The requirement for interferon-γ (IFNγ) in resolution of an HSV-2 vaginal infection and the cellular sources of this cytokine in the vaginal mucosa were assessed. IFNγ levels in vaginal secretions peaked on Days 2 and 5 following HSV-2 inoculation. Natural killer (NK) cell depletion greatly diminished the early production of IFNγ but had no significant effect on the rate of virus clearance. CD4+ T cells were primarily responsible for the second peak of IFNγ levels and neutralization of this IFNγ beginning 3 days after virus inoculation delayed, but did not prevent, virus clearance from the vagina. HSV-2 persisted in mice depleted of both CD4+ and CD8+ T cells while clearance was delayed in CD4+, but not CD8+ T cell-depleted mice, demonstrating the T cell dependence and predominant role of CD4+ T cells in resolution of the infection. Together, these data suggest that IFNγ is not essential for virus clearance but plays an important role in enhancing T cell-mediated clearance mechanisms. The implication of these results is that IFNγ produced locally in the genital tract enhances virus clearance and may ultimately be important for reducing the amount of virus available to infect sensory ganglia.
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