Autoantibodies in COVID-19 correlate with antiviral humoral responses and distinct immune signatures

Differential decline of SARS-CoV-2-specific antibody levels, innate and adaptive immune cells, and shift of Th1/inflammatory to Th2 serum cytokine levels long after first COVID-19

BACKGROUND

SARS-CoV-2 has triggered a pandemic and contributes to long-lasting morbidity. Several studies have investigated immediate cellular and humoral immune responses during acute infection. However, little is known about long-term effects of COVID-19 on the immune system.

METHODS

We performed a longitudinal investigation of cellular and humoral immune parameters in 106 non-vaccinated subjects ten weeks (10 w) and ten months (10 m) after their first SARS-CoV-2 infection. Peripheral blood immune cells were analyzed by multiparametric flow cytometry, serum cytokines were examined by multiplex technology. Antibodies specific for the Spike protein (S), the receptor-binding domain (RBD) and the nucleocapsid protein (NC) were determined. All parameters measured 10 w and 10 m after infection were compared with those of a matched, noninfected control group (n = 98).

RESULTS

Whole blood flow cytometric analyses revealed that 10 m after COVID-19, convalescent patients compared to controls had reduced absolute granulocyte, monocyte, and lymphocyte counts, involving T, B, and NK cells, in particular CD3+CD45RA+CD62L+CD31+ recent thymic emigrant T cells and non-class-switched CD19+IgD+CD27+ memory B cells. Cellular changes were associated with a reversal from Th1- to Th2-dominated serum cytokine patterns. Strong declines of NC- and S-specific antibody levels were associated with younger age (by 10.3 years, p < .01) and fewer CD3-CD56+ NK and CD19+CD27+ B memory cells. Changes of T-cell subsets at 10 m such as normalization of effector and Treg numbers, decline of RTE, and increase of central memory T cell numbers were independent of antibody decline pattern.

CONCLUSIONS

COVID-19 causes long-term reduction of innate and adaptive immune cells which is associated with a Th2 serum cytokine profile. This may provide an immunological mechanism for long-term sequelae after COVID-19.

Mendelian randomization and Bayesian model averaging of autoimmune diseases and Long COVID

Background

Following COVID-19, reports suggest Long COVID and autoimmune diseases (AIDs) in infected individuals. However, bidirectional causal effects between Long COVID and AIDs, which may help to prevent diseases, have not been fully investigated.

Methods

Summary-level data from genome-wide association studies (GWAS) of Long COVID (N = 52615) and AIDs including inflammatory bowel disease (IBD) (N = 377277), Crohn's disease (CD) (N = 361508), ulcerative colitis (UC) (N = 376564), etc. were employed. Bidirectional causal effects were gauged between AIDs and Long COVID by exploiting Mendelian randomization (MR) and Bayesian model averaging (BMA).

Results

The evidence of causal effects of IBD (OR = 1.06, 95% CI = 1.00-1.11, p = 3.13E-02), CD (OR = 1.10, 95% CI = 1.01-1.19, p = 2.21E-02) and UC (OR = 1.08, 95% CI = 1.03-1.13, p = 2.35E-03) on Long COVID was found. In MR-BMA, UC was estimated as the highest-ranked causal factor (MIP = 0.488, MACE = 0.035), followed by IBD and CD.

Conclusion

This MR study found that IBD, CD and UC had causal effects on Long COVID, which suggests a necessity to screen high-risk populations.

A case of rapidly progressive glomerulonephritis with double-positive anti-GBM antibody and MPO-ANCA after SARS-CoV-2 vaccination and relapse during 1 year follow-up

Although mRNA vaccines for COVID-19 are highly beneficial and are recommended for patients with kidney disease, adverse reactions in some patients after vaccination have been problematic. Various vasculitis and renal disorders have been reported after vaccination; however, a causal relationship has not yet been identified. In this report, we describe a case of rapidly progressive glomerulonephritis that developed after SARS-CoV-2 vaccination, in which both anti-glomerular basement membrane (anti-GBM) and myeloperoxidase antineutrophil cytoplasmic antibodies (MPO-ANCA) were present. The patient's renal biopsy showed that of the 48 glomeruli in total, four showed global sclerosis and none showed segmental sclerosis. The biopsy showed 11 cellular glomerular crescents and 5 fibrocellular glomerular crescents. Renal function improved with steroids, rituximab, and plasma exchange. Approximately 9 months later, MPO-ANCA was again elevated, and the pulmonary lesions worsened, again requiring multidisciplinary treatment. This case suggests that caution should be exercised in the development of double-positive disease after vaccination, and that long-term observation may be necessary because of the possibility of relapse.

