Unravelling shared mechanisms: insights from recent ME/CFS research to illuminate long COVID pathologies

Abstract:

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating chronic illness often triggered by an initiating acute event, mainly viral infections. The transition from acute to chronic disease remains unknown, but interest in this phenomenon has escalated since the COVID-19 pandemic and the post-COVID-19 illness, termed ‘long COVID’ (LC). Both ME/CFS and LC share many clinical similarities.

Here, we present recent findings in ME/CFS research focussing on proposed disease pathologies shared with LC. Understanding these disease pathologies and how they influence each other is key to developing effective therapeutics and diagnostic tests. Given that ME/CFS typically has a longer disease duration compared with LC, with symptoms and pathologies evolving over time, ME/CFS may provide insights into the future progression of LC.

Source: Annesley SJ, Missailidis D, Heng B, Josev EK, Armstrong CW. Unravelling shared mechanisms: insights from recent ME/CFS research to illuminate long COVID pathologies. Trends Mol Med. 2024 Mar 4:S1471-4914(24)00028-5. doi: 10.1016/j.molmed.2024.02.003. Epub ahead of print. PMID: 38443223. https://www.sciencedirect.com/science/article/pii/S1471491424000285 (Full text)

Ebbing Strength, Fading Power: Unveiling the Impact of Persistent Fatigue on Muscle Performance in COVID-19 Survivors

Abstract:

The total number of confirmed cases of COVID-19 caused by SARS-CoV-2 virus infection is over 621 million. Post-COVID-19 syndrome, also known as long COVID or long-haul COVID, refers to a persistent condition where individuals experience symptoms and health issues after the acute phase of COVID-19.

The aim of this study was to assess the strength and fatigue of skeletal muscles in people recovered from COVID-19. A total of 94 individuals took part in this cross-sectional study, with 45 participants (referred to as the Post-COVID Cohort, PCC) and 49 healthy age-matched volunteers (Healthy Control Cohort, HCC).

This research article uses the direct dynamometry method to provide a detailed analysis of post-COVID survivors’ strength and power characteristics. The Biodex System 4 Pro was utilized to evaluate muscle strength characteristics during the fatigue test. The fatigue work in extensors and flexors was significantly higher in the PCC.  The PCC also showed significantly less power in both extensors and flexors compared to the HCC.

In conclusion, this study provides compelling evidence of the impact of post-COVID-19 fatigue on muscle performance, highlighting the importance of considering these effects in the rehabilitation and care of individuals recovering from the virus. PCC achieved lower muscle strength values than HCC.

Source: Kowal M, Morgiel E, Winiarski S, Dymarek R, Bajer W, Madej M, Sebastian A, Madziarski M, Wedel N, Proc K, Madziarska K, Wiland P, Paprocka-Borowicz M. Ebbing Strength, Fading Power: Unveiling the Impact of Persistent Fatigue on Muscle Performance in COVID-19 Survivors. Sensors (Basel). 2024 Feb 15;24(4):1250. doi: 10.3390/s24041250. PMID: 38400407; PMCID: PMC10892381. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10892381/ (Full text)

Sex differences in symptomatology and immune profiles of Long COVID

Abstract:

Strong sex differences in the frequencies and manifestations of Long COVID (LC) have been reported with females significantly more likely than males to present with LC after acute SARS-CoV-2 infection1-7. However, whether immunological traits underlying LC differ between sexes, and whether such differences explain the differential manifestations of LC symptomology is currently unknown.

Here, we performed sex-based multi-dimensional immune-endocrine profiling of 165 individuals8 with and without LC in an exploratory, cross-sectional study to identify key immunological traits underlying biological sex differences in LC.

We found that female and male participants with LC experienced different sets of symptoms, and distinct patterns of organ system involvement, with female participants suffering from a higher symptom burden. Machine learning approaches identified differential sets of immune features that characterized LC in females and males. Males with LC had decreased frequencies of monocyte and DC populations, elevated NK cells, and plasma cytokines including IL-8 and TGF-β-family members.

