T cell responses to herpes simplex viruses in humans.

Much of the evidence that implicates cytotoxic T lymphocytes (CTLs) in the control of infections due to herpes simplex virus (HSV) is circumstantial. However, the ease of induction of HSV-specific CTLs in vitro, the evidence from clinical observations in humans, and the protection afforded by adoptively transferred CTLs all tend to support an important role for CTLs in the resolution of HSV disease. One salient feature of the response of human CTLs to HSV that has emerged quite clearly is the presence of CD4+ T cells as a predominant killer cell phenotype. Given the importance of CD4+ T cells in mediating delayed type hypersensitivity responses and in clearing local infections on adoptive transfer, this T cell subset probably plays a critical role in the resolution of HSV recrudescent disease. Moreover, it is tempting to speculate that viral agents that impair the function of CD4+ T cells, such as human immunodeficiency virus type 1, may predispose patients to severe local infections.