Persistent complement dysregulation with signs of thromboinflammation in active Long Covid

Long Covid is a debilitating condition of unknown etiology. We performed multimodal proteomics analyses of blood serum from COVID-19 patients followed up to 12 months after confirmed severe acute respiratory syndrome coronavirus 2 infection. Analysis of >6500 proteins in 268 longitudinal samples revealed dysregulated activation of the complement system, an innate immune protection and homeostasis mechanism, in individuals experiencing Long Covid. Thus, active Long Covid was characterized by terminal complement system dysregulation and ongoing activation of the alternative and classical complement pathways, the latter associated with increased antibody titers against several herpesviruses possibly stimulating this pathway. Moreover, markers of hemolysis, tissue injury, platelet activation, and monocyte-platelet aggregates were increased in Long Covid. Machine learning confirmed complement and thromboinflammatory proteins as top biomarkers, warranting diagnostic and therapeutic interrogation of these systems.

Brain Fog: a Narrative Review of the Most Common Mysterious Cognitive Disorder in COVID-19

It has been more than three years since COVID-19 impacted the lives of millions of people, many of whom suffer from long-term effects known as long-haulers. Notwithstanding multiorgan complaints in long-haulers, signs and symptoms associated with cognitive characteristics commonly known as "brain fog" occur in COVID patients over 50, women, obesity, and asthma at excessive. Brain fog is a set of symptoms that include cognitive impairment, inability to concentrate and multitask, and short-term and long-term memory loss. Of course, brain fog contributes to high levels of anxiety and stress, necessitating an empathetic response to this group of COVID patients. Although the etiology of brain fog in COVID-19 is currently unknown, regarding the mechanisms of pathogenesis, the following hypotheses exist: activation of astrocytes and microglia to release pro-inflammatory cytokines, aggregation of tau protein, and COVID-19 entry in the brain can trigger an autoimmune reaction. There are currently no specific tests to detect brain fog or any specific cognitive rehabilitation methods. However, a healthy lifestyle can help reduce symptoms to some extent, and symptom-based clinical management is also well suited to minimize brain fog side effects in COVID-19 patients. Therefore, this review discusses mechanisms of SARS-CoV-2 pathogenesis that may contribute to brain fog, as well as some approaches to providing therapies that may help COVID-19 patients avoid annoying brain fog symptoms.

Following Natural Autoantibodies: Further Immunoserological Evidence Regarding Their Silent Plasticity and Engagement in Immune Activation

Contradictory reports are available on vaccine-associated hyperstimulation of the immune system, provoking the formation of pathological autoantibodies. Despite being interconnected within the same network, the role of the quieter, yet important non-pathological and natural autoantibodies (nAAbs) is less defined. We hypothesize that upon a prompt immunological trigger, physiological nAAbs also exhibit a moderate plasticity. We investigated their inducibility through aged and recent antigenic triggers. Anti-viral antibodies (anti-MMR n = 1739 and anti-SARS-CoV-2 IgG n = 330) and nAAbs (anti-citrate synthase IgG, IgM n = 1739) were measured by in-house and commercial ELISAs using Croatian (Osijek) anonymous samples with documented vaccination backgrounds. The results were subsequently compared for statistical evaluation. Interestingly, the IgM isotype nAAb showed a statistically significant connection with anti-MMR IgG seropositivity (p < 0.001 in all cases), while IgG isotype nAAb levels were elevated in association with anti-SARS CoV-2 specific seropositivity (p = 0.019) and in heterogeneous vaccine regimen recipients (unvaccinated controls vector/mRNA vaccines p = 0.002). Increasing evidence supports the interplay between immune activation and the dynamic expansion of nAAbs. Consequently, further questions may emerge regarding the ability of nAAbs silently shaping the effectiveness of immunization. We suggest re-evaluating the impact of nAAbs on the complex functioning of the immunological network.

