ESTABLISHMENT OF A SERUM-FREE CULTURE CELL-LINE, CPK-NS, WHICH IS USEFUL FOR ASSAYS OF CLASSICAL SWINE FEVER VIRUS

A stable porcine kidney cell line, CPK-NS, was established and maintai ned in serum-free culture. A cytopathic effect (CPE) was observed clea rly in CPK-NS cells infected with some classical swine fever virus (CS FV) strains which did not show the exaltation of Newcastle disease vir us (END) phenomenon. Chromosome condensation and DNA fragmentation, a marker for apoptosis, were detected in cells infected with END phenome non-negative CSFV strains. By using the CPE induced by infection with an END phenomenon-negative CSFV strain in CPK-NS cells, assays of CSFV were established. The virus titer determined in CPK-NS cells shows a high correlation with the usual peroxidase-linked assay, dome disappea rance method and END method. Furthermore, the antibody titer by neutra lizing test with CPK-NS cells also correlated with that measured by th e usual neutralizing peroxidase-linked assay and dome disappearance me thod. These stable CPK-NS cells have the great advantage that a clear CPE was caused by infection with END phenomenon-negative CSFV strains and bovine serum is not necessary for cell culture and virus assays. ( C) 1998 Elsevier Science B.V. All rights reserved.