This month’s edition of the Research Digest highlights new biomedical findings on ME/CFS and long COVID, with a focus on immune dysfunction, autoimmunity, and potential biomarkers. Studies reveal shared pathways between the two conditions, including elevated autoantibodies and interferon activity. Research into B-cell receptors and BH4 metabolism adds to our understanding of immune and cardiovascular involvement in ME/CFS. A public article is also presented, reinforcing that ME/CFS is a serious, complex illness needing updated, evidence-based care.
Contributing Digesters: Solene, Jyothsna, Shan and Simone.
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Identification of putative serum autoantibodies associated with post-acute sequelae of COVID-19 via comprehensive protein array analysis
Authors: Hatayama Y, Miyakawa K, Kimura Y, Horikawa K, Hirahata K, Kimura H,…, Ryo A (Nat. Inst. of Infectious Diseases, Japan)
Name and Date of Publication: International Journal of Molecular Sciences; 19 February 2025.
Link: https://doi.org/10.3390/ijms26041751
Easy Read Overview: Scientists studied autoantibodies, antibodies that attack the body’s own cells, in people with long COVID. They found that some of these autoantibodies, like FBXO2 and PITX2, were higher in people with long COVID than in those who didn’t have long COVID. One of the antibodies, PITX2, may be linked to heart and brain problems seen in some patients. Another, FBXO2, may be connected to ongoing inflammation in the body. The scientists say more research is needed to learn when these autoantibodies appear and how they might cause long COVID symptoms.
Autoantibodies, antibodies which target the body’s own tissue, have emerged as important factors in the acute phase of COVID-19. However, their possible role in post-acute sequelae of COVID-19 (PASC) pathology remains unknown. This study aimed to identify novel serum autoantibodies associated with PASC and assess their potential as biomarkers.
The authors used protein bead array technology with high-throughput protein synthesis using wheat cell-free technology to identify autoantibodies from the serum of three PASC patients. Profile comparisons revealed ten elevated autoantibodies across all three patients. Of these, four candidates (FBXO2, AGPAT1, TRIM21, and ANAPC10) showed robust expression profiles. In addition, PITX2 demonstrated significant elevation in one patient and was detectable in another, suggesting potential diagnostic value.
To evaluate their potential as biomarkers of PASC, the authors used 139 serum samples from PASC patients, 40 non-PASC COVID-19 convalescents (non-PASC), and 100 pre-pandemic healthy controls (HC). After multiple regression analyses adjusting for confounding variables, FBXO2 and PITX2 autoantibodies demonstrated statistically significant elevation in PASC patients compared to non-PASC and HC groups.
Interestingly, PITX2 is a critical transcription factor for cardiac function that may be involved in the cardiovascular and neurocognitive symptoms observed in PASC patients. Autoantibodies targeting FBXO2, associated with the regulation of local inflammation, may explain the persistent inflammation associated with PASC.
Further longitudinal studies with larger cohorts, along with functional in vitro and in vivo studies, are needed to help understand the timing of autoantibody production and their possible role in PASC.
Tetrahydrobiopterin in myalgic encephalomyelitis/chronic fatigue syndrome: A friend or foe?
Authors: Rahman AFTM, Benko A, Bulbule S, Gottschalk CG, Arnold LA, & Roy A (University of Wisconsin-Milwaukee, USA)
Name and Date of Publication: Biomolecules; 10 January 2025
Link: https://www.mdpi.com/2218-273X/15/1/102
Easy Read Overview: BH4 is a chemical that helps make important brain signals, and control blood flow and the immune system. Some illnesses like Parkinson’s have low levels of BH4, but people with ME/CFS (especially those who have orthostatic intolerance) often have too much. This extra BH4 may come from problems with how their cells make energy, causing their bodies to produce too much of it. Too much BH4 can lead to high levels of nitric oxide, which can make blood vessels widen too much and cause symptoms like dizziness and fatigue. The researchers think this BH4 imbalance may be a key part of ME/CFS and could help doctors better understand, diagnose, and treat the illness.
