A Unifying Hypothesis of the Pathophysiology of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): Recognitions from the finding of autoantibodies against ß2-adrenergic receptors

The search for a blood-based biomarker for Myalgic Encephalomyelitis/ Chronic Fatigue Syndrome (ME/CFS): from biochemistry to electrophysiology

BACKGROUND

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a disease of unknown aetiology characterised by symptoms of post-exertional malaise (PEM) and fatigue leading to substantial impairment in functioning. Other key symptoms include cognitive impairment and unrefreshing sleep, with many experiencing pain. To date there is no complete understanding of the triggering pathomechanisms of disease, and no quantitative biomarker available with sufficient sensitivity, specificity, and adoptability to provide conclusive diagnosis. Clinicians thus eliminate differential diagnoses, and rely on subjective, unspecific, and disputed clinical diagnostic criteria-a process that often takes years with patients being misdiagnosed and receiving inappropriate and sometimes detrimental care. Without a quantitative biomarker, trivialisation, scepticism, marginalisation, and misunderstanding of ME/CFS continues despite the significant disability for many. One in four individuals are bed-bound for long periods of time, others have difficulties maintaining a job/attending school, incurring individual income losses of thousands, while few participate in social activities.

MAIN BODY

Recent studies have reported promising quantifiable differences in the biochemical and electrophysiological properties of blood cells, which separate ME/CFS and non-ME/CFS participants with high sensitivities and specificities-demonstrating potential development of an accessible and relatively non-invasive diagnostic biomarker. This includes profiling immune cells using Raman spectroscopy, measuring the electrical impedance of blood samples during hyperosmotic challenge using a nano-electronic assay, use of metabolomic assays, and certain techniques which assess mitochondrial dysfunction. However, for clinical application, the specificity of these biomarkers to ME/CFS needs to be explored in more disease controls, and their practicality/logistics considered. Differences in cytokine profiles in ME/CFS are also well documented, but finding a consistent, stable, and replicable cytokine profile may not be possible. Increasing evidence demonstrates acetylcholine receptor and transient receptor potential ion channel dysfunction in ME/CFS, though how these findings could translate to a diagnostic biomarker are yet to be explored.

CONCLUSION

Different biochemical and electrophysiological properties which differentiate ME/CFS have been identified across studies, holding promise as potential blood-based quantitative diagnostic biomarkers for ME/CFS. However, further research is required to determine their specificity to ME/CFS and adoptability for clinical use.

Key Pathophysiological Role of Skeletal Muscle Disturbance in Post COVID and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): Accumulated Evidence

BACKGROUND

Recent studies provide strong evidence for a key role of skeletal muscle pathophysiology in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). In a 2021 review article on the pathophysiology of ME/CFS, we postulated that hypoperfusion and ischemia can result in excessive sodium and calcium overload in skeletal muscles of ME/CFS patients to cause mitochondrial damage. Since then, experimental evidence has been provided that supports this concept.

METHODS

We collect, summarize and discuss the current state of knowledge for the key role of skeletal muscle pathophysiology. We try to explain which risk factors and mechanisms are responsible for a subgroup of patients with post COVID syndrome (PCS) to develop ME/CFS (PC-ME/CFS).

RESULTS

Mitochondrial dysfunction is a long-held assumption to explain cardinal symptoms of ME/CFS. However, mitochondrial dysfunction could not be convincingly shown in leukocytes. By contrast, recent studies provide strong evidence for mitochondrial dysfunction in skeletal muscle tissue in ME/CFS. An electron microscopy study could directly show damage of mitochondria in skeletal muscle of ME/CFS patients with a preferential subsarcolemmal localization but not in PCS. Another study shows signs of skeletal muscle damage and regeneration in biopsies taken one day after exercise in PC-ME/CFS. The simultaneous presence of necroses and signs of regeneration supports the concept of repeated damage. Other studies correlated diminished hand grip strength (HGS) with symptom severity and prognosis. A MRI study showed that intracellular sodium in muscles of ME/CFS patients is elevated and that levels correlate inversely with HGS. This finding corroborates our concept of sodium and consecutive calcium overload as cause of muscular and mitochondrial damage caused by enhanced proton-sodium exchange due to anaerobic metabolism and diminished activity of the sodium-potassium-ATPase. The histological investigations in ME/CFS exclude ischemia by microvascular obstruction, viral presence or immune myositis. The only known exercise-induced mechanism of damage left is sodium induced calcium overload. If ionic disturbance and mitochondrial dysfunction is severe enough the patient may be captured in a vicious circle. This energy deficit is the most likely cause of exertional intolerance and post exertional malaise and is further aggravated by exertion.

CONCLUSION

Based on this pathomechanism, future treatment approaches should focus on normalizing the cause of ionic disbalance. Current treatment strategies targeting hypoperfusion have the potential to improve the dysfunction of ion transporters.

Efficacy of repeated immunoadsorption in patients with post-COVID myalgic encephalomyelitis/chronic fatigue syndrome and elevated β2-adrenergic receptor autoantibodies: a prospective cohort study

Background

Since the pandemic, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become the leading trigger for myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Evidence indicates that autoimmunity plays an important pathophysiological role. We aimed to evaluate the effectiveness of IA treatment in post-COVID ME/CFS patients.

Methods

This pre-post study included 20 post-coronavirus disease 2019 (COVID) ME/CFS patients found to have elevated β2 adrenergic autoantibodies (β2 AR-AB) between October 2022 and October 2023. Patients, with a median disease duration of 22 months (IQR: 15-31), were treated with five immunoadsorption sessions at Charité - Universitätsmedizin Berlin, Germany. Seven were male and 13 female, with a median age of 40 years (IQR: 36-51). The primary end point was the change in the Short Form (36) Health Survey physical functioning domain (SF36 PF) from baseline to four weeks post immunoadsorption. Key symptoms were assessed via questionnaires over six months. Handgrip strength and EndoPAT® measurements were used to evaluate muscle fatigue and vascular dysfunction. Seven patients who worsened after an initial response received a second cycle.

Findings

The treatment was generally well tolerated, reducing total immunoglobulin G by 79% (CI: 73-84%) and β2 AR-AB by 77% (CI: 58-95%). Patients demonstrated a mean increase in the SF36 PF of 17.75 points (CI: 13.41-26.16), with the greatest improvement occurring between months two and three, and significant gains maintained through month six. 14/20 (70%) patients were categorized as responders with an increase in the SF36 PF of ≥ ten points. Further lasting improvements were reported in fatigue, post-exertional malaise, pain, cognitive, autonomic, and immunological symptoms. Female patients had increased repeat handgrip strength at month six.

Interpretation

Immunoadsorption may improve symptoms in post-COVID ME/CFS patients. The beneficial effects of IgG depletion suggest a significant role for autoantibodies and disturbed B-cell function in the condition's pathophysiology.

Funding

Funded by The Federal Ministry of Education and Research and the Weidenhammer Zöbele Research Foundation.

Exploring Physical Activity, Sleep, and Nutrition's Role in Fatigue Among Post-COVID-19 Patients

Background/Objectives: A significant number of patients experience prolonged symptoms following COVID-19 in particular cases of fatigue. Yet, pathomechanisms of COVID-19-related fatigue remain unclear. Methods: This study investigated patients after confirmed SARS-CoV-2 infection (PC) with relevant fatigue according to the Fatigue Assessment Scale (≥22 points) to rule out malnutrition as a driving factor for fatigue and to evaluate daily activity and sleep characteristics. Dietary behavior was recorded through food diaries and physical activity by self-reported (questionnaires) and objective (activity tracker) outcomes. Data were collected over a 7-day period and compared with a healthy control group (HC). A subgroup analysis of patients with fatigue and severe fatigue, as well as a sex-specific analysis, were included. Results: No significant differences in dietary intake were observed, but an indication toward a healthier Mediterranean diet in PC patients with a median Mediterranean Diet Score of 4 (IQR 3, 5) in HC vs. 5 (IQR 3, 6) in PC (p = 0.24). There were also no differences in physical activity, either by objective or subjective measures. However, the median sleep duration was 49 min longer in PC patients (p = 0.003). Conclusions: In conclusion, malnutrition did not significantly contribute to fatigue, yet patients with COVID-19-related fatigue showed increased sleep duration. As sleep characteristics play a crucial role in mental and physical wellbeing, the association of sleep, physical activity, and fatigue should be evaluated in further studies.

Chronic Fatigue Syndrome: Diagnosis, Treatment, and Future Direction

Myalgic encephalomyelitis (ME), also known as chronic fatigue syndrome (CFS), is a complex, chronic condition marked by persistent, debilitating fatigue that is not alleviated by rest and often worsens with physical or mental exertion. Along with fatigue, patients experience various symptoms, including cognitive impairments, post-exertional malaise, muscle and joint pain, sleep disturbances, and immune system dysfunction. Diagnosing CFS/ME is challenging due to the absence of definitive biomarkers, the overlap of symptoms with other conditions, and the lack of standardized diagnostic criteria. This comprehensive literature review aims to contribute to the understanding of CFS/ME, including its diagnosis, pathophysiology, differential diagnosis, treatment, and future directions.

[Multimodal Treatment Strategies for Homebound Patients with Severe ME/CFS: A Scoping Review]

PURPOSE

This scoping review aims to provide an overview of previously published treatment strategies that are multimodal, rather than purely drug-based and may be considered for home- or bedbound ME/CFS patients. Thus, the focus lies upon the analyses of telemedicine as well as home treatment elements. In addition, the evaluation and assessment methods used in these studies will be further discussed.

METHODS

Using the scoping review method, a literature analysis was conducted resulting in a total of 14 publications which met the predefined criteria. Inclusion was based on models applicable to housebound individuals with ME/CFS, focusing on social medicine and psychological support services rather than individual drug strategies.

