Virus-like particle-based countermeasures against Rift Valley fever virus.

Rift Valley fever virus (RVFV) is an arbovirus that causes significant morbidity and mortality in both humans and livestock. With increased world travel and the threat of bioterrorism, there is a real risk of RVFV spreading to naïve geographical areas (Trans. R. Soc. Trop. Med. Hyg., 73, 1979, 618; MMWR Morb. Mortal. Wkly Rep., 49, 2000, 905). The introduction of RVFV would cause critical public health, agricultural and economic damage. Despite the clear need for an efficacious vaccine, there are no United States (US) Food and Drug Administration or US Department of Agriculture approved vaccines against RVFV. To address this need, a virus-like particle (VLP)-based vaccine candidate was developed. First, a non-replicating chimeric RVF VLP vaccine candidate was generated that protected mice and rats against a lethal RVFV challenge. This was followed by the development and optimization of conditions for production of RVF VLPs in insect and mammalian cells. Immunological studies demonstrated that VLP-based vaccine candidates elicit both humoral and cellular immune responses. Subsequent challenge studies using a lethal wild-type RVFV strain under high-containment conditions showed that RVF VLP vaccine candidates can completely protect mice and rats.