Characterization of equine humoral antibody response to the nonstructural proteins of equine arteritis virus.

The research article focuses on the examination of the humoral immune response in horses to each nonstructural protein following infection by the equine arteritis virus (EAV). Findings emphasized unique immune response patterns in horses infected with EAV and those vaccinated with the modified live-virus vaccine, with implications for future methods in the serologic diagnosis of EAV infection.

Characterization of Equine Humoral Antibody

• The researchers’ primary objective was to understand the humoral immune response (antibody-mediated response) of horses to each nonstructural protein (nsp) post EAV infection. Nonstructural proteins are parts of the virus that do not make up the structure but have roles in the life cycle of the virus, such as replication.
• Part of the EAV replicase, two polyproteins (pp1a and pp1ab), were found to yield at least 13 nonstructural proteins (nsp1 to nsp12, with additional nsp7α and 7β) after undergoing posttranslational processing. This processing involves the modification of proteins after translation and often impacts the function of the protein.

Process of Experimentation

• The nonstructural proteins of the EAV were cloned and expressed in mammalian and bacterial systems in a lab setting.
• The researchers used an immunoprecipitation assay, a method used to investigate the interaction between proteins, utilizing serum samples from horses that were experimentally infected with different EAV strains (VB, KY77, and KY84), persistently infected stallions, and horses vaccinated with the modified live-virus strain.
• The protein-antibody complexes were then subjected to Western immunoblotting analysis using individual nsp-specific rabbit antisera, mouse anti-His antibody, or anti-FLAG tag antibody. Western immunoblotting analysis is a method used to detect specific proteins in a sample.

Findings and Future Implications

• Four of the nonstructural proteins, nsp2, nsp4, nsp5, and nsp12, were found to elicit a robust immune response in horses who were either experimentally or persistently infected.
• The sera from horses vaccinated with the modified live-virus vaccine did not react as strongly with nsp5 and nsp4, but were able to consistently immunoprecipitate nsp2 and nsp12 proteins.
• The study’s findings can assist in the development of better techniques for the serologic (blood serum-based) diagnostic testing of EAV infection in horses, as it provides insights into the specific antibody responses generated against EAV infection.