A Comparison of Test Materials for Differentiating Avian Leukosis Virus Group-Specific Antigens of Exogenous and Endogenous Origin

Abstract

Three groups of pullets--those lacking endogenous viral (ev) genes, those carrying ev3, which codes for avian leukosis virus (ALV) group-specific (gs) antigen but not complete virus, and those carrying ev2, which codes for complete endogenous virus--were reared to maturity free of exogenous ALV infection or reared separately after inoculation at 1 day with ALV. The enzyme-linked immunosorbent assay (ELISA) was used to detect gs antigen in feather pulp, cloacal swabs, sera, white blood cells, and albumens from the pullets and in embryos, combs, and meconia from their progeny. These results were used to identify methods to distinguish between endogenous ALV expression and exogenous ALV infection. Although the frequency and levels of gs antigen detection were higher in most of the ALV-positive than in ev-positive ALV-negative materials, albumens and cloacal swabs had the lowest frequency of gs antigen detection in the ev-positive ALV-negative materials. These two materials had a further advantage in that detection of gs antigen in them has been shown to be highly correlated with congenital transmission. Further studies using ELISA absorbance values and titer to quantitate gs antigen showed that ev-positive ALV-negative albumens had much lower levels of gs antigen than ALV-positive albumens. The same criteria were not useful for distinguishing cloacal swabs of these two types. We conclude that in these lines, high levels of gs antigen in albumen is a sensitive and practical means of identifying dams congenitally transmitting ALV, because there is a very low frequency of "false positives" due to endogenous gs antigen in this material.

Nested polymerase chain reaction for detection of the avian leukosis virus causing so-called fowl glioma

“…Considering the results of Groups 3 and 5, ELISA-positive birds may have shed not only FGV but also other ALV antigen. In addition, it can be also speculated that the birds may produce GSA derived from endogenous viral genes in their genome and shed it into the cloaca (Crittenden & Smith, 1984).…”

Avian leukosis virus subtype J in ovo -infected specific pathogen free broilers harbour the virus in their feathers and show feather abnormalities

“…However, higher levels of GSA of endogenous origin can be found in feather pulp than in albumen and cloacal swabs (Crittenden & Smith, 1984). It may thus give false-positive results.…”

Application of monoclonal antibodies in the dutch avian leukosis control programme

“…Congenital transmission (via the exogenous route of infection) of complete endogenous ALV, which should give rise to higher titres of endogenous gsa, seems to be restricted by its own gag gene products (Robinson and Eisenman, 1984). Discrimination between ALV-gsa of exogenous or endogenous origin can be pursued by testing serial dilutions of albumen samples as recently described by Crittenden and Smith (1984). We have examined by MCA-DAS-ELISA serial dilutions of a small number of albumen samples collected from three basic breeding flocks.…”