An avian leucosis group-specific complement fixation reaction. Application for the detection and assay of non-cytopathogenic leucosis viruses

Sera of hamsters bearing large primary or transplanted subcutaneous fibrosarcomas induced by the Schmidt-Ruppin (S-R) strain of Rous sarcoma virus contain complement-fixing (CF) antibodies reactive not only with the homologous virus, but also with antigens of other avian leucosis viruses. Using this group-specific reaction, a complement fixation test (the COFAL test) was developed for the specific detection and assay of viruses of the avian leucosis group; the test appears to be at least as sensitive and useful as the resistance-inducing factor (RIF) interference procedure. Virus was assayed by inoculating decimal dilutions of virus into chicken embryo fibroblast cultures grown in petri dishes or in roller tubes and testing the inoculated cultures for the development of CF viral antigens. End points for virus assays were obtained in petri dish cultures after one or two cell transfers and also in roller tube cultures without cell transfers. In both systems, virus diluted 10 −4 to 10 −5 was detected within 10 days of virus inoculation and final titration end points were often reached within 2 weeks. Rous-associated virus (RAV) was readily demonstrated in the Bryan strain but not in the S-R strain of Rous sarcoma virus. The test was effective in demonstrating naturally occurring avian lymphomatosis virus.