RESULTS

The analysis demonstrated that the appropriate treatment methods were predominantly home visits (n=5) or a telemedicine format (n=7). Studies which used alternative settings were included if conversion to a telemedicine format was viable. The important factors highlighted in several studies (n=8), when considering this patient group, were individualisation and flexibility of the treatment methods, and thus the ability to address the day-to-day levels of impairment. The explicit involvement of families in the treatment plan were described in a total of six studies. In ten articles, the treatment concept was additionally evaluated, predominantly using questionnaires (n=7), whilst the questionnaires used were not consistent. Qualitative evaluations were invariably conducted using Brown and Clarke's thematic analysis (n=3).

CONCLUSION

Publications on multimodal treatment strategies for homebound ME/CFS patients are rare. However approaches using home visits or telemedicine are described. The majority of identified publications addressed the need for individualised as well as flexible patient care, whilst some were dedicated to the added value of involving the patients' family. The data outline the specific challenges associated with the care of severely affected ME/CFS patients that should also be considered in the context of research.

Research progress on pathogenesis of chronic fatigue syndrome and treatment of traditional Chinese and Western medicine

Chronic Fatigue Syndrome (CFS) is a complex and perplexing medical disorder primarily characterized by persistent and debilitating fatigue, often accompanied by a constellation of symptoms, including weakness, dyspnea, arthromyalgia, sore throat, and disrupted sleep patterns. CFS is defined by its persistent or recurrent manifestation for a minimum duration of six months, marked by an enduring and unrelenting fatigue that remains refractory to rest. In recent decades, this condition has garnered significant attention within the medical community. While the precise etiology of CFS remains elusive, it is postulated to be multifactorial. CFS is potentially associated with various contributory factors such as infections, chronic stress, genetic predisposition, immune dysregulation, and psychosocial influences. The pathophysiological underpinnings of CFS encompass viral infections, immune system dysregulation, neuroendocrine aberrations, heightened oxidative stress, and perturbations in gut microbiota. Presently, clinical management predominantly relies on pharmaceutical interventions or singular therapeutic modalities, offering alleviation of specific symptoms but exhibiting inherent limitations. Traditional Chinese Medicine (TCM) interventions have emerged as a promising paradigm, demonstrating notable efficacy through their multimodal, multi-target, multi-pathway approach, and holistic regulatory mechanisms. These interventions effectively address the lacunae in contemporary medical interventions. This comprehensive review synthesizes recent advancements in the understanding of the etiological factors, pathophysiological mechanisms, and interventional strategies for CFS, drawing from a corpus of domestic and international literature. Its aim is to furnish valuable insights for clinicians actively involved in diagnosing and treating CFS, as well as for pharmaceutical researchers delving into innovative drug development pathways. Moreover, it seeks to address the intricate challenges confronted by clinical practitioners in managing this incapacitating condition.

[Interdisciplinary, collaborative D-A-CH (Germany, Austria and Switzerland) consensus statement concerning the diagnostic and treatment of myalgic encephalomyelitis/chronic fatigue syndrome]

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a severe, chronic multisystemic disease which, depending on its severity, can lead to considerable physical and cognitive impairment, loss of ability to work and the need for nursing care including artificial nutrition and, in very severe cases, even death.The aim of this D-A-CH (Germany, Austria, Switzerland) consensus statement is 1) to summarize the current state of knowledge on ME/CFS, 2) to highlight the Canadian Consensus Criteria (CCC) as clinical criteria for diagnostics with a focus on the leading symptom post-exertional malaise (PEM) and 3) to provide an overview of current options and possible future developments, particularly with regard to diagnostics and therapy. The D-A-CH consensus statement is intended to support physicians, therapists and valuer in diagnosing patients with suspected ME/CFS by means of adequate anamnesis and clinical-physical examinations as well as the recommended clinical CCC, using the questionnaires and other examination methods presented. The overview of the two pillars of therapy for ME/CFS, pacing and symptom-relieving therapy options, is intended not only to provide orientation for physicians and therapists, but also to support decision-makers from healthcare policy and insurance companies in determining which therapy options should already be reimbursable by them at this point in time for the indication ME/CFS.

Data-independent LC-MS/MS analysis of ME/CFS plasma reveals a dysregulated coagulation system, endothelial dysfunction, downregulation of complement machinery

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating chronic condition that is characterized by unresolved fatigue, post-exertion symptom exacerbation (PESE), cognitive dysfunction, orthostatic intolerance, and other symptoms. ME/CFS lacks established clinical biomarkers and requires further elucidation of disease mechanisms. A growing number of studies demonstrate signs of hematological and cardiovascular pathology in ME/CFS cohorts, including hyperactivated platelets, endothelial dysfunction, vascular dysregulation, and anomalous clotting processes. To build on these findings, and to identify potential biomarkers that can be related to pathophysiology, we measured differences in protein expression in platelet-poor plasma (PPP) samples from 15 ME/CFS study participants and 10 controls not previously infected with SARS-CoV-2, using DIA LC-MS/MS. We identified 24 proteins that are significantly increased in the ME/CFS group compared to the controls, and 21 proteins that are significantly downregulated. Proteins related to clotting processes - thrombospondin-1 (important in platelet activation), platelet factor 4, and protein S - were differentially expressed in the ME/CFS group, suggestive of a dysregulated coagulation system and abnormal endothelial function. Complement machinery was also significantly downregulated, including C9 which forms part of the membrane attack complex. Additionally, we identified a significant upregulation of lactotransferrin, protein S100-A9, and an immunoglobulin variant. The findings from this experiment further implicate the coagulation and immune system in ME/CFS, and bring to attention the pathology of or imposed on the endothelium. This study highlights potential systems and proteins that require further research with regards to their contribution to the pathogenesis of ME/CFS, symptom manifestation, and biomarker potential, and also gives insight into the hematological and cardiovascular risk for ME/CFS individuals affected by diabetes mellitus.

Cardiopulmonary and metabolic responses during a 2-day CPET in myalgic encephalomyelitis/chronic fatigue syndrome: translating reduced oxygen consumption to impairment status to treatment considerations

BACKGROUND

Post-exertional malaise (PEM), the hallmark symptom of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), represents a constellation of abnormal responses to physical, cognitive, and/or emotional exertion including profound fatigue, cognitive dysfunction, and exertion intolerance, among numerous other maladies. Two sequential cardiopulmonary exercise tests (2-d CPET) provide objective evidence of abnormal responses to exertion in ME/CFS but validated only in studies with small sample sizes. Further, translation of results to impairment status and approaches to symptom reduction are lacking.

METHODS

Participants with ME/CFS (Canadian Criteria; n = 84) and sedentary controls (CTL; n = 71) completed two CPETs on a cycle ergometer separated by 24 h. Two-way repeated measures ANOVA compared CPET measures at rest, ventilatory/anaerobic threshold (VAT), and peak effort between phenotypes and CPETs. Intraclass correlations described stability of CPET measures across tests, and relevant objective CPET data indicated impairment status. A subset of case-control pairs (n = 55) matched for aerobic capacity, age, and sex, were also analyzed.

RESULTS

Unlike CTL, ME/CFS failed to reproduce CPET-1 measures during CPET-2 with significant declines at peak exertion in work, exercise time, V ˙ e, V ˙ O2, V ˙ CO2, V ˙ T, HR, O2pulse, DBP, and RPP. Likewise, CPET-2 declines were observed at VAT for V ˙ e/ V ˙ CO2, PetCO2, O2pulse, work, V ˙ O2 and SBP. Perception of effort (RPE) exceeded maximum effort criteria for ME/CFS and CTL on both CPETs. Results were similar in matched pairs. Intraclass correlations revealed greater stability in CPET variables across test days in CTL compared to ME/CFS owing to CPET-2 declines in ME/CFS. Lastly, CPET-2 data signaled more severe impairment status for ME/CFS compared to CPET-1.

CONCLUSIONS

Presently, this is the largest 2-d CPET study of ME/CFS to substantiate impaired recovery in ME/CFS following an exertional stressor. Abnormal post-exertional CPET responses persisted compared to CTL matched for aerobic capacity, indicating that fitness level does not predispose to exertion intolerance in ME/CFS. Moreover, contributions to exertion intolerance in ME/CFS by disrupted cardiac, pulmonary, and metabolic factors implicates autonomic nervous system dysregulation of blood flow and oxygen delivery for energy metabolism. The observable declines in post-exertional energy metabolism translate notably to a worsening of impairment status. Treatment considerations to address tangible reductions in physiological function are proffered.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov, retrospectively registered, ID# NCT04026425, date of registration: 2019-07-17.

Exploring levels of TSH and FT4 in patients with chronic fatigue syndrome (CFS), fibromyalgia (FM) and healthy controls did not reveal any associations between fatigue score and level of thyroid hormones

AIM

The diagnoses of Chronic Fatigue Syndrome (CFS) and Fibromyalgia (FM) are highly associated with fatigue and pain, respectively. Physiologically and clinically an effect of thyroid status on fatigue and pain is expected. There may be clinically relevant differences in thyroid hormone axes though within values of reference in both patients with normal thyroid hormones, or in patients with well-regulated thyroid disease. These potential differences are explored in this study.

MATERIALS AND METHODS

In the present study, female patients with CFS (n = 49) and FM (n = 58) as well as female healthy controls (n = 53) were included. We explored plasma levels of TSH and FT4 between the groups using Kruskall-Wallis, and the relation between fatigue score and levels of TSH and FT4 by means of Spearman's rho.

RESULTS

There were no group differences between CFS patients, FM patients, and healthy controls in levels of TSH and FT4.

