Establishment of a cell line persistently infected with bovine herpesvirus-4 by use of a recombinant virus

Bovine herpesvirus-4 (BHV-4), a gammaherpesvirus lacking a clear disease as sociation, productively infects multiple cell lines of various species and causes cell death. A human rhabdomyosarcoma cell line, RD-4, infected with BHV-4 produced low levels of early and late viral RNAs and infectious virus , but exhibited no cytopathic effect. Using a recombinant BHV-4 containing a neomycin-resistance gene, we established RD-4-derived cell lines persiste ntly infected with BHV-4, The viral genome in these cells was predominantly circular, Because of drug selection, every cell contained a viral genome. In addition, all cells stained with a BHV-4-specific antiserum. Therefore, these cell lines are not carrier cultures. These cells produced infectious virus at all passages tested. Even though cells were selected and maintaine d at a concentration of geneticin at least 2.5 times that necessary to kill uninfected RD-4 cells, selected cells contained only approximately one vir al genome per diploid host cell genome. Persistently infected cells grew mo re slowly than uninfected cells, even in the absence of drug. The slower gr owth of these cells suggests that any growth advantage conferred by multipl e copies of the neomycin-gene-carrying viral genome might be offset by the detrimental effects of viral gene expression. This situation contrasts with other gammaherpesviruses, which are able to growth-transform cells.