A RECOMBINANT CLASSICAL SWINE FEVER VIRUS STABLY EXPRESSES A MARKER GENE

The gene coding for bacterial chloramphenicol acetyltransferase (CAT) was inserted in frame into the viral N-pro gene of the full-length cDN A clone pA187-1 of the classical swine fever virus (CSFV) strain Alfor t/187. RNA transcribed in vitro from the resulting plasmid was transfe cted into SK-6 porcine kidney cells. Infectious progeny virus vA187-CA T recovered from transfected cells had growth characteristics indistin guishable from those of parental virus vA187-1. In cells infected with vA187-CAT the predicted fusion protein, CAT-N-pro, was detected, and it retained the enzymatic activities of both CAT and N-pro. The CAT ge ne remained stably inserted in the viral genome after 10 virus passage s. Thus, marker virus vA187-CAT represents a useful tool for quantitat ive analysis of viral replication and gene expression.