CONSTITUTIVE PRODUCTION OF A MURINE RETROVIRUS IN THE HUMAN B-LYMPHOBLASTOID CELL-LINE, DG-75

During the screening of human lymphoblastoid cells as suitable hosts f or retrovirus transmission studies, the Epstein-Barr virus (EBV)-negat ive, B-lymphoblastoid cell line DG-75 was found to be chronically infe cted with a heretofore unrecognized retrovirus. Two DG-75 sublines obt ained from different sources (designated UW and KAR) were found to pro duce constitutively particles identified as retroviral by electron mic roscopy and reverse transcriptase activity. The ultrastructure, morpho genesis, and density in sucrose of the particles were typical of C-typ e retroviruses. Immunoblot analysis of the DG-75(UW) retrovirus protei ns showed antigenic similarity to Moloney murine leukemia virus. A thi rd DG-75 subline in early passage, designated HAD, was free of retrovi rus. The DG-75(UW) retrovirus was infectious and produced progeny viri ons that could be passaged to uninfected cells. We have thus demonstra ted that DG-75 cells, which have been used extensively in studies of t he biological effects of EBV-encoded genes and their promoters, may be chronically infected with a murine retrovirus and that an early passa ge subline is retrovirus free and available for such studies. (C) 1998 Academic Press.