Anti-SARS-CoV-2 spike protein S1 domain-IgA antibody may contribute to the early detection of new coronavirus infection

Abstract

Serological diagnosis of novel coronavirus (SARS-CoV-2) infection (COVID-19) is expected to be used as an adjunct diagnostic method. There are two main types of anti-SARS-CoV-2 antibody reagents that detect antibodies to the spike protein S1 domain (S) and nucleocapsid protein (N) of SARS-CoV-2. In this study, we tested anti-SARS-CoV-2 antibody reagents using S and N antigens in longitudinal samples from patients diagnosed as having COVID-19. EUROIMMUN S-IgA and IgG reagents and VITROS S-total and IgG reagents were used as anti-SARS-CoV-2 antibody reagents tested using the S antigen. ARCHITECT N-reagent and cobas N-reagent were used as anti-SARS-CoV-2 antibody reagents using N antigen. The results showed that IgA antibodies to EUROIMMUN S-IgA reagent were positive from the time of hospitalization (day X). Anti-SARS-CoV-2 antibodies to VITROS S-total reagent were positive from the X + 5th day of hospitalization. IgG antibodies to ARCHITECT N-reagent were positive from the X + 8th day. In this case, the anti-SARS-CoV-2 antibody reagent tested using the S antigen showed positive results from early in the course of the disease. In particular, the anti-SARS-CoV-2 S-IgA antibody was suggested to be potentially useful as an adjunct for the early diagnosis of COVID-19.