PRF1 and Zika virus infectious disease: The significant role of T cells in controlling ZIKV replication in animals with a DENV-middle convalescence period before ZIKV infection is reinforced by the significant increase of circulating cytolytic protein perforin at day 7 p.i. We hypothesize that this likely represents T cells acquisition of cytotoxic function [60] in that group compared to the other two groups and correlates with the higher expression of CD107a on the CD4+ T cells isolated from these animals.