Is COVID-19 severity unrelated to antinuclear antibodies?

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) induces an overreaction of the immune system, resulting in the production of auto-antibodies. Several studies have reported that autoantibodies are prevalent in COVID-19 patients. In our study, antinuclear antibodies were evaluated in patients with COVID-19. We examined 131 sera from patients (>17-year-old) with confirmed COVID-19. Samples were collected prior to receiving any medication and antinuclear antibodies (ANA) levels were measured by the indirect immunofluorescence (IIF) method. Furthermore, the immunoblotting test was used to determine the presence of anti-nuclear antigen antibodies. The IIF-ANA test was positive in 36.4% (48/131) of patients. Overall, non-ICU patients had higher IIF-ANA titers than ICU patients. In particular, ICU patients had fewer nuclear, cytoplasmic, and mitotic IIF-ANA antibodies than non-ICU patients. In conclusion, COVID-19 patients frequently have ANA possibly reflecting the immune dysregulation due to several damaged cells by SARS-CoV-2 virus.

Evaluating the serological status of COVID-19 patients using an indirect immunofluorescent assay, France.

An indirect in-house immunofluorescent assay was developed in order to assess the serological status of COVID-19 patients in Marseille, France. Performance of IFA was compared to a commercial ELISA IgG kit. We tested 888 RT-qPCR-confirmed COVID-19 patients (1302 serum samples) and 350 controls including 200 sera collected before the pandemic, 64 sera known to be associated with nonspecific serological interference, 36 sera from non-coronavirus pneumonia and 50 sera from patient with other common coronavirus to elicit false-positive serology. Incorporating an inactivated clinical SARS-CoV-2 isolate as the antigen, the specificity of the assay was measured as 100% for IgA titre ≥ 1:200, 98.6% for IgM titre ≥ 1:200 and 96.3% for IgG titre ≥ 1:100 after testing a series of negative controls. IFA presented substantial agreement (86%) with ELISA EUROIMMUN SARS-CoV-2 IgG kit (Cohen's Kappa = 0.61). The presence of antibodies was then measured at 3% before a 5-day evolution up to 47% after more than 15 days of evolution. We observed that the rates of seropositivity as well as the titre of specific antibodies were both significantly higher in patients with a poor clinical outcome than in patients with a favourable evolution. These data, which have to be integrated into the ongoing understanding of the immunological phase of the infection, suggest that detection anti-SARS-CoV-2 antibodies is useful as a marker associated with COVID-19 severity. The IFA assay reported here is useful for monitoring SARS-CoV-2 exposure at the individual and population levels.

Performance evaluation of Abbott ARCHITECT SARS-CoV-2 IgG immunoassay in comparison with indirect immunofluorescence and virus microneutralization test.

BACKGROUND: Serological tests for anti-SARS-CoV-2 antibodies are becoming of great interest to determine seroprevalence in a given population, define previous exposure and identify highly reactive human donors for the generation of convalescent serum as therapeutic. OBJECTIVES: We evaluated the diagnostic performance of the Abbott ARCHITECT SARS-CoV-2 IgG test, a fully automated indirect immunoassay that detects antibodies directed to a recombinant SARS-CoV-2 Nucleocapsid antigen. STUDY DESIGN: Abbott ARCHITECT SARS-CoV-2 IgG immunoassay was compared to an indirect immunofluorescence assay (IFA) on sera from patients with COVID-19 collected at different days after symptoms onset or infected by other human coronaviruses. Comparison with neutralization test was also performed. RESULTS: After 7, 14 and >14 days after onset ARCHITECT was positive on 8.3 %; 61.9 % and 100 % of the tested samples compared to 58.3 %; 85.7 % and 100 % by IFA. The sensitivity was 72 % vs. IFA and 66.7 % vs. a real-time PCR, the specificity was 100 %. On 18 samples with neutralizing activity, 17 were positive by Abbott ARCHITECT SARS-CoV-2 IgG. CONCLUSIONS: In our study, Abbott ARCHITECT SARS-CoV-2 IgG assay showed a satisfactory performance, with a very high specificity. IgG reactivity against SARSCoV-2 N antigen was detectable in all patients by two weeks after symptoms onset. In addition, concordance between this serological response and viral neutralization suggests that a strong humoral response may be predictive of a neutralization activity, regardless of the target antigens. This finding supports the use of this automated serological assay in diagnostic algorithm and public health intervention, especially for high loads of testing.