Towards a safe, effective vaccine for Rift Valley fever virus

Evaluation of: Bhardwaj N, Heise MT, Ross TM: Vaccination with DNA plasmids expressing Gn coupled to C3d or a-virus replicons expressing Gn protects mice against Rift Valley fever virus. PLoS Negl. Trop. Dis. 4(6), E725 (2010). Rift Valley fever virus (RVFV) is an important animal and human threat and leads to long-standing morbidity and mortality in susceptible hosts. Since no therapies currently exist to treat Rift Valley fever, it remains a public and animal health priority to develop safe, effective RVFV vaccines (whether for animals, humans, or both) that provide long-term protective immunity. In the evaluated article, Bhardwaj and colleagues describe the creation and testing of two successful vaccine strategies against RVFV, a DNA plasmid vaccine expressing Gn coupled to C3d, and an alpha-virus replicon vaccine expressing Gn protein. Both vaccines elicited strong neutralizing antibody responses, prevented morbidity and mortality in RVFV-challenged mice, and enabled protection of naive mice via passive antibody transfer from vaccinated mice. Both DNA and replicon RVFV vaccines have previously been shown to protect against RVFV challenge, but these results allow for direct comparison of the two methods and evaluation of a combined prime-boost method. The results also highlight the specific humoral and cell-mediated immune responses to vaccination.