Herpes simplex virus (HSV) is ubiquitous among HIV+ persons and is an important opportunistic infection (Ol), influencing both the clinical progression of HIV as well as enhancing its transmission and acquisition. Our initialstudies defining T cell responses to HSVamong HIV+ persons have indicated that HSV-specific CD8+ T cells play a prominent role in the control of HSV reactivation at mucosal sites in HIV+ persons. In particular, those with low precursor frequencies of HSV-specific CD8+ T cells have high reactivation rates of HSV. To our surprise, HAART therapy, while increasing HSV-specific CD4+ T cell responses, had little effect upon HSV reactivation rates, indicating that HSV differsfrom other herpesvirus infections in this regard. Our proposed studies are directed at defining the relationship between systemic and local HSV- specific CD8+ T cell responses and mucosal reactivation rates of HSV. During the initial phase of funding we have shown that the breadth of the CD8+ T cell response to HSV-2 is much greater than previously appreciated and there is significant variability between individuals. Specific Aim #1 uses ELISpot, intracellular cytokine staining and HLA/peptide tetramers, to quantitate the HSV-specific CD8+ T cell response in HSV-2 infected persons. Our hypothesis is that persons with increased magnitude and breadth of the CD8+ T cell response will have reduced rates of HSV reactivation. We have recently developed the technique of in situ staining of HSV specific tetramers using a novel quantum dot methodology and have shown that HSV specific CD8+ T cells persist at the dermal-epidermal junction and are located contiguous to peripheral neurons in this area; suggesting they may influence viral reactivation. Our proposed studies will evaluate the persistence of these HSV-2 specific CD8+ T cells in situ and define whether their egress is associated with subsequent viral reactivation. HSVspecific CD4+ and CD8+ T cells have altered in vivo functional profiles. Specific Aim 3 will be to use multiparameter flow cytometry to characterize these functional deficits. The above proposed studies will provide novel information about the role HSV-specific CD8+ T cell responses play on mucosal reactivation of an OI and offer the potential for providing novel therapeutic approaches for disease management.