We found higher GZMB expression by natural killer (NK) cells (CD8(+)CD3(-)), but not by T cells (CD8(+)CD3(+)), in G1(+) macaques prior to infection (P = 0.0163) and at the peak of virus replication on day 14 post-challenge (P = 0.0167) (Figure S2D in Additional file 2). Here, GZMB is linked to infection.