CONCLUSION

As one might clinically and physiologically expect an association between thyroid function and fatigue, which may be associated with clinical disorders such as CFS and FM, we suggest future studies to examine the field further by exploring the influence of thyroid receptors and responses of the thyroid hormone cascade.

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: the biology of a neglected disease

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a chronic, debilitating disease characterised by a wide range of symptoms that severely impact all aspects of life. Despite its significant prevalence, ME/CFS remains one of the most understudied and misunderstood conditions in modern medicine. ME/CFS lacks standardised diagnostic criteria owing to variations in both inclusion and exclusion criteria across different diagnostic guidelines, and furthermore, there are currently no effective treatments available. Moving beyond the traditional fragmented perspectives that have limited our understanding and management of the disease, our analysis of current information on ME/CFS represents a significant paradigm shift by synthesising the disease's multifactorial origins into a cohesive model. We discuss how ME/CFS emerges from an intricate web of genetic vulnerabilities and environmental triggers, notably viral infections, leading to a complex series of pathological responses including immune dysregulation, chronic inflammation, gut dysbiosis, and metabolic disturbances. This comprehensive model not only advances our understanding of ME/CFS's pathophysiology but also opens new avenues for research and potential therapeutic strategies. By integrating these disparate elements, our work emphasises the necessity of a holistic approach to diagnosing, researching, and treating ME/CFS, urging the scientific community to reconsider the disease's complexity and the multifaceted approach required for its study and management.

Expression of β1- and β2-adrenergic receptors in oral squamous cell carcinoma and their association with psychological and clinical factors

BACKGROUND

Psychological stressors have been related to tumor progression through the activation of beta-adrenergic receptors (β-AR) in several types of cancer.

PURPOSE

This study aimed to investigate the expressions of β1- and β2-AR and their association with psychological and clinicopathological variables in patients with oral squamous cell carcinoma.

METHODS

Tumor samples from 99 patients diagnosed with OSCC were subjected to immunohistochemical reaction to detect the expression of β1-AR and β2-AR. Anxiety and depression symptoms were assessed using the Beck Anxiety Inventory and Beck Depression Inventory (BDI), respectively. The Brunel Mood Scale was used for measuring affective mood states.

RESULTS

Univariate analyzes revealed that higher expression of β1-AR was associated with increased alcohol consumption (p = 0.032), higher education (p = 0.042), worse sleep quality (p = 0.044) and increased levels of pain related to the primary tumor (p < 0.001). Higher expression of β2-AR was related with regional metastasis (p = 0.014), increased levels of pain related to the primary tumor (p = 0.044), anxiety (p < 0.001) and depressive (p = 0.010) symptoms and higher mood scores of angry (p = 0.010) and fatigue (p = 0.010). Multivariate analysis identified that patients with advanced clinical stage had lower β1-AR expression (OR=0.145, 95% CI=0.025-0.828, p = 0.003). Higher anxiety symptoms and higher mood fatigue are independent factors for increased β2-AR expression (OR=4256, 95% CI=1439-12606, p = 0.009; OR=3816, 95% CI=1258-11,573, p = 0.018, respectively).

CONCLUSION

This study reveal that anxiety, fatigue symptoms, and clinical staging are associated with tumor expression of beta-adrenergic receptors in patients with oral cancer.

Herpesvirus Infection of Endothelial Cells as a Systemic Pathological Axis in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Understanding the pathophysiology of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is critical for advancing treatment options. This review explores the novel hypothesis that a herpesvirus infection of endothelial cells (ECs) may underlie ME/CFS symptomatology. We review evidence linking herpesviruses to persistent EC infection and the implications for endothelial dysfunction, encompassing blood flow regulation, coagulation, and cognitive impairment-symptoms consistent with ME/CFS and Long COVID. This paper provides a synthesis of current research on herpesvirus latency and reactivation, detailing the impact on ECs and subsequent systemic complications, including latent modulation and long-term maladaptation. We suggest that the chronicity of ME/CFS symptoms and the multisystemic nature of the disease may be partly attributable to herpesvirus-induced endothelial maladaptation. Our conclusions underscore the necessity for further investigation into the prevalence and load of herpesvirus infection within the ECs of ME/CFS patients. This review offers conceptual advances by proposing an endothelial infection model as a systemic mechanism contributing to ME/CFS, steering future research toward potentially unexplored avenues in understanding and treating this complex syndrome.

Myalgic encephalomyelitis/chronic fatigue syndrome from current evidence to new diagnostic perspectives through skeletal muscle and metabolic disturbances

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a demanding medical condition for patients and society. It has raised much more public awareness after the COVID-19 pandemic since ME/CFS and long-COVID patients share many clinical symptoms such as debilitating chronic fatigue. However, unlike long COVID, the etiopathology of ME/CFS remains a mystery despite several decades' research. This review moves from pathophysiology of ME/CFS through the compelling evidence and most interesting hypotheses. It focuses on the pathophysiology of skeletal muscle by proposing the hypothesis that skeletal muscle tissue offers novel opportunities for diagnosis and treatment of this syndrome and that new evidence can help resolve the long-standing debate on terminology.

Recent Research Trends in Neuroinflammatory and Neurodegenerative Disorders

Neuroinflammatory and neurodegenerative disorders including Alzheimer's disease (AD), Parkinson's disease (PD), traumatic brain injury (TBI) and Amyotrophic lateral sclerosis (ALS) are chronic major health disorders. The exact mechanism of the neuroimmune dysfunctions of these disease pathogeneses is currently not clearly understood. These disorders show dysregulated neuroimmune and inflammatory responses, including activation of neurons, glial cells, and neurovascular unit damage associated with excessive release of proinflammatory cytokines, chemokines, neurotoxic mediators, and infiltration of peripheral immune cells into the brain, as well as entry of inflammatory mediators through damaged neurovascular endothelial cells, blood-brain barrier and tight junction proteins. Activation of glial cells and immune cells leads to the release of many inflammatory and neurotoxic molecules that cause neuroinflammation and neurodegeneration. Gulf War Illness (GWI) and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) are chronic disorders that are also associated with neuroimmune dysfunctions. Currently, there are no effective disease-modifying therapeutic options available for these diseases. Human induced pluripotent stem cell (iPSC)-derived neurons, astrocytes, microglia, endothelial cells and pericytes are currently used for many disease models for drug discovery. This review highlights certain recent trends in neuroinflammatory responses and iPSC-derived brain cell applications in neuroinflammatory disorders.

Sex differences in vascular endothelial function related to acute and long COVID-19

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus has been at the forefront of health sciences research since its emergence in China in 2019 that quickly led to a global pandemic. As a result of this research, and the large numbers of infected patients globally, there were rapid enhancements made in our understanding of Coronavirus disease 2019 (COVID-19) pathology, including its role in the development of uncontrolled immune responses and its link to the development of endotheliitis and endothelial dysfunction. There were also some noted differences in the rate and severity of infection between males and females with acute COVID. Some individuals infected with SARS-CoV-2 also experience long-COVID, an important hallmark symptom of this being Myalgic Encephalomyelitis-Chronic Fatigue Syndrome (ME-CFS), also experienced differently between males and females. The purpose of this review is to discuss the impact of sex on the vasculature during acute and long COVID-19, present any link between ME-CFS and endothelial dysfunction, and provide evidence for the relationship between ME-CFS and the immune system. We also will delineate biological sex differences observed in other post viral infections and, assess if sex differences exist in how the immune system responds to viral infection causing ME-CFS.

[Systems thinking, subjective findings and diagnostic "pigeonholing" in ME/CFS: A mainly qualitative public health study from a patient perspective]

BACKGROUND

ME/CFS (Myalgic encephalomyelitis/chronic fatigue syndrome) is an illness that is predominantly viewed as a neuroimmunological multisystem disease, which is still unknown to many doctors in Germany or which they classify as a psychosomatic disease. From their perspective, ME/CFS patients report significant deficits in terms of medical treatment and a doctor-patient relationship (DP relationship) that is perceived as problematic. The aim of the present study is to more precisely analyse the process of finding a diagnosis as an influencing factor on the DP relationship in ME/CFS from the point of view of those affected.

METHOD

As part of an explorative qualitative survey, 544 ME/CFS patients (> 20 years; 455 ♀, 89 ♂) with a medical diagnosis of ME/CFS were asked in writing about their experiences with regard to the process of finding a diagnosis. The sampling was previously done by self-activation and via the snowball principle. The questionnaire to be answered was structured analogously to a focused, standardized guideline interview. The evaluation was carried out as part of a qualitative content analysis according to Mayring. Some of the results were subsequently quantified.

RESULTS

The participants described what they saw as the inadequate process of making a diagnosis as a central factor in a problematic DP relationship in ME/CFS. From their point of view, many doctors deny the existence of ME/CFS or classify it as a solely psychosomatic illness, insist on their level of knowledge, ignore patient knowledge and disregard scientific information provided. They follow the standard program, think in "pigeonholes" and are incapable of systemic thinking. This has a significant impact on the DP relationship.

DISCUSSION

From the point of view of ME/CFS patients, the process of making a diagnosis and the recognition of ME/CFS as a neuroimmunological multisystem disease are the central aspects of a DP relationship that they experience as problematic. In the past, findings classified as "subjective" and thus ignored, the pigeonholing that is characteristic of biomedically oriented medicine and a healthcare system that opposes systemic thinking when making a diagnosis have all been identified as factors that may have a significant impact on the DP relationship.

