Investigating the Genetic and Immunological Aetiology of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Abstract:

This thesis describes two investigations into the disease Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS), specifically its genetic aetiology and immune system alterations.

The first study investigated the genetic basis of ME/CFS using Genome-wide Association Studies (GWAS) by attempting to replicate and extend results previously found using UK Biobank cohort data. GWAS attempt to identify associations between DNA variants and phenotypes. T his GWAS was novel, conducted on new phenotypes constructed by combining those in the most up-to-date UK Biobank data release. A new, previously unseen, genome-wide significant association was found on chromosome 6 for males with ME/CFS within the gene PDE10A. Further results were not genome-wide significant, but many were suggestive and hence independent replication may justify further research.

A previous analysis on the UK Biobank cohort had identified an indicative association in females between variants around the SLC25A15 gene at genome-wide significance. I adopted a hypothesis that the dietary protein intake of people with the CFS risk variants would be lower than those with the alternative alleles, due to potentially reduced production of mitochondrial ornithine transporter 1 (ORNT1). However, this association with dietary protein intake was not supported by UK Biobank data.

Additionally, I investigated associations between the human leukocyte antigen (HLA) alleles and the ME/CFS phenotype using UK Biobank data. Associations between alleles within the HLA-C and -DQB1 genes had previously been found in a cohort of Norwegian people with ME/CFS, and my goal was to seek replication of these results in a larger dataset. None of the associations found in the UK Biobank proved to be genome-wide significant.

In my second study I investigated the use of T-cell clonal diversity as a potential biomarker for ME/CFS. This project used cells from CureME Biobank samples in collaboration with Systems Biology Laboratory (SBL). I developed a data analysis pipeline to analyse T-cell receptor (TCR) genomic DNA data based on the best practices currently used in the fields of immunology and mathematical biology. This approach used a mathematical notion of entropy as a measure for the diversity of TCR repertoires, in this way combining all of the most commonly used metrics in mathematical biology. When combined, these measures form a profile for each repertoire, a set of which can be sorted using a machine learning algorithm to partition the repertoires into subgroups.

My hypothesis was that the T-cell clonal expansion of people with ME/CFS would be greater than for healthy controls, and comparable to disease (multiple sclerosis) controls. Although this method was able to effectively classify TCR chains using simulated data, results from experimentally-derived data did not support the hypothesis, with the most effective classifications for both CD4+ and CD8+ cells failing to pass corrections for multiple hypothesis significance testing.

Lay summary

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a disease that affects millions of people around the world. Very little is understood about the cause or progression of the disease, and there is no known cure. At present, there is also no reliable clinical test to determine whether a person has ME/CFS.

This thesis explores the potential for a genetic or immunological basis for ME/CFS, with the goal to eventually find a biomarker that could be used in diagnosis.

The first part of this thesis investigates whether genetic variants are more (or less) common among those with ME/CFS than in the general population. In particular, the region of the genome that encodes immune system proteins was of interest, as previous studies have shown associations between this region and the disease.

Using strict statistical thresholds, none of the previously found associations were replicated. However, one new association was found, with the gene PDE10A, which is implicated in central nervous system diseases, such as Parkinsons and Huntingtons disease. This association has never been seen before, and would require replication in a new cohort before its role in ME/CFS could be confirmed. However, it represents a promising avenue for new research.

The second part of this thesis investigates T-cells. These are highly specialised immune cells in the blood, each of which targets an antigen (foreign substance) such as from a virus. When a T-cell recognises this antigen, it clones itself repeatedly. This clonal expansion is measurable, and can serve as evidence of immune system activation.

My hypothesis was that this immune signature could be used to distinguish people with ME/CFS from healthy controls and others diagnosed with another disease.

I used a mathematical measure of diversity and a machine learning method to sort their immune profiles into groups. However, the pattern of immune activation was not sufficiently clear to provide consistent classification. Hence, the role of the immune system in ME/CFS is still unclear, and the utility of this method as a diagnostic biomarker is not proved.

