Biological activity of proviral DNA isolated from cells infected with MAV-2(0) virus

The ability of DNA isolated from avian myeloblastosis-associated virus MAV-2(0)-infected fibroblasts to induce the synthesis of virus upon transfection of susceptible but not resistant cells was demonstrated. The virus obtained, when inoculated into 12-day-old embryos, led to the manifestation of osteopetrosis after prolonged incubation and to the induction of nephroblastomas in some cases. Positive transfection with DNA from the non-virus producing myeloblast cell line was not detected on bone marrow cells and fibroblasts preinfected with tdB77-C virus. After transfection with DNA from virus-producing myeloblasts, the reproduction of non-transforming virus was observed. This virus did not induce myeloblastosis upon infection of chickens but induced nephroblastomas on rare occasions.