title: Influence of the alv6 recombinant avian leukosis virus transgene on production traits and infection with avian tumor viruses in chickens.
abstract: The biological costs of the alv6 recombinant transgene that in chickens induces dominant resistance to the subgroup A avian leukosis virus (ALV), in terms of effects on production traits, were studied. Four generations of White Leghorn chickens of Line TR, segregating for alv6 but free of endogenous viral genes, as well as two generations of crosses between TR and Ottawa Line WG (WGTR) were tested under a specific-pathogen-free environment. In the birds studied, the transgene appeared unchanged compared to the original alv6: No major changes in alv6 DNA were detected by restriction analysis, the transgene did not express the group-specific antigen of ALV, and its presence was associated with absence of immune response to ALV. In most test years, and both TR and WGTR genomic backgrounds, alv6 was associated with delayed sexual maturity by 4 to 6 d, reduced egg production to 497 d of age by 20 to 46 eggs, and a 3.6 to 15% decline in egg production rate. No consistent effects on other traits, including mortality, were detected. When inoculated with the AC-1 isolate of Marek's disease virus in a separate experiment, TR birds with alv6 had a significantly lower body weight gain to 10 d of age than their sibs without the transgene. Thus, transgenesis has biological costs that have to be assessed against desirable effects of transgenes.
authors.affiliation: Centre for Food and Animal Research, Agriculture and Agri-Food Canada, Ottawa, Ontario.
authors.forename: J S
authors.initials: JS
authors.lastname: Gavora
authors.forename: B
authors.initials: B
authors.lastname: Benkel
authors.forename: J L
authors.initials: JL
authors.lastname: Spencer
authors.forename: C
authors.initials: C
authors.lastname: Gagnon
authors.forename: L B
authors.initials: LB
authors.lastname: Crittenden
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001353:Avian Leukosis / Q000276:immunology / Q000517:prevention & control*; D001354:Avian Leukosis Virus / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification; D001483:Base Sequence; D015139:Blotting, Southern / Q000662:veterinary; D001835:Body Weight; D002645:Chickens; D017931:DNA Primers; D005260:Female; D015683:Gene Products, gag / Q000235:genetics; D008380:Marek Disease / Q000517:prevention & control; D008969:Molecular Sequence Data; D010058:Oviposition; D016133:Polymerase Chain Reaction / Q000662:veterinary; D011201:Poultry Diseases / Q000276:immunology / Q000517:prevention & control* / Q000821:virology
chemical_list: D017931:DNA Primers; D015683:Gene Products, gag