Clearance of herpes simplex virus type 2 by CD8⁺ T cells requires gamma interferon and either perform- or Fas-mediated cytolytic mechanisms

The T-cell-mediated resolution of herpes simplex virus type 2 (HSV-2) genital infections is not fully understood. In these studies, the mechanisms by which CD8⁺ T cells clear virus from the genital epithelium were examined. Ovalbumin (OVA)-specific CD8⁺ T cells from OT-I transgenic mice cleared a thymidine kinase-deficient, ovalbumin-expressing HSV-2 virus (HSV-2 tk^- OVA) from the genital epithelium of recipient mice, and clearance was abrogated by in vivo neutralization of gamma interferon (IFN-γ). Further, CD8⁺ OT-I T cells deficient in IFN-γ were unable to clear HSV-2 tk^- OVA from the vaginal epithelium. The requirement for cytolytic mechanisms in HSV-2 tk^- OVA clearance was tested in radiation chimeras by adoptive transfer of wild-type or perforin-deficient OT-I T cells to irradiated Fas-defective or wild-type recipients. Although a dramatic decrease in viral load was observed early after challenge with HSV-2 tk^- OVA, full resolution of the infection was not achieved in recipients lacking both perform- and Fas-mediated cytolytic pathways. These results suggest that IFN-γ was responsible for an early rapid decrease in HSV-2 virus titer. However, either perforin- or Fas-mediated cytolytic mechanisms were required to achieve complete clearance of HSV-2 from the genital epithelium.