Females with LC had increased frequencies of exhausted T cells, cytokine-secreting T cells, higher antibody reactivity to latent herpes viruses including EBV, HSV-2, and CMV, and lower testosterone levels than their control female counterparts. Testosterone levels were significantly associated with lower symptom burden in LC participants over sex designation.

These findings suggest distinct immunological processes of LC in females and males and illuminate the crucial role of immune-endocrine dysregulation in sex-specific pathology.

Source: Julio Silva, Takehiro Takahashi, Jamie Wood, Peiwen Lu, Sasha Tabachnikova, Jeffrey Gehlhausen, Kerrie Greene, Bornali Bhattacharjee, Valter Silva Monteiro, Carolina Lucas, Rahul Dhodapkar, Laura Tabacof, Mario Pena-Hernandez, Kathy Kamath, Tianyang Mao, Dayna Mccarthy, Ruslan Medzhitov, David van Dijk, Harlan Krumholz, Leying Guan, David Putrino, Akiko Iwasaki. Sex differences in symptomatology and immune profiles of Long COVID. medRxiv 2024.02.29.24303568; doi: https://doi.org/10.1101/2024.02.29.24303568 https://www.medrxiv.org/content/10.1101/2024.02.29.24303568v1 (Full study available as PDF file)

Cognition and Memory after Covid-19 in a Large Community Sample

Abstract:

Background: Cognitive symptoms after coronavirus disease 2019 (Covid-19), the disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), are well-recognized. Whether objectively measurable cognitive deficits exist and how long they persist are unclear.

Methods: We invited 800,000 adults in a study in England to complete an online assessment of cognitive function. We estimated a global cognitive score across eight tasks. We hypothesized that participants with persistent symptoms (lasting ≥12 weeks) after infection onset would have objectively measurable global cognitive deficits and that impairments in executive functioning and memory would be observed in such participants, especially in those who reported recent poor memory or difficulty thinking or concentrating (“brain fog”).

Results: Of the 141,583 participants who started the online cognitive assessment, 112,964 completed it. In a multiple regression analysis, participants who had recovered from Covid-19 in whom symptoms had resolved in less than 4 weeks or at least 12 weeks had similar small deficits in global cognition as compared with those in the no-Covid-19 group, who had not been infected with SARS-CoV-2 or had unconfirmed infection (-0.23 SD [95% confidence interval {CI}, -0.33 to -0.13] and -0.24 SD [95% CI, -0.36 to -0.12], respectively); larger deficits as compared with the no-Covid-19 group were seen in participants with unresolved persistent symptoms (-0.42 SD; 95% CI, -0.53 to -0.31). Larger deficits were seen in participants who had SARS-CoV-2 infection during periods in which the original virus or the B.1.1.7 variant was predominant than in those infected with later variants (e.g., -0.17 SD for the B.1.1.7 variant vs. the B.1.1.529 variant; 95% CI, -0.20 to -0.13) and in participants who had been hospitalized than in those who had not been hospitalized (e.g., intensive care unit admission, -0.35 SD; 95% CI, -0.49 to -0.20). Results of the analyses were similar to those of propensity-score-matching analyses. In a comparison of the group that had unresolved persistent symptoms with the no-Covid-19 group, memory, reasoning, and executive function tasks were associated with the largest deficits (-0.33 to -0.20 SD); these tasks correlated weakly with recent symptoms, including poor memory and brain fog. No adverse events were reported.

Conclusions: Participants with resolved persistent symptoms after Covid-19 had objectively measured cognitive function similar to that in participants with shorter-duration symptoms, although short-duration Covid-19 was still associated with small cognitive deficits after recovery. Longer-term persistence of cognitive deficits and any clinical implications remain uncertain. (Funded by the National Institute for Health and Care Research and others.).

