Alphavirus replicon particles expressing the two major envelope proteins of equine arteritis virus induce high level protection against challenge with virulent virus in vaccinated horses.

This research studies the effectiveness of vaccine constructs, derived from a strain of Venezuelan equine encephalitis (VEE) virus, in providing horses immunity from equine arteritis virus (EAV). The study underscores that vaccines that express a heterodimer of the major envelope proteins of EAV are effective in inducing immunity and prevent significant disease symptoms following exposure to virulent strains of the virus.

Study Overview

• The research focused on the development of a novel vaccine approach by using replicon particles derived from a vaccine strain of the Venezuelan equine encephalitis (VEE) virus.
• The concept was to use these particles as vectors to express the major envelope proteins of the equine arteritis virus (EAV).

Experimentation and Results

• The envelope proteins, G(L) and M proteins of EAV, were expressed both individually and in conjunction (heterodimer form).
• The immunogenicity or ability to provoke an immune response of these different constructs was then tested in horses.
• Also evaluated was the potential of these constructs to protectively immunize horses when they were challenged with a virulent strain of EAV (EAV KY84) either intranasally or intrauterine.
• It was observed that horses which were immunized with replicons expressing both G(L) and M proteins together developed neutralizing antibodies against EAV.
• Also, these vaccinated horses shed significantly less virus and experienced minor or no signs of equine viral arteritis (EVA), which is the disease caused by EAV.

Comparative Study

• For comparisons, horses that were either not vaccinated at all or were immunized with replicons expressing either M or G(L) proteins individually were also studied.
• These horses shed virus for 6-10 days in their nasal secretions post challenge with a virulent strain of EAV and displayed severe signs of equine viral arteritis.
• Such findings solidify the evidence that co-expression of G(L) and M proteins is the key to inducing effective immunity.

Conclusion

• This study confirms that replicons co-expressing the G(L) and M envelope proteins are effective in inducing EAV-neutralizing antibodies and protective immunity in horses.
• The potential for severe symptoms of the disease can also be significantly reduced.