CD8A and infection: Despite the large variation in the percentage of PD-1-expressing MuV-specific CD8+ T cells between donors and between epitope specificities, the percentage of PD-1-expressing MuV-specific T cells was relatively high at 1.5 months after MuV infection (average of 50.78% ± 24.84%) (Figure S7A, gating of a representative donor is shown in Figure S7B) and significantly lower at 9 months post-infection (average of 43.10% ± 15.76).