Recovery of Memory B-cell Subsets and Persistence of Antibodies in Convalescent COVID-19 Patients

Rajamanickam, Anuradha; Kumar, Nathella Pavan; Nancy P, Arul; Selvaraj, Nandhini; Munisankar, Saravanan; Renji, Rachel Mariam; V, Vijayalakshmi; Murhekar, Manoj; Thangaraj, Jeromie Wesley Vivian; Kumar, Muthusamy Santhosh; Kumar, C P Girish; Bhatnagar, Tarun; Ponnaiah, Manickam; Sabarinathan, R; Kumar, V Saravana; Babu, Subash

It is essential to examine the longevity of the defensive immune response engendered by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. We examined the SARS-CoV-2-specific antibody responses and ex vivo memory B-cell subsets in seven groups of individuals with COVID-19 classified based on days since reverse-transcription polymerase chain reaction confirmation of SARS-CoV-2 infection. Our data showed that the levels of IgG and neutralizing antibodies started increasing from days 15 to 30 to days 61 to 90, and plateaued thereafter. The frequencies of naive B cells and atypical memory B cells decreased from days 15 to 30 to days 61 to 90, and plateaued thereafter. In contrast, the frequencies of immature B cells, classical memory B cells, activated memory B cells, and plasma cells increased from days 15 to 30 to days 61 to 90, and plateaued thereafter. Patients with severe COVID-19 exhibited increased frequencies of naive cells, atypical memory B cells, and activated memory B cells, and lower frequencies of immature B cells, central memory B cells, and plasma cells when compared with patients with mild COVID-19. Therefore, our data suggest modifications in memory B-cell subset frequencies and persistence of humoral immunity in convalescent individuals with COVID-19.