Tetrahydrobiopterin (BH4) is a vital cofactor in neurotransmitter synthesis and nitric oxide (NO) production, with key roles in brain function, cardiovascular regulation, and immune balance. While BH4 is typically depleted in many chronic conditions such as Parkinson’s disease, recent research reports elevated levels of BH4 and its oxidative form, BH2, in patients with ME/CFS. This paper explored the potential role of BH4 in ME/CFS patients with orthostatic intolerance (OI) and its contribution to cardiovascular dysfunction in this population.
The authors suggest that elevated BH4 in ME/CFS may be related to mitochondrial dysfunction, a hallmark of ME/CFS. When energy production is impaired, glucose metabolism shifts from glycolysis to the non-oxidative branch of the pentose phosphate pathway (PPP). This shift increases production of ribose-5-phosphate, a precursor for purine and BH4 synthesis, leading to excessive BH4 production. This process is amplified by upregulated BH4 metabolic enzymes such as GTP cyclohydrolase I (GTPCH1), dihydrofolate reductase (DHFR), and dihydropteridine reductase (DHPR).
Excess BH4 boosts NO production. While NO supports vascular health, in excess, it contributes to OI symptoms like dizziness, fatigue, and light-headedness by promoting excessive vasodilation. High NO levels also drive nitrosative stress through peroxynitrite formation, which promotes the non-enzymatic oxidation of BH4 to BH2. This generates reactive species and protons, triggering reductive stress.
This redox stress has cascading effects. It disrupts antioxidant systems like glutathione, induces endoplasmic reticulum stress, impairs autophagy, and inhibits NRF2, a key regulator of antioxidant responses. These reactions may lead to the chronic inflammation and fatigue seen in ME/CFS patients.
The authors propose that BH4 dysregulation could be a useful biomarker and therapeutic target in ME/CFS. Unlike other disorders marked by BH4 deficiency, ME/CFS appears to involve overproduction of BH4. This imbalance, driven by mitochondrial and redox dysfunction, may play a central role in ME/CFS pathogenesis, offering new insights for its diagnosis and treatment.
Correlation of interferons and autoimmune aspects in long COVID-19 patients
Authors: Hattori F, Nishiyama J, Hasuo H (Kansai Medical University, Japan)
Name and Date of Publication: International Immunology; 08 February 2025
Link: https://doi.org/10.1093/intimm/dxaf008
Easy Read Overview: Interferons are chemicals that help the body fight viruses, but having too much can cause problems. This study looked at people with long COVID and found high levels of interferons, along with other signs that the immune system was overactive. Some of these signs were similar to those seen in people with lupus, an autoimmune disease. Many long COVID patients had antibodies similar to those found in lupus, and a few in this study even met the full criteria for a lupus diagnosis. The researchers think long COVID may have two stages: a return of virus activity and then a long-lasting autoimmune reaction.
Interferons (IFNs) are signalling molecules involved in the upregulation of the immune system, predominantly acting as antiviral agents. Type I interferonopathies, such as multiple sclerosis, rheumatic arthritis, Sjögren’s syndrome, and systemic lupus erythematosus (SLE), feature excessive excretion of type I IFN. In a previously published paper, the authors noted that the continuous internal viral shedding and IFN activity observed in long COVID-19 (LC) patients was similar to the side effects observed in type I interferonopathy patients receiving IFN administration therapy. This study aims to examine the similarity between LC and SLE, as well as to determine the overall role of IFNs in LC.
The authors conducted a meta-analysis using publicly available RNA sequencing data from the Gene Expression Omnibus (GEO) Dataset. They examined samples of 11 patients with LC, including five with brain fog, and 12 healthy controls, five of whom who had recovered from acute COVID-19. This analysis revealed differential expression of type I and II IFNs, as well as upregulation of several genes involved in immune and autoimmune responses. These changes affected various biological processes, cellular components, and molecular functions.
