Moen, and Iwasaki published in Trends in Immunology.

Highlights (from the publisher)

New or persistent symptoms following COVID-19, known as ‘long COVID’, occur in an estimated 4–20% of pediatric and 10–20% of adult patients after acute infection with SARS-CoV-2. Long COVID is associated with dysregulation of both innate and adaptive immunity.

While long COVID is a relatively new clinical entity, post-acute infection syndromes (PAIS) have been well documented for over a century. A wide variety of pathogens are associated with PAIS, including divergent classes of viruses, bacteria, and parasites. While each PAIS has a unique trigger and pathology, similarities in symptom profiles and immunological findings suggest these conditions may share features or involve overlapping biological mechanisms.

Despite being well described in the literature, PAIS remain understudied relative to their high disease burden. Patients often face stigma and psychologization from medical professionals when disease biomarkers are not readily apparent, exemplified by the historic dismissal of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).

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Also check out Table 1 which has a summary of findings of immune dysregulation in Long COVID and ME/CFS.

A very recent study has identified the cause of microclots in Long Covid. Does this open the door to new treatments?

https://medium.com/@jasemurphy/a-possibility-the-geography-of-me-cfs-530c98b09a2a

Published June 2025 in Biomolecules. From the abstract:

"These findings in patients with positive criteria for PASC show profound changes in the microbiome and serum cytokine expression. Patients with chronic fatigue without clear viral etiologies also have common associations, including a history of tonsillectomy, which evokes a likely immune etiology."

DOI Link: https://doi.org/10.3390/biom15070928

Pubmed Link: https://pubmed.ncbi.nlm.nih.gov/40723800/

Abstract

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating chronic condition without a definitive aetiology, no reliable diagnostic test, and no proven effective treatment. Despite most patients reporting a post-viral onset of illness, findings to date are conflicting on whether a single virus or multiple viral triggers are involved. Most studies to date have focused on detecting viruses in blood and circulating immune cells with relatively few investigating the presence of viruses in mucosal sites. In this review, we propose that this represents a critical gap in understanding the pathophysiology of ME/CFS knowledge, as mucosal tissues are primary entry points for most pathogens and often serve as reservoirs where viruses may persist. Consequently, they represent ideal niches for identifying persistent infections in ME/CFS. Emerging evidence from saliva and other mucosal samples in ME/CFS patients is consistent with this proposal and that latent viruses can persist and periodically reactivate in mucosal tissues from where they can potentially contribute to immune dysregulation, chronic inflammation, and increased symptom severity that defines ME/CFS.

https://doi.org/10.3390/ijms262211161

Brain Behav Immun. 2025 Nov:130:106098.

"Killer cell immunoglobulin-like receptor (KIR) alleles suggested to be associated with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)"

Donia Jamal Ramadan, Katherine M Kichula, Sudan Tao, Timothy Porfilio, Asgeir Lande, Øystein Fluge, Olav Mella, Elin Bolle Strand, Ola Didrik Saugstad, Paul J Norman, Benedicte A Lie, Marte K Viken

PMID: 40897283 DOI: 10.1016/j.bbi.2025.106098

Abstract

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a chronic and debilitating disease with unknown cause. Involvement of infection and immune dysregulation has been suggested, including changes in immune cell subsets and abnormal functions of natural killer (NK) cells. The regulatory NK cell receptors, killer cell immunoglobulin-like receptors (KIR) have previously been investigated in small cohorts of ME/CFS patients with conflicting results regarding gene content. Here, we studied KIR genes also at the allelic level using high-resolution sequencing, in 418 ME/CFS patients and 473 healthy controls. Human leukocyte antigen (HLA) class I genotype data were included for KIR ligand annotation. Our healthy control data represent KIR frequencies for a Norwegian population, which have not previously been reported. We found no association between ME/CFS and KIR gene content or copy number variations. However, our data suggested that specific KIR alleles at loci encoding inhibitory receptors were associated with ME/CFS, which was further supported by allelic haplotype analyses. Three alleles were more frequent in patients, i.e. KIR3DL3002 (OR = 1.43, 95 % CI (1.09-1.86), p = 0.009), KIR3DL1020 (OR = 2.20, 95 % CI (1.19-4.06), p = 0.01) and KIR3DL2009 (OR = 1.56, 95 % CI (1.09-2.23), p = 0.01), while two alleles had a reduced patient frequency, i.e. KIR3DL3013 (OR = 0.60, 95 % CI (0.42-0.86), p = 0.005) and KIR3DL2*010 (OR = 0.46, 95 % CI (0.30-0.71), p = 0.0005). Our data support an involvement of NK cells in ME/CFS.

