Viral hemorrhagic fevers (VHF's) involve severe disease symptoms and high mortality rates, and the potential for natural reemergence and spread of the viral agents. There are also concerns about the possible intentional introduction of the etiologic agents by individual or state-sponsored acts of bioterrorism. In the present application, we focus on development of effective vaccines for two etiologic agents of hemorrhagic fever - LV, an arenavirus, and EBOV, a filovirus. Both are examples of viruses which can be transmitted via person-to-person contact, thus posing a higher threat of causing an epidemic outbreak. We are proposing to test the hypothesis that VLPs will serve as safe and effective vaccines to induce or boost protective systemic and/or mucosal immunity to these highly pathogenic viral agents. The glycoprotein (GP) and NP subunits of Ebola and Lassa viruses were selected as antigens for the initial focus of our efforts because immune responses against these viral antigens have been shown to prevent disease induced by the corresponding viruses in animal models. To develop a safe and effective vaccine, we will produce chimeric VLPs containing the envelope glycoproteins of LV or EBOV on their surfaces. Incorporation of expressed glycoproteins of LV or EBOV into the released VLPs is expected, based upon previous studies as well as our recent observation that coexpressed influenza HA protein is readily incorporated into such VLPs. We will compare production of VLPs obtained by recombinant baculovirus expression in insect cells versus expression from an inducible vector in CHO cells, and explore approaches to incorporate viral NP sequences into the VLPs. The immune responses to VLPs following systemic or mucosal immunization will be evaluated in serum and mucosal secretions. Intracellular cytokine staining, MHC tetramer staining and ELISPOT assays will be used to evaluate cellular immune responses to the VLP antigens. Vaccine preparations and immunization regimens, which result in optimal immune responses, will be evaluated for their ability to confer protection against virus challenge.