RESUMO
The novel SARS-CoV-2 virus emerged in late 2019 and has caused a global health and economic crisis. The characterization of the human antibody response to SARS-CoV-2 infection is vital for serosurveillance purposes as well for treatment options such as transfusion with convalescent plasma or immunoglobin products derived from convalescent plasma. In this study, we measured antibody responses in 844 longitudinal samples from 151 RT-PCR positive SARS-CoV-2 convalescent adults during the first 34 weeks after onset of symptoms. All donors were seropositive at the first sampling moment and only one donor seroreverted during follow-up analysis. Anti-RBD IgG and anti-nucleocapsid IgG levels slowly declined with median half-lifes of 62 and 59 days during 2-5 months after symptom onset, respectively. The rate of decline of antibody levels diminished during extended follow-up. In addition, the magnitude of the IgG response correlated with neutralization capacity measured in a classic plaque reduction assay as well in our in-house developed competition assay. The result of this study gives valuable insight into the longitudinal response of antibodies to SARS-CoV-2.
RESUMO
SARS-CoV-2 infections often cause only mild disease that may evoke relatively low antibody titers compared to patients admitted to hospitals. Generally, total antibody bridging assays combine good sensitivity with high selectivity. Therefore, we developed sensitive total antibody bridging assays for detection of SARS-CoV-2 antibodies to the receptor-binding domain (RBD) and nucleocapsid protein (NP), in addition to conventional isotype-specific assays. Antibody kinetics was assessed in PCR-confirmed hospitalized COVID-19 patients (n=41) and three populations of patients with COVID-19 symptoms not requiring hospital admission: PCR-confirmed convalescent plasmapheresis donors (n=182), PCR-confirmed hospital care workers (n=47), and a group of longitudinally sampled symptomatic individuals highly suspect of COVID-19 (n=14). In non-hospitalized patients, the antibody response to RBD is weaker but follows similar kinetics as has been observed in hospitalized patients. Across populations, the RBD bridging assay identified most patients correctly as seropositive. In 11/14 of the COVID-19-suspect cases, seroconversion in the RBD bridging assay could be demonstrated before day 12; NP antibodies emerged less consistently. Furthermore, we demonstrated the feasibility of finger prick sampling for antibody detection against SARS-CoV-2 using these assays. In conclusion, the developed bridging assays reliably detect SARS-CoV-2 antibodies in hospitalized and non-hospitalized patients, and are therefore well-suited to conduct seroprevalence studies.