Source: Hampshire A, Azor A, Atchison C, Trender W, Hellyer PJ, Giunchiglia V, Husain M, Cooke GS, Cooper E, Lound A, Donnelly CA, Chadeau-Hyam M, Ward H, Elliott P. Cognition and Memory after Covid-19 in a Large Community Sample. N Engl J Med. 2024 Feb 29;390(9):806-818. doi: 10.1056/NEJMoa2311330. PMID: 38416429. https://www.nejm.org/doi/10.1056/NEJMoa2311330 (Full text)

Severe COVID-19 and long COVID are associated with high expression of STING, cGAS and IFN-α

Abstract:

The cGAS-STING pathway appears to contribute to dysregulated inflammation during coronavirus disease 2019 (COVID-19); however, inflammatory factors related to long COVID are still being investigated.

In the present study, we evaluated the association of cGAS and STING gene expression levels and plasma IFN-α, TNF-α and IL-6 levels with COVID-19 severity in acute infection and long COVID, based on analysis of blood samples from 148 individuals, 87 with acute COVID-19 and 61 in the post-COVID-19 period.

Quantification of gene expression was performed by real-time PCR, and cytokine levels were quantified by ELISA and flow cytometry. In acute COVID-19, cGASSTING, IFN-α, TNF-α, and IL-6 levels were higher in patients with severe disease than in those with nonsevere manifestations (p < 0.05). Long COVID was associated with elevated cGASSTING and IFN-α levels (p < 0.05).

Activation of the cGAS-STING pathway may contribute to an intense systemic inflammatory state in severe COVID-19 and, after infection resolution, induce an autoinflammatory disease in some tissues, resulting in long COVID.

Source: Queiroz, M.A.F., Brito, W.R.S., Pereira, K.A.S. et al. Severe COVID-19 and long COVID are associated with high expression of STINGcGAS and IFN-α. Sci Rep 14, 4974 (2024). https://doi.org/10.1038/s41598-024-55696-0 https://www.nature.com/articles/s41598-024-55696-0 (Full text)

Spontaneous, persistent, T cell-dependent IFN-γ release in patients who progress to Long Covid

Abstract:

After acute infection with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), a proportion of patients experience persistent symptoms beyond 12 weeks, termed Long Covid. Understanding the mechanisms that cause this debilitating disease and identifying biomarkers for diagnostic, therapeutic, and monitoring purposes are urgently required.

We detected persistently high levels of interferon-γ (IFN-γ) from peripheral blood mononuclear cells of patients with Long Covid using highly sensitive FluoroSpot assays. This IFN-γ release was seen in the absence of ex vivo peptide stimulation and remains persistently elevated in patients with Long Covid, unlike the resolution seen in patients recovering from acute SARS-CoV-2 infection. The IFN-γ release was CD8+ T cell-mediated and dependent on antigen presentation by CD14+ cells.

Longitudinal follow-up of our study cohort showed that symptom improvement and resolution correlated with a decrease in IFN-γ production to baseline levels. Our study highlights a potential mechanism underlying Long Covid, enabling the search for biomarkers and therapeutics in patients with Long Covid.

Source: Krishna BA, Lim EY, Metaxaki M, Jackson S, Mactavous L; NIHR BioResource; Lyons PA, Doffinger R, Bradley JR, Smith KGC, Sinclair J, Matheson NJ, Lehner PJ, Sithole N, Wills MR. Spontaneous, persistent, T cell-dependent IFN-γ release in patients who progress to Long Covid. Sci Adv. 2024 Feb 23;10(8):eadi9379. doi: 10.1126/sciadv.adi9379. Epub 2024 Feb 21. PMID: 38381822; PMCID: PMC10881041. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10881041/ (Full text)

Cognitive domains affected post-COVID-19; a systematic review and meta-analysis

Abstract:

Background and purpose: This review aims to characterize the pattern of post-COVID-19 cognitive impairment, allowing better prediction of impact on daily function to inform clinical management and rehabilitation.

Methods: A systematic review and meta-analysis of neurocognitive sequelae following COVID-19 was conducted, following PRISMA-S guidelines. Studies were included if they reported domain-specific cognitive assessment in patients with COVID-19 at >4 weeks post-infection. Studies were deemed high-quality if they had >40 participants, utilized healthy controls, had low attrition rates and mitigated for confounders.