Source: Joshua James Dibble. Investigating the Genetic and Immunological Aetiology of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome. PhD Thesis [University of Edinburgh]  https://era.ed.ac.uk/bitstream/handle/1842/39763/DibbleJJ_2022.pdf?sequence=1&isAllowed=y (Full text)

Orthostatic Intolerance and Chronotropic Incompetence in Patients With Myalgic Encephalomyelitis or Chronic Fatigue Syndrome

Abstract:

Background: Orthostatic intolerance markedly affects the day-to-day activities of patients with myalgic encephalomyelitis (ME) or chronic fatigue syndrome. Chronotropic incompetence (CI), defined as an impaired chronotropic response or reduced increases in heart rate during exercise and resulting in lower exercise capacity, may also be observed during orthostasis in patients with ME.

Methods and Results: In this study, the recordings of 101 adult patients with ME (36 men, 65 women; mean [±SD] age 37±12 years) who underwent conventional active 10-min standing tests at least 3 times to determine the presence of CI were analyzed. Recordings were selected for 13 patients who experienced tests both with and without exhibiting postural orthostatic tachycardia syndrome (POTS; an increase in heart rate of ≥30 beats/min or an actual heart rate of ≥120 beats/min) while also both successfully completing and failing to complete 10-min standing on different occasions. Subjects in whom failure without POTS was observed in any test(s) while success was associated with POTS on other occasions were considered positive for CI during orthostasis. Of the 13 patients, 12 (92%) were CI positive, 5 (38%) of whom exclusively failed the tests without experiencing POTS.

Conclusions: Some patients with ME were CI positive during standing tests, suggesting impaired sympathetic activation. The presence of POTS appears to be essential for maintaining orthostasis in these patients.

Source: Kunihisa Miwa. Orthostatic Intolerance and Chronotropic Incompetence in Patients With Myalgic Encephalomyelitis or Chronic Fatigue Syndrome. Circulation Reports, Article ID CR-22-0114. https://www.jstage.jst.go.jp/article/circrep/advpub/0/advpub_CR-22-0114/_html/-char/en (Full text)

What interventions or best practice are there to support people with Long COVID, or similar post-viral conditions or conditions characterised by fatigue, to return to normal activities: a rapid review

Abstract:

Previous research has categorised symptoms of COVID-19 / Long COVID into 12 thematic areas including: fever, myalgia, fatigue, impaired cognitive function, and that COVID-19 survivors had reduced levels of physical function, activities of daily living, and health-related quality of life.

Our aim was to review the evidence for interventions or best practice to support people with Long COVID, or similar post-viral conditions characterised by fatigue, to return to normal activities.

Evidence was included from guidelines, systematic reviews (SR), and primary studies. The primary studies focussed on Long COVID (LC) indicated that there should be a needs-based focus to care for those with LC.

Consideration should be given to individuals living with LC in the same way as people with disabilities are accommodated in terms of workplace adjustment.

Two SRs indicated that non-pharmaceutical interventions (NPIs) for patients with LC or chronic fatigue syndrome could help improve function for activities of daily life. However, the third, most recent SR, concluded that there is a lack of robust evidence for NPIs.

LC fatigue management methods may be beneficial under certain conditions. One SR reported work capability as an outcome however they did not find any studies which evaluated the impact of interventions on return to work/ normal life.

One primary study, on individuals with CFS, described a written self-management programme. Following this intervention there was an 18% increase in the number of patients in employment.

Policy and practice implications: Long COVID is still being established as a post-viral condition with many symptoms. Patient-centred treatment options such as occupational therapy, self-management therapy and talking therapy may be considered in the same way as for other debilitating conditions. Return-to-work accommodations are needed for all workers unable to return to full-time employment.

Due to the nature of the studies included, there was little reported evidence of effectiveness of getting individuals back into their normal activities.

Source: Llinos Haf Spencer, Annie Hendry, Abraham Makanjuola, Bethany F Anthony, Jacob Davies, Kalpa Pisavadia, Dyfrig Hughes, Deb Fitzsimmons, Clare Wilkinson, Rhiannon Tudor Edwards, Ruth Lewis, Alison Cooper, Adrian Edwards. What interventions or best practice are there to support people with Long COVID, or similar post-viral conditions or conditions characterised by fatigue, to return to normal activities: a rapid review. medRxiv 2023.01.24.23284947; doi: https://doi.org/10.1101/2023.01.24.23284947 (Full text)

Stress-Induced Transcriptomic Changes in Females with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Reveal Disrupted Immune Signatures

Abstract:

