Investigation of the TVB Locus Polymorphisms at Denizli and Gerze Native Chicken Breeds

Abstract

Avian leukosis viruses (ALV) are tumor-forming retroviruses in chickens and no vaccine has yet been devel-oped against these viruses. The tumor viral B (TVB) locus encodes the surface receptors specific to groups that inhibit or mediate the viral input of the three subgroups of ALV. Two single nucleotide polymorphisms on bases 172 and 184 of this locus allow the differentiation of TVB*S1, TVB*S3, and TVB*R alleles. TVB*S1 encodes the ALVB, ALVD, and ALVE receptors that support three sub-viral inputs. TVB*S3 encodes receptors that provide the viral input of the ALVB and ALVD subgroups into the cell. The receptor encoded by TVB*R inhibits the viral introduction of ALVB, ALVD, and, ALVE subgroup into the cell. The aim of this study is to investigate the presence of the TVB*R' allele showing re-sistance to some ALV subtypes, TVB*S' allele and, possible mutations using DNA sequence analysis method in native Turkish chicken breeds, Denizli and Gerze. A total of 175 chicken samples, from four varieties of Denizli (n=148), reared in Denizli Rooster Production Station of Denizli Provincial Directorate and Gerze (n=27) reared in Gerze District Agriculture Directorate of Agriculture and Forest Ministry were used. Genomic DNA was isolated from blood samples taken from chickens. Among the 175 chickens, only two hens were typed as TVB*S1/R genotype, three chickens were typed as TVB*S1/S3, four chickens were typed as TVB*S1/S’ and others were homozygous for TVB*S1/*S1. The frequencies of TVB alleles detected in Denizli and Gerze populations were calculated as 0.9730, 0.9815 for TVB*S1, and 0.0034 and 0.0185 for TVB*R, respectively. TVB*S3 and TVB*S' alleles were not found in the Gerze population, and the frequencies of TVB*S3 and TVB*S' alleles in the Denizli population were calculated as 0.0101 and 0.0135, respectively.