Isolation of porcine respiratory coronavirus from pigs affected with porcine reproductive and respiratory syndrome.

Four cytopathogenic viruses were isolated in CPK cells derived from porcine kidneys from tonsils and lungs of 3 of 15 pigs affected with porcine reproductive and respiratory syndrome virus. Physicochemically and morphologically, the isolates were similar to a coronavirus. The isolates were not distinguished from transmissible gastroenteritis virus (TGEV) by a neutralization test using polyclonal antibodies, but differentiated from TGEV by monoclonal antibodies capable of discriminating between TGEV and porcine respiratory coronavirus (PRCV), indicating that the isolates were PRCV. In a serological survey of 30 serum samples each collected from about 50 days old pigs in the 2 affected farms, 29 (97%) and 15 (50%) sera were positive for neutralizing antibody against the isolate with the titers ranging from 2 to 64, respectively.