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a chronic, complex multi-organ illness characterized by unexplained debilitating fatigue and post-exertional malaise (PEM), which is defined as a worsening of symptoms following even minor physical or mental exertion. Our study aimed to evaluate transcriptomic changes in ME/CFS female patients undergoing an exercise challenge intended to precipitate PEM.
Our time points (baseline before exercise challenge, the point of maximal exertion, and after an exercise challenge) allowed for the exploration of the transcriptomic response to exercise and recovery in female patients with ME/CFS, as compared to healthy controls (HCs). Under maximal exertion, ME/CFS patients did not show significant changes in gene expression, while HCs demonstrated altered functional gene networks related to signaling and integral functions of their immune cells.
During the recovery period (commonly during onset of PEM), female ME/CFS patients showed dysregulated immune signaling pathways and dysfunctional cellular responses to stress. The unique functional pathways identified provide a foundation for future research efforts into the disease, as well as for potential targeted treatment options.
Source: Van Booven DJ, Gamer J, Joseph A, Perez M, Zarnowski O, Pandya M, Collado F, Klimas N, Oltra E, Nathanson L. Stress-Induced Transcriptomic Changes in Females with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Reveal Disrupted Immune Signatures. International Journal of Molecular Sciences. 2023; 24(3):2698. https://doi.org/10.3390/ijms24032698 https://www.mdpi.com/1422-0067/24/3/2698 (Full text)

Chronic viral coinfections differentially affect the likelihood of developing long COVID

Abstract:

BACKGROUND. The presence and reactivation of chronic viral infections, such as EBV, CMV, and HIV, have been proposed as potential contributors to long COVID (LC), but studies in well-characterized postacute cohorts of individuals with COVID-19 over a longer time course consistent with current case definitions of LC are limited.

METHODS. In a cohort of 280 adults with prior SARS-CoV-2 infection, we assessed the presence and types of LC symptoms and prior medical history (including COVID-19 history and HIV status) and performed serological testing for EBV and CMV using a commercial laboratory. We used covariate-adjusted binary logistic regression models to identify independent associations between variables and LC symptoms.

RESULTS. We observed that LC symptoms, such as fatigue and neurocognitive dysfunction, at a median of 4 months following initial diagnosis were independently associated with serological evidence suggesting recent EBV reactivation (early antigen–diffuse IgG positivity) or high nuclear antigen (EBNA) IgG levels but not with ongoing EBV viremia. Serological evidence suggesting recent EBV reactivation (early antigen–diffuse IgG positivity) was most strongly associated with fatigue (OR = 2.12). Underlying HIV infection was also independently associated with neurocognitive LC (OR = 2.5). Interestingly, participants who had serologic evidence of prior CMV infection were less likely to develop neurocognitive LC (OR = 0.52).

CONCLUSION. Overall, these findings suggest differential effects of chronic viral coinfections on the likelihood of developing LC and association with distinct syndromic patterns. Further assessment during the acute phase of COVID-19 is warranted.

Source: Peluso MJ, Deveau TM, Munter SE, Ryder D, Buck A, Beck-Engeser G, Chan F, Lu S, Goldberg SA, Hoh R, Tai V, Torres L, Iyer NS, Deswal M, Ngo LH, Buitrago M, Rodriguez A, Chen JY, Yee BC, Chenna A, Winslow JW, Petropoulos CJ, Deitchman AN, Hellmuth J, Spinelli MA, Durstenfeld MS, Hsue PY, Kelly JD, Martin JN, Deeks SG, Hunt PW, Henrich TJ. Chronic viral coinfections differentially affect the likelihood of developing long COVID. J Clin Invest. 2023 Feb 1;133(3):e163669. doi: 10.1172/JCI163669. PMID: 36454631. https://www.jci.org/articles/view/163669 (Full text)

Gastric dysmotility and gastrointestinal symptoms in myalgic encephalomyelitis/chronic fatigue syndrome

Abstract:

Background: Gastrointestinal symptoms are common in ME/CFS, but there is a knowledge gap in the literature concerning gastrointestinal motility features and detailed symptom description.

Objective: In this study, we aimed to characterize gastric motility and gastric symptoms in response to a liquid meal.

Methods: We included 20 patients with ME/CFS with abdominal complaints who were recruited to a double-blind randomized placebo-controlled trial of Rituximab. The patients of this sub study were examined with an ultrasound drink test, and gastrointestinal symptoms were evaluated using the Rome III questionnaire and Irritable Bowel Syndrome Symptom Severity Scale (IBS-SSS) questionnaire.

