Rapid oncogenesis in vivo by chicken retrovirus OK10

The OK10 virus complex is known to contain two detectable viruses: a) focue-forming virus OK10V that transforms chick embryo cells, and b) an associated virus OK10AV present in excess that converts the morphology of cultured chick embryo cells. The pathogenesis of OK10 virus infection was studied, using 2--4 day old Brown Leghorn chickens. A group of chickens was sacrificed at weekly intervals, serum samples were taken and tissues were examined for virus. Autopsies of the chicken were performed and gross and microscopic changes were registered. After intraperitoneal injection of 10(4) focus-forming units of OK10 virus, infectious OK10AV was detected after one week in Bursa Fabricius, thymus and liver, and OK10V after two weeks in Bursa Fabricius but in no other organ. Neutralizing serum antibodies developed within three weeks. The first malignant changes, in the mesentery, were detected after three weeks. The infection was lethal in all experiments within 6--8 weeks. In the mesentery, the tumors consisted of large tumour cells with clear cytoplasm, a large nucleus and prominent nucleoli. The origin of these cells could not be established. The cells were surrounded by lymphoid cells. From the tumours, vontinuous cell lines were established which produced both viruses OK10V and OK10AV and had blast-like morphology. After intravenous injection of OK10 virus, tumours could also be found in liver, kidneys and testes. The associated virus OK10AV was injectious for chickens and induced neutralizing serum antibodies. One out of seven chickens died of leukosis after 1 1/2 years. The OK10 virus complex, consisting of a tumour-forming and a weakly oncogenic associated virus, appears to have a multiple oncogenic potential in its rapid oncogenic action in vivo.