Variations in Endogenous Viral Gene Patterns in White Leghorn, Medium Heavy, White Plymouth Rock, and Cornish Chickens

Abstract

The endogenous viral (ev) gene patterns of White Leghorn (WL; 6 lines), medium heavy (MH; 4 lines), White Plymouth Rock (WPR; 8 lines), and Cornish types (2 lines) of commercial chickens were compared. Southern blot analysis of SstI-digested genomic DNA of 151 chickens revealed that the number of ev gene-containing fragments in a chicken from the MH, WPR, or Cornish type is about twice twice the number of that in WL chickens. Also, the number of hybridizing fragments of different size found within one line was twice as high in the broiler (on average 16.0 bands per line) and MH lines (20.5 bands per line) than in the WL lines (10.0 bands per line). In studies with subregion-specific probes, all ev fragments detected contained the env (3') part of the viral genome. Only eight ev fragments, found in 7 animals of 2 lines, lacked the gag (5') part of the viral genome. Studies with the ev-1-specific flanking probe, pGd111, revealed that ev-1 is commonly present in the DNA of the WL chickens, but not within the DNA of the WPR chickens. The results suggest that use of the standard nomenclature for the ev genes based on restriction fragment length is not feasible within the WPR, MH, and Cornish lines because of the complexity of the ev gene patterns found within these lines.

Genetic variation at the tumour virus B locus in commercial and laboratory chicken populations assessed by a medium-throughput or a high-throughput assay

“…We cannot explain the difference in frequency in TVB alleles in broilers versus egg-laying strains, but it is of interest that numerous studies have shown that the number and frequency of ALV-E genes is generally higher in broilers than in egg-laying strains (Ignjatovic, 1986; Kuhnlein et al, 1989;Aarts et al, 1991;Gavora, et al, 1991;Sabour et al, 1992). Indeed, Benkel (1998) has stated that the average modern egg chicken has only one to three ALV-E elements, whereas meat birds typically carry six to 10.…”

Endogenous Viral Gene Distribution in Populations of Meat-Type Chickens

“…Noninbred Leghorns usually have one to five ev loci (Rovigatti and Astrin, 1983;Aarts et al, 1991), but some have none (Astrin et al, 1979;Gavora et al, 1989).…”

Comparative analysis of avian leukosis virus-related endogenous viral genes in experimental strains of the domestic chicken

“…An eul-specific probe showed that the genomic insertion site for eul was not occupied by a viral insert in Fayoumi chickens although they carried the restriction fragments usually associated with an eul occupied site in White Leghorns, ie 9.5 kb with SacI and 5.2 kb with BamHI (Lamont et al, 1992). A similar approach revealed a much lower frequency of occupation of the eul site in White Plymouth Rock chickens than in White Leghorns (Aarts et al, 1991). The polymerase chain reaction has recently been proposed as a method to identify ALV-related ev genes in a locus-specific way (Benkel et al, 1992 Leghorn (Hughes et al, 1981).…”

“…Furthermore, the finding of a deletion in the gag region was useful to confirm the identification of ev6 in all the strains. Deletions within the gag region were found to be rare in a survey of several strains (Aarts et al, 1991) but more frequent in White or Brown Leghorns (Hughes et al, 1981;Gudkov et al, 1986;Ronfort et al, 1991 (Iraqi et al, 1991) and commercial broilers (Boulliou et al, 1991). This could suggest that ev6 is a very old retroviral insertion.…”

“…A classification of 22 different ev genes has been established from the study of restriction fragment length together with the determination of viral phenotypic expression (Smith, 1987;Crittenden, 1991 (Rovigatti and Astrin, 1983). Indeed, a very high level of polymorphism has been described for ev genes in commercial layers and broilers (Aarts et al, 1991;Boulliou et al, 1991;Iraqi et al, 1991;Sabour et al, 1992), and new ev genes were also found in other experimental strains (Gudkov et at, 1981;Ronfort et at, 1991;Lamont et al, 1992 (Merat and Bordas, 1982). The experimental Wyandotte strain (X55) was maintained for many generations as part of a conservation programme.…”