Influence of interferon on virus particle formation in different oncornavirus carrier cell lines

Three types of oncornavirus‐carrying mouse cell lines were studied. Replication of endogenous sarcoma or leukemia viruses in cell lines producing the infectious viruses was as sensitive to inter feron as that of exogenous vesicular stomatitis virus (VSV). Replication of non‐infectious C‐type virus in S+L− cells which carry a rescuable Moloney sarcoma virus (MSV) genome did not respond to interferon. However, this cell line was also found to be 70 times less responsive to interferon when tested by an exogenous VSV challenge. Finally, after exposure to interferon, M04 cells, which carry a rescuable MSV genome and produce non‐infectious A‐type particles, developed normal resistance to VSV. Yet, high doses of interferon could not prevent the induction of surplus A‐type particles by bromodeoxyuridine (BDU) and dimethylsulfoxide (DMSO). The results are interpreted as indicating that non‐infectious A‐type particles are synthetized by a mechanism different from that by which infectious C‐type particles are generated.