The authors then conducted their own assays on serum samples from 39 individuals with LC, and 18 human serum samples containing IFN in the normal range. LC sera showed higher overall IFN concentrations, which was not related to age or sex. Biological activity testing demonstrated elevated mRNA expression level of IFN-stimulated genes, including Mx1, levels of which are used to determine SLE disease progression. The authors also found a correlation between these genes, IFN expression levels, and anti-double-stranded DNA (anti-dsDNA) antigens. All LC samples contained anti-dsDNA, while this is not detectable in healthy serum. Furthermore, 33 LC samples were positive for anti-Smith (anti-Sm) antigens, another biomarker for SLE, and eight of these LC patients met the diagnostic criteria for SLE.
In highlighting the similarities between LC and SLE, these authors hypothesise a two-phase model of LC: a return of viral activity followed by a long-term autoimmune phase. The authors suggest that there is a need for further studies examining the relationship between IFN types and levels in multiple autoimmune diseases, but they believe their work expands the definition of interferonopathies beyond the upregulation of type I IFNs and their signalling pathways.
Deep sequencing of BCR heavy chain repertoires in myalgic encephalomyelitis/chronic fatigue syndrome
Authors: Ryback AA, Cowan GJM (University of Edinburgh, United Kingdom)
Name and Date of Publication:Frontiers in Immunology; 17 February 2025
Link: https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2025.1489312/full
Easy Read Overview: Many people with ME/CFS first get sick after an infection, so scientists think the immune system might play a role. This study looked at B cells, which help fight infections, in people with mild and severe ME/CFS, multiple sclerosis, and healthy people. Most results showed no major differences between groups, but one immune gene (IGHV3-30) was more common in people with mild ME/CFS. They also found a change in the balance of certain types of B cells (IgM and IgG) in this group. These findings suggest future studies should look more closely at B cell types to better understand ME/CFS.
ME/CFS symptoms are preceded by an infection in 60% of patients, and chronic infection and autoimmune responses are two possible mechanisms contributing to the disease. The goal of this study was to identify the immune or autoimmune responses in ME/CFS patients by analysing their adaptive immune receptor repertoire sequencing.
The authors characterised the receptors present on B cells from frozen samples of 25 participants with mild to moderate ME/CFS (ME/CFSmm), 36 participants with severe ME/CFS (ME/CFSsa), 28 participants with multiple sclerosis (MS), and 21 healthy individuals used as control from the CureME Biobank. All participants with ME/CFS met the Canadian Consensus Criteria or Fukuda criteria. All sequenced B-cell receptors (BCRs) from all participants were clustered into “clonotypes” to identify shared clonotypes between participants.
Although B cell counts varied widely across samples, no significant differences were observed between groups. Similarly, no differences in repertoire diversity were detected between ME/CFSmm, ME/CFSsa, and MS groups when compared with the control group. Interestingly, the authors replicated a previously published difference in IGHV3-30 gene usage. IGHV3-30 gene was increased in ME/CFSmm patients; however, they failed to observe the increased IGHV3-30-3 usage previously reported. Finally, they failed to predict ME/CFS cases using a logistic regression model trained on BCR repertoire features as previously described in a Japanese study.
Although no repertoire signatures related to infection or autoimmunity were detected in ME/CFS patients, a skewing of the ratio of IgM to IgG BCRs in ME/CFSmm patients was observed, indicating that future studies should investigate IgA, as well as IgM and IgG isotypes.
It’s not just ‘chronic fatigue’: ME/CFS is much more than being tired
Authors: Annesley S
Name and Date of Publication: The Conversation
Link: https://theconversation.com/its-not-just-chronic-fatigue-me-cfs-is-much-more-than-being-tired-258803
This article challenges the common misconception that ME/CFS is simply about being tired. It explains that the condition involves a wide range of debilitating symptoms, especially post-exertional malaise, and is backed by strong biomedical evidence, including neurological, immune, and metabolic abnormalities.
The article also highlights the ongoing harm caused by outdated terminology and treatment recommendations, such as graded exercise therapy, which has been removed from clinical guidelines in the US and UK but is still in use in Australia. With Australia now reviewing its clinical guidelines, the article stresses the need for updated and evidence-based approaches to management of the condition.