Microvascular Capillary and Precapillary Cardiovascular Disturbances Strongly Interact to Severely Affect Tissue Perfusion and Mitochondrial Function in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Evolving from the Post COVID-19 Syndrome

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a frequent, debilitating and still enigmatic disease. There is a broad overlap in the symptomatology of ME/CFS and the Post-COVID-19 Syndrome (PCS). A fraction of the PCS patients develop the full clinical picture of ME/CFS. New observations in microvessels and blood from patients suffering from PCS have appeared and include microclots and malformed pathological blood cells. Capillary blood flow is impaired not only by pathological blood components but also by prothrombotic changes in the vascular wall, endothelial dysfunction, and the expression of adhesion molecules in the capillaries. These disturbances can finally cause a low capillary flow and even capillary stasis. A low cardiac stroke volume due to hypovolemia and the inability of the capacitance vessels to adequately constrict to deliver the necessary cardiac preload generate an unfavorable low precapillary perfusion pressure. Furthermore, a predominance of vasoconstrictor over vasodilator influences exists, in which sympathetic hyperactivity and endothelial dysfunction play a strong role, causing the constriction of resistance vessels and of precapillary sphincters, which leads to a fall in capillary pressure behind the sphincters. The interaction of these two precapillary cardiovascular mechanisms causing a low capillary perfusion pressure is hemodynamically highly unfavorable in the presence of a primary capillary stasis, which is already caused by the pathological blood components and their interaction with the capillary wall, to severely impair organ perfusion. The detrimental coincidence of microcirculatory and precapillary cardiovascular disturbances may constitute the key disturbance of the Post-COVID-19 syndrome and finally lead to ME/CFS in predisposed patients because the interaction causes a particular kind of perfusion disturbance-capillary ischemia/reperfusion-which has a high potential of causing mitochondrial dysfunction by inducing sodium- and calcium-overload in skeletal muscles. The latter, in turn, worsens the vascular situation through the generation of reactive oxygen species to close a vicious cycle from which the patient can hardly escape.

One-year follow-up of young people with ME/CFS following infectious mononucleosis by Epstein-Barr virus

Background

Infectious mononucleosis after primary infection with Epstein-Barr virus (EBV-IM) has been linked to the development of myalgic encephalomyelitis/chronic fatigue-syndrome (ME/CFS) in children, adolescents, and young adults. Here, we present clinical phenotypes and follow-up data from a first German cohort of young people with ME/CFS following EBV-IM.

Methods

12 adolescents and 13 young adults were diagnosed with IM-triggered ME/CFS at our specialized tertiary outpatient service by clinical criteria requiring post-exertional malaise (PEM) and a history of confirmed EBV primary infection as triggering event. Demographic information, laboratory findings, frequency and severity of symptoms, physical functioning, and health-related quality of life (HRQoL) were assessed and re-evaluated 6 and 12 months later.

Results

Young adults displayed more severe symptoms as well as worsening of fatigue, physical and mental functioning, and HRQoL throughout the study, compared to adolescents. After one year, 6/12 (54%) adolescents no longer met the diagnostic criteria for ME/CFS while all young adults continued to fulfill the Canadian consensus criteria. Improvement in adolescents was evident in physical functioning, symptom frequency and severity, and HRQoL, while young adults showed little improvement. EBV serology and EBV DNA load did not correlate with distinct clinical features of ME/CFS, and clinical chemistry showed no evidence of inflammation. Remarkably, the median time from symptom onset to ME/CFS diagnosis was 13.8 (IQR: 9.1-34.9) months.

Conclusions

ME/CFS following EBV-IM is a severely debilitating disease often diagnosed late and with limited responses to conventional medical care, especially in adults. Although adolescents may have a better prognosis, their condition can fluctuate and significantly impact their HRQoL. Our data emphasize that biomarkers and effective therapeutic options are also urgently needed to improve medical care and pave the way to recovery.

Catalytic Antibodies May Contribute to Demyelination in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Here we report preliminary data demonstrating that some patients with myalgic encephalomyelitis/chronic fatiguesyndrome (ME/CFS) may have catalytic autoantibodies that cause the breakdown of myelin basic protein (MBP). We propose that these MBP-degradative antibodies are important to the pathophysiology of ME/CFS, particularly in the occurrence of white matter disease/demyelination. This is supported by magnetic resonance imagining studies that show these findings in patients with ME/CFS and could explain symptoms of nerve pain and muscle weakness. In this work, we performed a series of experiments on patient plasma samples where we isolated and characterized substrate-specific antibodies that digest MBP. We also tested glatiramer acetate (copaxone), an FDA approved immunomodulator to treat multiple sclerosis, and found that it inhibits ME/CFS antibody digestion of MBP. Furthermore, we found that aprotinin, which is a specific serine protease inhibitor, specifically prevents breakdown of MBP while the other classes of protease inhibitors had no effect. This coincides with the published literature describing catalytic antibodies as having serine protease-like activity. Postpandemic research has also provided several reports of demyelination in COVID-19. Because COVID-19 has been described as a trigger for ME/CFS, demyelination could play a bigger role in patient symptoms for those recently diagnosed with ME/CFS. Therefore, by studying proteolytic antibodies in ME/CFS, their target substrates, and inhibitors, a new mechanism of action could lead to better treatment and a possible cure for the disease.

Heterogenous circulating miRNA changes in ME/CFS converge on a unified cluster of target genes: A computational analysis

Myalgic Encephalomyelitis / Chronic Fatigue Syndrome is a debilitating, multisystem disease of unknown mechanism, with a currently ongoing search for its endocrine mediators. Circulating microRNAs (miRNA) are a promising candidate for such a mediator and have been reported as significantly different in the patient population versus healthy controls by multiple studies. None of these studies, however, agree with each other on which specific miRNA are under- or over-expressed. This discrepancy is the subject of the computational study presented here, in which a deep dive into the predicted gene targets and their functional interactions is conducted, revealing that the aberrant circulating miRNAs in ME/CFS, although different between patients, seem to mainly target the same specific set of genes (p ≈ 0.0018), which are very functionally related to each other (p ≲ 0.0001). Further analysis of these functional relations, based on directional pathway information, points to impairments in exercise hyperemia, angiogenic adaptations to hypoxia, antioxidant defenses, and TGF-β signaling, as well as a shift towards mitochondrial fission, corroborating and explaining previous direct observations in ME/CFS. Many transcription factors and epigenetic modulators are implicated as well, with currently uncertain downstream combinatory effects. As the results show significant similarity to previous research on latent herpesvirus involvement in ME/CFS, the possibility of a herpesvirus origin of these miRNA changes is also explored through further computational analysis and literature review, showing that 8 out of the 10 most central miRNAs analyzed are known to be upregulated by various herpesviruses. In total, the results establish an appreciable and possibly central role for circulating microRNAs in ME/CFS etiology that merits further experimental research.

Urine Metabolite Analysis to Identify Pathomechanisms of Long COVID: A Pilot Study

Background

Around 10% of people who had COVID-9 infection suffer from persistent symptoms such as fatigue, dyspnoea, chest pain, arthralgia/myalgia, sleep disturbances, cognitive dysfunction and impairment of mental health. Different underlying pathomechanisms appear to be involved, in particular inflammation, alterations in amino acid metabolism, autonomic dysfunction and gut dysbiosis.

Aim

As routine tests are often inconspicuous in patients with Long COVID (LC), similarly to patients suffering from myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), accessible biomarkers indicating dysregulation of specific pathways are urgently needed to identify underlying pathomechanisms and enable personalized medicine treatment. Within this pilot study we aimed to proof traceability of altered metabolism by urine analysis.

Patients and Methods

Urine metabolome analyses were performed to investigate the metabolic signature of patients with LC (n = 25; 20 women, 5 men) in comparison to healthy controls (Ctrl, n = 8; 7 women, 1 man) and individuals with ME/CFS (n = 8; 2 women, 6 men). Concentrations of neurotransmitter precursors tryptophan, phenylalanine and their downstream metabolites, as well as their association with symptoms (fatigue, anxiety and depression) in the patients were examined.

Results and Conclusion

Phenylalanine levels were significantly lower in both the LC and ME/CFS patient groups when compared to the Ctrl group. In many LC patients, the concentrations of downstream metabolites of tryptophan and tyrosine, such as serotonin, dopamine and catecholamines, deviated from the reference ranges. Several symptoms (sleep disturbance, pain or autonomic dysfunction) were associated with certain metabolites. Patients experiencing fatigue had lower levels of kynurenine, phenylalanine and a reduced kynurenine to tryptophan ratio (Kyn/Trp). Lower concentrations of gamma-aminobutyric acid (GABA) and higher activity of kynurenine 3-monooxygenase (KMO) were observed in patients with anxiety. Conclusively, our results suggest that amino acid metabolism and neurotransmitter synthesis is disturbed in patients with LC and ME/CFS. The identified metabolites and their associated dysregulations could serve as potential biomarkers for elucidating underlying pathomechanisms thus enabling personalized treatment strategies for these patient populations.

[Implications of the quality of the doctor-patient relationship on health in adult ME/CFS patients. A qualitative public health study from a patien perspective]

BACKGROUND

Most patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) are dissatisfied with medical care. They complain about e. g. the lack of medical recognition of ME/CFS as a neuroimmunological disease and the medical perception of those affected as "difficult patients".

METHOD

As part of an exploratory qualitative survey, 544 medically diagnosed ME/CFS patients (> 20 years; 455 ♀, 89 ♂) were asked about their subjective experiences with regard to the doctor-patient relationships (DP relationship) to their treating physicians. The questionnaire was structured analogously to a focused, standardized guideline interview. The written answers were evaluated using a qualitative content analysis according to Mayring.

RESULTS

The participants reported a significant deterioration in their health situation and their quality of life as a result of misdiagnoses and incorrect treatments, the strained DP relationship and the lack of support from the physicians. All of this leads to fear of visiting the doctor, a general loss of trust in physicians, a feeling of helplessness up to bitterness and resignation - with suicide as the last mental option for some patients to escape from this precarious situation. During medical consultations, other participants only addressed health problems that were not related to ME/CFS, or only went to the doctor in an emergency, or refrained from contacting doctors entirely.