Autoantibodies in COVID-19, a possible role in the pathogenesis of the disease

OBJECTIVES

In this study, we investigated whether SARS-CoV-2 stimulates autoantibody production.

METHODS

The study included 91 patients hospitalized due to COVID 19, with no previous history of immunological diseases. Immunofluorescence assays were performed to detect antinuclear antibodies (ANAs) and antineutrophil cytoplasmic antibodies (ANCAs), along with tests for specific autoantibodies.

RESULTS

The median age (57% male) was 74 years (range 38-95 years). Autoantibodies were positive in 67 (74%), ANA in 65 (71%), and ANCA in 11 (12%) patients. Female gender (p = 0.01), age (p = 0.005), and Charlson comorbidity index (p = 0.004) were significant predictors for the development of ANA/ANCA antibodies (p = 0.004). Nuclear mitotic apparatus (NuMA)-like, positivity was the strongest predictor of acute kidney injury (AKI), together with noninvasive ventilation and eGFR (χ2  = 49.01, P < 0.001).

CONCLUSION

Positive autoantibodies in a large proportion of patients suggest a role of autoimmunity in the pathophysiology of acute COVID-19 disease. NuMA was the strongest predictor of AKI.

Transient constrictive pericarditis: A complication of COVID-19 infection or first presentation of systemic lupus erythematous? A case report

Cardiovascular disorders are significantly associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Herein, we describe a case of myopericarditis and subsequent transient constrictive pericarditis after coronavirus disease 2019 (COVID-19). Three weeks following a mild SARS-CoV-2 illness, a 53-year-old woman was referred to the hospital with acute pleuritic chest pain, which was not attributable to any known cause and was only temporarily relieved. The pain persisted for the next few weeks until her second COVID-19 infection, which occurred 5 months after her first affliction. This time, Transthoracic echocardiography (TTE) revealed mild pericardial effusion, and cardiac magnetic resonance imaging (CMR) confirmed myopericarditis, leading to the administration of anti-inflammatory therapy for the patient. Despite a relative resolution of symptoms, her second CMR performed 8 months later revealed active perimyocarditis with transient constrictive pericarditis (CP). Additionally, fluorescent antinuclear antibody (FANA) and antimitochondrial Ab M2 (AMA) were tested positive for the first time. Thereafter, the patient was started on concurrent anti-inflammatory and immunosuppressant therapies, which were effective after 3 months. The transient CP was resolved, and there was no sign of active pericarditis on her last echocardiography. Acute pericarditis and its subsequent constrictive pericarditis are infrequent adverse outcomes of COVID-19. The unique feature of this case is the uncertainty regarding the underlying reason for cardiac complications, whether it is the first presentation of systemic lupus erythematosus (SLE) or viral-induced myopericarditis followed by a consequent transient CP.

Severe COVID-19 patients exhibit elevated levels of autoantibodies targeting cardiolipin and platelet glycoprotein with age: a systems biology approach

Age is a significant risk factor for the coronavirus disease 2019 (COVID-19) severity due to immunosenescence and certain age-dependent medical conditions (e.g., obesity, cardiovascular disorder, and chronic respiratory disease). However, despite the well-known influence of age on autoantibody biology in health and disease, its impact on the risk of developing severe COVID-19 remains poorly explored. Here, we performed a cross-sectional study of autoantibodies directed against 58 targets associated with autoimmune diseases in 159 individuals with different COVID-19 severity (71 mild, 61 moderate, and 27 with severe symptoms) and 73 healthy controls. We found that the natural production of autoantibodies increases with age and is exacerbated by SARS-CoV-2 infection, mostly in severe COVID-19 patients. Multiple linear regression analysis showed that severe COVID-19 patients have a significant age-associated increase of autoantibody levels against 16 targets (e.g., amyloid β peptide, β catenin, cardiolipin, claudin, enteric nerve, fibulin, insulin receptor a, and platelet glycoprotein). Principal component analysis with spectrum decomposition and hierarchical clustering analysis based on these autoantibodies indicated an age-dependent stratification of severe COVID-19 patients. Random forest analysis ranked autoantibodies targeting cardiolipin, claudin, and platelet glycoprotein as the three most crucial autoantibodies for the stratification of severe COVID-19 patients ≥50 years of age. Follow-up analysis using binomial logistic regression found that anti-cardiolipin and anti-platelet glycoprotein autoantibodies significantly increased the likelihood of developing a severe COVID-19 phenotype with aging. These findings provide key insights to explain why aging increases the chance of developing more severe COVID-19 phenotypes.

