Protracted yet Coordinated Differentiation of Long-Lived SARS-CoV-2-Specific CD8⁺ T Cells during Convalescence

CD8⁺ T cells can potentiate long-lived immunity against COVID-19. We screened longitudinally-sampled convalescent human donors against SARS-CoV-2 tetramers and identified a participant with an immunodominant response against residues 322 to 311 of nucleocapsid (Nuc_322-331), a peptide conserved in all variants of concern reported to date. We conducted 38-parameter cytometry by time of flight on tetramer-identified Nuc_322-331-specific CD8⁺ T cells and on CD4⁺ and CD8⁺ T cells recognizing the entire nucleocapsid and spike proteins, and took 32 serological measurements. We discovered a coordination of the Nuc_322-331-specific CD8⁺ T response with both the CD4⁺ T cell and Ab pillars of adaptive immunity. Over the approximately six month period of convalescence monitored, we observed a slow and progressive decrease in the activation state and polyfunctionality of Nuc_322-331-specific CD8⁺ T cells, accompanied by an increase in their lymph node-homing and homeostatic proliferation potential. These results suggest that following a typical case of mild COVID-19, SARS-CoV-2-specific CD8⁺ T cells not only persist but continuously differentiate in a coordinated fashion well into convalescence into a state characteristic of long-lived, self-renewing memory.