platelets – Page 2 – American ME and CFS Society

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

Abstract:

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.

Source: Jean M. Nunes, Douglas B. Kell, Etheresia Pretorius. Cardiovascular and haematological pathology in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS): A role for viruses. Blood reviews, 20 March 2023, 101075 [Epub ahead of print] https://www.sciencedirect.com/science/article/pii/S0268960X2300036X (Full text)

Organ and cell-specific biomarkers of Long-COVID identified with targeted proteomics and machine learning

Abstract:

Background: Survivors of acute COVID-19 often suffer prolonged, diffuse symptoms post-infection, referred to as “Long-COVID”. A lack of Long-COVID biomarkers and pathophysiological mechanisms limits effective diagnosis, treatment and disease surveillance. We performed targeted proteomics and machine learning analyses to identify novel blood biomarkers of Long-COVID.

Methods: A case-control study comparing the expression of 2925 unique blood proteins in Long-COVID outpatients versus COVID-19 inpatients and healthy control subjects. Targeted proteomics was accomplished with proximity extension assays, and machine learning was used to identify the most important proteins for identifying Long-COVID patients. Organ system and cell type expression patterns were identified with Natural Language Processing (NLP) of the UniProt Knowledgebase.

Results: Machine learning analysis identified 119 relevant proteins for differentiating Long-COVID outpatients (Bonferonni corrected P < 0.01). Protein combinations were narrowed down to two optimal models, with nine and five proteins each, and with both having excellent sensitivity and specificity for Long-COVID status (AUC = 1.00, F1 = 1.00). NLP expression analysis highlighted the diffuse organ system involvement in Long-COVID, as well as the involved cell types, including leukocytes and platelets, as key components associated with Long-COVID.

Conclusions: Proteomic analysis of plasma from Long-COVID patients identified 119 highly relevant proteins and two optimal models with nine and five proteins, respectively. The identified proteins reflected widespread organ and cell type expression. Optimal protein models, as well as individual proteins, hold the potential for accurate diagnosis of Long-COVID and targeted therapeutics.

Source: Patel MA, Knauer MJ, Nicholson M, Daley M, Van Nynatten LR, Cepinskas G, Fraser DD. Organ and cell-specific biomarkers of Long-COVID identified with targeted proteomics and machine learning. Mol Med. 2023 Feb 21;29(1):26. doi: 10.1186/s10020-023-00610-z. PMID: 36809921; PMCID: PMC9942653. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9942653/ (Full text)

Vascular “Long COVID”: A New Vessel Disease?

Abstract:

In medium/large-sized vessels, this corresponds to endothelial dysfunction, leading to an accelerated progression of pre-existing atherosclerotic plaques through an increased deposition of platelets, circulating inflammatory cells and proteins. Associated dysregulated immune and pro-coagulant conditions can directly cause thrombo-embolic arterial or venous complications. In order to implement appropriate treatment, physicians need to consider vascular pathologies observed after SARS-Cov-2 infections as possible “LC” disease.

Source: Zanini G, Selleri V, Roncati L, Coppi F, Nasi M, Farinetti A, Manenti A, Pinti M, Mattioli AV. Vascular “Long COVID”: A New Vessel Disease? Angiology. 2023 Jan 18:33197231153204. doi: 10.1177/00033197231153204. Epub ahead of print. PMID: 36652923. https://pubmed.ncbi.nlm.nih.gov/36652923/

Vascular “Long COVID”: A New Vessel Disease?

Abstract:

Vascular sequelae following (SARS-CoV-2 coronavirus disease) (COVID)-19 infection are considered as “Long Covid (LC)” disease, when occurring 12 weeks after the original infection. The paucity of specific data can be obviated by translating pathophysiological elements from the original Severe Acute Respiratory Syndrome-Corona Virus (SARS-CoV-2) infection (In a microcirculatory system, a first “endotheliitis,” is often followed by production of “Neutrophil Extracellular Trap,” and can evolve into a more complex leukocytoklastic-like and hyperimmune vasculitis. In medium/large-sized vessels, this corresponds to endothelial dysfunction, leading to an accelerated progression of pre-existing atherosclerotic plaques through an increased deposition of platelets, circulating inflammatory cells and proteins. Associated dysregulated immune and pro-coagulant conditions can directly cause thrombo-embolic arterial or venous complications. In order to implement appropriate treatment, physicians need to consider vascular pathologies observed after SARS-Cov-2 infections as possible “LC” disease.

