CD8A and infection: Using intracellular cytokine staining (ICS) and granzyme B (GzmB) expression assays, data revealed that VV-specific effector CD8+ T cells emerged on day 5 post-infection (p.i.), peaked on day 7 p.i. and gradually declined from days 14–28 p.i. with VV-WR (figure 2A and 2B).