Markers of Immune Activation and Inflammation in Individuals With Postacute Sequelae of Severe Acute Respiratory Syndrome Coronavirus 2 Infection

Assessing the effect of selective serotonin reuptake inhibitors in the prevention of post-acute sequelae of COVID-19

Background

Post-acute sequelae of COVID-19 (PASC) produce significant morbidity, prompting evaluation of interventions that might lower risk. Selective serotonin reuptake inhibitors (SSRIs) potentially could modulate risk of PASC via their central, hypothesized immunomodulatory, and/or antiplatelet properties although clinical trial data are lacking.

Materials and Methods

This retrospective study was conducted leveraging real-world clinical data within the National COVID Cohort Collaborative (N3C) to evaluate whether SSRIs with agonist activity at the sigma-1 receptor (S1R) lower the risk of PASC, since agonism at this receptor may serve as a mechanism by which SSRIs attenuate an inflammatory response. Additionally, determine whether the potential benefit could be traced to S1R agonism. Presumed PASC was defined based on a computable PASC phenotype trained on the U09.9 ICD-10 diagnosis code.

Results

Of the 17,908 patients identified, 1521 were exposed at baseline to a S1R agonist SSRI, 1803 to a non-S1R agonist SSRI, and 14,584 to neither. Using inverse probability weighting and Poisson regression, relative risk (RR) of PASC was assessed.A 29% reduction in the RR of PASC (0.704 [95% CI, 0.58-0.85]; P = 4 ×10-4) was seen among patients who received an S1R agonist SSRI compared to SSRI unexposed patients and a 21% reduction in the RR of PASC was seen among those receiving an SSRI without S1R agonist activity (0.79 [95% CI, 0.67 - 0.93]; P = 0.005).Thus, SSRIs with and without reported agonist activity at the S1R were associated with a significant decrease in the risk of PASC.

Neuro-molecular perspectives on long COVID-19 impacted cerebrovascular diseases - a role for dipeptidyl peptidase IV

The coronavirus disease 2019 (COVID-19) has caused immense devastation globally with many outcomes that are now extending to its long-term sequel called long COVID. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects not only lungs, but also the brain and heart in association with endothelial cell dysfunction, coagulation abnormalities, and thrombosis leading to cardio-cerebrovascular health issues. Fatigue, cognitive decline, and brain fog are common neurological symptoms in persisting long COVID. Neurodegenerative processes and SARS-CoV-2 infection manifest overlapping molecular mechanisms, such as cytokine dysregulation, inflammation, protein aggregation, mitochondrial dysfunction, and oxidative stress. Identifying the key molecules in these processes is of importance for prevention and treatment of this disease. In particular, Dipeptidyl peptidase IV (DPPIV), a multifunctional peptidase has recently drawn attention as a potential co-receptor for SARS-CoV-2 infection and cellular entry. DPPIV is a known co-receptor for some other COVID viruses including MERS-Co-V. DPPIV regulates the immune responses, obesity, glucose metabolism, diabetes, and hypertension that are associated with cerebrovascular manifestations including stroke. DPPIV likely worsens persisting COVID-19 by disrupting inflammatory signaling pathways and the neurovascular system. This review highlights the neurological, cellular and molecular processes concerning long COVID, and DPPIV as a potential key factor contributing to cerebrovascular dysfunctions following SARS-CoV-2 infection.

Understanding the mechanisms and treatments of long COVID to address future public health risks

The 2019 coronavirus disease (COVID-19), triggered by the severe acute respiratory syndrome coronavirus (SARS-CoV-2), has seen numerous individuals undergo and recover from it, drawing extensive attention to their health conditions. Extensive studies indicate that even after surpassing the acute phase of infection, patients continue to experience persistent symptoms such as fatigue, pain, depression, weakening, and anosmia. COVID-19 appears not to have concluded but rather to persist long-term in certain individuals, termed as "long COVID." This represents a heterogeneous ailment involving multiple organ systems, with a perceived complex and still elusive pathogenesis. Among patients with long COVID, observations reveal immune dysregulation, coagulation impairments, and microbial dysbiosis, considered potential mechanisms explaining sustained adverse outcomes post COVID-19. Based on the multifactorial nature, varied symptoms, and heterogeneity of long COVID, we have summarized several categories of current therapeutic approaches. Furthermore, the symptoms of long COVID resemble those of other viral illnesses, suggesting that existing knowledge may offer novel insights into long-term COVID implications. Here, we provide an overview of existing literature associated with long COVID and summarize potential mechanisms, treatment modalities, and other analogous conditions. Lastly, we underscore the inadequacies in long COVID treatment approaches and emphasize the significance of conducting further research and clinical trials.

Long COVID among people with HIV: A systematic review and meta-analysis

BACKGROUND

People with HIV might be at an increased risk of long COVID (LC) because of their immune dysfunction and chronic inflammation and alterations in immunological responses against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2; coronavirus disease 2019 [COVID-19]). This systematic review aimed to evaluate the association between HIV infection and LC and the prevalence and characteristics of and risk factors for LC among people with HIV.

METHODS

Multiple databases, including Embase, PubMed, PsycINFO, Web of Science, and Sociological Abstracts, were searched to identify articles published before June 2023. Published articles were included if they presented at least one LC outcome measure among people with HIV and used quantitative or mixed-methods study designs. For effects reported in three or more studies, meta-analyses using random-effects models were performed using R software.

RESULTS

We pooled 39 405 people with HIV and COVID-19 in 17 eligible studies out of 6158 publications in all the databases. It was estimated that 52% of people with HIV with SARS-CoV-2 infection developed at least one LC symptom. Results from the random-effects model showed that HIV infection was associated with an increased risk of LC (odds ratio 2.20; 95% confidence interval 1.25-3.86). The most common LC symptoms among people with HIV were cough, fatigue, and asthenia. Risk factors associated with LC among people with HIV included a history of moderate-severe COVID-19 illness, increased interferon-gamma-induced protein 10 or tumour necrosis factor-α, and decreased interferon-β, among others.

CONCLUSIONS

The COVID-19 pandemic continues to exacerbate health inequities among people with HIV because of their higher risk of developing LC. Our review is informative for public health and clinical communities to develop tailored strategies to prevent aggravated LC among people with HIV.

Frontal-striatal glucose metabolism and fatigue in patients with multiple sclerosis, long COVID, and COVID-19 recovered controls

This study compared brain glucose metabolism using FDG-PET in the caudate nucleus, putamen, globus pallidus, thalamus, and dorsolateral prefrontal cortex (DLPFC) among patients with Long COVID, patients with fatigue, people with multiple sclerosis (PwMS) patients with fatigue, and COVID recovered controls. PwMS exhibited greater hypometabolism compared to long COVID patients with fatigue and the COVID recovered control group in all studied brain areas except the globus pallidus (effect size range 0.7-1.5). The results showed no significant differences in glucose metabolism between patients with Long COVID and the COVID recovered control group in these regions. These findings suggest that long COVID fatigue may involve non-CNS systems, neurotransmitter imbalances, or psychological factors not captured by FDG-PET, while MS-related fatigue is associated with more severe frontal-striatal circuit dysfunction due to demyelination and neurodegeneration. Symmetrical standardized uptake values (SUVs) between hemispheres in all groups imply that fatigue in these conditions may be related to global or network-level alterations rather than hemisphere-specific changes. Future studies should employ fine-grained analysis methods, explore other brain regions, and control for confounding factors to better understand the pathophysiology of fatigue in MS and long COVID. Longitudinal studies tracking brain glucose metabolism in patients with Long COVID could provide insights into the evolution of metabolic patterns as the condition progresses.

Earlier vs. later time period of COVID-19 infection and emergent autoimmune signs, symptoms, and serologies

OBJECTIVE

Autoantibodies and autoimmune diseases after SARS-CoV-2 infection are widely reported. Given evolving variants, milder infections, and increasing population vaccination, we hypothesized that SARS-CoV-2 infection earlier in the pandemic would be associated with more autoimmune connective tissue disease (CTD) symptoms and immunologic abnormalities.

METHODS

Patients ≥18 years old with COVID-19 3/1/2020-8/15/2022 completed the CTD Screening Questionnaire and were tested for 27 autoimmune serologies, SARS-CoV-2 serologies, cell-bound complement activation products (CB-CAPs), and T and B lymphocyte immunophenotypes by flow cytometry. We assessed relationships between symptoms, serologies, and immunophenotypes in earlier (3/1/2020-1/31/2021) vs. later (2/1/2021-8/15/2022) periods, with different predominating SARS-CoV-2 viruses.

RESULTS

57 subjects had earlier and 23 had later pandemic COVID-19. 35 % of earlier vs. 17 % of later pandemic patients had CTD symptoms (p 0.18). More patients were antinuclear antibody (ANA) positive (44 % vs. 13 %, p 0.01) and had lupus anticoagulant (11 % vs. 4 %, p 0.67). After adjustment for age, race, and sex, earlier (vs. later) COVID-19 was associated with increased ANA positivity (OR 4.60, 95%CI 1.17, 18.15). No subjects had positive CB-CAPs. T and B cell immunophenotypes and SARS-CoV-2 serologies did not differ by group. In heatmap analyses, higher autoantibody variety was seen among those with infection in the early pandemic.

