Memory B cell and humoral responses elicited by Sputnik V in naïve and COVID-19-recovered vaccine recipients

ABSTRACT The development of effective vaccines against SARS-CoV-2 remains a global health priority. Despite extensive use, the effects of Sputnik V on B cell immunity need to be explored in detail. We show that B memory cell (MBC) and antibody responses to Sputnik V were heavily dependent on whether the vaccinee had a history of SARS-CoV-2 infection or not. In vitro stimulated MBCs from previously infected recipients of Sputnik V secreted a significant amount of anti-RBD IgG both on days 28 and 85 from the beginning of vaccination. These antibodies demonstrated robust neutralization of the Wuhan Spike-pseudotyped lentivirus. In the naïve group of vaccinees, the level of anti-RBD IgG secretion was five- to six-fold reduced compared to that of the recovered group, and maximum virus neutralization (Wuhan spike) was achieved only on day 85. Sera from all the recovered and most naïve Sputnik V recipients were neutralizing against the ancestral Wuhan and mutant B.1.351 viruses. Thus, our in-depth analysis of MBC responses in Sputnik V vaccinees complements traditional serological approaches and may provide important outlook into future B cell responses upon re-encounter with the emerging variants of SARS-CoV-2.