Development and evaluation of an ELISA using recombinant fusion protein to detect the presence of host antibody to equine arteritis virus

A recombinant glutathione-S-transferase fusion protein expressing amino acids 55–98 of equine arteritis virus (EAV) G(L) (rG(L)55–98) was tested in an ELISA for its ability to detect serum antibodies to EAV. Host antibodies induced following EAV infection bound the recombinant antigen by ELISA. The ELISA specificity and sensitivity were determined with a panel of equine sera including postinfection and postvaccination samples. A good correlation existed between EAV neutralizing antibody titers and ELISA absorbance values (r = 0.827). The sensitivity and specificity of the ELISA were 99.6 and 90.1%, respectively, compared with the EAV neutralization test and the recombinant antigen did not crossreact in ELISA with equine sera directed against other common equine respiratory viruses. Three post-EAV infection equine sera raised against different EAV isolates reacted strongly in the ELISA, as did two equine sera raised against EAV vaccines, indicating that the viral epitope was conserved between the viruses tested. Following vaccination with an inactivated whole virus vaccine, antibody detected with the recombinant antigen ELISA preceded the development of a virus-neutralizing response. The study demonstrates the potential application of rG(L)55–98 as a diagnostic antigen.