COVID-19-Related Bilateral Avascular Necrosis of the Femoral Head

Osteonecrosis is a pathologic process that involves focal bone infarction and death of bone tissue caused by trauma, infections, autoimmune conditions, and chronic steroid use; however, most cases go undiagnosed. The link between bilateral osteonecrosis and coronavirus disease 2019 (COVID-19) infections has not been fully investigated. This is the case of a 42-year-old Caucasian woman who presented to the emergency department for bilateral hip pain, which started three months prior. Initially, the pain was mild; however, her symptoms worsened, causing her to have difficulty ambulating. Co-incidentally she tested positive for COVID-19 10 days after the onset of pain. She denied any lower-extremity numbness, weakness, and loss of bowel or bladder function. X-ray of the hips showed significant sclerosis of bilateral femoral heads and acetabula, indicating avascular necrosis. She was given ketorolac injection intramuscularly for analgesia and remained in stable condition. Upon discharge, she was given a referral to orthopedic surgery for bilateral total hip arthroplasty. Atraumatic osteonecrosis of the femoral head can be caused by multiple etiologies, including exposure to medications, post-transplantation procedures, trauma, and hypercoagulable states. This condition is likely due to poor angiogenesis after an infarct, causing a domino effect of bone demineralization, trabecular thinning, and cortical collapse. A literature search demonstrated prior cases of unilateral femoral head necrosis associated with COVID-19 infection and steroid use. There have been no cases of bilateral osteonecrosis of the femoral head reported without long-term steroid use. Considering the disease severity in both hips and limited steroid use (only five days of prednisone), other common etiologies were sought and were ruled out. In our patient, the only event that was related to her initial onset of hip pain was a COVID-19 infection. We suggest a relationship between COVID-19 infection and avascular necrosis given the rapid progression of the disease. We acknowledge that this presentation of bilateral osteonecrosis is rare and warrants further investigation. More research should be performed to establish a tenable relationship between COVID-19 infection and osteonecrosis, with and without the use of steroids.

Postacute Sequelae of SARS-CoV-2: Musculoskeletal Conditions and Pain

Musculoskeletal and pain sequelae of COVID-19 are common in both the acute infection and patients experiencing longer term symptoms associated with recovery, known as postacute sequelae of COVID-19 (PASC). Patients with PASC may experience multiple manifestations of pain and other concurrent symptoms that complicate their experience of pain. In this review, the authors explore what is currently known about PASC-related pain and its pathophysiology as well as strategies for diagnosis and management.

SARS-CoV-2 infection is associated with anti-desmoglein 2 autoantibody detection

Post-acute cardiac sequelae, following SARS-CoV-2 infection, are well recognized as complications of COVID-19. We have previously shown the persistence of autoantibodies against antigens in skin, muscle, and heart in individuals following severe COVID-19; the most common staining on skin tissue displayed an inter-cellular cement pattern consistent with antibodies against desmosomal proteins. Desmosomes play a critical role in maintaining the structural integrity of tissues. For this reason, we analyzed desmosomal protein levels and the presence of anti-desmoglein (DSG) 1, 2, and 3 antibodies in acute and convalescent sera from patients with COVID-19 of differing clinical severity. We find increased levels of DSG2 protein in sera from acute COVID-19 patients. Furthermore, we find that DSG2 autoantibody levels are increased significantly in convalescent sera following severe COVID-19 but not in hospitalized patients recovering from influenza infection or healthy controls. Levels of autoantibody in sera from patients with severe COVID-19 were comparable to levels in patients with non-COVID-19-associated cardiac disease, potentially identifying DSG2 autoantibodies as a novel biomarker for cardiac damage. To determine if there was any association between severe COVID-19 and DSG2, we stained post-mortem cardiac tissue from patients who died from COVID-19 infection. This confirmed DSG2 protein within the intercalated discs and disruption of the intercalated disc between cardiomyocytes in patients who died from COVID-19. Our results reveal the potential for DSG2 protein and autoimmunity to DSG2 to contribute to unexpected pathologies associated with COVID-19 infection.