Transcriptional reprogramming from innate immune functions to a pro-thrombotic signature by monocytes in COVID-19

Abstract:

Although alterations in myeloid cells have been observed in COVID-19, the specific underlying mechanisms are not completely understood. Here, we examine the function of classical CD14⁺ monocytes in patients with mild and moderate COVID-19 during the acute phase of infection and in healthy individuals.

Monocytes from COVID-19 patients display altered expression of cell surface receptors and a dysfunctional metabolic profile that distinguish them from healthy monocytes. Secondary pathogen sensing ex vivo leads to defects in pro-inflammatory cytokine and type-I IFN production in moderate COVID-19 cases, together with defects in glycolysis.

COVID-19 monocytes switch their gene expression profile from canonical innate immune to pro-thrombotic signatures and are functionally pro-thrombotic, both at baseline and following ex vivo stimulation with SARS-CoV-2. Transcriptionally, COVID-19 monocytes are characterized by enrichment of pathways involved in hemostasis, immunothrombosis, platelet aggregation and other accessory pathways to platelet activation and clot formation. These results identify a potential mechanism by which monocyte dysfunction may contribute to COVID-19 pathology.

Source: Maher AK, Burnham KL, Jones EM, Tan MMH, Saputil RC, Baillon L, Selck C, Giang N, Argüello R, Pillay C, Thorley E, Short CE, Quinlan R, Barclay WS, Cooper N, Taylor GP, Davenport EE, Dominguez-Villar M. Transcriptional reprogramming from innate immune functions to a pro-thrombotic signature by monocytes in COVID-19. Nat Commun. 2022 Dec 26;13(1):7947. doi: 10.1038/s41467-022-35638-y. PMID: 36572683; PMCID: PMC9791976. https://www.nature.com/articles/s41467-022-35638-y (Full text)

Clinical and laboratory predictors of long-COVID in children: a single center retrospective study

Abstract:

Objective: The majority of children experience a mild course of acute Coronavirus Disease 2019 (COVID-19). Only few studies have looked at long-term recovery from COVID-19 infection in children. The purpose of this study was to identify the predictors of long-COVID by performing a thorough analysis of the clinical, laboratory, and demographic characteristics of children with COVID-19.

Patients and methods: Between August and October 2021, data were obtained retrospectively from the medical records of 251 children diagnosed with COVID-19 at a tertiary single-center hospital. The prognostic effects of admission-related factors were compared between patients who experienced long-lasting symptoms and those who did not.

Results: Long-COVID symptoms were noted in 12.4% of patients. Joint pain (7.6%), lumbago (4.8%), and headache (3.2%) were the most common symptoms. The mean onset of long-COVID symptoms was 1.35±0.49 months. The onset of long-COVID symptoms was 4 weeks after initial diagnosis in 64.5% of patients and 4-8 weeks later in 35.5% of the patients. The mean duration of long-COVID symptoms was 5.32±2.51 months. Children with long-COVID had higher leukocytes, neutrophils, monocytes, basophils, platelets, and D-dimer when compared with patients without long-COVID (p < 0.001). Leukocytes, neutrophils, monocytes, platelets, and D-dimer had the highest AUC in the ROC analysis (0.694, 0.658, 0.681, 0.667, and 0.612, respectively) and were statistically significant.

Conclusions: Despite the majority of children with COVID-19 having mild or asymptomatic acute disease, the majority of long-COVID symptoms were associated with functional impairment between 1 and 9 months after the start of the infection. Increased leukocytes, monocytes, neutrophils, platelets, and D-dimer appear to be the most powerful laboratory predictors for long-COVID and monitoring these predictors may assist clinicians to identify and follow-up patients with higher risk for long-COVID.