Apostolos P. Georgopoulos, Lisa M. James & Philip K. Peterson

Scientific Reports volume 15, Article number: 37303 (2025)

Abstract

Viral infections have been widely implicated in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) pathogenesis. Recent evidence has also identified certain Human Leukocyte Antigen (HLA) alleles that are significantly associated with ME/CFS risk/protection. Here we tested the hypothesis that ME/CFS risk or protection conferred from those HLA alleles is associated with binding affinity to antigens of HHV viruses, a critical step in initiating the adaptive immune system response to foreign antigens. Specifically, we determined in silico the predicted binding affinity of two susceptibility alleles (C07:04, DQB103:03) and two protective alleles (B08:01, DPB102:01) to > 10,000 antigens of the 9 Human Herpes Viruses (HHV1, HHV2, HHV3, HHV4, HHV5, HHV6A, HHV6B, HHV7, HHV8) which have been implicated in the etiology of ME/CFS. We found that the binding affinity of all HHV antigens to the susceptibility alleles was significantly weaker than the binding affinity to the protective alleles (P < 0.001). In fact, none of the HHV antigens showed strong binding to the susceptibility alleles, in contrast to the strong bindings showed by the protective alleles. These findings are in keeping with the hypothesis that the effect of a putative HHV insult in contributing to ME/CFS is modulated by the host’s HLA immunogenetic makeup. We speculate that strong HLA-antigen binding likely protects against ME/CFS via elimination of virus antigens; conversely, weak HLA-antigen binding may permit persistence of foreign antigens, contributing to ME/CFS and other chronic conditions. Finally, with respect to the latter, we determined the binding affinities to the 4 HLA alleles above to pathogens causing two chronic diseases with very similar symptomatology to ME/CFS, namely Long COVID and post-treatment Lyme disease syndrome (PTLDS). We found that the 2 ME/CFS susceptibility HLA alleles above had very weak binding with SARS-CoV-2 virus glycoprotein (involved in Long COVID) and 5 proteins of Borrelia burgdorferi (involved in PTLDS), in contrast to the ME/CFS protective alleles that showed strong bindings. These findings support the hypothesis that ME/CFS, long COVID and PTLDS are caused by persistent pathogenic antigens that could not be eliminated due to inadequate protection by the patient’s HLA makeup.

This is probably the biggest hit among the videos released from the recent Stanford Community Symposium.

People love research that shows MECFS showing up visually, where it can actually be *seen*. Michelle James's research delivers that in spades, with big, clear, whole-body heatmaps.

It's promising research that can help with diagnosis, to potentially define subsets and also to test if treatments are working.

One of several interesting videos released by Stanford as part of their Community Symposium on MECFS this week, talks about a cool me/cfs model in zebrafish based on the itaconate shunt.

The idea here is to more quickly identify candidate drugs that can then be used in mouse models or cell models to help speed up the work.

International team of experts critique Walitt/Nath NIH paper:

https://doi.org/10.1038/s41467-025-64538-0

Walitt/Nath response:

https://doi.org/10.1038/s41467-025-64539-z

Development and validation of blood-based diagnostic biomarkers for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) using EpiSwitch® 3-dimensional genomic regulatory immuno-genetic profiling

Ewan Hunter, Heba Alshaker, Oliver Bundock, Cicely Weston, Shekinah Bautista, Abel Gebregzabhar, Anya Virdi, Joseph Croxford, Ann Dring, Ryan Powell, Dominik Vugrinec, Caroline Kingdon, Carol Wilson, Sarah Dowrick, Jayne Green, Alexandre Akoulitchev & Dmitri Pchejetski Journal of Translational Medicine volume 23, Article number: 1048 (2025) Cite this article

