Recombinant canarypoxvirus vaccine carrying the prM/E genes of West Nile virus protects horses against a West Nile virus-mosquito challenge.

The research paper explores the creation and efficacy of a recombinant canarypoxvirus vaccine, named vCP2017, which carries two genes from a 1999 New York isolate of West Nile virus (WNV). When administered to horses, the vaccine was shown to elicit an immune response, reducing the risk of WNV infection considerably.

Creation of the vCP2017 Vaccine

• The researchers constructed the vaccine using ALVAC, a type of canarypoxvirus.
• From a 1999 New York-isolated strain of West Nile virus, the prM and E genes were taken and used to create the recombinant vaccine vCP2017.

Assessment of the vCP2017 Vaccine

• Two experiments were conducted to evaluate the vaccine’s protective efficacy in horses.
• The first experiment was a dose titration study examining serum neutralising antibody responses and duration of immunity against WNV.
• The second experiment assessed the onset of protection.
• A total of 28 adult horses received two doses of the vaccine via intramuscular injections at 5-week intervals, while 16 horses were kept as non-vaccinated controls for comparison.

Immunological Response to the vCP2017 Vaccine

• Horses were periodically tested for neutralising antibodies against WNV, results showing that all vaccinated horses had developed such antibodies.
• The horses were later exposed to WNV-infected mosquitoes, then monitored for clinical signs of disease, WNV viremia, and the presence of antibodies.
• Judging by these observations, neither vaccinated nor control horses displayed any clinical symptoms of WNV.
• Upon examination two weeks after primary vaccination, none of the nine vaccinated horses challenged showed detectable viremia; even one year following vaccination, only one out of ten vaccinated horses showed signs of viremia, compared to over 80% of the control group.

Conclusion

• The results conclusively demonstrated that a primary course of two doses of vCP2017 can provide an early immune response in horses against WNV viremia, as well as an antibody response; indicating a promising tool for WNV prevention.