Analysis of Humoral Immune Responses in Patients With Severe Acute Respiratory Syndrome Coronavirus 2 Infection

Background. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has caused a pandemic with tens of millions of cases and hundreds of thousands of deaths. The infection causes coronavirus disease 2019 (COVID-19), a disease of the respiratory system of divergent severity. In the current study, humoral immune responses were characterized in a cohort of 143 patients with COVID-19 from the University Hospital Frankfurt am Main, Germany. Methods. SARS-CoV-2-specific-antibodies were detected by enzyme-linked immunosorbent assay (ELISA). SARS-CoV-2 and human coronavirus NL63 neutralization activity was analyzed with pseudotyped lentiviral vectors. Results. The severity of COVID-19 increased with age, and male patients encountered more serious symptoms than female patients. Disease severity was correlated with the amount of SARS-CoV-2-specific immunoglobulin (Ig) G and IgA and the neutralization activity of the antibodies. The amount of SARS-CoV-2-specific IgG antibodies decreased with time after polymerase chain reaction conformation of the infection, and antibodies directed against the nucleoprotein waned faster than spike protein-directed antibodies. In contrast, for the common flu coronavirus NL63, COVID-19 disease severity seemed to be correlated with low NL63-neutralizing activities, suggesting the possibility of cross-reactive protection. Conclusion. The results describe the humoral immune responses against SARS-CoV-2 and might aid the identification of correlates of protection needed for vaccine development.

Automated summary

The study found that the severity of COVID-19 is correlated with patient age, gender, the amount of SARS-CoV-2-specific antibodies, and their neutralization activity. The levels of specific antibodies decrease over time, with faster decline in nucleoprotein antibodies. NL63 neutralizing activities are associated with COVID-19 severity, suggesting potential cross-reactive protection.