CONCLUSION

In this sample, having COVID-19 infection in the earlier (pre-2/1/2021) vs. later pandemic was associated with more CTD symptoms, ANA positivity, and autoantibody reactivities. Earlier SARS-CoV-2 variants circulating in a less vaccinated population with less natural immunity may have been more immunogenic.

Early biological markers of post-acute sequelae of SARS-CoV-2 infection

To understand the roles of acute-phase viral dynamics and host immune responses in post-acute sequelae of SARS-CoV-2 infection (PASC), we enrolled 136 participants within 5 days of their first positive SARS-CoV-2 real-time PCR test. Participants self-collected up to 21 nasal specimens within the first 28 days post-symptom onset; interviewer-administered questionnaires and blood samples were collected at enrollment, days 9, 14, 21, 28, and month 4 and 8 post-symptom onset. Defining PASC as the presence of any COVID-associated symptom at their 4-month visit, we compared viral markers (quantity and duration of nasal viral RNA load, infectious viral load, and plasma N-antigen level) and host immune markers (IL-6, IL-10, TNF-α, IFN-α, IFN-γ, MCP, IP-10, and Spike IgG) over the acute period. Compared to those who fully recovered, those reporting PASC demonstrated significantly higher maximum levels of SARS-CoV-2 RNA and N-antigen, burden of RNA and infectious viral shedding, and lower Spike-specific IgG levels within 9 days post-illness onset. No significant differences were identified among a panel of host immune markers. Our results suggest early viral dynamics and the associated host immune responses play a role in the pathogenesis of PASC, highlighting the importance of understanding early biological markers in the natural history of PASC.

Different polarization and functionality of CD4+ T helper subsets in people with post-COVID condition

Introduction

After mild COVID-19 that does not require hospitalization, some individuals develop persistent symptoms that may worsen over time, producing a multisystemic condition termed Post-COVID condition (PCC). Among other disorders, PCC is characterized by persistent changes in the immune system that may not be solved several months after COVID-19 diagnosis.

Methods

People with PCC were recruited to determine the distribution and functionality of CD4+ T helper (Th) subsets in comparison with individuals with mild, severe, and critical presentations of acute COVID-19 to evaluate their contribution as risk or protective factors for PCC.

Results

People with PCC showed low levels of Th1 cells, similar to individuals with severe and critical COVID-19, although these cells presented a higher capacity to express IFNγ in response to stimulation. Th2/Th1 correlation was negative in individuals with acute forms of COVID-19, but there was no significant Th2/Th1 correlation in people with PCC. Th2 cells from people with PCC presented high capacity to express IL-4 and IL-13, which are related to low ventilation and death associated with COVID-19. Levels of proinflammatory Th9 and Th17 subsets were significantly higher in people with PCC in comparison with acute COVID-19, being Th1/Th9 correlation negative in these individuals, which probably contributed to a more pro-inflammatory than antiviral scenario. Th17 cells from approximately 50% of individuals with PCC had no capacity to express IL-17A and IL-22, similar to individuals with critical COVID-19, which would prevent clearing extracellular pathogens. Th2/Th17 correlation was positive in people with PCC, which in the absence of negative Th1/Th2 correlation could also contribute to the proinflammatory state. Finally, Th22 cells from most individuals with PCC had no capacity to express IL-13 or IL-22, which could increase tendency to reinfections due to impaired epithelial regeneration.

Discussion

People with PCC showed skewed polarization of CD4+ Th subsets with altered functionality that was more similar to individuals with severe and critical presentations of acute COVID-19 than to people who fully recovered from mild disease. New strategies aimed at reprogramming the immune response and redirecting CD4+ Th cell polarization may be necessary to reduce the proinflammatory environment characteristic of PCC.

Post-Acute Sequelae and Mitochondrial Aberration in SARS-CoV-2 Infection

This review investigates links between post-acute sequelae of SARS-CoV-2 infection (PASC), post-infection viral persistence, mitochondrial involvement and aberrant innate immune response and cellular metabolism during SARS-CoV-2 infection. Advancement of proteomic and metabolomic studies now allows deeper investigation of alterations to cellular metabolism, autophagic processes and mitochondrial dysfunction caused by SARS-CoV-2 infection, while computational biology and machine learning have advanced methodologies of predicting virus-host gene and protein interactions. Particular focus is given to the interaction between viral genes and proteins with mitochondrial function and that of the innate immune system. Finally, the authors hypothesise that viral persistence may be a function of mitochondrial involvement in the sequestration of viral genetic material. While further work is necessary to understand the mechanisms definitively, a number of studies now point to the resolution of questions regarding the pathogenesis of PASC.

Immune activation and immune-associated neurotoxicity in Long-COVID: A systematic review and meta-analysis of 103 studies comprising 58 cytokines/chemokines/growth factors

BACKGROUND

Multiple studies have shown that Long COVID (LC) disease is associated with heightened immune activation, as evidenced by elevated levels of inflammatory mediators. However, there is no comprehensive meta-analysis focusing on activation of the immune inflammatory response system (IRS) and the compensatory immunoregulatory system (CIRS) along with other immune phenotypes in LC patients.

OBJECTIVES

This meta-analysis is designed to explore the IRS and CIRS profiles in LC patients, the individual cytokines, chemokines, growth factors, along with C-reactive protein (CRP) and immune-associated neurotoxicity.

METHODS

To gather relevant studies for our research, we conducted a thorough search using databases such as PubMed, Google Scholar, and SciFinder, covering all available literature up to July 5th, 2024.

RESULTS

The current meta-analysis encompassed 103 studies that examined multiple immune profiles, C-reactive protein, and 58 cytokines/chemokines/growth factors in 5502 LC patients versus 5962 normal controls (NC). LC patients showed significant increases in IRS/CIRS ratio (standardized mean difference (SMD: 0.156, confidence interval (CI): 0.062;0.250), IRS (SMD: 0.338, CI: 0.236;0.440), M1 macrophage (SMD: 0.371, CI: 0.263;0.480), T helper (Th)1 (SMD: 0.316, CI: 0.185;0.446), Th17 (SMD: 0.439, CI: 0.302;0.577) and immune-associated neurotoxicity (SMD: 0.384, CI: 0.271;0.497). In addition, CRP and 21 different cytokines displayed significantly elevated levels in LC patients compared to NC.

CONCLUSION

LC disease is characterized by IRS activation and increased immune-associated neurotoxicity.

Long COVID as a disease of accelerated biological aging: An opportunity to translate geroscience interventions

It has been four years since long COVID-the protracted consequences that survivors of COVID-19 face-was first described. Yet, this entity continues to devastate the quality of life of an increasing number of COVID-19 survivors without any approved therapy and a paucity of clinical trials addressing its biological root causes. Notably, many of the symptoms of long COVID are typically seen with advancing age. Leveraging this similarity, we posit that Geroscience-which aims to target the biological drivers of aging to prevent age-associated conditions as a group-could offer promising therapeutic avenues for long COVID. Bearing this in mind, this review presents a translational framework for studying long COVID as a state of effectively accelerated biological aging, identifying research gaps and offering recommendations for future preclinical and clinical studies.

COVID-19 in the Initiation and Progression of Atherosclerosis: Pathophysiology During and Beyond the Acute Phase

The incidence of atherosclerotic cardiovascular disease is increasing globally, especially in low- and middle-income countries, despite significant efforts to reduce traditional risk factors. Premature subclinical atherosclerosis has been documented in association with several viral infections. The magnitude of the recent COVID-19 pandemic has highlighted the need to understand the association between SARS-CoV-2 and atherosclerosis. This review examines various pathophysiological mechanisms, including endothelial dysfunction, platelet activation, and inflammatory and immune hyperactivation triggered by SARS-CoV-2 infection, with specific attention on their roles in initiating and promoting the progression of atherosclerotic lesions. Additionally, it addresses the various pathogenic mechanisms by which COVID-19 in the post-acute phase may contribute to the development of vascular disease. Understanding the overlap of these syndromes may enable novel therapeutic strategies. We further explore the need for guidelines for closer follow-up for the often-overlooked evidence of atherosclerotic cardiovascular disease among patients with recent COVID-19, particularly those with cardiometabolic risk factors.