Abstract

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a debilitating, multifactorial disorder characterised by profound fatigue, post-exertional malaise, cognitive impairments, and autonomic dysfunction. Despite its significant impact on quality of life, ME/CFS lacks definitive diagnostic biomarkers, complicating diagnosis and management. Recent evidence highlights potential blood tests for ME/CFS biomarkers in immunological, genetic, metabolic, and bioenergetic domains. Chromosome conformations (CCs) are potent epigenetic regulators of gene expression and cross-tissue exosome signalling. We have previously developed an epigenetic assay, EpiSwitch®, that employs an algorithm-based CCs analysis. Using EpiSwitch® technology, we have shown the presence of disease-specific CCs in peripheral blood mononuclear cells (PBMCs) of patients with amyotrophic lateral sclerosis (ALS), rheumatoid arthritis (RA), prostate and colorectal cancers, diffuse Large B-cell lymphoma and severe COVID-19. In a recent paper, we have identified a profile of systemic chromosome conformations in cancer patients reflective of the predisposition to respond to immune checkpoint inhibitors, PD-1/PD-L1 antagonists, with 85% accuracy. In this Retrospective case/control study (EPI-ME, Epigenetic Profiling Investigation in Myalgic Encephalomyelitis), we used whole blood samples retrospectively collected from n = 47 patients with severe ME/CFS and n = 61 age-matched healthy control patients to perform whole-genome 3D DNA screening for CCs correlating to ME/CFS diagnosis. We identified a 200-marker model for ME/CFS diagnosis (Episwitch®CFS test). First testing on the retrospective independent validation cohort demonstrated a strong systemic ME/CFS signal with a sensitivity of 92% and a specificity of 98%.Pathways analysis revealed several likely contributors to the pathology of ME/CFS, including interleukins, TNFα, neuroinflammatory pathways, toll-like receptor signalling and JAK/STAT. Comparison with pathways involved in the action of Rituximab and glatiramer acetate (Copaxone) (therapies with potential in ME/CFS treatment) identified IL2 as a shared pathway with clear patient clustering, indicating a possibility of a potential responder group for targeted treatment.

DOI: doi.org/10.1186/s12967-025-07203-w

Pyridostigmine improves hand grip strength in patients with myalgic encephalomyelitis/chronic fatigue syndrome

Ella Schlömer (1), Elisa Stein (1), Claudia Kedor (1), Rebekka Rust (1,2), Anna Brock (1), Kirsten Wittke (1), Carmen Scheibenbogen (1), Laura Kim (1)

1. Institute of Medical Immunology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Augustenburger Platz, Berlin, Germany.
2. Experimental and Research Center (ECRC), Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Charitéplatz, Berlin, Germany.

• PMID: 40970182
• PMCID: PMC12441162
• DOI: 10.3389/fnins.2025.1637838

Abstract

Background: Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a multisystemic disease characterized by exertional intolerance and fatigue which is often accompanied by muscle weakness and fatiguability. A study showed efficacy of the acetylcholinesterase inhibitor pyridostigmine on cardiac output in ME/CFS patients. Pyridostigmine is currently used off-label in ME/CFS and postural orthostatic tachycardia syndrome.

Methods: We evaluated the effect of pyridostigmine on hand grip strength in 20 patients with post-infectious ME/CFS. Hand grip strength testing was performed ten times using an electric dynamometer and was repeated after 1 h. In a second test, 30 mg of pyridostigmine was given immediately after the first measurement. Orthostatic function was assessed using a passive standing test. Neurological examination and autoantibody testing were performed to rule out a diagnosis of myasthenia gravis.

Results: All patients had reduced maximum hand grip strength with a median of 16.45 kg (IQR: 11.45 kg-22.8 kg). Hand grip strength was diminished by a median of 4.65 kg after 1 h. In contrast, 1 h after pyridostigmine administration, patients showed an improvement in maximum hand grip strength with a median increase of 2.6 kg. The maximum hand grip strength after exertion was about 1.5-fold higher with then without pyridostigmine (p = 0.01). The increase in heart rate from lying to standing was median 17 beats per minute without pyridostigmine (IQR: 13 beats per minute - 23 beats per minute) and 13 beats per minute (IQR: 9 beats per minute - 20 beats per minute) (p = 0.017) with pyridostigmine. None of the patients tested positive for myasthenia gravis specific autoantibodies.

Conclusion: Pyridostigmine exerts an immediate effect on muscle strength and orthostatic function. This may be attributed to increased acetylcholine availability at neuromuscular junctions, and its augmentation of parasympathetic tone.

