In vivo effect of three transformation-defective mutants of subgroup C avian sarcoma viruses.

Three transformation-defective mutants derived from avian sarcoma viruses of subgroup C, td PR-RSV-C (Vogt), td B77 (Toyoshima) and td daPR-RSV-C (isolated in our laboratory), were injected intravenously into 12-day-old chicken embryos and intraperitoneally into newly-hatched chickens. Both Brown Leghorn chickens and F1 hybrids of two inbred chicken lines (C X I) were used. Haematological changes and formation of visible tumours were evaluated in animals kept for 8-9 months. All three td mutants produced in a significant proportion of intraembryonally injected animals haematological disorders which, in certain cases, resembled the anaemic and proliferative type of erythroblastosis. Most conspicuous symptoms of erythroblastosis were seen after td daPR-RSV-C which also gave rise to two sarcomas, containing transforming viruses. The possible character of oncogenic information retained or acquired by the TD mutants is discussed.