PRF1 and infection: Immune responses elicited by vaccination followed by infection were >3-orders of magnitude higher than that generated by infection only (at 10 dpi) and were mediated by multifunctional lymphocytes abundantly secreting pro-inflammatory cytokines, such as IFNγ and TNFα, capable of translocating the CD107a and perforin molecules to the cell surface, and producing cytotoxic activity against infected target cells.