ANTIGENIC COMPARISON OF CANADIAN AND US ISOLATES OF PORCINE REPRODUCTIVE AND RESPIRATORY SYNDROME VIRUS USING MONOCLONAL-ANTIBODIES TO THE NUCLEOCAPSID PROTEIN

Fifteen Canadian field isolates of porcine reproductive and respirator y syndrome (PRRS) virus from Quebec and Ontario were compared with 5 U S PRRS virus (PRRSV) isolates and with the European Lelystad isolate u sing monoclonal antibodies (MAbs) SDOW17, EP147, and VO17 directed to the 15-kDa nucleocapsid protein of PRRSV, All Canadian and US isolates tested by indirect immunofluorescence were recognized by the 3 MAbs, and individual titers of MAbs towards Canadian and US PRRSV isolates w ere similar as well, In contrast, the Lelystad virus isolate reacted o nly with the SDOW17 MAb and showed no reactivity with either EP147 or VO17, The reactivity pattern with these MAbs suggests that the Canadia n isolates of PRRSV tested are antigenically similar to US isolates of PRRSV, and that these North American isolates share highly conserved epitopes on the 15-kDa nucleocapsid protein that clearly differentiate them from the European Lelystad virus isolate.