Booster effect of inactivated Parapoxvirus ovis on EHV-1 neutralising antibodies when co-injected with equine herpesvirus 1/4 vaccine
Résumé
Background: Equid herpesvirus 1 (EHV-1) is regularly responsible for outbreaks in many parts of the world, with a significant impact on the equine industry. Protection against EHV-1 relies on sanitary measures including vaccination, but the efficacy and duration of protection offered by existing vaccines is often limited and vaccines do not show protection against all forms of the disease.
Objectives: The aim of this study is to improve the vaccine efficacy and the benefit of immune stimulation with inactivated Parapoxvirus ovis (iPPVO), a substance already marketed as an immunostimulant.
Study Design: experimental challenge. Methods; Antibody response was measured after a semi-annual boost of EHV-1/4 vaccine with or without Zylexis added. Carbopol-adjuvanted inactivated EHV-1/4 vaccine was administered alone (n = 9) or combined with iPPVO injections at D0, D2 and D4 after vaccination (n = 10) to adult horses as a booster vaccination (i.e., 6 months after the last immunization). EHV-1 neutralising antibody titres were measured by classical serum neutralization and by a real-time neutralising assay 1, 3 and 6 months after vaccination.
Results: The results showed that iPPVO was safe and the horses had higher antibody levels than the control group injected with EHV-1/4 vaccine alone. In contrast to horses that received the vaccine alone, antibody titres increased or were at least maintained up to 3 months after immunization in horses that received the vaccine plus iPPVO.
Main Limitations: It should be noticed that in this experimental protocol, iPPVO was not mixed and co-injected with the vaccine, but administered near the injection site of the vaccine.
Conclusions iPPVO could be used to improve vaccination protocols against EHV-1 in horses
Key manufacturer: 1 Zylexis, Zoetis, USA https://www.zoetisus.com/content/_assets/docs/vmips/safety-data-sheets/zylexis.pdf
Ethical animal research: Approved by the CENOMEXA no 54 ethics committee (No APAFIS 2021081914235114_V3 (#32718)) and the Ministry of Higher Education, Research and Innovation.
Informed consent: Not applicable.
Competing interests: None declared.
Funding: Fonds Eperon OVERLORD N12-2017, Normandy County Council (17E01598/17EP04324), the IFCE (Institut Français du Cheval et de l’Equitation) grant number Rech-CS-2022-2023-019-VacAdEq_HVE. CENTAURE European project co-funded by Normandy County Council, European Union in the framework of the ERDF-ESF operational program 2014–2020.