In vitro transformation with avian myelocytomatosis virus strain CMII: characterization of the virus and its target cells.

Avian myelocytomatosis virus strain CMII induced an in vitro transformation in cells from various hematopoietic tissues and could be quantitated by focus and soft agar colony assay techniques. The CMII-transformed bone marrow cells had a high proliferative capacity in comparison to uninfected controls. The cells closely resembled hematopoietic cells transformed by strain MC29 myelocytomatosis virus, but differed from avian myeloblastosis virus (AMV)-transformed cells. They were phagocytic, became adherent under certain conditions of culturing, and required colony-stimulating factor for colony formation in semisolid medium. These properties are characteristic for cells of the granulocyte/macrophage lineage of differentiation. In contrast to avian erythroblastosis virus, CMII effectively transformed macrophage cultures suggesting that the target cell belongs to the corresponding differentiation lineage. That it is not identical to normal granulocyte/macrophage colony-forming cells was demonstrated by cell separation experiments. In addition to hematopoietic cells, CMII induced a morphological transformation in chicken fibroblasts. CMII was found to consist of a mixture of a transforming component and an associated nontransforming virus of subgroup B or D. The transforming component is defective for replication and could be complemented by standard helper viruses of subgroups B, C, and D.