Source: Güven D, Buluş AD. Clinical and laboratory predictors of long-COVID in children: a single center retrospective study. Eur Rev Med Pharmacol Sci. 2022 Oct;26(20):7695-7704. doi: 10.26355/eurrev_202210_30046. PMID: 36314341. https://www.europeanreview.org/article/30046 (Full text)

Single-cell transcriptomics of the immune system in ME/CFS at baseline and following symptom provocation

Summary:

ME/CFS is a serious and poorly understood disease. To understand immune dysregulation in ME/CFS, we used single-cell RNA-seq (scRNA-seq) to examine immune cells in cohorts of patients and controls. Post-exertional malaise (PEM), an exacerbation of symptoms following strenuous exercise, is a characteristic symptom of ME/CFS. Thus, to detect changes coincident with PEM, we also performed scRNA-seq on the same cohorts following exercise. At baseline, ME/CFS patients displayed dysregulation of classical monocytes suggestive of inappropriate differentiation and migration to tissue. We were able to identify both diseased and more normal monocytes within patients, and the fraction of diseased cells correlated with metrics of disease severity. Comparing the transcriptome at baseline and post-exercise challenge, we discovered patterns indicative of improper platelet activation in patients, with minimal changes elsewhere in the immune system. Taken together, these data identify immunological defects present at baseline in patients and an additional layer of dysregulation following exercise.

Highlights ME/CFS is a debilitating disease with unknown causes. Here, we provide, for the first time, an extensive single cell resolution dataset detailing the gene expression programs of circulating immune cells of ME/CFS cases at baseline and after symptom provocation. We were able to detect robust dysregulation in certain immune cells from patients, with dysregulation of classical monocytes manifesting the strongest signal. Indeed, the fraction of aberrant monocytes in ME/CFS patients correlated with the degree of disease severity. Surprisingly, platelet transcriptomes were also altered in ME/CFS, and they were the only component of the immune system that showed large-scale changes following symptom provocation.

Source: Faraz Ahmed, Luyen Tien Vu, Hongya Zhu, David Shing Huk Iu, Elizabeth A. Fogarty, Yeonui Kwak, Weizhong Chen, Carl J. Franconi, Paul R. Munn, Susan M. Levine, Jared Stevens, Xiangling Mao, Dikoma C. Shungu, Geoffrey E. Moore, Betsy A. Keller, Maureen R. Hanson, Jennifer K. Grenier, Andrew Grimson. Single-cell transcriptomics of the immune system in ME/CFS at baseline and following symptom provocation. bioRxiv 2022.10.13.512091; doi: https://doi.org/10.1101/2022.10.13.512091 https://www.cell.com/cell-reports-medicine/fulltext/S2666-3791(23)00602-X (Full text)

Prevalence of symptoms, comorbidities, fibrin amyloid microclots and platelet pathology in individuals with Long COVID/Post-Acute Sequelae of COVID-19 (PASC)

Abstract:

Background: Fibrin(ogen) amyloid microclots and platelet hyperactivation previously reported as a novel finding in South African patients with the coronavirus 2019 disease (COVID-19) and Long COVID/Post-Acute Sequelae of COVID-19 (PASC), might form a suitable set of foci for the clinical treatment of the symptoms of Long COVID/PASC. A Long COVID/PASC Registry was subsequently established as an online platform where patients can report Long COVID/PASC symptoms and previous comorbidities.

Methods: In this study, we report on the comorbidities and persistent symptoms, using data obtained from 845 South African Long COVID/PASC patients. By using a previously published scoring system for fibrin amyloid microclots and platelet pathology, we also analysed blood samples from 80 patients, and report the presence of significant fibrin amyloid microclots and platelet pathology in all cases.

Results: Hypertension, high cholesterol levels (dyslipidaemia), cardiovascular disease and type 2 diabetes mellitus (T2DM) were found to be the most important comorbidities. The gender balance (70% female) and the most commonly reported Long COVID/PASC symptoms (fatigue, brain fog, loss of concentration and forgetfulness, shortness of breath, as well as joint and muscle pains) were comparable to those reported elsewhere. These findings confirmed that our sample was not atypical. Microclot and platelet pathologies were associated with Long COVID/PASC symptoms that persisted after the recovery from acute COVID-19.