CONCLUSIONS

The DP relationship described by the participants as problematic in their opinion has significant negative health consequences for them. It is therefore of great urgency to develop a patient-centred treatment concept that focuses on ME/CFS patients as experts on their own illness.

Understanding, diagnosing, and treating Myalgic encephalomyelitis/chronic fatigue syndrome - State of the art: Report of the 2nd international meeting at the Charité Fatigue Center

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a devastating disease affecting millions of people worldwide. Due to the 2019 pandemic of coronavirus disease (COVID-19), we are facing a significant increase of ME/CFS prevalence. On May 11th to 12th, 2023, the second international ME/CFS conference of the Charité Fatigue Center was held in Berlin, Germany, focusing on pathomechanisms, diagnosis, and treatment. During the two-day conference, more than 100 researchers from various research fields met on-site and over 700 attendees participated online to discuss the state of the art and novel findings in this field. Key topics from the conference included: the role of the immune system, dysfunction of endothelial and autonomic nervous system, and viral reactivation. Furthermore, there were presentations on innovative diagnostic measures and assessments for this complex disease, cutting-edge treatment approaches, and clinical studies. Despite the increased public attention due to the COVID-19 pandemic, the subsequent rise of Long COVID-19 cases, and the rise of funding opportunities to unravel the pathomechanisms underlying ME/CFS, this severe disease remains highly underresearched. Future adequately funded research efforts are needed to further explore the disease etiology and to identify diagnostic markers and targeted therapies.

Functional autoantibodies: Definition, mechanisms, origin and contributions to autoimmune and non-autoimmune disorders

A growing body of evidence underscores the relevance of functional autoantibodies in the development of various pathogenic conditions but also in the regulation of homeostasis. However, the definition of functional autoantibodies varies among studies and a comprehensive overview on this emerging topic is missing. Here, we do not only explain functional autoantibodies but also summarize the mechanisms underlying the effect of such autoantibodies including receptor activation or blockade, induction of receptor internalization, neutralization of ligands or other soluble extracellular antigens, and disruption of protein-protein interactions. In addition, in this review article we discuss potential triggers of production of functional autoantibodies, including infections, immune deficiency and tumor development. Finally, we describe the contribution of functional autoantibodies to autoimmune diseases including autoimmune thyroid diseases, myasthenia gravis, autoimmune pulmonary alveolar proteinosis, autoimmune autonomic ganglionopathy, pure red cell aplasia, autoimmune encephalitis, pemphigus, acquired thrombotic thrombocytopenic purpura, idiopathic dilated cardiomyopathy and systemic sclerosis, as well as non-autoimmune disorders such as allograft rejection, infectious diseases and asthma.

Evaluation of a Webinar to Increase Health Professionals' Knowledge about Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a severe chronic illness and patients with ME/CFS are often medically underserved in Germany and other countries. One contributing factor is health professionals' lack of knowledge about epidemiology, diagnostic criteria, and treatment of ME/CFS. Opportunities are scarce for health professionals to receive continuing medical education on ME/CFS. The current research addressed this need for further education and investigated the gain of knowledge from a webinar for German-speaking health professionals. In two studies (total sample: N = 378), participants in the intervention condition completed a knowledge test twice (before and after webinar participation). Study 2 also included a waiting-list control condition with repeated response to the knowledge test without webinar participation between measurements. Results showed that at baseline, most participants had seen patients with ME/CFS, but confidence in diagnosing and treating ME/CFS was only moderate-to-low. In the intervention condition, but not in the control condition, knowledge about ME/CFS increased between the first and the second knowledge test. These results indicate that the webinar was successful in increasing health professionals' knowledge about ME/CFS. We concluded that webinars can be a cost-efficient and effective tool in providing health professionals with large-scale continuing medical education about ME/CFS.

Characterizing Sjögren-Associated Fatigue: A Distinct Phenotype from ME/CFS

Fatigue is the most commonly reported and debilitating extraglandular symptom of primary Sjögren's syndrome (pSS). Fatigue and exertional intolerance are hallmark symptoms of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). We aimed to characterize fatigue and further symptoms among pSS patients and to determine whether there is a symptom overlap in pSS and ME/CFS. In 19 patients with pSS, we assessed pSS symptom severity and disease activity via questionnaires as well as the Canadian Consensus Criteria (CCC) for ME/CFS. Hand grip strength (HGS) and levels of α1-, α2-, β1-, β2-, M3- and M4-receptor-autoantibodies were measured. A subgroup of pSS patients exhibited severe fatigue and had higher severity of pain (p = 0.045), depression (p = 0.021) and sleep disturbances (p = 0.020) compared to those with less fatigue. Four of eighteen pSS patients fulfilled the CCC. HGS parameters strongly correlated with fatigue severity (p < 0.05), but strength fully recovered one hour after exertion in contrast to ME/CFS. Levels of β1-, β2- and M4-receptor-autoantibodies were elevated and correlated significantly with disease activity assessed by the ESSDAI (p < 0.05), but not fatigue severity. Only a minor subgroup of pSS patients fulfills the CCC, and post exertional malaise (PEM) is atypical, as it is primarily triggered by mental/emotional but not physical exertion. HGS assessment is an objective measure to assess overall fatigue severity.

Cardiovascular and haematological pathology in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS): A role for viruses

ME/CFS is a debilitating chronic condition that often develops after viral or bacterial infection. Insight from the study of Long COVID/Post Acute Sequelae of COVID-19 (PASC), the post-viral syndrome associated with SARS-CoV-2 infection, might prove to be useful for understanding pathophysiological mechanisms of ME/CFS. Disease presentation is similar between the two conditions, and a subset of Long COVID patients meet the diagnostic criteria for ME/CFS. Since Long COVID is characterized by significant vascular pathology - including endothelial dysfunction, coagulopathy, and vascular dysregulation - the question of whether or not the same biological abnormalities are of significance in ME/CFS arises. Cardiac abnormalities have for a while now been documented in ME/CFS cohorts, with recent studies demonstrating major deficits in cerebral blood flow, and hence vascular dysregulation. A growing body of research is demonstrating that ME/CFS is accompanied by platelet hyperactivation, anomalous clotting, a procoagulant phenotype, and endothelial dysfunction. Endothelial damage and dysregulated clotting can impair substance exchange between blood and tissues, and result in hypoperfusion, which may contribute to the manifestation of certain ME/CFS symptoms. Here we review the ME/CFS literature to summarize cardiovascular and haematological findings documented in patients with the condition, and, in this context, briefly discuss the potential role of previously-implicated pathogens. Overall, cardiac and haematological abnormalities are present within ME/CFS cohorts. While atherosclerotic heart disease is not significantly associated with ME/CFS, suboptimal cardiovascular function defined by reduced cardiac output, impaired cerebral blood flow, and vascular dysregulation are, and these abnormalities do not appear to be influenced by deconditioning. Rather, these cardiac abnormalities may result from dysfunction in the (autonomic) nervous system. Plenty of recently published studies are demonstrating significant platelet hyperactivity and endothelial dysfunction in ME/CFS, as well as anomalous clotting processes. It is of particular importance to determine to what extent these cardiovascular and haematological abnormalities contribute to symptom severity, and if these two systems can be targeted for therapeutic purposes. Viral reservoirs of herpesviruses exist in ME/CFS, and most likely contribute to cardiovascular and haematological dysfunction directly or indirectly. This review highlights the potential of studying cardiac functioning, the vasculature, and coagulation system in ME/CFS.

ME/CFS and Long COVID share similar symptoms and biological abnormalities: road map to the literature

Some patients remain unwell for months after "recovering" from acute COVID-19. They develop persistent fatigue, cognitive problems, headaches, disrupted sleep, myalgias and arthralgias, post-exertional malaise, orthostatic intolerance and other symptoms that greatly interfere with their ability to function and that can leave some people housebound and disabled. The illness (Long COVID) is similar to myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) as well as to persisting illnesses that can follow a wide variety of other infectious agents and following major traumatic injury. Together, these illnesses are projected to cost the U.S. trillions of dollars. In this review, we first compare the symptoms of ME/CFS and Long COVID, noting the considerable similarities and the few differences. We then compare in extensive detail the underlying pathophysiology of these two conditions, focusing on abnormalities of the central and autonomic nervous system, lungs, heart, vasculature, immune system, gut microbiome, energy metabolism and redox balance. This comparison highlights how strong the evidence is for each abnormality, in each illness, and helps to set priorities for future investigation. The review provides a current road map to the extensive literature on the underlying biology of both illnesses.

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) and Comorbidities: Linked by Vascular Pathomechanisms and Vasoactive Mediators?

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is often associated with various other syndromes or conditions including mast cell activation (MCA), dysmenorrhea and endometriosis, postural tachycardia (POTS) and small fiber neuropathy (SFN). The causes of these syndromes and the reason for their frequent association are not yet fully understood. We previously published a comprehensive hypothesis of the ME/CFS pathophysiology that explains the majority of symptoms, findings and chronicity of the disease. We wondered whether some of the identified key pathomechanisms in ME/CFS are also operative in MCA, endometriosis and dysmenorrhea, POTS, decreased cerebral blood flow and SFN, and possibly may provide clues on their causes and frequent co-occurrence. Our analysis indeed provides strong arguments in favor of this assumption, and we conclude that the main pathomechanisms responsible for this association are excessive generation and spillover into the systemic circulation of inflammatory and vasoactive tissue mediators, dysfunctional β2AdR, and the mutual triggering of symptomatology and disease initiation. Overall, vascular dysfunction appears to be a strong common denominator in these linkages.

