Detection of avian leukosis virus antigens by the ELISA and its use for detecting infectious virus after cultivation of samples and partial characterization of specific pathogen-free chicken lines maintained in this laboratory.

An enzyme-linked immunosorbent assay (ELISA) for detecting avian leukosis virus (ALV) antigens was developed with rabbit anti-ALV serum. The ELISA detected purified ALV of subgroups A and B at a concentration of 0.4 ng/well and about 10(3) infectious units/well estimated by a resistance-inducing factor (RIF) test, and antigens in culture fluids from chicken embryo fibroblasts infected with subgroups A, B or E of ALV. These results showed that common antigens among the subgroups were detected by the ELISA. When virus titration was performed, virus infectivity could be determined by the ELISA within 7 days after cultivation. The titer was similar to that obtained by the RIF test on 19 days after 3 subcultures. These results indicate that the ALV-isolation test by the ELISA was superior to the RIF test in rapidity and applicability to large-scale field trials. Four specific pathogen-free (SPF) chicken lines maintained in this laboratory were examined for endogenous ALV antigens by the ELISA. Sera from laying hens had considerably high absorbance (A) values, whereas albumen samples showed low A values except for some samples (7/40 hens). Although most of sera from 1-day-old SPF chicks showed lower A values than those from laying hens, some sera showed A values as high as those from viremic chicks in 2 lines. Endogenous ALV was isolated from sera from laying hens (6/40) and their albumens (4/7) with high A values. Two SPF chicken lines were found to produce endogenous virus at a high frequency.