In vivo selection of two agents differing in hepatoma-inducing activity from strain MC29 avian leukosis virus.

MC29 virus induces acute leukemia (myelocytomatosis) and primary tumors of liver (hepatomas) in turkey poults. By in vivo passages two viruses were selected; designated "liver" and "bone marrow" variants, differing in hepatoma-inducing activity. The "liver" variant induces hepatoma and acute leukemia, the "bone marrow" variant induces acute leukemia. The variants differ in leukemogenic activity. The "bone marrow" variant induces high grade leukocytosis, while the "liver" variant causes lymphocytosis and heteropenia. The variants also induce the appearance of primitive myeloid cells in the blood. The kinetics of accumulation of viral gs protein (p27) and the presence of viruses inducing hepatoma and leukemia were studied in organs of infected turkeys. The differences between the variants showed no relationship with their selective reproduction capacity in liver and/or bone marrow cells. The results obtained suggest that different viral particles are responsible for the induction of leukemia and hepatoma.