Astragalus polysaccharide ameliorated complex factor-induced chronic fatigue syndrome by modulating the gut microbiota and metabolites in mice

Chronic fatigue syndrome (CFS) is a debilitating disease with no symptomatic treatment. Astragalus polysaccharide (APS), a component derived from the traditional Chinese medicine A. membranaceus, has significant anti-fatigue activity. However, the mechanisms underlying the potential beneficial effects of APS on CFS remain poorly understood. A CFS model of 6-week-old C57BL/6 male mice was established using the multiple-factor method. These mice underwent examinations for behavior, oxidative stress and inflammatory indicators in brain and intestinal tissues, and ileum histomorphology. 16 S rDNA sequencing analysis indicated that APS regulated the abundance of gut microbiota and increased production of short chain fatty acids (SCFAs) and anti-inflammatory bacteria. In addition, APS reversed the abnormal expression of Nrf2, NF-κB, and their downstream factors in the brain-gut axis and alleviated the reduction in SCFAs in the cecal content caused by CFS. Further, APS modulated the changes in serum metabolic pathways induced by CFS. Finally, it was verified that butyrate exerted antioxidant and anti-inflammatory effects in neuronal cells. In conclusion, APS could increase the SCFAs content by regulating the gut microbiota, and SCFAs (especially butyrate) can further regulate the oxidative stress and inflammation in the brain, thus alleviating CFS. This study explored the efficacy and mechanism of APS for CFS from the perspective of gut-brain axis and provides a reference to further explore the efficacy of APS and the role of SCFAs in the central nervous system.

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS): A preliminary survey among patients in Switzerland

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a multi-factorial systemic chronic debilitating disease of poorly understood etiology and limited systematic evidence. The questionnaire and interview-based survey included 169 ME/CFS patients from the Swiss ME/CFS association. The majority of patients were females (72.2%), single (55.7%) and without children (62.5%). Only one third were working (full/part-time). The mean onset of ME/CFS was 31.6 years of age with 15% of patients being symptomatic before their 18th birthday. In this cohort, patients had documented ME/CFS for a mean 13.7 years, whereby half (50.3%) stated their condition was progressively worsening. Triggering events and times of disease onset were recalled by 90% of the participants. An infectious disease was associated with a singular or part of multiple events by 72.9% and 80.6%, respectively. Prior to disease onset, a third of the patients reported respiratory infections; followed by gastro-intestinal infections (15.4%) and tick-borne diseases (16.2%). Viral infections were recalled by 77.8% of the respondents, with Epstein Barr Virus being the most commonly reported agent. Patients self-reported an average number of 13 different symptoms, all described specific triggers of symptoms exacerbation and 82.2% suffered from co-morbidities. This study collated clinically relevant information on ME/CFS patients in Switzerland, highlighting the extent of disease severity, the associated factors negatively affecting daily life activities and work status as well as potential socio-economic impact.

Association between the Ile164 β2 Adrenergic Receptor Polymorphism and Fatigue in Patients with Rheumatoid Arthritis

INTRODUCTION

In the present work, the frequency of inherited polymorphisms of the beta 2 adrenergic receptor (β2AR) gene and their association with fatigue in patients with rheumatoid arthritis (RA) was examined.

METHODS

An allele-specific polymerase chain reaction was used to determine the common variants of the β2AR at position 16, 27, and 164 in 92 German RA outpatients. Health Assessment Questionnaire (HAQ-DI), Beck Depression Inventory (BDI), Perceived Stress Questionnaire (PSQ-30), Multidimensional Fatigue Inventory (MFI-20) were utilized.

RESULTS

34.7% of German RA patients were diagnosed with associated fatigue. Fatigued patients were more likely to carry the Ile allele at position 164 (OR 7.33, 95% CI 1.09-59.8, p = 0.049). Comparing these risk factors' contribution to different fatigue dimensions revealed that Ile164 carriers only had significantly higher MFI-20 mean values for general fatigue (p = 0.014) while the clinical difference among other MFI subscales was the largest for mental fatigue (carrier: 8.23, SD: 4.22, noncarrier: 5.67, SD: 1.56, p = 0.089, Cohen's d = 0.629). Disease activity, perceived stress, and depression were also associated with fatigue with higher mean values for DAS28CRP (p = 0.038), PSQ (p < 0.001), and BDI-II (p < 0.001) in fatigued patients. Physical fatigue was correlated with disease activity (p = 0.009) and depression (p = 0.001) while mental fatigue showed associations with depression (p = 0.001) and perceived stress (p = 0.028).

CONCLUSION

The discovery study indicates that the Ile164 polymorphism might in contrast to other β2AR polymorphisms affect fatigue levels in RA patients. This association was observed especially with mental fatigue. Further replication studies are warranted to determine further role of β2AR polymorphisms in RA patients.

Autoantibodies targeting G protein-coupled receptors: An evolving history in autoimmunity. Report of the 4th international symposium

G protein-coupled receptors (GPCR) are involved in various physiological and pathophysiological processes. Functional autoantibodies targeting GPCRs have been associated with multiple disease manifestations in this context. Here we summarize and discuss the relevant findings and concepts presented in the biennial International Meeting on autoantibodies targeting GPCRs (the 4th Symposium), held in Lübeck, Germany, 15-16 September 2022. The symposium focused on the current knowledge of these autoantibodies' role in various diseases, such as cardiovascular, renal, infectious (COVID-19), and autoimmune diseases (e.g., systemic sclerosis and systemic lupus erythematosus). Beyond their association with disease phenotypes, intense research related to the mechanistic action of these autoantibodies on immune regulation and pathogenesis has been developed, underscoring the role of autoantibodies targeting GPCRs on disease outcomes and etiopathogenesis. The observation repeatedly highlighted that autoantibodies targeting GPCRs could also be present in healthy individuals, suggesting that anti-GPCR autoantibodies play a physiologic role in modeling the course of diseases. Since numerous therapies targeting GPCRs have been developed, including small molecules and monoclonal antibodies designed for treating cancer, infections, metabolic disorders, or inflammatory conditions, anti-GPCR autoantibodies themselves can serve as therapeutic targets to reduce patients' morbidity and mortality, representing a new area for the development of novel therapeutic interventions.

Impact of Misdiagnosis in Case-Control Studies of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Misdiagnosis of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) can occur when different case definitions are used by clinicians (relative misdiagnosis) or when failing the genuine diagnosis of another disease (misdiagnosis in a strict sense). This problem translates to a recurrent difficulty in reproducing research findings. To tackle this problem, we simulated data from case-control studies under misdiagnosis in a strict sense. We then estimated the power to detect a genuine association between a potential causal factor and ME/CFS. A minimum power of 80% was obtained for studies with more than 500 individuals per study group. When the simulation study was extended to the situation where the potential causal factor could not be determined perfectly (e.g., seropositive/seronegative in serological association studies), the minimum power of 80% could only be achieved in studies with more than 1000 individuals per group. In conclusion, current ME/CFS studies have suboptimal power under the assumption of misdiagnosis. This power can be improved by increasing the overall sample size using multi-centric studies, reporting the excluded illnesses and their exclusion criteria, or focusing on a homogeneous cohort of ME/CFS patients with a specific pathological mechanism where the chance of misdiagnosis is reduced.

Autoantibody Correlation Signatures in Fibromyalgia and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Association with Symptom Severity

Recent studies provide some evidence for the contribution of antibody-mediated autoimmune mechanisms to the nature of fibromyalgia (FM) and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Much attention was paid to the autoantibodies (AAb) targeting G protein-coupled receptors as natural components of the immune system. However, the natural AAb network is much more extensive, and has not been previously investigated in these disorders. The enzyme immunoassays ELI-Viscero-Test and ELI-Neuro-Test were used to determine changes in serum content of 33 natural AAb to neural, organ-specific and non-tissue-specific autoantigens (a) in 11 ME/CFS patients with comorbid FM; (b) in 11 ME/CFS patients without FM; (c) in 11 healthy controls. Individual AAb profiles and their correlation with some clinical symptoms were analyzed. Both patients with ME/CFS(-)FM and ME/CFS(+)FM were characterized by more frequent and pronounced deviations in the immunoreactivity to GABA-receptors than healthy controls. Although the level of other natural AAb did not differ between study groups, AAb correlation signatures were altered in patients compared to healthy controls. Both in patients and healthy controls the level of natural AAb to various neural and tissue-specific antigens correlated with the severity of fatigue, bodily pain, depression, anxiety, physical and mental health-related quality of life. Notably, widely different correlation patterns were observed between study groups. Findings from this pilot study provide some evidence that the homeostasis of autoimmune relationships, which are possibly a physiological part of our immune system, may be altered in FM and ME/CFS. The correlation of disease-induced perturbations in individual AAb profiles with some clinical symptoms may arise from the immune system's ability to reflect qualitative and quantitative changes in antigenic composition of the body.

Health system support among patients with ME/CFS in Switzerland

Objectives

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex chronic and debilitating multifactorial disease. Adequate patient care is challenged by poor knowledge among health care professionals and the historical misconception that the disease is psychological in nature. This study assessed the health-related challenges faced by patients with ME/CFS in Switzerland and examined whether they receive adequate health care.

Methods

Quantitative and qualitative data were collected through a self-administered questionnaire between June and September of 2021, among 169 patients with ME/CFS in Switzerland.

Results

The mean age at diagnosis was 38.8 years. Only one-third of ME/CFS affected children and youth were correctly diagnosed before their 18th birthday. The mean time from disease onset to diagnosis was 6.7 years, and patients had an average of 11.1 different appointments and 2.6 misdiagnoses. A poor diagnosis rate and insufficient disease knowledge among health professionals in Switzerland led 13.5% of the patients to travel abroad to seek a diagnosis. Most patients (90.5%) were told at least once that their symptoms were psychosomatic. Swiss patients expressed high dissatisfaction with the health system and indicated that physicians lacked knowledge regarding ME/CFS. Therapies prescribed by physicians or tried by patients, as well as their perceived efficacy, were described. Graded Exercise Therapy (GET) was perceived as harmful by patients, whereas pacing, complementary/alternative medicine, and dietary supplements and medications to alleviate symptoms were reported to be helpful to varying degrees.