Multisystem inflammatory syndrome in children: A dysregulated autoimmune disorder following COVID-19

Multisystem inflammatory syndrome in children (MIS-C) is a dysregulated autoimmune-mediated illness in genetically susceptible patients following COVID-19 with an interval of 2-6 weeks. The median age of patients with MIS-C is 6-11 years. Most common manifestations are involvement of gastrointestinal tract, cardiovascular system, hematological system, and mucocutaneous system. Respiratory tract, neurological system, musculoskeletal system, and kidney are less frequently affected. Mucocutaneous manifestations and coronary artery abnormalities characteristic for Kawasaki disease (KD) may be observed in a significant proportion of MIS-C patients that may make the differential diagnosis be difficult for some patients, especially in the post-pandemic era. The mortality rate is 1-3%. Management and prognosis of MIS-C are similar to that of KD. MIS-C and KD may share a common pathogenic process. Based on the observation of MIS-C-like illness in uninfected neonates, i.e. multisystem inflammatory syndrome in neonates, both MIS-C and KD may be a consequence of dysregulated, over-exaggerated humoral immune responses triggered by a specific infectious agent.

Diagnosis and management of post-COVID (Long COVID) in children: a moving target

PURPOSE OF REVIEW

This review describes recent findings about post-COVID condition (PCC, or Long COVID) in children, including current knowledge about its epidemiology, clinical presentation, pathogenesis and care.

RECENT FINDINGS

There is no internationally agreed definition of PCC, although now most researchers agree that it is a complex clinical symptomatology persisting for at least 3 months after COVID-19, without an alternative diagnosis. There are several uncertainties about paediatric PCC. So far, available literature suggest that 1-3% of recognized children with Severe Acute Respiratory Syndrome COronaVirus 2 (SARS-CoV-2) infection may develop PCC. Its pathogenesis is unknown, although there is increasing evidence about possible abnormalities in the immune responses, cellular metabolism and intestinal microbiota, along with chronic endothelitis.

SUMMARY

Management of PCC in children is complex and require a multidisciplinary approach, with the goal of offering the best care possible to support diagnostics, research, mental health and access to research projects.

The immune paradox of SARS-CoV-2: Lymphocytopenia and autoimmunity evoking features in COVID-19 and possible treatment modalities

SARS-CoV-2 causes multiorgan damage to vital organs and tissue that are known to be due to a combination of tissue tropisms and cytokine-mediated damage that it can incite in COVID-19. The effects of SARS-Co-2 on the lymphocytes and therefore on the immune response have attracted attention recently in COVID-19 to understand its effects in causing a chronic state of ongoing infection with Long-COVID. The associated lymphopaenia and autoimmune disease state, which is an apparent paradox, needs to be researched to dissect possible mechanisms underlying this state. This paper attempts to unravel the aforesaid immune paradox effects of SARS-CoV-2 on the lymphocytes and discusses appropriate treatment modalities with antiviral drugs and nutraceuticals which could prove virucidal in SARS-CoV-2 seeding monocytes and lymphocytes in patients with COVID-19 and Long-COVID. Importantly it proposes a new in vitro treatment modality of immune regulating cells that can help patients fight the lymphopaenia associated with COVID-19 and Long-COVID.

Changing face of non-infectious pediatric uveitis in the pre-pandemic and pandemic periods: a comparison study

OBJECTIVE

Our aim in this study was to reveal the clinical features of pediatric uveitis in the pandemic period and to compare it with the pre-pandemic era.

METHODS

This retrospective study included 187 children diagnosed with uveitis between the 11^th of March 2017 and the 11^th of March 2022. The patients were divided into two groups based on the date of diagnosis as follows; Group 1: Patients diagnosed in the pre-pandemic period (11^th March 2017-11^th March 2020); Group 2: Patients diagnosed in the pandemic period (12^th March 2020-11^th March 2022). Demographic data, characteristics of uveitis, underlying diseases, systemic treatment modalities, and complications were compared between the two groups.