Results: Five of the seven primary Diagnostic and Statistical Manual of Mental Disorders (DSM-5) cognitive domains were assessed by enough high-quality studies to facilitate meta-analysis. Medium effect sizes indicating impairment in patients post-COVID-19 versus controls were seen across executive function (standardised mean difference (SMD) -0.45), learning and memory (SMD -0.55), complex attention (SMD -0.54) and language (SMD -0.54), with perceptual motor function appearing to be impacted to a greater degree (SMD -0.70). A narrative synthesis of the 56 low-quality studies also suggested no obvious pattern of impairment.

Conclusions: This review found moderate impairments across multiple domains of cognition in patients post-COVID-19, with no specific pattern. The reported literature was significantly heterogeneous, with a wide variety of cognitive tasks, small sample sizes and disparate initial disease severities limiting interpretability. The finding of consistent impairment across a range of cognitive tasks suggests broad, as opposed to domain-specific, brain dysfunction. Future studies should utilize a harmonized test battery to facilitate inter-study comparisons, whilst also accounting for the interactions between COVID-19, neurological sequelae and mental health, the interplay between which might explain cognitive impairment.

Source: Fanshawe JB, Sargent BF, Badenoch JB, Saini A, Watson CJ, Pokrovskaya A, Aniwattanapong D, Conti I, Nye C, Burchill E, Hussain ZU, Said K, Kuhoga E, Tharmaratnam K, Pendered S, Mbwele B, Taquet M, Wood GK, Rogers JP, Hampshire A, Carson A, David AS, Michael BD, Nicholson TR, Paddick SM, Leek CE. Cognitive domains affected post-COVID-19; a systematic review and meta-analysis. Eur J Neurol. 2024 Feb 20:e16181. doi: 10.1111/ene.16181. Epub ahead of print. PMID: 38375608. https://onlinelibrary.wiley.com/doi/10.1111/ene.16181 (Full text)

Impact of sleep disruption on cognitive function in patients with postacute sequelae of SARS-CoV-2 infection: initial findings from a Neuro-COVID-19 clinic

Abstract:

Introduction: Fatigue, brain fog, and sleep disturbance are among the most common symptoms of postacute sequelae of SARS-CoV-2 infection (PASC). We sought to determine the impact of sleep disruption on cognition and quality of life in patients with neurologic manifestations of PASC (Neuro-PASC).
Methods: Thirty-nine patients were recruited from Neuro-COVID-19 clinic. Mean age was 48.1 years, 71.8% were female, and 82% were never hospitalized for COVID-19. Patients were evaluated via clinical assessment, quality-of-life measures in domains of cognitive function, fatigue, sleep disturbance, anxiety, and depression, NIH Toolbox cognitive tests, and 7 days of wrist actigraphy.
Results: The median number of neurologic symptoms attributed to PASC was 6, with brain fog being the most common in 89.7%. Regarding non-neurologic symptoms, 94.9% complained of fatigue and 74.4% of insomnia. Patients reported significant impairment in all quality-of-life domains and performed worse in a task of attention compared to a normative US population. Actigraphy showed Neuro-PASC patients had lower sleep efficiency, longer sleep latency (both p < 0.001), and later sleep midpoint (p = 0.039) compared to 71 age-matched healthy controls with no PASC history. Self-reported cognitive symptoms correlated with the severity of fatigue (p < 0.001), anxiety (p = 0.05), and depression (p < 0.01). Objective evidence of sleep disruption measured by wakefulness after sleep onset, sleep efficiency, and latency were associated with decreased performance in attention and processing speed.
Conclusion: Prospective studies including larger populations of patients are needed to fully determine the interplay of sleep disruption on the cognitive function and quality of life of patients with PASC.

