Isolation and identification of porcine reproductive and respiratory syndrome virus in cell cultures.

Three strains of porcine reproductive and respiratory syndrome virus (PRRSV) were isolated in porcine lung macrophage (PLM) cultures from three swine herds. This has been the first successful isolation of PRRSV in the Czech Republic and the strains received the designations CAPM V-501, CAPM V-502 and CAPM V-503, respectively. All the three isolates in PLM were identified by immunofluorescence and immunoperoxidase tests and the strain CAPM V-502 also by electron microscopy using the ultrathin section technique. The strain CAPM V-502 has been adapted to the cell line MARC-145. Viral RNA in PLM cultures infected with any of the isolated PRRSV strains was demonstrated by RT-PCR targeted to the more conserved ORF 7 genomic region encoding the nucleocapsid protein. The assessment of PCR products in agarose gel revealed a uniform size of 394 bp in all the three isolates and the European prototype strain Lelystad used as positive control.