SARS-CoV-2 specific memory B cells frequency in recovered patient remains stable while antibodies decay over time

The breadth of the humoral immune response following SARS-CoV-2 infection was indicated to be important for recovery from COVID-19. Recent studies have provided valuable insights regarding the dynamics of the antibody response in symptomatic COVID-19 patients. However, the information regarding the dynamics of the serological and cellular memory in COVID-19 recovered patients in scarce. It is imperative to determine the persistence of humoral memory in COVID-19 recovered patients as it will help to evaluate the susceptibility of recovered patients to re-infection. Here, we describe the dynamics of both the SARS-CoV-2 specific serological and B cell response in COVID-19 recovered patients. We found that symptomatic SARS-CoV-2 patients mount a robust antibody response following infection however, the serological memory decays in recovered patients over the period of 6 months. On the other hand, the B cell response as observed in the SARS-CoV-2 specific memory B cell compartment, was found to be stable over time. Moreover, the frequency of SARS-CoV-2 specific B cell plasmablasts was found to be associated with the SARS-CoV-2 specific antibody levels. These data, suggests that the differentiation of short-lived plasmablasts to become long-lived plasma cells is impaired and the main contributor of antibody production are the short-lived plasmablasts. Overall, our data provides insights regarding the humoral memory persistence in recovered COVID-19 patients. Notwithstanding the insights from this study, it is still to be determined if the persistence of SARS-CoV-2 memory B cells can be considered as a correlate of protection in the absence of serological memory.