A rabies virus persistent infection in BHK21 cells.

A rabies virus persistent infection in BHK21 S13 cells was established and maintained in culture for more than 4 years. Initially, the cultures produced a large plaque virus similar to that produced by the original virus, but between the 10th and 20th passage, this was replaced by a small plaque variant. By the 200th passage, infectious virus could no longer be detected in the medium. After further cell passages (greater than or equal to 300) no infectious particles could be detected in the medium. At various passage levels, the persistently infected cells were labelled with [35S]methionine and the virus antigens immunoprecipitated and analysed by polyacrylamide gel electrophoresis. No changes in the virus polypeptides were observed in the establishment of the persistent state. However, after the 20th passage (predominance of small plaque variant) there was an increase in the size of the glycoprotein. This was followed (164th passage) by a change in the MI polypeptide which was subsequently further modified in the defective state (greater than or equal to 300 passages). Virus isolated from the 400th passage by treatment of the cells with DEAE-dextran, was also modified in the glycoprotein and M1 polypeptides and contained less L polypeptide than the original virus. This virus grew more slowly, to a lower titre and was no longer pathogenic in suckling mice.