Printed in Great Britain The Complement-fixation Test for Avian Leukosis

Sera from hamsters bearing tumours induced by the Schmidt-Ruppin strain of Rous sarcoma virus (sR-RSV) contain antibodies to the avian leukosis group specific antigen and an antigen of chick origin. The 'chick embryo antigen ' is found in chick embryos infected and uninfected with avian leukosis viruses and in chicken tumours induced by avian leukosis viruses; for example, Rous sarcoma wing web tumour and plasma from avian myeloblastosis virus infected chickens. The 'chick embryo antigen' has been detected in sR-RSV hamster tumour cells. Cultured chick fibro-blasts do not contain the ' chick embryo antigen ' and thus the avian-leukosis group specific antigen can be specifically detected by complement fixation using SR-RSV tumour-bearing hamster sera. This COFAL test is as sensitive as the Rubin interference t st (RIF test) and unlike the RIF test will detect all known avian leukosis viruses. 2