Conclusion

This study highlights that poor disease knowledge among health care providers in Switzerland has led to high patient dissatisfaction, and delays in ME/CFS diagnoses and prescription of inappropriate therapies, thus adding to patient distress and disease burden.

Assessment of Hearing and Vestibular Functions in a Post-COVID-19 Patient: A Clinical Case Study

SARS-CoV-2 infection may cause such complications as post-COVID-19 syndrome, which includes chronic fatigue, myalgia, arthralgia, as well as a variety of neurological manifestations, e.g., neuropathy of small fibers, hearing and vestibular dysfunction, and cognitive impairment. This clinical case describes a 41-year-old patient suffering from post-COVID-19 syndrome and chronic fatigue syndrome. A detailed examination was performed, including an in-depth study of peripheral and central hearing and vestibular functions, as well as small nerve fibers length and density in the skin and cornea of the eye. Contrary to expectations, no peripheral nervous system dysfunction was detected, despite the presence of dizziness and gait instability in the patient. Hearing tests (gap detection test and dichotic test) showed central auditory processing disorders. The evaluated lesion in the processing of temporal and verbal auditory information can be a significant factor contributing to additional overload of the neural activity and leading to chronic fatigue when performing daily activities in patients with CFS and post-COVID-19 complications.

Muscle sodium content in patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

BACKGROUND

Muscle fatigue and pain are key symptoms of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). Although the pathophysiology is not yet fully understood, there is ample evidence for hypoperfusion which may result in electrolyte imbalance and sodium overload in muscles. Therefore, the aim of this study was to assess levels of sodium content in muscles of patients with ME/CFS and to compare these to healthy controls.

METHODS

Six female patients with ME/CFS and six age, BMI and sex matched controls underwent ²³Na-MRI of the left lower leg using a clinical 3T MR scanner before and after 3 min of plantar flexion exercise. Sodium reference phantoms with solutions of 10, 20, 30 and 40 mmol/L NaCl were used for quantification. Muscle sodium content over 40 min was measured using a dedicated plugin in the open-source DICOM viewer Horos. Handgrip strength was measured and correlated with sodium content.

RESULTS

Baseline tissue sodium content was higher in all 5 lower leg muscle compartments in ME/CFS compared to controls. Within the anterior extensor muscle compartment, the highest difference in baseline muscle sodium content between ME/CFS and controls was found (mean ± SD; 12.20 ± 1.66 mM in ME/CFS versus 9.38 ± 0.71 mM in controls, p = 0.0034). Directly after exercise, tissue sodium content increased in gastrocnemius and triceps surae muscles with + 30% in ME/CFS (p = 0.0005) and + 24% in controls (p = 0.0007) in the medial gastrocnemius muscle but not in the extensor muscles which were not exercised. Compared to baseline, the increase of sodium content in medial gastrocnemius muscle was stronger in ME/CFS than in controls with + 30% versus + 17% to baseline at 12 min (p = 0.0326) and + 29% versus + 16% to baseline at 15 min (p = 0.0265). Patients had reduced average handgrip strength which was associated with increased average muscle tissue sodium content (p = 0.0319, R² = 0.3832).

CONCLUSION

Muscle sodium content before and after exercise was higher in ME/CFS than in healthy controls. Furthermore, our findings indicate an inverse correlation between muscle sodium content and handgrip strength. These findings provide evidence that sodium overload may play a role in the pathophysiology of ME/CFS and may allow for potential therapeutic targeting.

Orthostatic Intolerance after COVID-19 Infection: Is Disturbed Microcirculation of the Vasa Vasorum of Capacitance Vessels the Primary Defect?

Following COVID-19 infection, a substantial proportion of patients suffer from persistent symptoms known as Long COVID. Among the main symptoms are fatigue, cognitive dysfunction, muscle weakness and orthostatic intolerance (OI). These symptoms also occur in myalgic encephalomyelitis/chronic fatigue (ME/CFS). OI is highly prevalent in ME/CFS and develops early during or after acute COVID-19 infection. The causes for OI are unknown and autonomic dysfunction is hypothetically assumed to be the primary cause, presumably as a consequence of neuroinflammation. Here, we propose an alternative, primary vascular mechanism as the underlying cause of OI in Long COVID. We assume that the capacitance vessel system, which plays a key role in physiologic orthostatic regulation, becomes dysfunctional due to a disturbance of the microvessels and the vasa vasorum, which supply large parts of the wall of those large vessels. We assume that the known microcirculatory disturbance found after COVID-19 infection, resulting from endothelial dysfunction, microthrombus formation and rheological disturbances of blood cells (altered deformability), also affects the vasa vasorum to impair the function of the capacitance vessels. In an attempt to compensate for the vascular deficit, sympathetic activity overshoots to further worsen OI, resulting in a vicious circle that maintains OI. The resulting orthostatic stress, in turn, plays a key role in autonomic dysfunction and the pathophysiology of ME/CFS.

Mucosal Immunity and the Gut-Microbiota-Brain-Axis in Neuroimmune Disease

Recent advances in next-generation sequencing (NGS) technologies have opened the door to a wellspring of information regarding the composition of the gut microbiota. Leveraging NGS technology, early metagenomic studies revealed that several diseases, such as Alzheimer's disease, Parkinson's disease, autism, and myalgic encephalomyelitis, are characterized by alterations in the diversity of gut-associated microbes. More recently, interest has shifted toward understanding how these microbes impact their host, with a special emphasis on their interactions with the brain. Such interactions typically occur either systemically, through the production of small molecules in the gut that are released into circulation, or through signaling via the vagus nerves which directly connect the enteric nervous system to the central nervous system. Collectively, this system of communication is now commonly referred to as the gut-microbiota-brain axis. While equally important, little attention has focused on the causes of the alterations in the composition of gut microbiota. Although several factors can contribute, mucosal immunity plays a significant role in shaping the microbiota in both healthy individuals and in association with several diseases. The purpose of this review is to provide a brief overview of the components of mucosal immunity that impact the gut microbiota and then discuss how altered immunological conditions may shape the gut microbiota and consequently affect neuroimmune diseases, using a select group of common neuroimmune diseases as examples.

Biomarkers in the diagnostic algorithm of myalgic encephalomyelitis/chronic fatigue syndrome

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex disease that is mainly diagnosed based on its clinical symptoms. Biomarkers that could facilitate the diagnosis of ME/CFS are not yet available; therefore, reliable and clinically useful disease indicators are of high importance. The aim of this work was to analyze the association between ME/CFS clinical course severity, presence of HHV-6A/B infection markers, and plasma levels of autoantibodies against adrenergic and muscarinic acetylcholine receptors. A total of 134 patients with ME/CFS and 33 healthy controls were analyzed for the presence of HHV-6A/B using PCRs, and antibodies against beta2-adrenergic receptors (β2AdR) and muscarinic acetylcholine receptors (M3 AChR and M4 AChR) using ELISAs. HHV-6A/B U3 genomic sequence in whole-blood DNA was detected in 19/31 patients with severe ME/CFS, in 18/73 moderate ME/CFS cases, and in 7/30 mild ME/CFS cases. Severity-related differences were found among those with a virus load of more than 1,000 copies/10⁶ PBMCs. Although no disease severity-related differences in anti-β2AdR levels were observed in ME/CFS patients, the median concentration of these antibodies in plasma samples of ME/CFS patients was 1.4 ng/ml, while in healthy controls, it was 0.81 ng/ml, with a statistically significant increased level in those with ME/CFS (p = 0.0103). A significant difference of antibodies against M4 AChR median concentration was found between ME/CFS patients (8.15 ng/ml) and healthy controls (6.45 ng/ml) (p = 0.0250). The levels of anti-M4 plotted against disease severity did not show any difference; however, increased viral load correlates with the increase in anti-M4 level. ME/CFS patients with high HHV-6 load have a more severe course of the disease, thus confirming that the severity of the disease depends on the viral load—the course of the disease is more severe with a higher viral load. An increase in anti-M4 AchR and anti-β2AdR levels is detected in all ME/CFS patient groups in comparison to the control group not depending on ME/CFS clinical course severity. However, the increase in HHV-6 load correlates with the increase in anti-M4 level, and the increase in anti-M4 level, in turn, is associated with the increase in anti-β2AdR level. Elevated levels of antibodies against β2AdR and M4 receptors in ME/CFS patients support their usage as clinical biomarkers in the diagnostic algorithm of ME/CFS.

Quantum tunnelling in the context of SARS-CoV-2 infection

The SARS-CoV-2 pandemic has added new urgency to the study of viral mechanisms of infection. But while vaccines offer a measure of protection against this specific outbreak, a new era of pandemics has been predicted. In addition to this, COVID-19 has drawn attention to post-viral syndromes and the healthcare burden they entail. It seems integral that knowledge of viral mechanisms is increased through as wide a research field as possible. To this end we propose that quantum biology might offer essential new insights into the problem, especially with regards to the important first step of virus-host invasion. Research in quantum biology often centres around energy or charge transfer. While this is predominantly in the context of photosynthesis there has also been some suggestion that cellular receptors such as olfactory or neural receptors might employ vibration assisted electron tunnelling to augment the lock-and-key mechanism. Quantum tunnelling has also been observed in enzyme function. Enzymes are implicated in the invasion of host cells by the SARS-CoV-2 virus. Receptors such as olfactory receptors also appear to be disrupted by COVID-19. Building on these observations we investigate the evidence that quantum tunnelling might be important in the context of infection with SARS-CoV-2. We illustrate this with a simple model relating the vibronic mode of, for example, a viral spike protein to the likelihood of charge transfer in an idealised receptor. Our results show a distinct parameter regime in which the vibronic mode of the spike protein enhances electron transfer. With this in mind, novel therapeutics to prevent SARS-CoV-2 transmission could potentially be identified by their vibrational spectra.