Results: We found that patients commonly reported fullness/bloating (75%), abdominal pain (45%) and nausea (35%). Ultrasound measurements revealed lower proximal measurements of the stomach after a meal (p < 0.01) and larger fasting antral area (p = 0.019) compared to healthy controls. The patients had a stronger symptomatic response to the liquid meal compared to healthy controls regarding epigastric pain, discomfort and nausea (p < 0.05). Ninety percent of the patients reported bowel movement frequencies within the normal range but scored high on bowel habit dissatisfaction and life disruption.

Conclusion: The patients presented with fullness/bloating, nausea and epigastric pain, showed signs of impaired gastric accommodation and visceral hypersensitivity, showing that the gastrointestinal symptoms of ME/CFS patients are similar to functional dyspepsia.

Key summary:

  • Gastrointestinal symptoms are common in ME/CFS, but there is a knowledge gap in the literature concerning gastrointestinal motility features and detailed symptom description.

  • In this study, patients with ME/CFS had signs of impaired gastric accommodation after a liquid meal.

  • Out of 20 patients, 15 patients reported fullness/bloating, 9 reported abdominal pain, and 7 reported nausea. The patients showed signs of visceral hypersensitivity on a drink test.

  • Our findings suggest that patients with ME/CFS share many similarities with patients with Functional Dyspepsia. The findings were not typical for Irritable Bowel Syndrome.

Source: Steinsvik EK, Hausken T, Fluge Ø, Mella O, Gilja OH. Gastric dysmotility and gastrointestinal symptoms in myalgic encephalomyelitis/chronic fatigue syndrome. Scand J Gastroenterol. 2023 Feb 2:1-8. doi: 10.1080/00365521.2023.2173533. Epub ahead of print. PMID: 36728717. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0280942 (Full text)

Endothelial dysfunction in ME/CFS patients

Abstract:

Objective: A few earlier studies have found impaired endothelial function in patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). The present study investigated large-vessel and small-vessel endothelial function in patients with ME/CFS.

Study design: The study was a substudy of the RituxME trial, a national, multicenter, randomized, double-blind, placebo-controlled phase III study on the effect of rituximab vs. placebo in ME/CFS patients in Norway. Flow-mediated dilation (FMD) and post-occlusive reactive hyperemia (PORH) was measured at baseline and after 18 months of treatment in 39 patients and compared with healthy controls. Other outcome measures were symptom severity and various physical function measures.

Results: ME/CFS patients had markedly reduced FMD compared to healthy controls at baseline (5.1% vs. 8.2%, p< 0.0001, adjusted for arterial diameter and sex), and significantly lower microvascular regulation measured by PORH than healthy controls (1354 PU vs. 2208 PU, p = 0.002). There were no differences between the treatment and placebo groups in symptom changes or vascular measures. As a group, the ME/CSF patients experienced a slight, but significant improvement in clinical symptoms after 18 months. PORH, but not FMD, was similarly improved (1360 to 1834 PU, p = 0.028). There was no significant correlation between FMD and PORH. There were non-significant tendencies towards associations between symptom severity/physical function measures and lower FMD and PORH, and a significant correlation between PORH and steps per 24 hours at baseline.

Conclusions: ME/CFS patients had reduced macro- and microvascular endothelial function, indicating that vascular homeostasis may play a role in the clinical presentation of this disease.

Source: Sandvik MK, Sørland K, Leirgul E, Rekeland IG, Stavland CS, Mella O, Fluge Ø. Endothelial dysfunction in ME/CFS patients. PLoS One. 2023 Feb 2;18(2):e0280942. doi: 10.1371/journal.pone.0280942. PMID: 36730360; PMCID: PMC9894436. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9894436/ (Full text)

Circulating microRNA expression signatures accurately discriminate myalgic encephalomyelitis from fibromyalgia and comorbid conditions

Abstract:

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), and fibromyalgia (FM) are two chronic complex diseases with overlapping symptoms affecting multiple systems and organs over time. Due to the absence of validated biomarkers and similarity in symptoms, both disorders are misdiagnosed, and the comorbidity of the two is often unrecognized.

Our study aimed to investigate the expression profiles of 11 circulating miRNAs previously associated with ME/CFS pathogenesis in FM patients and individuals with a comorbid diagnosis of FM associated with ME/CFS (ME/CFS + FM), and matched sedentary healthy controls. Whether these 11 circulating miRNAs expression can differentiate between the two disorders was also examined.

