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Abstract

Rift Valley Fever (RVF) is a major public health and veterinary concern in Africa and the neighboring regions. One approach that is a priority for preventing epidemics of RVF is to develop and deliver an effective vaccine for livestock and humans. The aim of this study was to evaluate the Bioject ZetaJet needle-free vaccine delivery device for use to vaccinate animals with a very promising live recombinant RVF MP-12?NSm vaccine candidate. A preliminary assessment of the device was conducted in young adult Wistar Furth rats with and without a spacer, suggesting an subcutaneous or intramuscular route of delivery, respectively. Two doses of the RVF MP-12?NSm vaccine of 1 x 103 and 1 x 105 plaque forming units (PFU) were administered using the needle-free device (NFD) to each of 2 groups of 5 animals each. Also, a dose of 1 x 105 PFU of the RVF MP-12?NSm vaccine and of the RVF MP-12 parent vaccine was administered via the intraperitoneal (IP) route to groups of rats using a needle. Blood samples collected from rats before vaccination and at 7, 11, 15, and 25 days post-vaccination (DPV) were tested for antibody by the plaque reduction neutralization assay. Most animals (80-100%) vaccinated with the NFD developed detectable neutralizing antibody by 7 DPV that persisted through 25 DPV or the duration of the experiment, with antibody titers ranging from 1:20 to 1:1280, with no significant difference in the titers observed for the groups IP vaccinated with RVF MP-12 ?NSm and RVF MP-12 vaccine versus the groups that received RVF MP-12 ?NSm using the NFD at 25 DPV. These results suggest that needle-free vaccine delivery may be a more convenient and effective method of vaccinating animals with RVF vaccines.