Reduction of long COVID symptoms after stellate ganglion block: A retrospective chart review study

The SARS-CoV-2 pandemic has left millions of individuals with a host of post-viral symptoms that can be debilitating and persist indefinitely. To date there are no definitive tests or treatments for the collection of symptoms known as "Long COVID" or Post-acute sequelae of COVID-19 (PASC). Following our initial case report detailing improvement of Long COVID symptoms after sequential bilateral stellate ganglion blockade (SGB), we performed a retrospective chart analysis study on individuals treated with the same protocol over the course of six months (2021-2022) in our clinic. Patients self-reported symptoms on a 10-point scale as part of optional patient follow-up using an online survey. After one month or more following treatment, patients reported striking reductions in Fatigue, Worsening of Symptoms following Mental and Physical Activity, Memory Problems, Problems Concentrating, Sleep Problems, Anxiety, and Depression. Loss of Taste and Loss of Smell in some individuals did not respond to treatment, likely indicating structural damage following infection. This study suggests that neuromodulation may provide relief of Long COVID symptoms for at least a subset of individuals, and provides support for prospective studies of this potential treatment.

sMR and PTX3 levels associate with COVID-19 outcome and survival but not with Long COVID

Biomarkers for monitoring COVID-19 disease course are lacking. Study aim was to identify biomarkers associated with disease severity, survival, long-term outcome, and Long COVID. As excessive macrophages activation is a hallmark of COVID-19 and complement activation is key in this, we selected the following proteins involved in these processes: PTX3, C1q, C1-INH, C1s/C1-INH, and sMR. EDTA-plasma concentrations were measured in 215 patients and 47 controls using ELISA. PTX3, sMR, C1-INH, and C1s/C1-INH levels were associated with disease severity. PTX3 and sMR were also associated with survival and long-term immune recovery. Lastly, sMR levels associate with ICU admittance. sMR (AUC 0.85) and PTX3 (AUC 0.78) are good markers for disease severity, especially when used in combination (AUC 0.88). No association between biomarker levels and Long COVID was observed. sMR has not previously been associated with COVID-19 disease severity, ICU admittance or survival and may serve as marker for disease course.

Inflammatory profiles are associated with long COVID up to 6 months after COVID-19 onset: A prospective cohort study of individuals with mild to critical COVID-19

BACKGROUND

After initial COVID-19, immune dysregulation may persist and drive post-acute sequelae of COVID-19 (PASC). We described longitudinal trajectories of cytokines in adults up to 6 months following SARS-CoV-2 infection and explored early predictors of PASC.

METHODS

RECoVERED is a prospective cohort of individuals with laboratory-confirmed SARS-CoV-2 infection between May 2020 and June 2021 in Amsterdam, the Netherlands. Serum was collected at weeks 4, 12 and 24 of follow-up. Monthly symptom questionnaires were completed from month 2 after COVID-19 onset onwards; lung diffusion capacity (DLCO) was tested at 6 months. Cytokine concentrations were analysed by human magnetic Luminex screening assay. We used a linear mixed-effects model to study log-concentrations of cytokines over time, assessing their association with socio-demographic and clinical characteristics that were included in the model as fixed effects.

RESULTS

186/349 (53%) participants had ≥2 serum samples and were included in current analyses. Of these, 101/186 (54%: 45/101[45%] female, median age 55 years [IQR = 45-64]) reported PASC at 12 and 24 weeks after COVID-19 onset. We included 37 reference samples (17/37[46%] female, median age 49 years [IQR = 40-56]). In a multivariate model, PASC was associated with raised CRP and abnormal diffusion capacity with raised IL10, IL17, IL6, IP10 and TNFα at 24 weeks. Early (0-4 week) IL-1β and BMI at COVID-19 onset were predictive of PASC at 24 weeks.

CONCLUSIONS

Our findings indicate that immune dysregulation plays an important role in PASC pathogenesis, especially among individuals with reduced pulmonary function. Early IL-1β shows promise as a predictor of PASC.

Tissue-based T cell activation and viral RNA persist for up to 2 years after SARS-CoV-2 infection

The mechanisms of postacute medical conditions and unexplained symptoms after SARS-CoV-2 infection [Long Covid (LC)] are incompletely understood. There is growing evidence that viral persistence, immune dysregulation, and T cell dysfunction may play major roles. We performed whole-body positron emission tomography imaging in a well-characterized cohort of 24 participants at time points ranging from 27 to 910 days after acute SARS-CoV-2 infection using the radiopharmaceutical agent [18F]F-AraG, a selective tracer that allows for anatomical quantitation of activated T lymphocytes. Tracer uptake in the postacute COVID-19 group, which included those with and without continuing symptoms, was higher compared with prepandemic controls in many regions, including the brain stem, spinal cord, bone marrow, nasopharyngeal and hilar lymphoid tissue, cardiopulmonary tissues, and gut wall. T cell activation in the spinal cord and gut wall was associated with the presence of LC symptoms. In addition, tracer uptake in lung tissue was higher in those with persistent pulmonary symptoms specifically. Increased T cell activation in these tissues was also observed in many individuals without LC. Given the high [18F]F-AraG uptake detected in the gut, we obtained colorectal tissue for in situ hybridization of SARS-CoV-2 RNA and immunohistochemical studies in a subset of five participants with LC symptoms. We identified intracellular SARS-CoV-2 single-stranded spike protein-encoding RNA in rectosigmoid lamina propria tissue in all five participants and double-stranded spike protein-encoding RNA in three participants up to 676 days after initial COVID-19, suggesting that tissue viral persistence could be associated with long-term immunologic perturbations.

Altered serum concentrations of IL-8, IL-32 and IL-10 in patients with lung impairment 6 months after COVID-19

Post-COVID symptoms are reported in 10-35 % of patients not requiring hospitalization, and in up to 80 % of hospitalized patients and patients with severe disease. The pathogenesis of post-COVID syndrome remains largely unknown. Some evidence suggests that prolonged inflammation has a key role in the pathogenesis of most post-COVID manifestations. We evaluated a panel of inflammatory and immune-mediated cytokines in individuals with altered HRCT features and in patients without any long-term COVID symptoms. Blood samples of 89 adult patients previously hospitalized with COVID-19 were collected and stratified as patients with and without HRCT evidence of fibrotic lung alterations. Serum analyte concentrations of IL-4, IL-2, CXCL10 (IP-10), IL-1β, TNF-α, CCL2 (MCP-1), IL-17A, IL-6, IL-10, IFN-γ, IL-12p70 and TGF-β1 (free active form) were quantified by bead-based multiplex assay. Clinical and functional data were recorded in a database. With the use of machine learning approach, IL-32, IL-8, and IL-10 proved to be associated with the development of HRCT evidence of lung sequelae at follow-up. Direct comparison of cytokine levels in the two groups showed increased levels of IL-32 and decreased levels of IL-8 in patients with lung impairment. After further stratification of patients by severity (severe versus mild/moderate) during hospitalization, IL-10 emerged as the only cytokine showing decreased levels in severe patients. These findings contribute to a better understanding of the immune response and potential prognostic markers in patients with lung sequelae after COVID-19.

Diverse immunological dysregulation, chronic inflammation, and impaired erythropoiesis in long COVID patients with chronic fatigue syndrome

A substantial number of patients recovering from acute SARS-CoV-2 infection present serious lingering symptoms, often referred to as long COVID (LC). However, a subset of these patients exhibits the most debilitating symptoms characterized by ongoing myalgic encephalomyelitis or chronic fatigue syndrome (ME/CFS). We specifically identified and studied ME/CFS patients from two independent LC cohorts, at least 12 months post the onset of acute disease, and compared them to the recovered group (R). ME/CFS patients had relatively increased neutrophils and monocytes but reduced lymphocytes. Selective T cell exhaustion with reduced naïve but increased terminal effector T cells was observed in these patients. LC was associated with elevated levels of plasma pro-inflammatory cytokines, chemokines, Galectin-9 (Gal-9), and artemin (ARTN). A defined threshold of Gal-9 and ARTN concentrations had a strong association with LC. The expansion of immunosuppressive CD71+ erythroid cells (CECs) was noted. These cells may modulate the immune response and contribute to increased ARTN concentration, which correlated with pain and cognitive impairment. Serology revealed an elevation in a variety of autoantibodies in LC. Intriguingly, we found that the frequency of 2B4+CD160+ and TIM3+CD160+ CD8+ T cells completely separated LC patients from the R group. Our further analyses using a multiple regression model revealed that the elevated frequency/levels of CD4 terminal effector, ARTN, CEC, Gal-9, CD8 terminal effector, and MCP1 but lower frequency/levels of TGF-β and MAIT cells can distinguish LC from the R group. Our findings provide a new paradigm in the pathogenesis of ME/CFS to identify strategies for its prevention and treatment.

