MULTIPLE FACTORS INCLUDING SUBGENOMIC RNAS AND REDUCED VIRAL PROTEIN EXPRESSION ARE ASSOCIATED WITH A PERSISTENT INFECTION BY PORCINE RUBULAVIRUS (LPMV)

The synthesis of virus specific RNA and the expression of viral protei ns in PK-15 cells persistently infected with the porcine rubulavirus L PMV have been studied at two different cell-passages following establi shment of persistency (passages 25 and 65). Protein analysis of persis tently infected cells and the virus particles released from these fail ed to demonstrate the presence of the polymerase (L) protein. A decrea se in the amount of the phospho-(P) protein was also noted. The genome and mRNAs, both mono- and bicistronic, could readily be identified in the persistently infected cells with the exception of the L mRNA. By analysis of transcription gradients generated using the NIH Image anal ysis software, as well as analysis of the editing frequency, it was co ncluded that the changes in viral protein levels in persistently infec ted cells could be associated with a reduction in the amount of L mRNA and a shift in editing of the P gene. In addition, several large subg enomic RNAs of both the internally deleted and copy-back type were fou nd in the persistently infected cells. The relevance of these findings to the persistent state is discussed.