Characterization of Autoantibodies in PASC

Introduction: Multiple epidemiologic studies have demonstrated an increased incidence of autoimmune diseases since the start of the pandemic, indirectly linked to infection. Autoantibodies are a hallmark autoimmunity and have been shown by our group to be triggered by SARS-CoV-2 infection in hospitalized patients. It is unknown if autoantibodies also are enriched in patients with Long COVID. This study is characterizing autoantibodies using custom protein arrays, and anti-viral antibody responses using protein and peptide arrays. We are also characterizing FcR and signaling in innate blood cells.

Objective: The overall objective of this study is to characterize autoimmune and inflammatory pathways that could lead to generation of autoantibodies, immune complexes containing viral proteins or self antigens, and how these could trigger aberrant immune responses through FcRs on innate immune cells.

Methods: This proposal has two independent specific aims. Aim 1 (Utz lab) is testing the hypothesis that SARS-CoV-2 causes development of autoantibodies that are associated with specific RECOVER post-acute sequelae of SARS-CoV-2 (PASC) clinical phenotypes. We hypothesize that SARS-CoV-2 infections can trigger autoantibody production linked to specific subsets of Long COVID. We further hypothesize that some autoantibodies are functionally active and can modulate the activity of cytokines resulting in decreased innate immunity or pro-inflammatory effects. More specifically, we are exploring whether antibodies against a panel of cytokines, chemokines, interferons, and growth factors that have the ability to activate or block specific signaling pathways might be found in Long COVID. Protein and peptide arrays are also being used to characterize antibody responses against all known human herpesviruses. Aim 2 (Wang lab) is characterizing IgG effector functions of autoantibodies in PASC. This aim is testing the hypothesis that clinical manifestations of Long COVID have an inflammatory component that is mediated, in part, by autoantibody/antigen IC-FcγR interactions. These studies have largely been focused on characterizing FcR distribution on innate immune cells, with a goal to correlate results with specific risk factors for Long COVID.

Results: Aim 1. We have generated multiple results in Aim 1 and are currently in the process of validating results, then assembling 2 manuscripts. We have constructed and validated protein and peptide arrays for release for these studies. All samples from all time points have now been run on the autoantigen and viral protein arrays. For traditional autoantigens, we have shown that IgG autoantibody levels do not differ between any of the groups (recent infection Long COVID, recent infection no Long COVID, healthy uninfected controls). We have identified no anti-interferon or anti-chemokine autoantibody differences. Most interesting is the finding of very high IgA antibodies against a subset of herpesviruses, including HHV6 in the Long COVID group. Aim 2 results are pending.

Conclusion/Discussion: This study has clearly shown that traditional autoantibodies, anti-type I interferons, and anti-cytokine antibodies are not prevalent in Long COVID, nor are putative protective anti-chemokine antibodies published by another group. While negative, this is still an important result to report. We have identified a potentially very interesting association of new antibodies against a subset of herpesviruses that may be mechanistically relevant. Discussion and conclusions for studies of innate immune cell biology are pending final analysis and results.

Key Topics:

• Assay and in vitro studies to gain mechanistic insights
• Biomarker, in-depth phenotyping assays and in vitro studies using tissue and other biospecimens
• Chronic immune dysfunction
• Clinical manifestations of chronic viral infections, biological pathways, immune-autoimmune disorders, systems, organs, or diseases
• Collaborative and systems biology approaches
• Validation of published studies on potential mechanisms of Long COVID using data and biospecimens from RECOVER cohorts
• Viral persistence/reactivation