T-cell responses in COVID-19 survivors 6-8 months after infection: A longitudinal cohort study in Pune.

Abstract

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immune response is crucial for disease management, although diminishing immunity raises the possibility of reinfection. We examined the immunological response to SARS-CoV-2 in a cohort of convalescent COVID-19 patients in matched samples collected at 1 and 6-8 months after infection. The peripheral blood mononuclear cells were isolated from enrolled study participants and flow cytometry analysis was done to assess the lymphocyte subsets of naive, effector, central memory, and effector memory CD4+ or CD8+ T cells in COVID-19 patients at 1 and 6-8 months after infection. Immunophenotypic characterization of immune cell subsets was performed on individuals who were followed longitudinally for 1 month (n = 44) and 6-8 months (n = 25) after recovery from COVID infection. We observed that CD4 +T cells in hospitalized SARS-CoV-2 patients tended to decrease, whereas CD8+ T cells steadily recovered after 1 month, while there was a sustained increase in the population of effector T cells and effector memory T cells. Furthermore, COVID-19 patients showed persistently low B cells and a small increase in the NK cell population. Our findings show that T cell responses were maintained at 6-8 months after infection. This opens new pathways for further research into the long-term effects in COVID-19 immunopathogenesis.