Ring-necked pheasant virus, an avian leukosis virus, when injected into 10-day old chick embryos, caused angiosarcomas in the lungs of infected chickens within a short time. Angiosarcomas appeared as localized foci of proliferating cells in the lungs as early as 2 weeks posthatch, and by 6 weeks, the lungs of the infected chickens were frequently filled with tumor cells. Between 3 and 10 weeks of age, 80% of infected chickens died of the angiosarcomas; the 20% which lived 8 weeks or longer had small lung lesions and also developed fibrosarcomas, osteopetrosis, nephroblastoma, and lymphoid leukosis. Chickens with lung tumors were cyanotic, had breathing difficulty, and had packed cell volumes in excess of 50%. Other changes not necessarily correlated with lung tumor mass were stunting, lymphoid organ involution, and profuse diarrhea. Ring-necked pheasant virus has a genome RNA of 8.2 kb. This observation, together with its replication and disease induction after repeated plaque purification, suggests that ring-necked pheasant virus is a replication-competent avian retrovirus. Therefore, our results suggest that ring-necked pheasant virus is an avian leukosis virus which causes angiosarcomas rapidly at high incidence and which, therefore, may induce this type of tumor by a mechanism different from the induction of sarcomas by avian sarcoma viruses.
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