West Nile virus-specific immunoglobulin isotype responses in vaccinated and infected horses.

The study looks at the antibody responses of horses that have been naturally infected with the West Nile virus (WNV) alongside horses that have been vaccinated against it. The goal was to determine whether vaccination affects the diagnosis of WNV infection and to understand the longevity of antibody responses after vaccination.

Research Methodology

• The study involved horses that had been naturally infected with WNV and adult WNV-naïve horses before and after vaccination with two types of vaccines – a live canarypox virus-vectored vaccine and a killed virus vaccine.
• To measure the IgM responses, an established WNV IgM capture ELISA was used. Other newly developed capture ELISAs were used to measure the responses of eight other WNV-specific immunoglobulin isotypes.
• To determine anti-WNV antibody titers, a serum neutralization assay was used.

Research Findings

• It was found that WNV-specific IgM responses were generally detected in the sera of WNV-infected horses but not in the serum of horses vaccinated against WNV.
• Natural infection with and vaccination against WNV induced an immunoglobulin response that was primarily made up of IgG1.
• The presence of WNV-specific IgG1 was noticed in the serum of majority of horses 14 days post vaccination.
• It was found that serum anti-WNV IgG1 and neutralizing antibody responses induced by the killed-virus vaccines were higher and lasted longer as compared to those induced by the live canarypox virus-vectored vaccine.

Conclusions and Recommendations

• Based on these findings, it was recommended that horses be vaccinated against WNV annually near the beginning of mosquito season.
• It was also suggested that both the IgM and IgG1responses against WNV should be measured to differentiate between natural infection and vaccination.
• For the monitoring of anti-WNV antibodies in vaccinated horses, the use of a WNV IgG1 ELISA was recommended.