MONOCLONAL-ANTIBODIES TO EQUINE ARTERITIS VIRUS PROTEINS IDENTIFY THE G(L) PROTEIN AS A TARGET FOR VIRUS NEUTRALIZATION

Monoclonal antibodies (MAbs) to equine arteritis virus (EAV) proteins were produced and characterized. The protein specificities of eight MAbs were determined definitively by immunoprecipitation of EAV proteins expressed from vaccinia virus recombinants (VVRs). Included were two new VVRs produced for this study, expressing the M and the G(L) proteins, respectively. Three MAbs were determined to be N-specific and five MAbs recognized the G(L) protein. One G(L)-specific MAb, 17F5, of the IgA class, efficiently neutralized EAV infectivity. In competitive binding assays (CBAs), the N-specific MAbs defined a single antigenic domain on this protein. Four G(L)-specific MAbs, including MAb 17F5, demonstrated strong reciprocal competition in binding to the G(L) protein but differed in their virus-neutralizing ability. Thus the antigenic domain defined by these MAbs is probably composed of overlapping or closely adjacent epitopes. The fifth G(L)-specific MAb, a nonneutralizing antibody, may define an epitope adjacent to this antigenic domain as reciprocal CBAs demonstrated lower competition.