CD4 and infection: Similar to the observations in patients with heterotypic DENV secondary infection, CD4+ and CD8+ T cells from DENV-immune humans (naturally infected or vaccinated) are mostly TEM/TEMRA, express more polyfunctional cytokines, and display higher levels of cytotoxicity and activation markers (granzyme B, PD-1) than cells from ZIKV-infected DENV-naïve individuals (36, 40, 56).