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

BACKGROUND: Several autoimmune features occur during coronavirus disease 2019 (COVID-19), with possible implications for disease course, immunity, and autoimmune pathology. In this study, we longitudinally screened for clinically relevant systemic autoantibodies to assess their prevalence, temporal trajectory, and association with immunity, comorbidities, and severity of COVID-19. METHODS: We performed highly sensitive indirect immunofluorescence assays to detect antinuclear antibodies (ANA) and antineutrophil cytoplasmic antibodies (ANCA), along with serum proteomics and virome-wide serological profiling in a multicentric cohort of 175 COVID-19 patients followed up to 1 year after infection, eleven vaccinated individuals, and 41 unexposed controls. RESULTS: Compared with healthy controls, similar prevalence and patterns of ANA were present in patients during acute COVID-19 and recovery. However, the paired analysis revealed a subgroup of patients with transient presence of certain ANA patterns during acute COVID-19. Furthermore, patients with severe COVID-19 exhibited a high prevalence of ANCA during acute disease. These autoantibodies were quantitatively associated with higher SARS-CoV-2-specific antibody titers in COVID-19 patients and in vaccinated individuals, thus linking autoantibody production to increased antigen-specific humoral responses. Notably, the qualitative breadth of antibodies cross-reactive with other coronaviruses was comparable in ANA-positive and ANA-negative individuals during acute COVID-19. In autoantibody-positive patients, multiparametric characterization demonstrated an inflammatory signature during acute COVID-19 and alterations of the B-cell compartment after recovery. CONCLUSION: Highly sensitive indirect immunofluorescence assays revealed transient autoantibody production during acute SARS-CoV-2 infection, while the presence of autoantibodies in COVID-19 patients correlated with increased antiviral humoral immune responses and inflammatory immune signatures.

Systemic and mucosal antibody responses specific to SARS-CoV-2 during mild versus severe COVID-19.

BACKGROUND: Whereas severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific antibody tests are increasingly being used to estimate the prevalence of SARS-CoV-2 infection, the determinants of these antibody responses remain unclear. OBJECTIVES: Our aim was to evaluate systemic and mucosal antibody responses toward SARS-CoV-2 in mild versus severe coronavirus disease 2019 (COVID-19) cases. METHODS: Using immunoassays specific for SARS-CoV-2 spike proteins, we determined SARS-CoV-2-specific IgA and IgG in sera and mucosal fluids of 2 cohorts, including SARS-CoV-2 PCR-positive patients (n = 64) and PCR-positive and PCR-negtive health care workers (n = 109). RESULTS: SARS-CoV-2-specific serum IgA titers in patients with mild COVID-19 were often transiently positive, whereas serum IgG titers remained negative or became positive 12 to 14 days after symptom onset. Conversely, patients with severe COVID-19 showed a highly significant increase of SARS-CoV-2-specific serum IgA and IgG titers after symptom onset. Very high titers of SARS-CoV-2-specific serum IgA were correlated with severe acute respiratory distress syndrome. Interestingly, some health care workers with negative SARS-CoV-2-specific serum antibody titers showed SARS-CoV-2-specific IgA in mucosal fluids with virus-neutralizing capacity in some cases. SARS-CoV-2-specific IgA titers in nasal fluids were inversely correlated with age. CONCLUSIONS: Systemic antibody production against SARS-CoV-2 develops mainly in patients with severe COVID-19, with very high IgA titers seen in patients with severe acute respiratory distress syndrome, whereas mild disease may be associated with transient production of SARS-CoV-2-specific antibodies but may stimulate mucosal SARS-CoV-2-specific IgA secretion.

Sex-specific effects of TLR9 promoter variants on spontaneous clearance of HCV infection.

OBJECTIVE: As pathogen sensors, Toll-like receptors (TLR) play a role in the first defence line during HCV infection. However, the impact of the DNA sensor TLR9 on the natural course of HCV infection is unknown. To address this, TLR9 promoter polymorphisms (single nucleotide polymorphisms (SNPs)) rs187084 and rs5743836 were investigated for their effect on disease progression. DESIGN: Therefore, the TLR9 SNPs and the interferon lambda 4 (IFNL4) rs12979860 were genotyped in chronically HCV type 1 infected (n=333), in patients who spontaneously cleared the infection (n=161), in the Swiss HCV cohort (n=1057) and the well-characterised German (n=305) and Irish (n=198) 'anti-D' cohorts. Functional analyses were done with promoter reporter constructs of human TLR9 in B cells and assessing TLR9 mRNA levels in whole blood of healthy volunteers. RESULTS: The TLR9 rs187084 C allele was associated with spontaneous virus clearance in women of the study cohort (OR=2.15 (95% CI 1.18 to 3.90) p=0.012), of the Swiss HCV cohort (OR=2.06 (95% CI 1.02 to 4.18) p=0.044) and in both 'anti-D' cohorts (German: OR=2.01 (95% CI 1.14 to 3.55) p=0.016; Irish: OR=1.93 (95% CI 1.10 to 3.68) p=0.047). Multivariate analysis in the combined study and Swiss HCV cohorts supported the results (OR=1.99 (95% CI 1.30 to 3.05) p=0.002). Functional analyses revealed higher transcriptional activities for both TLR9 variants and an association of the C allele of rs5743836 with allele-specific TLR9 mRNA regulation by oestrogens in women. CONCLUSIONS: TLR9 promoter SNPs are associated with the natural course of HCV infection and show higher transcriptional activities. Our results imply the DNA sensor TLR9 in natural immunity against the RNA virus, HCV.

Continuous population-level monitoring of SARS-CoV-2 seroprevalence in a large European metropolitan region.

Effective public health measures against SARS-CoV-2 require granular knowledge of population-level immune responses. We developed a Tripartite Automated Blood Immunoassay (TRABI) to assess the IgG response against three SARS-CoV-2 proteins. We used TRABI for continuous seromonitoring of hospital patients and blood donors (n = 72'250) in the canton of Zurich from December 2019 to December 2020 (pre-vaccine period). We found that antibodies waned with a half-life of 75 days, whereas the cumulative incidence rose from 2.3% in June 2020 to 12.2% in mid-December 2020. A follow-up health survey indicated that about 10% of patients infected with wildtype SARS-CoV-2 sustained some symptoms at least twelve months post COVID-19. Crucially, we found no evidence of a difference in long-term complications between those whose infection was symptomatic and those with asymptomatic acute infection. The cohort of asymptomatic SARS-CoV-2-infected subjects represents a resource for the study of chronic and possibly unexpected sequelae.