Investigation of the Systemic Antibody Response and Antigen Detection Following Intranasal Administration of Two Commercial Equine Herpesvirus-1 Vaccines to Adult Horses.

This research article investigates the effectiveness of two commercially available equine herpesvirus-1 (EHV-1) vaccines when administered intranasally. Specifically, it examines whether these vaccines can trigger an immune response and the detection time of EHV-1 in nasal secretions following vaccination.

Study Rationale

• The primary focus of this study is to understand the efficacy of two commercial EHV-1 vaccines, Calvenza and Rhinomune, when delivered intranasally. This is because intranasal vaccine administration is often used during equine herpesvirus myeloencephalopathy outbreak emergencies, despite a lack of clarity regarding its effectiveness and the resultant diagnostic challenges.

Study Design

• Thirty healthy adult horses without a recent EHV-1 vaccination history were divided into three groups: Rhinomune, Calvenza, and an unvaccinated control group.
• The goals were twofold: first, whether the vaccines could spur a detectable systemic antibody response post-administration, and secondly, to understand the timeframe for detecting EHV-1 in nasal secretions following the vaccine administration.

Findings

• Across all groups, there were no marked differences, pre- and post-vaccination, in total Ig and isotype-specific IgG4/7 against EHV-1, indicating that neither vaccine stimulated a systemic immune response.
• Vaccine-derived EHV-1 was detected only in the vaccinated groups, with 90% and 80% of horses in the Rhinomune and Calvenza groups, respectively, testing qPCR-positive for EHV-1 one to three days post-administration.
• There was no major difference between the two vaccine groups in terms of the count of horses testing qPCR-positive for EHV-1 and the absolute measurement of EHV-1 in the nasal secretions.

Conclusion

• The study concludes that neither of the two vaccines prompted a systemic immune response when administered intranasally, suggesting that their effectiveness may be limited in this delivery mode.
• Furthermore, traces of the vaccine-derived EHV-1 could be detected in the majority of vaccinated horses, revealing potential implications for the interpretation of EHV-1 diagnostics during outbreaks.