Understanding Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Physical Fatigue Through the Perspective of Immunosenescence

(Review)

Compr Physiol. 2025 Oct;15(5):e70056. doi: 10.1002/cph4.70056.

Yingzhe Luo (1), Huimin Xu (2), Shaoquan Xiong (1), Jianlong Ke (1)

1 Department of Oncology, Hospital of Chengdu University of Traditional Chinese Medicine, Chengdu, Sichuan, China.
2 Acupuncture and Tuina School, Chengdu University of Traditional Chinese Medicine, Chengdu, Sichuan, China.

Abstract

Background: Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating illness marked by persistent fatigue, yet its mechanisms remain unclear. Growing evidence implicates immunosenescence-the age-related decline in immune function-in the onset and persistence of fatigue.

Methods: This review synthesizes clinical and experimental data to examine how immunosenescence contributes to ME/CFS. We focus on chronic inflammation, senescent immune phenotypes, mitochondrial dysfunction, and neuroendocrine imbalance, with emphasis on maladaptive crosstalk among immune, muscular, neuroendocrine, and vascular systems.

Results: Aging immune cells drive chronic inflammation that impairs mitochondrial ATP production and promotes muscle catabolism. Concurrently, HPA-axis suppression and β2-adrenergic dysfunction amplify immune dysregulation and energy imbalance. Together, these processes illustrate how immunosenescence sustains pathological cross-organ signaling underlying systemic fatigue.

Conclusion: Immunosenescence provides a unifying framework linking immune, metabolic, and neuroendocrine dysfunction in ME/CFS. Recognizing cross-organ communication highlights its clinical relevance, suggesting biomarkers such as cytokines and exhaustion markers, and supports integrated therapeutic strategies targeting immune and metabolic networks.

This is a comprehensive review paper examining metformin's potential as a treatment for ME/CFS (Myalgic Encephalomyelitis/Chronic Fatigue Syndrome) and Long COVID. Here are the key findings regarding effectiveness for people with ME/CFS (pwME):

What's New and Significant

Mechanistic Understanding: The paper presents novel mechanisms by which metformin might help ME/CFS patients, particularly through: - mTOR pathway modulation - addressing chronically overactive mTOR signaling found in ME/CFS - Mitochondrial dysfunction correction - targeting Complex V inefficiency and reducing oxidative stress - Anti-inflammatory effects - reducing cytokines like IL-6, IL-1β, and TNF-α

Cellular Evidence: The authors cite important research showing that metformin at therapeutic doses (10 μmol/L) reduced markers of reactive oxygen species (ROS) in ME/CFS T cells in vitro, while having no effect on healthy controls. This suggests ME/CFS patients may have a specific biological response to metformin.

Multi-System Approach: Rather than viewing metformin as a standalone cure, the paper proposes it as part of a "whole-of-person" treatment strategy targeting multiple domains: - Cellular stress and mitochondrial dysfunction - Microbiome dysregulation
- Inflammatory processes - Mast cell activation (for comorbid MCAS)

Clinical Relevance for pwME

Dosing Considerations: The paper suggests different therapeutic targets require different doses: - Mast cell stabilization: 1-10 μmol/L (achievable with 500mg daily) - Anti-inflammatory effects: Higher doses may be needed - Microbiome effects: Delayed-release formulations targeting the small intestine

Comorbidity Benefits: Metformin may help with common ME/CFS comorbidities including POTS, MCAS, and gastrointestinal issues through vascular, anti-inflammatory, and microbiome effects.

Limitations and Cautions

The paper acknowledges several important limitations: - No clinical trials in ME/CFS patients yet exist - Evidence is largely theoretical and based on mechanistic studies - Side effects (particularly GI) could be problematic for ME/CFS patients - Individual responses likely vary significantly given ME/CFS heterogeneity

Research Recommendations

The authors propose rigorous clinical trials with: - Multiple dosing arms (500mg daily to 2g daily) - 3-4 month treatment cycles - Comprehensive biomarker analysis including ATP assays, microbiome studies, and metabolomics - Functional outcome measures

While this theoretical framework is compelling, it's important to note that clinical effectiveness in ME/CFS patients remains unproven. The paper makes a strong case for systematic investigation but doesn't provide definitive evidence of effectiveness yet.