Genetic variation at the TVB locus in Turkish and Iranian native chicken breeds

Abstract

Avian leukosis viruses (ALVs) are retroviruses that can induce tumors, as well as reduce growth rate and productivity in chicken. The tumor virus B (TVB) locus encodes the cellular receptor that mediates an infection through ALVB, ALVD, and ALVE subgroups of ALV. Two single nucleotide polymorphisms (SNPs) at nucleotide positions 172 and 184 of the autosomal TVB locus account for the three alleles, TVB*S1, TVB*S3, and TVB*R. The receptor encoded by TVB*R allele prevents viral entry into the cell of ALVB, ALVD, or ALVE subgroups. In this study, both SNPs at the TVB locus of 2 Turkish and 7 Iranian native chicken breeds were investigated by using a PCR-RFLP technique to determine genotypes and gene frequencies at TVB locus. The frequency of TVB*S1, and TVB*S3 alleles changed from 0.857 to 1.000, and from 0.022 to 0.143, respectively, in all studied breeds. The TVB*R allele for resistance to ALV-related viruses was not determined. As a result, it can be concluded that Turkish and Iranian native chickens are strongly susceptible to the infection of ALV-related viruses.