Broad and strong memory CD4+ and CD8+ T cells induced by SARS-CoV-2 in UK convalescent individuals following COVID-19

The development of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines and therapeutics will depend on understanding viral immunity. We studied T cell memory in 42 patients following recovery from COVID-19 (28 with mild disease and 14 with severe disease) and 16 unexposed donors, using interferon-γ-based assays with peptides spanning SARS-CoV-2 except ORF1. The breadth and magnitude of T cell responses were significantly higher in severe as compared with mild cases. Total and spike-specific T cell responses correlated with spike-specific antibody responses. We identified 41 peptides containing CD4 + and/or CD8 + epitopes, including six immunodominant regions. Six optimized CD8 + epitopes were defined, with peptide–MHC pentamer-positive cells displaying the central and effector memory phenotype. In mild cases, higher proportions of SARS-CoV-2-specific CD8 + T cells were observed. The identification of T cell responses associated with milder disease will support an understanding of protective immunity and highlights the potential of including non-spike proteins within future COVID-19 vaccine design. Questions have arisen as to whether patients with severe COVID-19 disease can generate a T cell response against SARS-CoV-2. Tao Dong and colleagues report that convalescent patients with COVID-19 harbor functional memory CD4 + and CD8 + T cells that recognize multiple epitopes that span the viral proteome. CD4 + T cells predominated the memory response in patients with severe disease, whereas higher proportions of CD8 + T cells were found in patients with mild disease.