Dysregulated autoantibodies targeting vaso- and immunoregulatory receptors in Post COVID Syndrome correlate with symptom severity

Most patients with Post COVID Syndrome (PCS) present with a plethora of symptoms without clear evidence of organ dysfunction. A subset of them fulfills diagnostic criteria of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Symptom severity of ME/CFS correlates with natural regulatory autoantibody (AAB) levels targeting several G-protein coupled receptors (GPCR). In this exploratory study, we analyzed serum AAB levels against vaso- and immunoregulatory receptors, mostly GPCRs, in 80 PCS patients following mild-to-moderate COVID-19, with 40 of them fulfilling diagnostic criteria of ME/CFS. Healthy seronegative (n=38) and asymptomatic post COVID-19 controls (n=40) were also included in the study as control groups. We found lower levels for various AABs in PCS compared to at least one control group, accompanied by alterations in the correlations among AABs. Classification using random forest indicated AABs targeting ADRB2, STAB1, and ADRA2A as the strongest classifiers (AABs stratifying patients according to disease outcomes) of post COVID-19 outcomes. Several AABs correlated with symptom severity in PCS groups. Remarkably, severity of fatigue and vasomotor symptoms were associated with ADRB2 AAB levels in PCS/ME/CFS patients. Our study identified dysregulation of AAB against various receptors involved in the autonomous nervous system (ANS), vaso-, and immunoregulation and their correlation with symptom severity, pointing to their role in the pathogenesis of PCS.

Association of SARS-CoV-2 Seropositivity With Myalgic Encephalomyelitis and/or Chronic Fatigue Syndrome Among Children and Adolescents in Germany

IMPORTANCE

During the COVID-19 pandemic, a reduction in quality of life and physical and mental health among children and adolescents has been reported that may be associated with SARS-CoV-2 infection and/or containment measures.

OBJECTIVE

To assess the association of SARS-CoV-2 seropositivity with symptoms that may be related to myalgic encephalomyelitis and/or chronic fatigue syndrome (ME/CFS) among children and adolescents.

DESIGN, SETTING, AND PARTICIPANTS

This substudy of the cross-sectional SARS-CoV-2 seroprevalence surveys in Germany (SARS-CoV-2 KIDS) was performed in 9 pediatric hospitals from May 1 to October 31, 2021. Pediatric patients were recruited during an inpatient or outpatient visit regardless of the purpose of the visit. Parental questionnaires and serum samples were collected during clinically indicated blood draws. The parental questionnaire on demographic and clinical information was extended by items according to the DePaul Symptom Questionnaire, a pediatric screening tool for ME/CFS in epidemiological studies in patients aged 5 to 17 years.

EXPOSURES

Seropositivity was determined by SARS-CoV-2 IgG antibodies in serum samples using enzyme-linked immunosorbent assays.

MAIN OUTCOMES AND MEASURES

Key symptoms of ME/CFS were evaluated separately or as clustered ME/CFS symptoms according to the DePaul Symptom Questionnaire, including fatigue.

RESULTS

Among 634 participants (294 male [46.4%] and 340 female [53.6%]; median age, 11.5 [IQR, 8-14] years), 198 (31.2%) reported clustered ME/CFS symptoms, including 40 of 100 SARS-CoV-2-seropositive (40.0%) and 158 of 534 SARS-CoV-2-seronegative (29.6%) children and adolescents. After adjustment for sex, age group, and preexisting disease, the risk ratio for reporting clustered ME/CFS symptoms decreased from 1.35 (95% CI, 1.03-1.78) to 1.18 (95% CI, 0.90-1.53) and for substantial fatigue from 2.45 (95% CI, 1.24-4.84) to 2.08 (95% CI, 1.05-4.13). Confinement to children and adolescents with unknown previous SARS-CoV-2 infection status (n = 610) yielded lower adjusted risks for all symptoms except joint pain ME/CFS-related symptoms. The adjusted risk ratio was 1.08 (95% CI, 0.80-1.46) for reporting clustered ME/CFS symptoms and 1.43 (95% CI, 0.63-3.23) for fatigue.

CONCLUSIONS AND RELEVANCE

These findings suggest that the risk of ME/CFS in children and adolescents owing to SARS-CoV-2 infection may be very small. Recall bias may contribute to risk estimates of long COVID-19 symptoms in children. Extensive lockdowns must be considered as an alternative explanation for complex unspecific symptoms during the COVID-19 pandemic.

Analysis of post COVID-19 condition and its overlap with myalgic encephalomyelitis/chronic fatigue syndrome

BACKGROUND

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) disease (COVID-19) triggers the development of numerous pathologies and infection-linked complications and exacerbates existing pathologies in nearly all body systems. Aside from the primarily targeted respiratory organs, adverse SARS-CoV-2 effects were observed in nervous, cardiovascular, gastrointestinal/metabolic, immune, and other systems in COVID-19 survivors. Long-term effects of this viral infection have been recently observed and represent distressing sequelae recognised by the World Health Organisation (WHO) as a distinct clinical entity defined as post-COVID-19 condition. Considering the pandemic is still ongoing, more time is required to confirm post COVID-19 condition diagnosis in the COVID-19 infected cohorts, although many reported post COVID-19 symptoms overlap with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).

AIMS OF REVIEW

In this study, COVID-19 clinical presentation and associated post-infection sequelae (post-COVID-19 condition) were reviewed and compared with ME/CFS symptomatology.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The onset, progression, and symptom profile of post COVID-19 condition patients have considerable overlap with ME/CFS. Considering the large scope and range of pro-inflammatory effects of this virus, it is reasonable to expect development of post COVID-19 clinical complications in a proportion of the affected population. There are reports of a later debilitating syndrome onset three months post COVID-19 infection (often described as long-COVID-19), marked by the presence of fatigue, headache, cognitive dysfunction, post-exertional malaise, orthostatic intolerance, and dyspnoea. Acute inflammation, oxidative stress, and increased levels of interleukin-6 (IL-6) and tumor necrosis factor α (TNFα), have been reported in SARS-CoV-2 infected patients. Longitudinal monitoring of post COVID-19 patients is warranted to understand the long-term effects of SARS-CoV-2 infection and the pathomechanism of post COVID-19 condition.

A prospective observational study of post-COVID-19 chronic fatigue syndrome following the first pandemic wave in Germany and biomarkers associated with symptom severity

A subset of patients has long-lasting symptoms after mild to moderate Coronavirus disease 2019 (COVID-19). In a prospective observational cohort study, we analyze clinical and laboratory parameters in 42 post-COVID-19 syndrome patients (29 female/13 male, median age 36.5 years) with persistent moderate to severe fatigue and exertion intolerance six months following COVID-19. Further we evaluate an age- and sex-matched postinfectious non-COVID-19 myalgic encephalomyelitis/chronic fatigue syndrome cohort comparatively. Most post-COVID-19 syndrome patients are moderately to severely impaired in daily live. 19 post-COVID-19 syndrome patients fulfill the 2003 Canadian Consensus Criteria for myalgic encephalomyelitis/chronic fatigue syndrome. Disease severity and symptom burden is similar in post-COVID-19 syndrome/myalgic encephalomyelitis/chronic fatigue syndrome and non-COVID-19/myalgic encephalomyelitis/chronic fatigue syndrome patients. Hand grip strength is diminished in most patients compared to normal values in healthy. Association of hand grip strength with hemoglobin, interleukin 8 and C-reactive protein in post-COVID-19 syndrome/non-myalgic encephalomyelitis/chronic fatigue syndrome and with hemoglobin, N-terminal prohormone of brain natriuretic peptide, bilirubin, and ferritin in post-COVID-19 syndrome/myalgic encephalomyelitis/chronic fatigue syndrome may indicate low level inflammation and hypoperfusion as potential pathomechanisms.

Phenotypic characteristics of peripheral immune cells of Myalgic encephalomyelitis/chronic fatigue syndrome via transmission electron microscopy: A pilot study

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex chronic multi-systemic disease characterized by extreme fatigue that is not improved by rest, and worsens after exertion, whether physical or mental. Previous studies have shown ME/CFS-associated alterations in the immune system and mitochondria. We used transmission electron microscopy (TEM) to investigate the morphology and ultrastructure of unstimulated and stimulated ME/CFS immune cells and their intracellular organelles, including mitochondria. PBMCs from four participants were studied: a pair of identical twins discordant for moderate ME/CFS, as well as two age- and gender- matched unrelated subjects-one with an extremely severe form of ME/CFS and the other healthy. TEM analysis of CD3/CD28-stimulated T cells suggested a significant increase in the levels of apoptotic and necrotic cell death in T cells from ME/CFS patients (over 2-fold). Stimulated Tcells of ME/CFS patients also had higher numbers of swollen mitochondria. We also found a large increase in intracellular giant lipid droplet-like organelles in the stimulated PBMCs from the extremely severe ME/CFS patient potentially indicative of a lipid storage disorder. Lastly, we observed a slight increase in platelet aggregation in stimulated cells, suggestive of a possible role of platelet activity in ME/CFS pathophysiology and disease severity. These results indicate extensive morphological alterations in the cellular and mitochondrial phenotypes of ME/CFS patients' immune cells and suggest new insights into ME/CFS biology.