Biochemical analysis of rabies virus proteins in three persistently infected BHK-21 cell lines

Three BHK-21 cell lines persistently infected with the CVS strain of rabies virus were passaged for 2.5 years at 37 degrees C. These cells contained relatively stable amounts of N, M1 and L proteins. Comparison of tryptic peptide maps of proteins from persistently infected (PI) cells and from purified virions did not reveal any changes in the N protein, whereas M1 had undergone several modifications. Phosphorylation of M1 seemed to be greater in PI cells than in acutely infected cells, whereas phosphorylation of N was equivalent. Amounts of viral G and M2 proteins in PI cells were less than 10% of those present in acutely infected cells incubated for 24 h. Stability of the N protein, limited genetic evolution of the M1 protein probably implicated in transcription and replication of the virus, and reduction of the quantity of the membrane proteins G and M2 were general characteristics of our three PI cell lines. Decrease of the quantity of virus proteins associated with external membranes could explain why cells survive to the persistent infection. The composition of viral material released from PI cells was different from that of the virions produced from acutely infected cells. Substantial reduction of L, G and M2, and/or M1 was observed and the particles were of low infectivity.