Isolation and characterization of a new rubella variang with DNA polymerase activity.

A rubella variant (HPV-RV) was isolated from high passage rubella virus preparations propagated at 37 degrees C in baby hamster kidney BHK21/WI-2 cells. HPV-RV formed clear plaques in HeLa cells and primary cells of the Rhesus monkey kidney although wild type rubella virus did not produce plaques in these cells. Cells persistently infected with rubella virus were insensitive to infection by HPV-RV at both 34 degrees and 39.5 degrees C. HPV-RV agglutinated one day old chick, human group O and sheep erythrocytes. This hemagglutinating activity was inhibited by anti-BHK latent virus serum but not by anti-rubella virus serum. The plaque forming ability of HPV-RV was neutralized by anti-BHK latent virus serum although the same antiserum did not affect the plaque forming ability of wild type rubella virus. Furthermore, HPV-RV was found to have the complement fixation antigen of rubella virus and DNA polymerase activity. From these findings, it is concluded that HPV-RV is a hybrid between rubella virus and a latent virus of BHK21/WI-2 cells.