Incomplete viral synthesis in Friend leukemia virus-induced reticulum cell sarcomas.

Tissue-culture-passaged, Friend leukemia virus (FV)-induced reticulum cell sarcomas from BALB/c mice (FVTCT-BALB) did not produce infectious FV, although retrieval of infectious FV occurred when these cells were co-cultivated with cell lines replicating non-defective murine leukemia viruses (MLVs). The level of FV expression in the FVTCT-BALB cell line was studied to understand better the process of FV retrieval. 3H-uridine labelling techniques and reverse transcriptase assays showed that FVTCT-BALB cells did not release C-type virus particles. Nucleic acid hybridization techniques demonstrated that the level of viral RNA synthesis in the FVTCT-BALB non-producer cell line was indistinguishable from that in cell lines productively infected with MLVs. These data suggest that in the FVTCT-BALB cell line the synthesis of FV is blocked in some late stage of virus assembly.