PRF1 and bacterial infectious disease: The activated phenotype of MAIT cells during SHIV infection resembles the phenotype observed during certain viral infections (influenza, DENV, and HCV) (52, 53) and bacterial infections (26, 40, 54), which express higher levels of IL-18R, CD69, IFN-gamma, granzyme-B, perforin, and Ki-67 (10, 53).