Evidence that use of an inactivated equine herpesvirus vaccine induces serum cytotoxicity affecting the equine arteritis virus neutralisation test.

The research investigates how a particular equine herpesvirus vaccine introduces an issue in testing for the equine arteritis virus (EAV), due to a created serum cytotoxicity that complicates interpretation of results. They found that alternative EAV tests reduced these effects notably but did not entirely resolve the issue, recommending the evaluation of ELISA-based tests as a possible solution.

Background of the Study

• The study deals with an issue faced by laboratories worldwide with the serological testing for the equine arteritis virus (EAV), a disease that could disrupt equine breeding and disease surveillance.
• This problem involves serum cytotoxicity during the virus neutralisation test (VN) which uses the rabbit kidney (RK-13) indicator cells as prescribed by the Office International des Epizooties (OIE).
• While cytotoxicity can be mistaken for a viral cytopathic effect, its appearance has constituted major difficulties in test interpretation.

Observations and Findings

• The researchers used both experimental and field-derived data to investigate this issue.
• Their findings indicate that this serum cytotoxicity might be related to the usage of a tissue-culture-derived equine herpesvirus vaccine.
• This is most likely due to a vaccine-induced anti-cellular antibody response that’s directed against the RK-13 cells.

Experiments with Alternative Test Methods

• The research studied two alternative EAV virus neutralisation methods to see if they could mitigate the effects of cytotoxicity in vaccinated horses.
• These alternatives indeed significantly reduced the prevalence of cytotoxicity from 73 to less than 5%s,

Further Recommendations

• Despite the noted reduction, these alternative methods did not completely eliminate the cytotoxicity problem.
• Consequently, the researchers suggest the evaluation of ELISA-based tests for screening equine sera for EAV VN antibodies might be essential.
• Although ELISA-based tests aren’t currently recognized international standards, they aren’t affected by serum cytotoxicity, making them a possibly useful backup method.