Conclusions: Fibrin amyloid microclots that block capillaries and inhibit the transport of O₂ to tissues, accompanied by platelet hyperactivation, provide a ready explanation for the symptoms of Long COVID/PASC. Removal and reversal of these underlying endotheliopathies provide an important treatment option that urgently warrants controlled clinical studies to determine efficacy in patients with a diversity of comorbidities impacting on SARS-CoV-2 infection and COVID-19 severity. We suggest that our platelet and clotting grading system provides a simple and cost-effective diagnostic method for early detection of Long COVID/PASC as a major determinant of effective treatment, including those focusing on reducing clot burden and platelet hyperactivation.

Source: Pretorius E, Venter C, Laubscher GJ, Kotze MJ, Oladejo SO, Watson LR, Rajaratnam K, Watson BW, Kell DB. Prevalence of symptoms, comorbidities, fibrin amyloid microclots and platelet pathology in individuals with Long COVID/Post-Acute Sequelae of COVID-19 (PASC). Cardiovasc Diabetol. 2022 Aug 6;21(1):148. doi: 10.1186/s12933-022-01579-5. PMID: 35933347; PMCID: PMC9356426. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9356426/ (Full text)

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

Abstract:

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.

Source: Jahanbani F, Maynard RD, Sing JC, Jahanbani S, Perrino JJ, Spacek DV, Davis RW, Snyder MP. Phenotypic characteristics of peripheral immune cells of Myalgic encephalomyelitis/chronic fatigue syndrome via transmission electron microscopy: A pilot study. PLoS One. 2022 Aug 9;17(8):e0272703. doi: 10.1371/journal.pone.0272703. PMID: 35943990. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0272703 (Full text)

The occurrence of hyperactivated platelets and fibrinaloid microclots in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)

Abstract:

We have previously demonstrated that platelet poor plasma (PPP) obtained from patients with LongCovid/Post-Acute Sequelae of COVID-19 (PASC) is characterized by a hypercoagulable state reflected in hyperactivated platelets and the presence of considerable numbers of fibrin(ogen) amyloid microclots or fibrinaloid microclots. Due to substantial overlap in symptoms and aetiology between PASC and ME/CFS, we investigated whether coagulopathies, platelet hyperactivation and/or fibrin amyloid formation differed between individuals exhibiting ME/CFS and gender- and age-matched healthy controls.

ME/CFS patients were statistically far more hypercoagulable as judged by thromboelastography of both whole blood and platelet-poor plasma. The area of plasma images containing fibrinaloid microclots was commonly more than 10-fold greater in untreated platelet-poor plasma from individuals with ME/CFS than in that of healthy controls. A similar difference was found when the plasma samples were treated with thrombin. Using fluorescently labelled PAC-1, which recognizes glycoprotein IIb/IIIa, and CD62P, which binds P-selectin, we observed massive hyperactivation and spreading of platelets in samples from individuals with ME/CFS. Using a quantitative scoring system, this was found to have a score of 2.72 ± 1.24 vs 1.00 (activation with pseudopodia formation) for healthy controls.

We conclude that ME/CFS is accompanied by substantial and measurable changes in coagulability, platelet hyperactivation, and fibrinaloid microclot formation. However, fibrinaloid microclot load was not as prevalent as was previously noted in PASC. Fibrinaloid microclots, in particular can provide a ready explanation, via (temporary) blockage of microcapillaries and hence ischaemia, for many of the symptoms, such as fatigue, seen in patients with ME/CFS. The discovery of these biomarkers pointing to significant and systemic endothelial inflammation, represents an important development in ME/CFS research. It also points at novel treatment strategies using known drugs and/or nutraceuticals that target systemic vascular pathology and endothelial inflammation.

Source: Massimo Nunes, Arneaux Kruger, Amy Proal et al. The occurrence of hyperactivated platelets and fibrinaloid microclots in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS), 08 June 2022, PREPRINT (Version 1) available at Research Square https://doi.org/10.21203/rs.3.rs-1727226/v1 (Full text)