Viral replication in HeLa/fibroblast hybrid cells infected with human cytomegalovirus

Three human hybrid cell lines were generated by the fusion of D 98OR, a HeLa cell variant, and TIG human diploid fibroblasts. Chromosome numbers of the hybrid cells fell between that of D 98OR cells and the combined chromosome number of the two cell lines, with three marker chromosomes identical to those of D 98OR cells. One hybrid, B-3, produced large amounts of human fibronectin as analyzed by immunohistochemistry. Only human cytomegalovirus (HCMV) infected B-3 cells showed positive fluorescence as detected by human antiserum to HCMV. Further cloning of B-3 by limiting dilution resulted in two cloned hybrids with markedly enhanced virus production as compared with B-3 cells. Treatment of these two clones with phorbol ester further enhanced virus production. These cloned hybrids may provide a tool to analyze host cell factors controlling the transcription and replication of HCMV.