Detection of antibodies to equine arteritis virus by a monoclonal antibody-based blocking ELISA

A potent ELISA antigen was prepared from equine arteritis virus (EAV) by di fferential centrifugation of EAV-infected cell culture fluid, followed by s olubilization of the preparation by Triton X-100 treatment. Using this anti gen and a mouse monoclonal antibody against the G(L) protein of EAV, a reli able blocking ELISA (bELISA) was developed for the detection of EAV antibod ies lin equine sera. The bELISA was evaluated using a total of 837 test ser um samples. The relative sensitivity (n = 320) of the bELISA compared to th e serum neutralization (SN) test was 99.4%. The bELISA arrears to be a high ly specific test, the specificity of which did not appear to be adversely a ffected by previous exposure of horses to non-EAV-containing biologicals. O f 119 serum samples, 21 from horses without any history of exposure to EAV and 98 from racetrack Thoroughbreds, 118 were negative in the SN test and b ELISA. One sample was SN-negative but suspicious with the bELISA. Based on testing 465 SN-negative field samples and 52 SN-negative samples from exper imental horses, and excluding any sera giving a suspicious reaction, the re lative specificity of the bELISA was 97.7%. Samples should be examined undi luted and diluted 1/10 in the bELISA because the testing of sera of high ne utralizing antibody titer may be affected by a prozone-like phenomenon. The bELISA is a more rapid and cost-efficient test than the SN test for the de tection of EAV antibodies in equine sera.