New-onset IgG autoantibodies in hospitalized patients with COVID-19

COVID-19 is associated with a wide range of clinical manifestations, including autoimmune features and autoantibody production. Here we develop three protein arrays to measure IgG autoantibodies associated with connective tissue diseases, anti-cytokine antibodies, and anti-viral antibody responses in serum from 147 hospitalized COVID-19 patients. Autoantibodies are identified in approximately 50% of patients but in less than 15% of healthy controls. When present, autoantibodies largely target autoantigens associated with rare disorders such as myositis, systemic sclerosis and overlap syndromes. A subset of autoantibodies targeting traditional autoantigens or cytokines develop de novo following SARS-CoV-2 infection. Autoantibodies track with longitudinal development of IgG antibodies recognizing SARS-CoV-2 structural proteins and a subset of non-structural proteins, but not proteins from influenza, seasonal coronaviruses or other pathogenic viruses. We conclude that SARS-CoV-2 causes development of new-onset IgG autoantibodies in a significant proportion of hospitalized COVID-19 patients and are positively correlated with immune responses to SARS-CoV-2 proteins.


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One patient from the paired sample cohort was excluded from the viral array data analysis due to technical failure of a control antigen.
Samples were successfully run in duplicate using the Luminex assay with the exception of the aforementioned patient. One patient sample was successfully run in quadruplicate. All ANA positive samples (those having nuclear staining at a titer of 1:160 or above) were imaged by fluorescence microscopy. 5 different images were successfully collected for each sample and one representative image was chosen for display in Supplementary Figure 1c. Supplementary Table 7 includes all samples that were tested in the ANA and shows which of these samples were used for imaging. ELISAs were successfully performed once independently Samples from the four hospital systems were allocated into the "hospitalized COVID-19" experimental group based on patients meeting criteria for COVID-19. Healthy control samples were anonymously collected from Stanford Blood Bank and Stanford Hospital and Clinics from healthy donors before the pandemic.
Luminex microarray experiments were run blinded. Data analyses to statistically identify autoantibody positive hits in the COVID-19 patient samples were not performed blinded because statistical tests compared MFI values between the two experimental groups and standard deviation cutoffs to determine autoantibody positive hits were calculated from healthy controls.
The only primary antibody used in this study was an anti-His tag antibody (R&D Systems, Cat# MAB050-SP) that was run as a sample in Luminex experiments. The primary antibody was used as a control to verify conjugation of bead to antigens with His tags. Validation of the anti-His tag antibody was performed in the viral array experiment as evidenced by high reactivity, measured by MFI, towards antigens with His tags.
Hep-2 cells affixed to glass slides (Inova Diagnostics, Cat # 708100) were purchased as a kit from the vendor but were not independently authenticated by the authors.
Hep-2 cells affixed to glass slides (Inova Diagnostics, Cat # 708100) were purchased as a kit from the vendor but were not independently tested for mycoplasma contamination by the authors. Morphological changes consistent with mycoplasma infection were not observed.
Hep-2 cells affixed to glass slides (Inova Diagnostics, Cat # 708100) were used in our study to perform ANAs by indirect immunofluorescence.