RESULTS

A total of 187 (pre-pandemic 71, and pandemic 114) pediatric uveitis patients were recruited to the study. Fifty one percent (51%) of the patients were female. The number of patients diagnosed with uveitis increased approximately twice during the pandemic period compared to the pre-pandemic period. The frequency of anterior uveitis was found to be significantly higher in the pandemic period than in the pre-pandemic period (p = 0.037). It was mostly presented as symptomatic uveitis. There was a decrease in the diagnosis of JIA-related uveitis. ANA positivity increased in the pandemic period (p = 0.029). The response to treatment was better and the complication rate decreased in the pandemic period.

CONCLUSION

The present study involved a large number of pediatric patients with uveitis. There are some differences in the characteristics of pediatric uveitis cases comparing the pandemic period and the pre-pandemic period. This increased frequency and changing clinical features of pediatric uveitis seems to be a result of COVID-19 infection.

Innate and Adaptive Immunity during SARS-CoV-2 Infection: Biomolecular Cellular Markers and Mechanisms

The coronavirus 2019 (COVID-19) pandemic was caused by a positive sense single-stranded RNA (ssRNA) severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, other human coronaviruses (hCoVs) exist. Historical pandemics include smallpox and influenza, with efficacious therapeutics utilized to reduce overall disease burden through effectively targeting a competent host immune system response. The immune system is composed of primary/secondary lymphoid structures with initially eight types of immune cell types, and many other subtypes, traversing cell membranes utilizing cell signaling cascades that contribute towards clearance of pathogenic proteins. Other proteins discussed include cluster of differentiation (CD) markers, major histocompatibility complexes (MHC), pleiotropic interleukins (IL), and chemokines (CXC). The historical concepts of host immunity are the innate and adaptive immune systems. The adaptive immune system is represented by T cells, B cells, and antibodies. The innate immune system is represented by macrophages, neutrophils, dendritic cells, and the complement system. Other viruses can affect and regulate cell cycle progression for example, in cancers that include human papillomavirus (HPV: cervical carcinoma), Epstein-Barr virus (EBV: lymphoma), Hepatitis B and C (HB/HC: hepatocellular carcinoma) and human T cell Leukemia Virus-1 (T cell leukemia). Bacterial infections also increase the risk of developing cancer (e.g., Helicobacter pylori). Viral and bacterial factors can cause both morbidity and mortality alongside being transmitted within clinical and community settings through affecting a host immune response. Therefore, it is appropriate to contextualize advances in single cell sequencing in conjunction with other laboratory techniques allowing insights into immune cell characterization. These developments offer improved clarity and understanding that overlap with autoimmune conditions that could be affected by innate B cells (B1+ or marginal zone cells) or adaptive T cell responses to SARS-CoV-2 infection and other pathologies. Thus, this review starts with an introduction into host respiratory infection before examining invaluable cellular messenger proteins and then individual immune cell markers.

Reliability and reproducibility of antinuclear antibody testing in pediatric rheumatology practice

Antinuclear antibody (ANA) testing is common practice among health care practitioners when evaluating children and adolescents with non-specific symptoms including fatigue and aches and pains. When positive, ANA results often lead to referrals to pediatric rheumatologists as these antibodies may be key indicators for specific pediatric rheumatologic diagnoses. The reliability and reproducibility of ANA tests varies with assay techniques and validation and interpretation of results. In the following article, review of ANA testing in pediatrics is provided along with case examples that demonstrate the reliability and reproducibility of these results in specific scenarios common in the practice of pediatric rheumatology. Guidelines for more accurate utilization of ANA testing are presented with the aim to improve testing and interpretation by ordering clinicians.

TLR7 and IgM: Dangerous Partners in Autoimmunity

The B cell antigen receptor (BCR)-repertoire is capable of recognizing a nearly unlimited number of antigens. Inevitably, the random nature of antibody gene segment rearrangement, needed in order to provide mature B cells, will generate autoreactive specificities. Once tolerance mechanisms fail to block the activation and differentiation of autoreactive B cells, harmful autoantibodies may get secreted establishing autoimmune diseases. Besides the hallmark of autoimmunity, namely IgG autoantibodies, IgM autoantibodies are also found in many autoimmune diseases. In addition to pathogenic functions of secreted IgM the IgM-BCR expressing B cell might be the initial check-point where, in conjunction with innate receptor signals, B cell mediated autoimmunity starts it fateful course. Recently, pentameric IgM autoantibodies have been shown to contribute significantly to the pathogenesis of various autoimmune diseases, such as rheumatoid arthritis (RA), autoimmune hemolytic anemia (AIHA), pemphigus or autoimmune neuropathy. Further, recent studies suggest differences in the recognition of autoantigen by IgG and IgM autoantibodies, or propose a central role of anti-ACE2-IgM autoantibodies in severe COVID-19. However, exact mechanisms still remain to be uncovered in detail. This article focuses on summarizing recent findings regarding the importance of autoreactive IgM in establishing autoimmune diseases.

