Evaluation of a prototype sub-unit vaccine against equine arteritis virus comprising the entire ectodomain of the virus large envelope glycoprotein (G(L)): induction of virus-neutralizing antibody and assessment of protection in ponies.

The research article discusses the successful evaluation of a prototype sub-unit vaccine against equine arteritis virus (EAV) derived from the virus’s large envelope glycoprotein (G(L)). The study notes that the vaccine was capable of inducing virus-neutralizing antibodies and offering a degree of protection to ponies.

Experimental Design and Methods

• The researchers created a recombinant protein derived from the full external domain of the EAV glycoprotein G(L) using Escherichia coli. This protein, called 6hisG(L)ecto, is an antigen that triggers immune responses in animals.
• The protein was used to vaccinate three different groups of four ponies. Each group received varying doses of the protein—35, 70, or 140 micrograms.
• A booster was administered after week 5 and the resultant virus-neutralizing antibody (VNAb) responses were monitored at specific periods—1-2 weeks, 13 weeks, and 53 weeks after the booster vaccination.
• Both vaccinated and unvaccinated control ponies were infected with EAV at various times post-vaccination to assess the level of protection offered by the prototype vaccine relative to the pre-challenge VNAb levels.

Research Findings

• Vaccines triggered a VNAb response in all tested animals, with peak titres going from 1.8-3.1 within the 1-2 weeks post-booster and gradually reducing over the 13 and 53 weeks timeframes.
• Vaccination proved to offer varying degrees of protection as identified by reduced or absent symptoms such as pyrexia (fever), viraemia (presence of viruses in the blood), and reduced excretion of the virus in the nasopharynx.
• The degree of protection showed a significant correlation to the levels of pre-challenge VNAb, and particularly with rates of virus excretion. The higher the VNAb levels before the EAV challenge, the better the protection.

Implications of Results

• This research provides the first evidence of a sub-unit vaccine offering protection in equines against an EAV infection, demonstrating a significant milestone in equine health protection.
• The sub-unit vaccine used in the research could be coupled with a differential diagnostic test based on other EAV antigens. This would render possible the serological discrimination between equines that have been naturally infected and those that have been vaccinated, improving diagnostic precision and treatment approach.