CD8A and coinfection: Further, in a separate experiment, co-infection with X31 and CA/E3/09 virus resulted in a similar pattern of distinct X31NP366 and CANP366 tetramer specific CD8 T cells (Fig. 4C), though X31NP366 tetramer staining of cells from CA/E3/09 infected mice showed a slightly higher frequency (0.94 vs 0.57%).