Sex differences and immune correlates of Long COVID development, persistence, and resolution

Sex differences have been observed in acute COVID-19 and Long COVID (LC) outcomes, with greater disease severity and mortality during acute infection in males and a greater proportion of females developing LC. We hypothesized that sex-specific immune dysregulation contributes to the pathogenesis of LC. To investigate the immunologic underpinnings of LC development and persistence, we used single-cell transcriptomics, single-cell proteomics, and plasma proteomics on blood samples obtained during acute SARS-CoV-2 infection and at 3 and 12 months post-infection in a cohort of 45 patients who either developed LC or recovered. Several sex-specific immune pathways were associated with LC. Specifically, males who would develop LC at 3 months had widespread increases in TGF-β signaling during acute infection in proliferating NK cells. Females who would develop LC demonstrated increased expression of XIST, an RNA gene implicated in autoimmunity, and increased IL1 signaling in monocytes at 12 months post infection. Several immune features of LC were also conserved across sexes. Both males and females with LC had reduced co-stimulatory signaling from monocytes and broad upregulation of NF-κB transcription factors. In both sexes, those with persistent LC demonstrated increased LAG3, a marker of T cell exhaustion, reduced ETS1 transcription factor expression across lymphocyte subsets, and elevated intracellular IL-4 levels in T cell subsets, suggesting that ETS1 alterations may drive an aberrantly elevated Th2-like response in LC. Altogether, this study describes multiple innate and adaptive immune correlates of LC, some of which differ by sex, and offers insights toward the pursuit of tailored therapeutics.

Post-acute sequelae of SARS-CoV-2 infection (Long COVID) in older adults

Long COVID, also known as PASC (post-acute sequelae of SARS-CoV-2), is a complex infection-associated chronic condition affecting tens of millions of people worldwide. Many aspects of this condition are incompletely understood. Among them is how this condition may manifest itself in older adults and how it might impact the older population. Here, we briefly review the current understanding of PASC in the adult population and examine what is known on its features with aging. Finally, we outline the major gaps and areas for research most germane to older adults.

Cognitive profile, neuroimaging and fluid biomarkers in post-acute COVID-19 syndrome

We aimed to characterize the cognitive profile of post-acute COVID-19 syndrome (PACS) patients with cognitive complaints, exploring the influence of biological and psychological factors. Participants with confirmed SARS-CoV-2 infection and cognitive complaints ≥ 8 weeks post-acute phase were included. A comprehensive neuropsychological battery (NPS) and health questionnaires were administered at inclusion and at 1, 3 and 6 months. Blood samples were collected at each visit, MRI scan at baseline and at 6 months, and, optionally, cerebrospinal fluid. Cognitive features were analyzed in relation to clinical, neuroimaging, and biochemical markers at inclusion and follow-up. Forty-nine participants, with a mean time from symptom onset of 10.4 months, showed attention-executive function (69%) and verbal memory (39%) impairment. Apathy (64%), moderate-severe anxiety (57%), and severe fatigue (35%) were prevalent. Visual memory (8%) correlated with total gray matter (GM) and subcortical GM volume. Neuronal damage and inflammation markers were within normal limits. Over time, cognitive test scores, depression, apathy, anxiety scores, MRI indexes, and fluid biomarkers remained stable, although fewer participants (50% vs. 75.5%; p = 0.012) exhibited abnormal cognitive evaluations at follow-up. Altered attention/executive and verbal memory, common in PACS, persisted in most subjects without association with structural abnormalities, elevated cytokines, or neuronal damage markers.

Heart Rate Variability Modulation Through Slow-Paced Breathing in Health Care Workers with Long COVID: A Case-Control Study

BACKGROUND

Long COVID is a syndrome persisting 12+ weeks after COVID-19 infection, impacting life and work ability. Autonomic nervous system imbalance has been hypothesized as the cause. This study aims to investigate cardiovascular autonomic function in health care workers (HCWs) with Long COVID and the effectiveness of slow-paced breathing (SPB) on autonomic modulation.

METHODS

From December 1, 2022 to March 31, 2023, 6655 HCWs of the University Hospitals of Trieste (Northeast Italy) were asked to participate in the study by company-email. Inclusion/exclusion criteria were assessed. Global health status and psychosomatic disorders were evaluated through validated questionnaires. Heart rate variability was assessed by finger-photoplethysmography during spontaneous breathing and SPB, which stimulate vagal response. Long COVID HCWs (G1) were contrasted with Never infected (G2) and Fully recovered COVID-19 workers (G3).

RESULTS

There were 126 HCWs evaluated. The 58 Long COVID were assessed at a median time because COVID-19 of 419.5 days (interquartile range 269-730) and had significantly more psychosomatic symptoms and lower detectability of spontaneous systolic pressure oscillation at 0.1 Hz (Mayer wave - baroreflex arc) during spontaneous breathing compared with 53 never-infected and 14 fully-recovered HCWs (19%, 42%, and 40%, respectively, P = .027). During SPB, the increase in this parameter was close to controls (91.2%, 100%, and 100%, respectively, P = .09). No other differences in heart rate variability parameters were found among groups.

CONCLUSIONS

Resting vascular modulation was reduced in Long COVID, while during SPB, baroreflex sensitivity effectively improved. Long-term studies are needed to evaluate whether multiple sessions of breathing exercises can restore basal vascular reactivity and reduce cardiovascular risk in these patients.

Clinical and serological predictors of post COVID-19 condition-findings from a Canadian prospective cohort study

Introduction

More than 3 years into the pandemic, there is persisting uncertainty as to the etiology, biomarkers, and risk factors of Post COVID-19 Condition (PCC). Serological research data remain a largely untapped resource. Few studies have investigated the potential relationships between post-acute serology and PCC, while accounting for clinical covariates.

Methods

We compared clinical and serological predictors among COVID-19 survivors with (n = 102 cases) and without (n = 122 controls) persistent symptoms ≥12 weeks post-infection. We selected four primary serological predictors (anti-nucleocapsid (N), anti-Spike, and anti-receptor binding domain (RBD) IgG titres, and neutralization efficiency), and specified clinical covariates a priori.

Results

Similar proportions of PCC-cases (66.7%, n = 68) and infected-controls (71.3%, n = 87) tested positive for anti-N IgG. More cases tested positive for anti-Spike (94.1%, n = 96) and anti-RBD (95.1%, n = 97) IgG, as compared with controls (anti-Spike: 89.3%, n = 109; anti-RBD: 84.4%, n = 103). Similar trends were observed among unvaccinated participants. Effects of IgG titres on PCC status were non-significant in univariate and multivariate analyses. Adjusting for age and sex, PCC-cases were more likely to be efficient neutralizers (OR 2.2, 95% CI 1.11-4.49), and odds was further increased among cases to report deterioration in quality of life (OR 3.4, 95% CI 1.64-7.31). Clinical covariates found to be significantly related to PCC included obesity (OR 2.3, p = 0.02), number of months post COVID-19 (OR 1.1, p < 0.01), allergies (OR 1.8, p = 0.04), and need for medical support (OR 4.1, p < 0.01).

Conclusion

Despite past COVID-19 infection, approximately one third of PCC-cases and infected-controls were seronegative for anti-N IgG. Findings suggest higher neutralization efficiency among cases as compared with controls, and that this relationship is stronger among cases with more severe PCC. Cases also required more medical support for COVID-19 symptoms, and described complex, ongoing health sequelae. More data from larger cohorts are needed to substantiate results, permit subgroup analyses of IgG titres, and explore for differences between clusters of PCC symptoms. Future assessment of IgG subtypes may also elucidate new findings.

Transcutaneous vagus nerve stimulation improves Long COVID symptoms in a female cohort: a pilot study

Background

Long COVID, also known as Post-COVID-19 syndrome, is characterized by multisystemic symptoms that persists for weeks to years beyond acute infection. It disproportionately affects women and those with pre-existing anxiety/depression, conditions more prevalent in females. The vagus nerve, with its extensive innervation and regulation of critical bodily functions, has become a focal point for therapeutic interventions. Transcutaneous vagus nerve stimulation (t-VNS) has emerged as a promising non-invasive treatment for COVID-19 conditions.

Methods

This pilot study assessed the efficacy of t-VNS in 24 female Long COVID patients (45.8 ± 11.7 years old; 20.2 ± 7.1 months since infection), who underwent a 10-day t-VNS intervention at home (30 min/session, twice a day). Cognition was considered the primary outcome, with anxiety, depression, sleep, fatigue, and smell as secondary outcomes. Outcomes were measured at baseline, post-intervention, and 1-month follow-up.

Results

Significant improvements were observed in various cognitive functions, anxiety, depression, and sleep at post-intervention, with benefits remaining or progressing at 1-month follow-up. Improvements in fatigue were delayed, reaching statistical significance at 1-month follow-up compared to baseline. No significant changes were noted in olfactory performance.

Conclusion

This pilot study provides preliminary evidence supporting the potential of t-VNS as a therapeutic intervention for female Long COVID patients. The encouraging results justify further rigorous investigation through larger, randomized controlled trials to confirm the efficacy of t-VNS, assess its generalizability to male cohorts, and explore biological markers to inform personalized treatment approaches. Our findings support the allocation of resources to conduct such trials and advance the understanding of t-VNS as a potential treatment for Long COVID.

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

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.