[SARS-CoV-2-induced non-bacterial endomyocarditis with the development of acquired heart defects]

Patients with damage of the mitral, aortic and tricuspid valves and systolic myocardial dysfunction associated with previous SARS-CoV-2 infection are described. The diagnosis of acquired defect was established in 4 patients based on medical history, electrocardiography, echocardiography, magnetic resonance imaging of the heart, endomyocardial or intraoperative myocardial biopsy, and in one case, autopsy. The study of the myocardium included H&E, Van Gieson staining, immunohistochemical (IHC) study with antibodies to CD3, CD20, CD45, CD68, to the nucleocapsid and Spike proteins of SARS-CoV-2. Previous valve diseases (prolapse, bicuspid aortic valve) served as a background for the development of the defect in 2 patients. In all cases, IHC studies revealed coronavirus proteins, lymphocytic endocarditis and myocarditis, moderate fibrosis, and signs of connective tissue disorganization. High titers of anticardiac antibodies indicated an autoimmune mechanism for carditis. No signs of infective endocarditis or thromboembolic complications were identified in any case. In patients with an unclear nature of valvular heart defects, a previous new coronavirus infection should be identified and taken into account as a possible etiological factor. The simultaneous development of lymphocytic myocarditis significantly increases the risk of surgical intervention on the valves and requires an integrated approach to treatment.

Molecular states during acute COVID-19 reveal distinct etiologies of long-term sequelae

Post-acute sequelae of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection are debilitating, clinically heterogeneous and of unknown molecular etiology. A transcriptome-wide investigation was performed in 165 acutely infected hospitalized individuals who were followed clinically into the post-acute period. Distinct gene expression signatures of post-acute sequelae were already present in whole blood during acute infection, with innate and adaptive immune cells implicated in different symptoms. Two clusters of sequelae exhibited divergent plasma-cell-associated gene expression patterns. In one cluster, sequelae associated with higher expression of immunoglobulin-related genes in an anti-spike antibody titer-dependent manner. In the other, sequelae associated independently of these titers with lower expression of immunoglobulin-related genes, indicating lower non-specific antibody production in individuals with these sequelae. This relationship between lower total immunoglobulins and sequelae was validated in an external cohort. Altogether, multiple etiologies of post-acute sequelae were already detectable during SARS-CoV-2 infection, directly linking these sequelae with the acute host response to the virus and providing early insights into their development.

Immune profiles to distinguish hospitalized versus ambulatory COVID-19 cases in older patients

A fraction of patients with COVID-19 develops severe disease requiring hospitalization, while the majority, including high-risk individuals, experience mild symptoms. Severe disease has been associated with higher levels of antibodies and inflammatory cytokines but often among patients with diverse demographics and comorbidity status. This study evaluated hospitalized vs. ambulatory patients with COVID-19 with demographic risk factors for severe COVID-19: median age of 63, >80% male, and >85% black and/or Hispanic. Sera were collected four to 243 days after symptom onset and evaluated for binding and functional antibodies as well as 48 cytokines and chemokines. SARS-CoV-2-specific antibody levels and functions were similar in ambulatory and hospitalized patients. However, a strong correlation between anti-S2 antibody levels and the other antibody parameters, along with higher IL-27 levels, was observed in hospitalized but not ambulatory cases. These data indicate that antibodies against the relatively conserved S2 spike subunit and immunoregulatory cytokines such as IL-27 are potential immune determinants of COVID-19.

