A West Nile virus (WNV) recombinant canarypox virus vaccine elicits WNV-specific neutralizing antibodies and cell-mediated immune responses in the horse

Successful vaccination against West Nile virus (WNV) requires induction of both neutralizing antibodies and cell-mediated immune responses. In this study, we have assessed the ability of a recombinant ALVAC®-WNV vaccine (RECOMBITEK® WNV) to elicit neutralizing antibodies and virus-specific cell-mediated immune responses in horses. In addition, we examined whether prior exposure to ALVAC®-WNV vaccine would inhibit B and cell-mediated immune responses against the transgene product upon subsequent booster immunizations with the same vaccine. The results demonstrated that the recombinant ALVAC®-WNV vaccine induced neutralizing antibodies and prM/E insert-specific IFN-γ+ producing cells against WNV in vaccinated horses. Prior exposure to ALVAC®-WNV vaccine did not impair the ability of horses to respond to two subsequent booster injections with the same vaccine, although anti-vector-specific antibody and cell-mediated immune responses were induced in vaccinated horses. This report describes, for the first time, the induction of antigen-specific cell-mediated responses following vaccination with an ALVAC® virus recombinant vaccine encoding WNV antigens. Moreover, we showed that both WNV-specific IFN-γ producing cells and anti-WNV neutralizing antibody responses, are not inhibited by subsequent vaccinations with the same vector vaccine.