The effects of ultraviolet irradiation of the skin on herpes simplex virus infection: alteration in immune function mediated by epidermal cells and in the course of infection.

Previously, we demonstrated that Ia+ epidermal cells (EC) have herpes simplex virus (HSV) antigen-presenting capacity in vitro and play an important role in resistance to HSV infection in vivo. In the present study, we investigated the effects of in vivo ultraviolet (UV) irradiation of the skin on the HSV-immunity function of EC both in vitro and in vivo and on the pathogenesis of HSV infection. Immune T cells cultured with EC and HSV antigen showed a proliferative response in vitro. Exposure of the skin to UV light 1 to 3 days before preparation of EC resulted in dose-dependent impairment of this proliferation. This UV-induced impairment of the accessory cell function of EC was accompanied by a parallel reduction of the number of Ia+ EC. We also transferred these EC-stimulated T cells to intracutaneously infected nude mice. Immune T cells stimulated with EC obtained from irradiated mice did not effectively clear HSV and allowed development of zosteriform skin lesions. In contrast normal-EC-stimulated immune T cells completely prevented the formation of a zosteriform rash. In addition, mice irradiated with UV on shaved midflank skin 2 days before intracutaneous inoculation of HSV showed increased severity of infection and a higher incidence of latency compared with control mice. These studies indicate that in vivo UV irradiation of the skin abrogates the immune function of EC both in vitro and in vivo, and affects HSV pathogenesis. The implication of our results for the better understanding of the effect of UV on acute and recurrent HSV infections is discussed.