Mechanisms regulating neutrophil responses in immunity, allergy, and autoimmunity

Neutrophil granulocytes, or neutrophils, are the most abundant circulating leukocytes in humans and indispensable for antimicrobial immunity, as exemplified in patients with inborn and acquired defects of neutrophils. Neutrophils were long regarded as the foot soldiers of the immune system, solely destined to execute a set of effector functions against invading pathogens before undergoing apoptosis, the latter of which was ascribed to their short life span. This simplistic understanding of neutrophils has now been revised on the basis of insights gained from the use of mouse models and single-cell high-throughput techniques, revealing tissue- and context-specific roles of neutrophils in guiding immune responses. These studies also demonstrated that neutrophil responses were controlled by sophisticated feedback mechanisms, including directed chemotaxis of neutrophils to tissue-draining lymph nodes resulting in modulation of antimicrobial immunity and inflammation. Moreover, findings in mice and humans showed that neutrophil responses adapted to different deterministic cytokine signals, which controlled their migration and effector function as well as, notably, their biologic clock by affecting the kinetics of their aging. These mechanistic insights have important implications for health and disease in humans, particularly, in allergic diseases, such as atopic dermatitis and allergic asthma bronchiale, as well as in autoinflammatory and autoimmune diseases. Hence, our improved understanding of neutrophils sheds light on novel therapeutic avenues, focusing on molecularly defined biologic agents.

Correlates with Vaccine Protective Capacity and COVID-19 Disease Symptoms Identified by Serum Proteomics in Vaccinated Individuals

In the last two years, the coronavirus disease 19 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been a scientific and social challenge worldwide. Vaccines have been the most effective intervention for reducing virus transmission and disease severity. However, genetic virus variants are still circulating among vaccinated individuals with different disease symptomatology. Understanding the protective- or disease-associated mechanisms in vaccinated individuals is relevant to advances in vaccine development and implementation. To address this objective, serum-protein profiles were characterized by quantitative proteomics and data-analysis algorithms in four cohorts of uninfected and SARS-CoV-2-infected vaccinated individuals with asymptomatic, non-severe, and severe disease symptomatology. The results show that immunoglobulins were the most overrepresented proteins in infected cohorts when compared to PCR-negative individuals. The immunoglobulin profile varied between different infected cohorts and correlated with protective- or disease-associated capacity. Overrepresented immunoglobulins in PCR-positive individuals correlated with protective response against SARS-CoV-2, other viruses, and thrombosis in asymptomatic cases. In non-severe cases, correlates of protection against SARS-CoV-2 and HBV together with risk of myasthenia gravis and allergy and autoantibodies were observed. Patients with severe symptoms presented risk for allergy, chronic idiopathic thrombocytopenic purpura, and autoantibodies. The analysis of underrepresented immunoglobulins in PCR-positive compared to PCR-negative individuals identified vaccine-induced protective epitopes in various coronavirus proteins, including the spike receptor-binding domain RBD. Non-immunoglobulin proteins were associated with COVID-19 symptoms and biological processes. These results evidence host-associated differences in response to vaccination and the possibility of improving vaccine efficacy against SARS-CoV-2.

Small Fiber Neuropathy Associated With the Moderna SARS-CoV-2 Vaccine

Efforts of controlling viral transmission began soon after the first cases of coronavirus disease 2019 (COVID-19) infections were identified. Initial efforts were related to contact precautions, hand hygiene, and mask-wearing; however, it was soon evident that a robust global immunization drive was the most effective way to curb disease transmission. In the United States, the first doses of COVID-19 vaccines were rolled out soon after the FDA granted emergency use authorization for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine. What this also meant was that many of the routine phases that any new drug or vaccine goes through before being released publicly were bypassed. Over the past two years, various side effects and reactions have been seen after COVID-19 vaccine administration, the most common being local injection site events (e.g., pain, redness, swelling) and systemic effects (e.g., fatigue, headaches, myalgias). We report the case of a 64-year-old female who developed bilateral lower extremity numbness and tingling within weeks of receiving the third dose of Moderna SARS-CoV-2 vaccine. The patient underwent extensive testing to ascertain the diagnosis. She had negative autonomic testing and normal nerve conduction study/electromyography (EMG), which did not reveal large fiber neuropathy. Eventually, the patient underwent a skin biopsy, which revealed small fiber neuropathy. This case report highlights the importance of keeping a broad differential for rare side effects, such as small fiber neuropathy, that are currently being seen and reported in the literature.