Growth Differentiation Factor-15 Is Considered a Predictive Biomarker of Long COVID in Non-hospitalized Patients

Mitochondrial dysfunction is associated with various diseases. Mitochondria plays a regulatory role during infection. The association between mitokines and subsequent COVID progression has not been previously studied. The retrospective cohort study aimed to investigate the potential of serum mitokines as long COVID biomarkers in non-hospitalized patients. Patients with confirmed SARS-CoV-2 infection and blood test reports between January 2021 and April 2023 were included. Patients were categorized into two groups, the recovered and long COVID groups, based on fatigue, decline in focus, and pain. Serum levels of growth differentiation factor 15 (GDF-15) and fibroblast growth factor-21 (FGF-21), which are affected by mitochondrial function, along with inflammatory and vascular endothelium markers, were measured using enzyme-linked immunosorbent assays (ELISA). A receiver operating characteristic curve was used to screen the biomarkers. The threshold value of GDF-15 in the acute phase was 965 pg/mL (sensitivity: 71.4%, specificity: 83.3%), indicating that GDF-15 may be associated with the presence of symptoms three months post onset. No association with inflammatory markers and vascular structures was observed. Therefore, elevated GDF-15 levels in the acute phase may act as a predictive biomarker of long COVID.

Identification of inflammatory clusters in long-COVID through analysis of plasma biomarker levels

Mechanisms underlying long COVID remain poorly understood. Patterns of immunological responses in individuals with long COVID may provide insight into clinical phenotypes. Here we aimed to identify these immunological patterns and study the inflammatory processes ongoing in individuals with long COVID. We applied an unsupervised hierarchical clustering approach to analyze plasma levels of 42 biomarkers measured in individuals with long COVID. Logistic regression models were used to explore associations between biomarker clusters, clinical variables, and symptom phenotypes. In 101 individuals, we identified three inflammatory clusters: a limited immune activation cluster, an innate immune activation cluster, and a systemic immune activation cluster. Membership in these inflammatory clusters did not correlate with individual symptoms or symptom phenotypes, but was associated with clinical variables including age, BMI, and vaccination status. Differences in serologic responses between clusters were also observed. Our results indicate that clinical variables of individuals with long COVID are associated with their inflammatory profiles and can provide insight into the ongoing immune responses.

Persistence of SARS-CoV-2 colonization and high expression of inflammatory factors in cardiac tissue 6 months after COVID-19 recovery: a prospective cohort study

Background

The presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in myocardial autopsy tissues has been observed in certain individuals with coronavirus disease 2019 (COVID-19). However, the duration of cardiac involvement remains uncertain among recovered COVID-19 patients. Our study aims to evaluate the long-term persistence of SARS-CoV-2 within cardiac tissue.

Methods

We prospectively and consecutively evaluated the patients undergoing mitral valve replacement (MVR) and left atrial (LA) volume reduction surgery from May 25 to June 10, 2023 at our center, who had been approximately 6 months of recovery after Omicron wave. Patients tested positive for SARS-CoV-2 upon admission were excluded. The surgical LA tissue was collected in RNA preservation solution and stored at -80 ℃ immediately. Then SARS-CoV-2, interleukin-6 (IL-6) and interleukin-1β (IL-1β) RNA expression in LA tissues were assessed through thrice-repeated reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analyses. Categorical variables were assessed using the Chi-square or Fisher's exact tests, and continuous variables was analyzed using the Mann-Whitney U test.

Results

Nine of 41 patients were enrolled, all of whom tested negative for SARS-CoV-2 upon admission (two antigen and PCR tests). In four of nine patients, SARS-CoV-2 RNA was detected in their LA tissue, indicating viral colonization. Among the four positive cases, the IL-6 and IL-1β relative expression levels in the LA tissue of one patient were increased approximately 55- and 110-fold, respectively, compared to those of SARS-CoV-2 (-) patients. Increased expression of IL-6 and IL-1β were observed in the myocardium of this patient. Another patient demonstrated a remarkable 7-fold increase in both IL-6 and IL-1β expression, surpassing that of SARS-CoV-2 (-) patients. Additionally, no other cardiac inflammation-related diseases or conditions were presented in these two patients. The IL-6 and IL-1β expression levels of the remaining two patients were not significantly different from those of SARS-CoV-2 (-) patients. The relative expression levels of IL-6 and IL-1β in cardiac tissues of all SARS-CoV-2 (-) patients were relatively low. Interestingly, despite abnormally elevated levels of IL-6 and IL-1β within their cardiac tissue, two patients did not show a significant increase in serum IL-6 and IL-1β levels when compared to other patients.

Conclusions

Our research suggests that certain COVID-19-recovered patients have persistent colonization of SARS-CoV-2 in their cardiac tissue, accompanied by a local increase in inflammatory factors.

Pathophysiological Mechanisms in Long COVID: A Mixed Method Systematic Review

INTRODUCTION

Long COVID (LC) is a global public health crisis affecting more than 70 million people. There is emerging evidence of different pathophysiological mechanisms driving the wide array of symptoms in LC. Understanding the relationships between mechanisms and symptoms helps in guiding clinical management and identifying potential treatment targets.

METHODS

This was a mixed-methods systematic review with two stages: Stage one (Review 1) included only existing systematic reviews (meta-review) and Stage two (Review 2) was a review of all primary studies. The search strategy involved Medline, Embase, Emcare, and CINAHL databases to identify studies that described symptoms and pathophysiological mechanisms with statistical analysis and/or discussion of plausible causal relationships between mechanisms and symptoms. Only studies that included a control arm for comparison were included. Studies were assessed for quality using the National Heart, Lung, and Blood Institute quality assessment tools.

RESULTS

19 systematic reviews were included in Review 1 and 46 primary studies in Review 2. Overall, the quality of reporting across the studies included in this second review was moderate to poor. The pathophysiological mechanisms with strong evidence were immune system dysregulation, cerebral hypoperfusion, and impaired gas transfer in the lungs. Other mechanisms with moderate to weak evidence were endothelial damage and hypercoagulation, mast cell activation, and auto-immunity to vascular receptors.

CONCLUSIONS

LC is a complex condition affecting multiple organs with diverse clinical presentations (or traits) underpinned by multiple pathophysiological mechanisms. A 'treatable trait' approach may help identify certain groups and target specific interventions. Future research must include understanding the response to intervention based on these mechanism-based traits.

Long COVID and its association with neurodegenerative diseases: pathogenesis, neuroimaging, and treatment

Corona Virus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), has presented unprecedented challenges to the world. Changes after acute COVID-19 have had a significant impact on patients with neurodegenerative diseases. This study aims to explore the mechanism of neurodegenerative diseases by examining the main pathways of central nervous system infection of SARS-CoV-2. Research has indicated that chronic inflammation and abnormal immune response are the primary factors leading to neuronal damage and long-term consequences of COVID-19. In some COVID-19 patients, the concurrent inflammatory response leads to increased release of pro-inflammatory cytokines, which may significantly impact the prognosis. Molecular imaging can accurately assess the severity of neurodegenerative diseases in patients with COVID-19 after the acute phase. Furthermore, the use of FDG-PET is advocated to quantify the relationship between neuroinflammation and psychiatric and cognitive symptoms in patients who have recovered from COVID-19. Future development should focus on aggressive post-infection control of inflammation and the development of targeted therapies that target ACE2 receptors, ERK1/2, and Ca2+.

Serological markers and long COVID-A rapid systematic review

BACKGROUND

Long COVID is highly heterogeneous, often debilitating, and may last for years after infection. The aetiology of long COVID remains uncertain. Examination of potential serological markers of long COVID, accounting for clinical covariates, may yield emergent pathophysiological insights.

METHODS

In adherence to PRISMA guidelines, we carried out a rapid review of the literature. We searched Medline and Embase for primary observational studies that compared IgG response in individuals who experienced COVID-19 symptoms persisting ≥12 weeks post-infection with those who did not. We examined relationships between serological markers and long COVID status and investigated sources of inter-study variability, such as severity of acute illness, long COVID symptoms assessed and target antigen(s).

RESULTS

Of 8018 unique records, we identified 29 as being eligible for inclusion in synthesis. Definitions of long COVID varied. In studies that reported anti-nucleocapsid (N) IgG (n = 10 studies; n = 989 participants in aggregate), full or partial anti-Spike IgG (i.e. the whole trimer, S1 or S2 subgroups, or receptor binding domain, n = 19 studies; n = 2606 participants), or neutralizing response (n = 7 studies; n = 1123 participants), we did not find strong evidence to support any difference in serological markers between groups with and without persisting symptoms. However, most studies did not account for severity or level of care required during acute illness, and other potential confounders.

CONCLUSIONS

Pooling of studies would enable more robust exploration of clinical and serological predictors among diverse populations. However, substantial inter-study variations hamper comparability. Standardized reporting practices would improve the quality, consistency and comprehension of study findings.

Baseline Characteristics in the Remote Diet Intervention to REduce long-COVID Symptoms Trial (ReDIRECT)

Background

The persistence of symptoms for ≥12 weeks after a COVID-19 infection is known as Long COVID (LC), a condition with unclear pathophysiology and no proven treatments to date. Living with obesity is a risk factor for LC and has symptoms which may overlap with and aggravate LC.

