DIFFERENTIAL REACTIVITY OF A MONOCLONAL-ANTIBODY DIRECTED TO THE MEMBRANE-PROTEIN OF PORCINE REPRODUCTIVE AND RESPIRATORY SYNDROME VIRUS

A monoclonal antibody (2C12) against the 19 kDa membrane (M) protein o f a Canadian isolate of porcine reproductive and respiratory syndrome (PRRS) virus was produced, By indirect immunofluorescence (IIF) cytopl asmic fluorescence was observed in infected cells, but the pattern of fluorescence was generally different and intensity was weaker than tha t observed using the nucleocapsid protein-directed monoclonal antibody SDOW17. When tested by IIF towards a total of 26 PRRS virus isolates from Canada, 122 isolates from the US and 13 isolates from Europe the 2C12 MAb reacted with all the North American isolates tested including the VR-2332 isolate and the vaccine (RespPRRS) isolate, However no re activity was observed towards the European isolates tested including t he Lelystad virus, This reactivity pattern suggests that the epitope r ecognized by this MAb on the M protein of ERRS virus appears highly co nserved among North American isolates but absent or weakly expressed o n European isolates of PRRS virus.