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SUMMARYAn enzyme-linked immunosorbent assay (ELISA) for avian leukosis/ sarcoma virus (ALV) group-specific (gs) antigens was used to study the identification of hens which congenitally excrete exogenous ALV. The sensitivity of this assay was compared with that of the phenotypic mixing test (PMT) and the direct complement fixation test (CFT) by testing limiting dilutions of purified avian myeloblastosis virus (AMV), embryo homogenates and albumens. About 0.4 ng/ml of purified AMV protein could be detected by ELISA and 23.8 ng/ml of AMV protein was demonstrable by the CFT. The lowest levels of gs-antigen detection corresponded with about 100 median tissue culture infectious doses (TCID 50 ) of infectious ALV. Albumens and embryos of three White Leghorn flocks and one White Plymouth Rock flock were tested for the presence of avian leukosis virus (ALV) gs-antigens by the complement fixation test (CFT) and the enzyme-linked immunosorbent assay (ELISA) and exogenous ALV employing the phenotypic mixing test (PMT). The highest number of ALVgs antigen positive samples of egg albumens was obtained by the ELISA. In embryo homogenates prepared from eggs of the four flocks under study 100% scores for gs-antigens were obtained by ELISA. A differentiation between gs-antigens of endogenous and exogenous ALV was made by testing of supernatant fluids after one chick embryo fibroblast passage of the C/E phenotype. Endogenous viral (ev) genes leading to the expression of endogenous ALV gs-antigens were apparently present in practically all chickens of the four flocks under study. Complete endogenous ALV (subgroup E) was detected in embryos (41%) from the White Plymouth Rock grandparent flock, but was not found in embryos of two White Leghorn basic breeder flocks. The results indicate that both flocks of White Leghorn chickens are endowed with ev 3 genes. Circumstantial evidence was obtained for the prevalence of endogenous ALV gs-antigens in albumen samples of eggs from flocks with gs + chf + and V-E + phenotype respectively.

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Summary Six hybridoma cell lines have been established that secrete monoclonal antibodies (MCAs) directed against bovine leukemia virus (BLV) core protein p24. Various enzyme‐linked immunosorbent assays (ELISA) were tested for the applicability of these MCAs in BLV antibody detection. A highly sensitive IDAS‐ELISA that detects antibody against BLV‐p24 was developed, but non‐specific reactivity made this test unsuited for routine enzootic bovine leukosis (EBL) screening. Non‐specific reactivity was not observed in a Complex‐trapping‐blocking (CTB)‐ELISA in which MCA anti‐BLV‐p24‐coated plates were simultaneously incubated with undiluted serum and BLV antigen, followed by addition of another MCA anti‐BLV‐p24 labelled with horseradish peroxidase (HRP). The CTB‐ELISA‐p24 was not sensitive enough to screen milk samples. Test results obtained with sera, however, matched markedly well with those obtained in agar gel precipitation tests (AGPT) and in ELISAs detecting antibodies against BLV‐gp51. In sequentially collected serum samples from BLV‐infected calves, antibodies were demonstrated at about the same time by CTB‐ELISA‐p24 and AGPT‐gp51. Different routes and doses of BLV exposure caused major differences in the first appearance of antibodies. Zusammenfassung Identifizierung von Leukämievirus (BLV)‐infizierten Rindern durch Einsatz monoklonaler Antikörper gegen BLV‐p24 in einem “Complex‐trapping‐blocking (CTB)‐ELISA” Es wurden sechs Hybridoma‐Zell‐Linien entwickelt, die monoklonale Antikörper (MCA) gegen das Coreprotein p24 des bovinen Leukämievirus (BLV) sezernieren. Mehrere ELISA‐Testanordnungen zur Eignung dieser MCA für den BLV‐Antikörpernachweis wurden erprobt. Es wurde ein hochsensitiver IDAS‐ELISA entwickelt, der Antikörper gegen das Protein BLV‐p24 ermittelt, allerdings lassen unspezifische Reaktionen einen routinemäßigen Einsatz zum Screening der enzootischen bovinen Leukose nicht zu. In einem “Complex‐trapping‐blocking (CTB)‐ELISA” trat keine unspezifische Reaktion auf. Hierzu wurden die mit Anti‐BLV‐p24‐MCA‐beschichteten Platten gleichzeitig mit unverdünntem Serum und BLV‐Antigen inkubiert. Anschließend wurde ein anderer, Meerrettichperoxidase (HRP)‐konjugierter, Anti‐BLV‐p24‐MCA zugegeben. Der CTB‐ELISA war nicht empfindlich genug, um Milchproben zu testen. Testergebnisse jedoch, die an Untersuchungen von Seren erhalten werden, stimmten ausgesprochen gut mit solchen überein, die in der Agargel‐Präzipitation (AGPT) und in ELISA's ermittelt wurden, die Antikörper gegen das BLV‐gp51 nachweisen. In Serum‐Verlaufsuntersuchungen BLV‐infizierter Kälber, wurden Antikörper im CTB‐ELISA‐p24 und in der AGPT‐gp51 annähernd zur selben Zeit nachgewiesen. Unterschiedliche Applikationswege und Dosierungen des BLV hatten größere Abweichungen im erstmaligen Auftreten von Antikörpern zu Folge.