Currently, aluminum compounds and more recently MPL are the only adjuvants approved by the FDA for use in humans in the U.S. Because of its ineffectiveness for some antigens and inability to augment cell mediated immune responses, there is still a need to discover new, more potent, and safer adjuvants for human vaccination. Dendritic cells play a central role in guiding the development of adaptive immunity. Due to their intrinsic properties, harnessing dendritic cells for vaccination will likely result in a more robust immune response. We have demonstrated that high mobility group box protein 1 (HMGB1) and its fragments can act as potent maturation stimuli for human and mouse dendritic cells and are therefore promising candidates for adjuvants. The overall goal of this project is to investigate the efficacy of and develop the HMGB1-derived peptide Hp91 as vaccine adjuvant for herpes simplex virus 2 infections in mouse and guinea pig models. In Aim 1 we will assess the efficacy of the Hp91 adjuvant in combination with 3 HSV-2 antigens for protection against virus challenge and identify the most potent peptide format and formulation. In Aim 2 we will determine to what extent the most potent vaccine format provides HSV-2 protection in the guinea pig model that mimics human genital disease. In Aim 3 we will evaluate the safety profile of the vaccine. In Aim 4 we will determine the mechanism by which the peptide induces immune responses. We will perform structure function studies to determine critical amino acids and investigate receptor involvement. Overall these studies will determine to what extent the HMGB1-derived peptide Hp91 act as adjuvants in eliciting protective immune responses to HSV-2. These studies will provide the basis for testing its broad applicability to other clinically relevant antigens.