Source: Kathryn J Reid, Louis T Ingram, Millenia Jimenez, Zachary S Orban, Sabra M Abbott, Daniela Grimaldi, Kristen L Knutson, Phyllis C Zee, Igor J Koralnik, Mathew B Maas, Impact of sleep disruption on cognitive function in patients with postacute sequelae of SARS-CoV-2 infection: initial findings from a Neuro-COVID-19 clinic, SLEEP Advances, Volume 5, Issue 1, 2024, zpae002, https://doi.org/10.1093/sleepadvances/zpae002 https://academic.oup.com/sleepadvances/article/5/1/zpae002/7517273 (Full text)

People with Long Covid and ME/CFS Exhibit Similarly Impaired Dexterity and Bimanual Coordination: A Case-Case-Control Study

Abstract:

Purpose: Dexterity and bimanual coordination had not previously been compared between people with long COVID and people with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). Therefore, this study determined dexterity and bimanual coordination in people with long COVID (∼16 month illness duration; n=21) and ME/CFS (∼16 year illness duration; n=20), versus age-matched healthy controls (n=20).

Methods: Dexterity, and bimanual coordination was determined using the Purdue pegboard test.

Results: The main findings of the present investigation were that people with ME/CFS and people with long COVID were generally comparable for Purdue pegboard tests (p>0.556 and d<0.36 for pairwise comparisons). It is worth noting however, that both these patient groups performed poorer in the Perdue pegboard test than healthy controls (p<0.169 and d>0.40 for pairwise comparisons).

Conclusions: These data suggest that both people with long COVID and people with ME/CFS have similarly impaired dexterity, and bimanual coordination. Therefore, there is an urgent need for interventions to target dexterity and bimanual coordination in people with ME/CFS, and given the current pandemic, people with long COVID.

Source: Sanal-Hayes NEM, Hayes LD, Mclaughlin M, Berry ECJ, Sculthorpe NF. People with Long Covid and ME/CFS Exhibit Similarly Impaired Dexterity and Bimanual Coordination: A Case-Case-Control Study. Am J Med. 2024 Feb 23:S0002-9343(24)00091-3. doi: 10.1016/j.amjmed.2024.02.003. Epub ahead of print. PMID: 38403179. https://www.amjmed.com/article/S0002-9343(24)00091-3/fulltext (Full text)

Navigating the Spectrum of Two Pediatric COVID-19 Complications: Multi-System Inflammatory Syndrome in Children and Post-Acute Sequelae of SARS-CoV-2 Infection

Abstract:

Purpose: This review summarizes the current scope of understanding associated with two common post-infectious complications associated with COVID-19 infection: Multi-System Inflammatory Syndrome in Children (MIS-C) and Post-Acute Sequelae of SARS-CoV-2 infection (PASC). It identifies current gaps in the knowledge and issues that may limit the ability to fill these gaps. This review provides a framework to drive continued research.

Methods: A comprehensive review of the current literature was performed, identifying seminal articles describing the emergence of MIS-C and PASC, and works from the literature focused on the clinical implications and pathophysiologic understanding of these disorders.

Findings: Although pediatric patients experienced few severe cases of acute COVID-19 infection, the burden of disease from post-infectious sequelae is substantial. Mortality is low, but morbidity is significant. There are still numerous unknowns about the pathophysiology of both MIS-C and PASC; however, with widespread immunity developing after increased vaccination and prior infection, it may be difficult to perform adequate prospective studies to answer pathophysiologic questions. Long-term sequalae of MIS-C seem to be minimal whereas, by definition, PASC is an ongoing problem and may be severe.

Implications: The rapid sharing of information regarding novel conditions such as MIS-C and PASC are key to interventions related to future post-infectious sequelae outside of those stemming from COVID-19. Although MIS-C seems unlikely to return as a clinical condition in substantial numbers, there is still significant learning that can be gleaned from existing patients about general aspects of epidemiology, equity, and pathophysiology. There is significant morbidity associated with PASC and additional resources need to be dedicated to determining appropriate and effective therapies moving forward.

Source: Parzen-Johnson S, Katz BZ. Navigating the Spectrum of Two Pediatric COVID-19 Complications: Multi-System Inflammatory Syndrome in Children and Post-Acute Sequelae of SARS-CoV-2 Infection. J Clin Med. 2024 Feb 18;13(4):1147. doi: 10.3390/jcm13041147. PMID: 38398460. https://www.mdpi.com/2077-0383/13/4/1147 (Full text)