India is one of the countries most affected by the recent COVID-19 pandemic. Characterization of humoral responses to SARS-CoV-2 infection MESHD
, including immunoglobulin isotype usage, neutralizing activity and memory B cell generation, is necessary to provide critical insights on the formation of immune memory in Indian subjects. In this study, we evaluated SARS-CoV-2 receptor-binding domain (RBD)-specific IgG, IgM, and IgA antibody SERO
responses, neutralization of live virus, and RBD-specific memory B cell responses in pre-pandemic healthy versus convalescent COVID-19 individuals from India. We observed substantial heterogeneity in the formation of humoral and B cell memory post COVID-19 recovery. While a vast majority (38/42, 90.47%) of COVID-19 recovered individuals developed SARS-CoV-2 RBD-specific IgG responses, only half of them had appreciable neutralizing antibody SERO
titers. RBD-specific IgG titers correlated with these neutralizing antibody SERO
titers as well as with RBD-specific memory B cell frequencies. In contrast, IgG titers measured against SARS-CoV-2 whole virus preparation, which includes responses to additional viral proteins besides RBD, did not show robust correlation. Our results suggest that assessing RBD-specific IgG titers can serve as a surrogate assay to determine the neutralizing antibody SERO
response. These observations have timely implications for identifying potential plasma SERO
therapy donors based on RBD-specific IgG in resource-limited settings where routine performance SERO
of neutralization assays remains a challenge.
ImportanceOur study provides an understanding of SARS-CoV-2-specific neutralizing antibodies SERO
, binding antibodies SERO
and memory B cells in COVID-19 convalescent subjects from India. Our study highlights that PCR-confirmed convalescent COVID-19 individuals develop SARS-CoV-2 RBD-specific IgG antibodies SERO
, which correlate strongly with their neutralizing antibody SERO
titers. RBD-specific IgG titers, thus, can serve as a valuable surrogate measurement for neutralizing antibody SERO
responses. These finding have timely significance for selection of appropriate individuals as donors for plasma SERO
intervention strategies, as well as determining vaccine efficacy.