Our results highlight differential circulating miRNAs expression signatures between ME/CFS, FM and ME/CFS + FM, which also correlate to symptom severity between ME/CFS and ME/CFS + FM groups. We provided a prediction model, by using a machine-learning approach based on 11 circulating miRNAs levels, which can be used to discriminate between patients suffering from ME/CFS, FM and ME/CFS + FM. These 11 miRNAs are proposed as potential biomarkers for discriminating ME/CFS from FM.

The results of this study demonstrate that ME/CFS and FM are two distinct illnesses, and we highlight the comorbidity between the two conditions. Proper diagnosis of patients suffering from ME/CFS, FM or ME/CFS + FM is crucial to elucidate the pathophysiology of both diseases, determine preventive measures, and establish more effective treatments.

Source: Nepotchatykh E, Caraus I, Elremaly W, Leveau C, Elbakry M, Godbout C, Rostami-Afshari B, Petre D, Khatami N, Franco A, Moreau A. Circulating microRNA expression signatures accurately discriminate myalgic encephalomyelitis from fibromyalgia and comorbid conditions. Sci Rep. 2023 Feb 2;13(1):1896. doi: 10.1038/s41598-023-28955-9. PMID: 36732593. https://www.nature.com/articles/s41598-023-28955-9 (Full text)

Treatment Harms To Patients With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Abstract:

Despite evidence of physiological and cellular abnormalities in myalgic encephalomyelitis (ME)/chronic fatigue syndrome (CFS), the dominant therapeutic approach has been cognitive behaviour therapy (CBT) and graded exercise therapy (GET).  Patients report distress and dissatisfaction following healthcare encounters based on GET and CBT. A significant body of research suggests that CBT and GET are harmful for many patients with ME/CFS. These findings raise ethical concerns and suggest that more collaborative working between scientists, therapists and patients would be helpful in making scientific progress in this difficult field.

Source: David F Marks. (2023). Treatment Harms To Patients With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome. Qeios. doi:10.32388/XUG3PT.2. https://www.qeios.com/read/XUG3PT.2 (Full text)

Cardiac Autonomic Function in Long COVID-19 Using Heart Rate Variability: An Observational Cross-Sectional Study

Abstract:

Background: Heart rate variability is a non-invasive, measurable, and established autonomic nervous system test. Long-term COVID-19 sequelae are unclear; however, acute symptoms have been studied.

Objectives: To determine autonomic cardiac differences between long COVID-19 patients and healthy controls and evaluate associations among symptoms, comorbidities, and laboratory findings.

Methods: This single-center study included long COVID-19 patients and healthy controls. The heart rate variability (HRV), a quantitative marker of autonomic activity, was monitored for 24 h using an ambulatory electrocardiogram system. HRV indices were compared between case and control groups. Symptom frequency and inflammatory markers were evaluated. A significant statistical level of 5% (p-value 0.05) was adopted.

Results: A total of 47 long COVID-19 patients were compared to 42 healthy controls. Patients averaged 43.8 (SD14.8) years old, and 60.3% were female. In total, 52.5% of patients had moderate illness. Post-exercise dyspnea was most common (71.6%), and 53.2% lacked comorbidities. CNP, D-dimer, and CRP levels were elevated (p-values of 0.0098, 0.0023, and 0.0015, respectively). The control group had greater SDNN24 and SDANNI (OR = 0.98 (0.97 to 0.99; p = 0.01)). Increased low-frequency (LF) indices in COVID-19 patients (OR = 1.002 (1.0001 to 1.004; p = 0.030)) and high-frequency (HF) indices in the control group (OR = 0.987 (0.98 to 0.995; p = 0.001)) were also associated.

Conclusions: Patients with long COVID-19 had lower HF values than healthy individuals. These variations are associated with increased parasympathetic activity, which may be related to long COVID-19 symptoms and inflammatory laboratory findings.

Source: Menezes Junior ADS, Schröder AA, Botelho SM, Resende AL. Cardiac Autonomic Function in Long COVID-19 Using Heart Rate Variability: An Observational Cross-Sectional Study. J Clin Med. 2022 Dec 22;12(1):100. doi: 10.3390/jcm12010100. PMID: 36614901; PMCID: PMC9821736. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9821736/ (Full text)