Single nucleotide polymorphism variants within tva and tvb receptor genes in Chinese chickens

Abstract

Avian leukosis is an immunosuppressive neoplastic disease caused by avian leukosis viruses (ALV), which causes tremendous economic losses in the worldwide poultry industry. The susceptibility or resistance of chicken cells to subgroup A ALV and subgroup B, D, and E ALV are determined by the receptor genes tumor virus locus A (tva) and tumor virus locus B (tvb), respectively. Four genetic resistant loci (tvar1, tvar2, tvar3, and tvar4) in tva receptor gene and a genetic resistant locus tvbr in the tvb receptor gene have been identified in inbred lines of White Leghorn. To evaluate the genetic resistance to subgroup A, B, D, and E ALV, genetic variations within resistant loci in tva and tvb genes were screened in Chinese local chicken breeds and commercial broiler lines. Here, the heterozygote tvas1/r1 and the resistant genotype tvar2/r2, tvar3/r3, and tvar4/r4 were detected in Chinese chickens by direct sequencing. The heterozygote tvas1/r1 was detected in Huiyang Bearded chicken (HYBC), Rizhaoma chicken, and commercial broiler line 13 to 15 (CB13 to CB15), with the frequencies at 0.08, 0.18, 0.17, 0.25, and 0.15, respectively. The resistant genotype tvar2/r2 was detected in Jiningbairi chicken (JNBRC), HYBC, and CB15, with the frequencies at 0.03, 0.08, and 0.06, respectively, whereas tvar3/r3 and tvar4/r4 were detected in 19 and 17 of the 25 Chinese chickens tested, with the average frequencies at 0.13 and 0.20, respectively. Furthermore, the resistant genotype tvbr/r was detected in JNBRC, CB07, CB12, CB14, and CB15 by pyrosequencing assay, with the frequencies at 0.03, 0.03, 0.11, 0.09, and 0.15, respectively. These results demonstrated that the potential for genetic improvement of resistance to subgroup A, B, D, and E ALV were great both in Chinese local chickens and commercial broilers. This study provides valuable insight into the selective breeding for chickens genetically resistant to ALV.