IMMUNOHISTOCHEMICAL DETECTION OF PORCINE REPRODUCTIVE AND RESPIRATORYSYNDROME VIRUS USING COLLOIDAL GOLD

Two cytopathic agents were isolated on porcine alveolar macrophages fo llowing inoculation with homogenates of lung tissues from pigs showing respiratory problems. These isolates were identified as porcine repro ductive and respiratory syndrome (PRRS) virus isolates by indirect imm unofluorescence using a PRRS virus (PRRSV) specific monoclonal antibod y (MAb) and were designated as LHVA-92-1 and LHVA-92-2. Immunogold ele ctron microscopy, using a porcine PRRS positive serum pool and protein A-gold resulted in an intense labelling of aggregates of viral partic les. Dark specific cytoplasmic staining of porcine alveolar macrophage s infected with both virus isolates could be observed by immunogold si lver staining (IGSS) using the specific MAb. This method proved effect ive in detecting PRRSV antigens in several ethanol-fixed tissues of pi glets intranasally inoculated with the supernatants of macrophages inf ected with each isolate. Immunogold silver staining was also successfu lly used for the detection of PRRSV antigens on sections of formalin-f ixed paraffin-embedded lung tissues and on frozen sections of lungs. T he present results indicate that colloidal gold may be useful for the identification and immunohistochemical detection of PRRSV in tissues.