Immune responses in mice, cattle and horses to a DNA vaccine for vesicular stomatitis

Vesicular stomatitis (VS) virus causes an important clinical disease of cattle and horses in North America. In order for a vaccine to be useful in the control of VS, it must not only protect against disease, but allow ready differentiation of infected and vaccinated animals. In these studies, we evaluated neutralizing antibody responses in outbred mice, calves, and horses that received a DNA vaccine that expressed the glycoprotein (G) gene of VS New Jersey virus. The vaccine elicited antibody titers in individuals from each species, especially when two doses were administered, but the level of neutralizing antibody needed to confer protection is not known. In mice, co-administration of a plasmid that expressed interleukin-2 resulted in a significant, though modest, increase in antibody titers relative to use of the G gene vaccine alone. The effect of co-injecting putative immunostimulatory oligonucleotides was also evaluated. This treatment had no apparent effect in horses and was found to suppress immune responses to the G gene vaccine in mice. If the immune responses obtained in these studies prove to protect cattle and horses from infection with VS virus, DNA vaccination may become a useful tool for control of this disease.