The mucosal humoral immune response of the horse to infective challenge and vaccination with equine herpesvirus-1 antigens.

This research investigates the immune response in horses following infection or vaccination against equine herpesvirus-1 (EHV-1). Results from the study show that antibodies developed following natural viral infection are most effective in fighting the virus, and can potentially decrease EHV-1 spreading.

Objective and Methodology

• This study was designed to understand the immune response in horses—specifically foals—after being exposed to the equine herpesvirus-1 (EHV-1) either through natural infection or vaccination.
• Twenty weanling (young, recently weaned) horses were divided into five distinct groups, each subjected to different protocols of virus exposure or vaccinations.
• Then, all the horses were exposed to a specific strain of EHV-1 known as Army 183 (A183).

Data Collection

• Nasal wash and blood serum samples were collected from the horses at different time intervals until 13 weeks after exposure to the virus.
• An indirect, quantitative ELISA (enzyme-linked immunosorbent assay) was used to screen the nasal samples for specific types of antibodies (IgGa, IgGb, IgG(T), IgA, IgM).
• Overall antibody responses in the bloodstream were monitored and any clinical signs of disease were recorded for each horse.

Results and Findings

• The primary type of antibody detected in the mucosal (relating to the mucus membranes) response in horses infected with A183 was IgA.
• Neither vaccine administered—whether introduced through injection or administered intranasally—resulted in detectable antibody development in the mucus membranes.
• The presence of virus-specific antibodies inhibited the formation of EHV-1 plaques in laboratory tests indicating in vitro neutralization capability, suggesting that these antibodies could decrease the virus’ ability to spread from the respiratory tracts of infected horses.

Conclusions

• These findings highlight the importance and effectiveness of IgA antibodies in combating EHV-1 in infected horses.
• However, it appears that the currently available vaccines may not be effective in encouraging the production of these beneficial antibodies in the horses’ mucosal immune system.
• Further research is necessary to design more effective vaccination strategies and to increase our understanding of equine immune responses.