Responses of regressor and progressor lines of chickens to intracerebral inoculations of Rous sarcoma virus.

Two-day-old chickens of the Arkansas B1 progressor (Pr) line and the B1 regressor (R) line were inoculated intracerebrally with three dilutions of Rous sarcoma virus. Chickens that died between 7 and 42 days postinoculation were examined for lesions attributable to Rous sarcomas. Mortality was 93% for the progressor chickens as compared with 65% for the regressor chicken. Macroscopic lesions were found on the head in 64 chickens, as hemorrhage in the brain in 38, on the heart in 15, on the liver in 9, and in the parenchyma of the brain in one chicken, from a total of 117 chickens inoculated. Surviving chickens were inoculated in the wingweb with Rous sarcoma virus. Of the progressor line chickens three of four developed tumors and two died. The third chicken exhibited abnormal neurological behavior. Of the regressor line, 15 of 20 were immune and of the five that developed tumors, four had complete regressions. The fifth chicken also showed neurological abnormality. The two chickens with neurological dysfunction were sacrificed, and their histopathology examinations revealed lesions in the brain with features belonging to Rous sarcomas, paralleling those reported for other types of sarcomas.