Methods

ReDIRECT is a remotely delivered trial assessing whether weight management can reduce LC symptoms. We recruited people with LC and BMI >27kg/m 2. The intervention was delivered remotely by dietitians, with online data collection (medical and dietary history, COVID-19 infection and vaccination, body composition, LC history/symptoms, blood pressure, quality of life, sociodemographic data). Participants self-selected the dominant LC symptoms they most wanted to improve from the intervention.

Results

Participants (n=234) in England (64%) and Scotland (30%) were mainly women (85%) of white ethnicity (90%), with 13% living in the 20% most deprived areas, a mean age of 46 (SD10) years, and median BMI of 35kg/m 2 (IQR 32-40). Before starting the study, 30% reported more than one COVID-19 infection (82% confirmed with one or more positive tests). LC Diagnosis was mainly by GPs (71%), other healthcare professionals (9%), or self-diagnosed (21%). The median total number of symptoms was 6 (IQR 4-8). Self-selected dominant LC symptoms included fatigue (54%), breathlessness (16%), pain (12%), anxiety/depression (1%) and "other" (17%). At baseline, 82% were taking medication, 57% reported 1+ other medical conditions. Quality of life was poor; 20% were on long-term sick leave or reduced working hours. Most (92%) reported having gained weight since contracting COVID-19 (median weight change +11.5 kg, range -11.5 to +45.3 kg).

Conclusions

Symptoms linked to LC and overweight are diverse and complex. Remote trial delivery enabled rapid recruitment across the UK yet certain groups (e.g. men and those from ethnic minority groups) were under-represented.

Trial registration

ISRCTN registry ( ISRCTN12595520, 25/11/2021).

[Long covid and disability]

Long covid is a health problem that will entail a high hidden cost attributable to the pandemic years after it because it affects the work capacity of many workers. Given the millions of covid-19 cases worldwide and current research showing that one in 7covid-19 patients remain symptomatic at 12 weeks, the number of long covid patients is likely to be substantial. Long covid is characterized by heterogeneous sequelae that often affect multiple systems, organs with an impact on the functioning and capacity of the worker. Workers with long covid symptoms can return to their occupation but this involves a complex individualized approach to the impact of symptoms on work, adjustments and modifications to the workplace. Patients with long covid typically report prolonged multisystem involvement and signicant disability. The psychological cost to the worker must also be addressed. A survey by the Community of Madrid (CCOO, SATSE, CSIF, AMYTS) in 2022 reveals that 24.5% of those affected by long covid were sick for more than 12 months; 30% of those affected by persistent covid need and adaption to their workplace. In Spain, more than 10million people infected with SARS-CoV-2 have been reported since the pandemic began, so it is estimated that there could be one million people with persistent covid. In 2021 alone there were more than 2.6 million sick leave due to covid-19 in Spain, the average duration of which was 10 days. One hundred million people around the world suffer from persistent covid, but few countries officially count them, nor do they help those affected with employment. In advanced countries, like the United States, long covid is treated as a disability,and the number of people with disabilities working or looking for work increased by 1.36 million, an increase of 23%, between January 2021 and January 2022. In the United Kingdom, some 200,000 people are not working or are not looking for work due to long-term health problems attributable to long covid, since the pandemic began.

Systems analysis of innate and adaptive immunity in Long COVID

Since the onset of the COVID-19 pandemic, significant progress has been made in developing effective preventive and therapeutic strategies against severe acute SARS-CoV-2 infection. However, the management of Long COVID (LC), an infection-associated chronic condition that has been estimated to affect 5-20% of individuals following SARS-CoV-2 infection, remains challenging due to our limited understanding of its mechanisms. Although LC is a heterogeneous disease that is likely to have several subtypes, immune system disturbances appear common across many cases. The extent to which these immune perturbations contribute to LC symptoms, however, is not entirely clear. Recent advancements in multi-omics technologies, capable of detailed, cell-level analysis, have provided valuable insights into the immune perturbations associated with LC. Although these studies are largely descriptive in nature, they are the crucial first step towards a deeper understanding of the condition and the immune system's role in its development, progression, and resolution. In this review, we summarize the current understanding of immune perturbations in LC, covering both innate and adaptive immune responses, and the cytokines and analytes involved. We explore whether these findings support or challenge the primary hypotheses about LC's underlying mechanisms. We also discuss the crosstalk between various immune system components and how it can be disrupted in LC. Finally, we emphasize the need for more tissue- and subtype-focused analyses of LC, and for enhanced collaborative efforts to analyze common specimens from large cohorts, including those undergoing therapeutic interventions. These collective efforts are vital to unravel the fundaments of this new disease, and could also shed light on the prevention and treatment of the larger family of chronic illnesses linked to other microbial infections.

Role of the SARS-CoV-2 Virus in Brain Cells

COVID-19, caused by the SARS-CoV-2 virus, can have neurological effects, including cognitive symptoms like brain fog and memory problems. Research on the neurological effects of COVID-19 is ongoing, and factors such as inflammation, disrupted blood flow, and damage to blood vessels may contribute to cognitive symptoms. Notably, some authors and existing evidence suggest that the SARS-CoV-2 virus can enter the central nervous system through different routes, including the olfactory nerve and the bloodstream. COVID-19 infection has been associated with neurological symptoms such as altered consciousness, headaches, dizziness, and mental disorders. The exact mechanisms and impact on memory formation and brain shrinkage are still being studied. This review will focus on pathways such as the olfactory nerve and blood-brain barrier disruption, and it will then highlight the interactions of the virus with different cell types in the brain, namely neurons, astrocytes, oligodendrocytes, and microglia.

Long-term risks of respiratory diseases in patients infected with SARS-CoV-2: a longitudinal, population-based cohort study

Background

In the post-pandemic era, growing apprehension exists regarding the potential sequelae of COVID-19. However, the risks of respiratory diseases following SARS-CoV-2 infection have not been comprehensively understood. This study aimed to investigate whether COVID-19 increases the long-term risk of respiratory illness in patients with COVID-19.

Methods

In this longitudinal, population-based cohort study, we built three distinct cohorts age 37-73 years using the UK Biobank database; a COVID-19 group diagnosed in medical records between January 30th, 2020 and October 30th, 2022, and two control groups, a contemporary control group and a historical control group, with cutoff dates of October 30th, 2022 and October 30th, 2019, respectively. The follow-up period of all three groups was 2.7 years (the median (IQR) follow-up time was 0.8 years). Respiratory outcomes diagnosed in medical records included common chronic pulmonary diseases (asthma, bronchiectasis, chronic obstructive pulmonary disease (COPD), interstitial lung disease (ILD), pulmonary vascular disease (PVD), and lung cancer. For the data analysis, we calculated hazard ratios (HRs) along with their 95% CIs using Cox regression models, following the application of inverse probability weights (IPTW).

Findings

A total of 3 cohorts were included in this study; 112,311 individuals in the COVID-19 group with a mean age (±SDs) of 56.2 (8.1) years, 359,671 in the contemporary control group, and 370,979 in the historical control group. Compared with the contemporary control group, those infected with SARS-CoV-2 exhibited elevated risks for developing respiratory diseases. This includes asthma, with a HR of 1.49 and a 95% CI 1.28-1.74; bronchiectasis (1.30; 1.06-1.61); COPD (1.59; 1.41-1.81); ILD (1.81; 1.38-2.21); PVD (1.59; 1.39-1.82); and lung cancer (1.39; 1.13-1.71). With the severity of the acute phase of COVID-19, the risk of pre-described respiratory outcomes increases progressively. Besides, during the 24-months follow-up, we observed an increasing trend in the risks of asthma and bronchiectasis over time. Additionally, the HR of lung cancer for 0-6 month follow-up was 3.07 (CI 1.73-5.44), and the association of lung cancer with COVID-19 disease disappeared at 6-12 month follow-up (1.06; 0.43-2.64) and at 12-24 months (1.02; 0.45-2.34). Compared to those with one SARS-CoV-2 infection, reinfected patients were at a higher risk of asthma (3.0; 1.32-6.84), COPD (3.07; 1.42-6.65), ILD (3.61; 1.11-11.8), and lung cancer (3.20; 1.59-6.45). Similar findings were noted when comparing with a historical cohort serving as a control group, including asthma (1.31; 1.13-1.52); bronchiectasis (1.53; 1.23-1.89); COPD (1.41; 1.24-1.59); ILD (2.53; 2.05-3.13); PVD (2.30; 1.98-2.66); and lung cancer (2.23; 1.78-2.79).

Interpretation

Our research suggests that patients with COVID-19 may have an increased risk of developing respiratory diseases, and the risk increases with the severity of infection and reinfection. Even during the 24-month follow-up, the risk of asthma and bronchiectasis continued to increase. Hence, implementing appropriate follow-up strategies for these individuals is crucial to monitor and manage potential long-term respiratory health issues. Additionally, the increased risk in lung cancer in the COVID-19 individuals was probably due to the diagnostic tests conducted and incidental diagnoses.

