No abstract

Immunoglobulins from antiserum raised against chromatographically purified avian myeloblastosis virus (AMV) group-specific (gs) antigens were used in enzyme-linked immunosorbent assay (ELISA). Readily discernible color was produced with 2--3 ng of AMV protein in microplate wells coated with 4 micrograms of salt-precipitated immunoglobulins. When a biological assay, i.e., phenotypic mixing (PM), was the criterion for the infectious status of specimens, the ELISA consistently identified a greater percentage of virus-positive specimens than direct complement-fixation (DCF) tests. Over 95% concordance was obtained between the ELISA and PM bioassays when meconia and whole-blood samples were tested. Moreover, three DCF(-) egg albumens from one virus shedder hen were positive by the direct ELISA. Complete agreement was found between a biological assay for endogenous virus and the ELISA when blood and albumens from inbred chickens were tested. The ELISA is a rapid and convenient alternative to the DCF test for identifying infected chickens in eradication programs, because virus-rich sources such as meconia and blood that are unsuitable for DCF can be tested directly.

Hens from a commercial source were selected because they were infected with lymphoid leukosis virus (LLV). LLV was detected in vaginal swabs from 17 viremic hens and from 27 of 44 hens that were not viremic. All hens that were positive on the vaginal swab test (VST) produced one or more eggs with virus in albumen or in embryos, whereas in comparable tests, virus was detected only in eggs from 5 of 17 hens that were negative on VST. Congenital transmission of LLV was erratic and neither the VST nor tests for virus in egg albumen prior to incubating eggs identified all hens that transmitted infection. For example, 14 hens negative on VST produced 50 eggs negative for virus in albumen and yet one of the embryos from these eggs was infected. Eggs from other hens had infectious virus in albumen and about half of the embryos from these were infected. Tests for virus in cloacal swabs from one-day-old chicks were as sensitive as tests on embryos for detecting congenital transmission. Titers of LLV in the meconium of congenitally infected chicks were as high as 10(7) infectious units per ml. The cloacal swab test should be a valuable adjunct to the VST and tests on egg albumen in programs designed to eradicate lymphoid leukosis from chickens.

No abstract

Genome sequences of two recent field isolates of avian leukosis viruses in the DNA of normal and neoplastic chicken cells were studied by DNA-RNA hybridization under conditions of DNA excess. Comparisons were made between 60-70S RNA from these viruses and that of a chicken endogenous type C virus (RAV-0), and of a series of "laboratory" leukosis and sarcoma viruses, by competitive hybridization analysis. A minimum of 18% of the genome sequences of both ALV isolates detected in DNA from lymphomas they induced were not detected in normal chicken DNA. The vast majority of the fraction of RNA sequences from ALV which do form hybrids with normal chick DNA appear to be reacting with the endogenous provirus of RAV-0. The genomic representation of a variety of avian leukosis and sarcoma viruses in normal chicken cells could not be distinguished by these methods (except that 13% of the RAV-0 genome was not shared with any of the other viruses). In contrast, the portion of the ALV genome exogenous to the normal chicken geome showed significant divergence from that of two sarcoma viruses (Pr RSV-C and B-77). The increased hybridization of ALV RNA with lymphoma DNA was used to detect the appearance of ALV specific sequences in the bursa of Fabricius following infection.increased hybridization was correlated with both the time after infection and the extent of replacement of the bursa by lymphoma. About one half of the increase in hybridization preceded histologic evidence of transformation.