Immunological response in horses following West Nile virus vaccination with inactivated or recombinant vaccine.

This study aimed to compare the effectiveness of two different types of vaccines for the West Nile virus in horses: one using an inactivated virus strain and the other using a live recombinant canarypox virus. The researchers found that the vaccine using the live canarypox virus resulted in a stronger and longer-lasting immunological response.

Study Design and Methodology

• The researchers selected 40 horses that tested negative for the West Nile virus (WNV). These horses were divided into two groups of 20.
• One group was vaccinated with a strain of the virus that had been inactivated, and given a booster shot 28 days later. The second group received a vaccination derived from a live recombinant canarypox virus, which had been genetically engineered to express genes associated with the WNV.
• The presence and levels of IgM, IgG and neutralizing antibodies were monitored for 360 days after vaccination, using class specific ELISAs (enzyme-linked immunosorbent assays) and a serum neutralization assay.

Findings

• In both groups of horses, IgM antibodies were first detected 7 days after vaccination, indicating that the horse’s immune systems has started to respond to the virus. However, in horses vaccinated with the inactivated vaccine, IgM antibodies were only detected up to day 42 after vaccination. In the group vaccinated with the recombinant vaccine, they were detectable up to day 52 after vaccination.
• Both vaccines also prompted a response in IgG antibodies, which showed up from day 7 post-vaccination and lasted till the end of the trial.
• Both vaccines also elicited a response in WNV-specific neutralizing antibodies, which helps to protect the body against the virus. However, the group given the recombinant vaccine showed a higher average level of these antibodies, and the levels lasted longer than in the group given the inactivated virus vaccine.
• Even one year after vaccination, neutralizing antibodies were still detectable in horses that received the canarypox virus-based vaccine, but not in those vaccinated with the killed virus product.

Conclusion

• The findings of this study suggest that the live canarypox virus-vectored vaccine could provide better and longer-term protection against WNV for horses compared to the inactivated virus vaccine.
• The use of vaccines is a valuable tool in controlling WNV in endemic areas by preventing disease in horses and lowering the risk of spread to other animals and humans.