Funding

The National Natural Science Foundation of China of China Regional Innovation and Development Joint Foundation; National Natural Science Foundation of China; Program for High-level Foreign Expert Introduction of China; Natural Science Foundation for Distinguished Young Scholars of Guangdong Province; Guangdong Basic and Applied Basic Research Foundation; Climbing Program of Introduced Talents and High-level Hospital Construction Project of Guangdong Provincial People's Hospital; VA Clinical Merit and ASGE clinical research funds.

Cardiovascular dysautonomia in postacute sequelae of SARS-CoV-2 infection

Coronavirus disease 2019 (COVID-19) has led to a worldwide pandemic that continues to transform but will not go away. Cardiovascular dysautonomia in postacute sequelae of severe acute respiratory syndrome coronavirus 2 infection has led to persistent symptoms in a large number of patients. Here, we define the condition and its associated symptoms as well as potential mechanisms responsible. We provide a careful and complete overview of the topic addressing novel studies and a generalized approach to the management of individuals with this complex and potentially debilitating problem. We also discuss future research directions and the important knowledge gaps to be addressed in ongoing and planned studies.

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

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, cGAS, STING, 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 cGAS, STING 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.

COVID-19 Recovery: Consistent Absence of Cerebrospinal Fluid Biomarker Abnormalities in Patients With Neurocognitive Post-COVID Complications

BACKGROUND

To investigate evidence of residual viral infection, intrathecal immune activation, central nervous system (CNS) injury, and humoral responses in cerebrospinal fluid (CSF) and plasma in patients recovering from coronavirus disease 2019 (COVID-19), with or without neurocognitive post-COVID condition (PCC).

METHODS

Thirty-one participants (25 with neurocognitive PCC) underwent clinical examination, lumbar puncture, and venipuncture ≥3 months after COVID-19 symptom onset. Healthy volunteers were included. CSF and plasma severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid and spike antigen (N-Ag, S-Ag), and CSF biomarkers of immune activation and neuronal injury were analyzed.

RESULTS

SARS-CoV-2 N-Ag or S-Ag were undetectable in all samples and no participant had pleocytosis. We detected no significant differences in CSF and plasma cytokine concentrations, albumin ratio, IgG index, neopterin, β2M, or in CSF biomarkers of neuronal injury and astrocytic damage. Furthermore, principal component analysis (PCA1) analysis did not indicate any significant differences between the study groups in the marker sets cytokines, neuronal markers, or anti-cytokine autoantibodies.

CONCLUSIONS

We found no evidence of ongoing viral replication, immune activation, or CNS injury in plasma or CSF in patients with neurocognitive PCC compared with COVID-19 controls or healthy volunteers, suggesting that neurocognitive PCC is a consequence of events suffered during acute COVID-19 rather than persistent viral CNS infection or residual CNS inflammation.

SARS-CoV-2 and innate immunity: the good, the bad, and the "goldilocks"

An ancient conflict between hosts and pathogens has driven the innate and adaptive arms of immunity. Knowledge about this interplay can not only help us identify biological mechanisms but also reveal pathogen vulnerabilities that can be leveraged therapeutically. The humoral response to SARS-CoV-2 infection has been the focus of intense research, and the role of the innate immune system has received significantly less attention. Here, we review current knowledge of the innate immune response to SARS-CoV-2 infection and the various means SARS-CoV-2 employs to evade innate defense systems. We also consider the role of innate immunity in SARS-CoV-2 vaccines and in the phenomenon of long COVID.

Autoimmunity and long COVID in children

Numerous hypotheses regarding the pathogenetic mechanisms of long COVID have been proposed. Immune dysregulation and autoimmunity are among the leading hypotheses. In this article, we present two clinical cases of long COVID. The first case demonstrates the phenotype of long COVID with pain and musculoskeletal symptoms, which is often associated with autoimmunity and mimics systemic connective tissue diseases. In the second case, a high titer of antinuclear antibodies was observed after SARS-CoV-2 infection, but the clinical symptoms were limited to fever and headache. Only a comprehensive evaluation of clinical symptoms and thorough objective examination can confirm or exclude autoimmune diseases after a previous SARS-CoV-2 infection. A systematic search in the PubMed Medline database was carried out for studies focusing on immune dysregulation, autoimmunity, and its association with the clinical phenotype of long COVID. The question of the role of autoimmunity in the development of long COVID and the management approaches are discussed.

The demographic, laboratory and genetic factors associated with long Covid-19 syndrome: a case-control study

Long Covid-19 syndrome (LCS) manifests with a wide range of clinical symptoms, yet the factors associated with LCS remain poorly understood. The current study aimed to investigate the relationships that demographic characteristics, clinical history, laboratory indicators, and the frequency of HLA-I alleles have with the likelihood of developing LCS. We extracted the demographic characteristics and clinical histories from the medical records of 88 LCS cases (LCS+ group) and 96 individuals without LCS (LCS- group). Furthermore, we evaluated the clinical symptoms, serum levels of interleukin (IL)-6 and tumor necrosis factor-α, laboratory parameters, and the frequencies of HLA-I alleles. Following this we used multiple logistic regression to investigate the association these variables had with LCS. Subjects in the LCS+ group were more likely to have experienced severe Covid-19 symptoms and had higher body mass index (BMI), white blood cell, lymphocyte counts, C-reactive protein (CRP), and IL-6 levels than those in the LCS- group (for all: P < 0.05). Moreover, the frequencies of the HLA-A*11, -B*14, -B*38, -B*50, and -C*07 alleles were higher in the LCS+ group (for all: P < 0.05). After adjusting for the most important variables, the likelihood of suffering from LCS was significantly associated with BMI, CRP, IL-6, the HLA-A*11, and -C*07 alleles, as well as a positive history of severe Covid-19 (for all: P < 0.05). Our study showed that a history of severe Covid-19 during the acute phase of the disease, the HLA-A*11, and -C*07 alleles, higher BMI, as well as elevated serum CRP and IL-6 levels, were all associated with an increased likelihood of LCS.

High Plasma Osteopontin Levels Are Associated with Serious Post-Acute-COVID-19-Related Dyspnea

COVID-19 survivors commonly report persistent symptoms. In this observational study, we investigated the link between osteopontin (OPN) and post-acute COVID-19 symptoms and lung functional/imaging abnormalities. We recorded symptoms and lung imaging/functional data from previously hospitalized COVID-19 patients, who were followed for 4-84 weeks (122 patients/181 visits) post-symptom onset at our outpatient clinic. Circulating OPN was determined using ELISA. Plasma OPN levels were higher in symptomatic patients (compared with the asymptomatic ones); those with dyspnea (compared with those without dyspnea);those with a combination of serious symptoms, i.e., the presence of at least one of the following: dyspnea, fatigue and muscular weakness (compared with those with none of these symptoms); and those with dyspnea and m-MRC > 1 (compared with those with m-MRC = 0-1). Plasma OPN levels were inversely correlated with EQ-VAS (visual analog scale of the EQ-5D-5L health-related quality-of-life questionnaire) values. High-resolution CT or diffusion lung capacity (DLCO) findings were not related to circulating OPN. In the multiple logistic regression, the presence of symptoms, dyspnea, or the combination of serious symptoms were linked to female gender, increased BMI and pre-existing dyspnea (before the acute disease), while increased plasma OPN levels, female gender and pre-existing dyspnea with m-MRC > 1 were independently associated with severe post-COVID-19 dyspnea (m-MRC > 1). Using a correlation matrix to investigate multiple correlations between EQ-VAS, OPN and epidemiological data, we observed an inverse correlation between the OPN and EQ-VAS values. Increased circulating OPN was linked to the persistence of severe exertional dyspnea and impaired quality of life in previously hospitalized COVID-19 patients.

Single-cell RNA sequencing reveals characteristics of myeloid cells in post-acute sequelae of SARS-CoV-2 patients with persistent respiratory symptoms

Background

Although our understanding of the immunopathology and subsequent risk and severity of COVID-19 disease is evolving, a detailed account of immune responses that contribute to the long-term consequences of pulmonary complications in COVID-19 infection remains unclear. Few studies have detailed the immune and cytokine profiles associated with post-acute sequelae of SARS-CoV-2 infection (PASC) with persistent pulmonary symptoms. The dysregulation of the immune system that drives pulmonary sequelae in COVID-19 survivors and PASC sufferers remains largely unknown.

