CD8+ T cell responses are critical to the control of replication and reactivation associated with gammaherpesvirus infection. Type I interferons (IFNs) have been shown to have direct and indirect roles in supporting CD8+ T cell development and function during viral infection; however, the role of type I interferons during latent viral infection has not been examined. Mice deficient in type I IFN signaling (IFNAR1-/- mice) have high levels of reactivation during infection with murine gammaherpesvirus 68 (MHV68), a murine gammaherpesvirus model for Epstein-Barr virus. We hypothesized that type I IFNs function to enhance the anti-gammaherpesvirus CD8+ T cell response. To test this, IFNAR1-/- mice were infected with MHV68 and the CD8+ T cell response was analyzed. In the absence of type I IFN signaling, there was a marked increase in short-lived effector CD8+ T cells, and MHV68-specific CD8+ T cells had upregulated expression of PD-1 and reduced tumor necrosis factor alpha (TNF-), gamma IFN (IFN-γ), and interleukin-2 (IL-2) production. Suppressing MHV68 replication early in infection using the antiviral cidofovir rescued CD8+ T cell cytokine production and reduced PD-1 expression. However, suppressing high levels of reactivation in IFNAR1-/- mice failed to improve CD8+ T cell cytokine production during latency. T cell-specific abrogation of type I IFN signaling showed that the effects of type I IFNs on the CD8+ T cell response during MHV68 infection are independent of direct type I IFN signaling on T cells. Our findings support a model in which type I IFNs likely suppress MHV68 replication, thus limiting viral antigen and facilitating an effective gammaherpesvirus-directed CD8+ T cell response. [ABSTRACT FROM AUTHOR]