Rift Valley fever is a mosquito-borne zoonotic disease (ruminants and humans) endemic to Africa. Rift Valley fever virus (RVFV) is a segmented negative-stranded RNA virus, which belongs to the genus Phlebovirus of family Bunyaviridae. RVFV is classified as Category A Priority Pathogen by NIH/NIAID, and an overlap select agent by CDC and USDA. Vaccination is an efficient strategy to prevent RVFV spread. Our laboratory undertakes a basic research to understand the safety and efficacy of the live-attenuated MP-12 vaccine and the recombinant variants. Using reverse genetics, we identified attenuation mutations for MP-12 vaccine. We also characterized the efficacy of recombinant MP-12 lacking NSs gene for DIVA (differentiation of infectious from vaccinated animals) purpose. More recently, we identified temperature-sensitive mutations for MP-12 vaccine, and characterized the genetic stability of key mutations for MP-12 vaccine. As a part of vaccine development project, we also analyze the basic aspect of reassortant and recombination between RVFV and other buyaviruses. Using high containment facilities at UTMB, we generated several pathogenic RVFV strains by reverse genetics. We plan to study vaccine efficacy, viral pathogenesis, and host-virus interaction with established resource and environment.