Results

To characterize the immunological features of pulmonary PASC (PPASC), we performed droplet-based single-cell RNA sequencing (scRNA-seq) to study the transcriptomic profiles of peripheral blood mononuclear cells (PBMCs) from a participant naïve to SARS-CoV-2 (Control) (n=1) and infected with SARS-CoV-2 with chronic pulmonary symptoms (PPASC) (n=2). After integrating scRNA-seq data with a naïve participant from a published dataset, 11 distinct cell populations were identified based on the expression of canonical markers. The proportion of myeloid-lineage cells ([MLCs]; CD14+/CD16+monocytes, and dendritic cells) was increased in PPASC (n=2) compared to controls (n=2). MLCs from PPASC displayed up-regulation of genes associated with pulmonary symptoms/fibrosis, while glycolysis metabolism-related genes were downregulated. Similarly, pathway analysis showed that fibrosis-related (VEGF, WNT, and SMAD) and cell death pathways were up-regulated, but immune pathways were down-regulated in PPASC. Further comparison of PPASC with scRNA-seq data with Severe COVID-19 (n=4) data demonstrated enrichment of fibrotic transcriptional signatures. In PPASC, we observed interactive VEGF ligand-receptor pairs among MLCs, and network modules in CD14+ (cluster 4) and CD16+ (Cluster 5) monocytes displayed a significant enrichment for biological pathways linked to adverse COVID-19 outcomes, fibrosis, and angiogenesis. Further analysis revealed a distinct metabolic alteration in MLCs with a down-regulation of glycolysis/gluconeogenesis in PPASC compared to SARS-CoV-2 naïve samples.

Conclusion

Analysis of a small scRNA-seq dataset demonstrated alterations in the immune response and cellular landscape in PPASC. The presence of elevated MLC levels and their corresponding gene signatures associated with fibrosis, immune response suppression, and altered metabolic states suggests a potential role in PPASC development.

Reduced monocyte proportions and responsiveness in convalescent COVID-19 patients

Introduction

The clinical manifestations of acute severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) infection and coronavirus disease 2019 (COVID-19) suggest a dysregulation of the host immune response that leads to inflammation, thrombosis, and organ dysfunction. It is less clear whether these dysregulated processes persist during the convalescent phase of disease or during long COVID. We sought to examine the effects of SARS-CoV-2 infection on the proportions of classical, intermediate, and nonclassical monocytes, their activation status, and their functional properties in convalescent COVID-19 patients.

Methods

Peripheral blood mononuclear cells (PBMCs) from convalescent COVID-19 patients and uninfected controls were analyzed by multiparameter flow cytometry to determine relative percentages of total monocytes and monocyte subsets. The expression of activation markers and proinflammatory cytokines in response to LPS treatment were measured by flow cytometry and ELISA, respectively.

Results

We found that the percentage of total monocytes was decreased in convalescent COVID-19 patients compared to uninfected controls. This was due to decreased intermediate and non-classical monocytes. Classical monocytes from convalescent COVID-19 patients demonstrated a decrease in activation markers, such as CD56, in response to stimulation with bacterial lipopolysaccharide (LPS). In addition, classical monocytes from convalescent COVID-19 patients showed decreased expression of CD142 (tissue factor), which can initiate the extrinsic coagulation cascade, in response to LPS stimulation. Finally, we found that monocytes from convalescent COVID-19 patients produced less TNF-α and IL-6 in response to LPS stimulation, than those from uninfected controls.

Conclusion

SARS-CoV-2 infection exhibits a clear effect on the relative proportions of monocyte subsets, the activation status of classical monocytes, and proinflammatory cytokine production that persists during the convalescent phase of disease.

Long Covid

Long COVID, also known as post-acute sequelae of SARS-CoV-2 infection (PASC), refers to a constellation of persistent symptoms and health issues that continue beyond the acute phase of COVID-19. This chapter provides an overview of the pathogenesis, risk factors, manifestations, major findings, and diagnosis and treatment strategies associated with Long COVID. Hypotheses regarding the pathogenesis of Long COVID are discussed, encompassing various factors such as persistent viral reservoirs, immune dysregulation with or without reactivation of herpesviruses (e.g., Epstein-Barr Virus and human herpesvirus), dysbiosis, autoimmunity triggered by infection, endothelial dysfunction, microvessel blood clotting, and dysfunctional brainstem and/or vagal signaling. The chapter also highlights the risk factors associated with Long COVID and its occurrence in children. The major findings of Long COVID, including immune dysregulation, vessel and tissue damage, neurological and cognitive pathology, eye symptoms, endocrinal issues, myalgic encephalomyelitis and chronic fatigue syndrome, reproductive system involvement, respiratory and gastrointestinal symptoms, and the chronology of symptoms, are thoroughly explored. Lastly, the chapter discusses the challenges and current approaches in the diagnosis and treatment of Long COVID, emphasizing the need for multidisciplinary care and individualized management strategies.

Low growth hormone secretion associated with post-acute sequelae SARS-CoV-2 infection (PASC) neurologic symptoms: A case-control pilot study

OBJECTIVE

To determine if patients that develop lingering neurologic symptoms of fatigue and "brain fog" after initial recovery from coronavirus disease 2019 (COVID-19) have persistent low growth hormone (GH) secretion as seen in other conditions with similar symptom etiology.

DESIGN

In this case-control observational pilot study, patients reporting lingering neurologic post-acute sequelae of SARS-CoV-2 (PASC, n = 10) symptoms at least 6 months after initial infection were compared to patients that recovered from COVID-19 without lingering symptoms (non-PASC, n = 13). We compared basic blood chemistry and select metabolites, lipids, hormones, inflammatory markers, and vitamins between groups. PASC and non-PASC subjects were tested for neurocognition and GH secretion, and given questionnaires to assess symptom severity. PASC subjects were also tested for glucose tolerance and adrenal function.

RESULTS

PASC subjects reported significantly worse fatigue, sleep quality, depression, quality of life, and gastrointestinal discomfort compared to non-PASC. Although PASC subjects self-reported poor mental resilience, cognitive testing did not reveal significant differences between groups. Neurologic PASC symptoms were not linked to inflammatory markers or adrenal insufficiency, but were associated with reduced growth hormone secretion.

CONCLUSIONS

Neurologic PASC symptoms are associated with gastrointestinal discomfort and persistent disruption of GH secretion following recovery from acute COVID-19. (www.

CLINICALTRIALS

gov; NCT04860869).

Landscape of molecular crosstalk between SARS-CoV-2 infection and cardiovascular diseases: emphasis on mitochondrial dysfunction and immune-inflammation

BACKGROUND

SARS-CoV-2, the pathogen of COVID-19, is a worldwide threat to human health and causes a long-term burden on the cardiovascular system. Individuals with pre-existing cardiovascular diseases are at higher risk for SARS-CoV-2 infection and tend to have a worse prognosis. However, the relevance and pathogenic mechanisms between COVID-19 and cardiovascular diseases are not yet completely comprehended.

METHODS

Common differentially expressed genes (DEGs) were obtained in datasets of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) infected with SARS-CoV-2 and myocardial tissues from heart failure patients. Further GO and KEGG pathway analysis, protein-protein interaction (PPI) network construction, hub genes identification, immune microenvironment analysis, and drug candidate predication were performed. Then, an isoproterenol-stimulated myocardial hypertrophy cell model and a transverse aortic constriction-induced mouse heart failure model were employed to validate the expression of hub genes.

RESULTS

A total of 315 up-regulated and 78 down-regulated common DEGs were identified. Functional enrichment analysis revealed mitochondrial metabolic disorders and extensive immune inflammation as the most prominent shared features of COVID-19 and cardiovascular diseases. Then, hub DEGs, as well as hub immune-related and mitochondria-related DEGs, were screened. Additionally, nine potential therapeutic agents for COVID-19-related cardiovascular diseases were proposed. Furthermore, the expression patterns of most of the hub genes related to cardiovascular diseases in the validation dataset along with cellular and mouse myocardial damage models, were consistent with the findings of bioinformatics analysis.

CONCLUSIONS

The study unveiled the molecular networks and signaling pathways connecting COVID-19 and cardiovascular diseases, which may provide novel targets for intervention of COVID-19-related cardiovascular diseases.

Persisting Shadows: Unraveling the Impact of Long COVID-19 on Respiratory, Cardiovascular, and Nervous Systems

The coronavirus disease 2019 (COVID-19), instigated by the zoonotic Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), rapidly transformed from an outbreak in Wuhan, China, into a widespread global pandemic. A significant post-infection condition, known as 'long- COVID-19' (or simply 'long- COVID'), emerges in a substantial subset of patients, manifesting with a constellation of over 200 reported symptoms that span multiple organ systems. This condition, also known as 'post-acute sequelae of SARS-CoV-2 infection' (PASC), presents a perplexing clinical picture with far-reaching implications, often persisting long after the acute phase. While initial research focused on the immediate pulmonary impact of the virus, the recognition of COVID-19 as a multiorgan disruptor has unveiled a gamut of protracted and severe health issues. This review summarizes the primary effects of long COVID on the respiratory, cardiovascular, and nervous systems. It also delves into the mechanisms underlying these impacts and underscores the critical need for a comprehensive understanding of long COVID's pathogenesis.