Biomedical subjects

I Davidson

Publications and source records attributed to I Davidson.

147 records · Page 9Linked to original sources

PubMedDate not supplied

Multiple infection of chickens and turkeys with avian oncogenic viruses: prevalence and molecular analysis.

The avian herpesvirus, Marek's disease virus (MDV) and several retroviruses, reticuloendotheliosis virus (REV), avian leukosis virus (ALV) (chickens) and lymphoproliferative disease virus (turkeys) are oncogenic and immunosuppressive agents. These viruses were detected either alone, or in various combinations in blood and tumor DNAs of commercial birds using PCR. We present a 5-year retrospective study that included 207 chicken and 52 turkey flocks. Of these, 32 chicken and 18 turkey flocks were negative. Of the positive chicken and turkey flocks 76% and 75%, respectively, had a single, while the rest, 24% and 25%, had a multiple virus infection. In the chickens of the multiple virus-infected flocks, 14% and 17% of the blood and tumor DNAs carry dual MDV and REV and/or ALV sequences, that is about 30% of the PCR-positive, and about 5% of the total DNAs analysed. Multiple virus sequences were detected only in the turkey blood DNAs-11% of 84 samples. Following that quantitation we aimed to analyse the molecular status of the retrovirus sequences in order to determine whether retrovirus sequences were integrated into the herpesvirus genome. We focused on the MDV BamH1-H 132 bp tandem repeat fragment proximity using a combined PCR (cPCR) to identify chimeric PCR products. That included amplification with heterologous combinations of the MDV and retroviral LTR primers. In 13 of 35 DNAs that had both MDV and retrovirus sequences new products were produced. Of 4 MDV + REV chimeric products that were sequenced, one was homologous to the Chicken Repeat element 1 non-LTR type retrotransposon. No evidence for a retrovirus LTR integration was found in the 132 bp repeat proximity, but in two of these products we detected nucleotide stretches of 20 bp and 21 bp with a 70% and 71% homology to the REV-LTR. Also, the amplification of the chimeric products using a retrovirus primer denoted that at least short nucleotide stretches homologous to retroviral LTR primer were present in these DNAs, and that they might resemble ancient retroviral insertions, as previously demonstrated (Isfort et al., 1992).

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PubMedDate not supplied

In vivo events of retroviral long terminal repeat integration into Marek's disease virus in commercial poultry: detection of chimeric molecules as a marker.

The present study demonstrated, for the first time, that not only in vitro, but also in vivo, coinfections with Marek's disease virus (MDV) and each of the three avian retroviruses (reticuloendotheliosis virus [REV], avian lymphoid leukosis virus [ALV], and ALV-J) lead to retroviral long terminal repeat (LTR) integration into MDV. A total of 306 chicken and 59 turkey commercial flocks, submitted for differential avian oncogenic virus diagnosis, served to evaluate the flock mixed virus infection rate, the rate of birds with a multiple virus infection, and the issue of retroviral LTR integration into MDV in vivo. About a quarter of the tumor-bearing commercial flocks carried a mixed MDV and retrovirus infection. A total of 2926 DNA samples were analyzed, including 2428 chicken and 498 turkey DNA samples. Of these, 991 DNAs originated from flocks with a multiple virus infection. In 103 DNA preparations from that group (103/991, 10.4%), including 38 and 56 from chicken blood and tumor tissues, respectively, and nine samples from turkey blood, multiple virus sequences were detected by polymerase chain reaction (PCR). Fifty-six of the 103 samples were further analyzed by the previously developed hot spot-combined (HS-cPCR assay, of which 48% (27/56) contained chimeric MDV and retroviral LTR molecules. When extrapolated to the total samples derived from the flocks with multiple virus infection, that rate implies that about 5% of the DNA samples would carry MDV-retrovirus integration events. Several birds held a variety of chimeric molecules, indicating that several recombination events occurred simultaneously. The validation of the MDV and retroviral LTR chimeric constitution of these molecules was derived by the MDV and retroviral heterologous primers used for their creation by the HS-cPCR assay, Southern blotting and their detection by retroviral LTR probes, and LTR amplification from the gel-purified chimeric molecules. From several molecules, the LTR was sequenced, and a 161-bp retroviral LTR sequence was demonstrated. Our biochemical data imply that a recent integration occurred in the birds. The viability of recombinant viruses represented by the chimeric molecules will be further approached.

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PubMedDate not supplied

Enzyme immunoassay studies on the serological response of turkeys to hemorrhagic enteritis virus.

An enzyme-linked immunosorbent assay (ELISA) was developed for the detection of antibodies in turkey serum to hemorrhagic enteritis virus. The ELISA antigen was extracted from turkey spleens and partially purified with fluorocarbon. Antibodies were demonstrated in serum samples of breeding and meat flocks that had been naturally exposed to infection. These samples were also examined in parallel by agar-gel precipitin (AGP); most of the sera were AGP-positive. ELISA, however, was more sensitive in detecting antibodies in day-old sera that were AGP-negative. The passively acquired antibodies were no longer detected by 4 weeks of age. A brisk but short-lived secondary response was detected by ELISA in the sera of turkeys immunized with beta-propiolactone-inactivated extract of infected spleens.

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