Genetic mutations within tva receptor gene confer resistance to ALV-A and ALV-K infection in chickens

Avian leukosis virus subgroup A (ALV-A) and the newly emerging subgroup K (ALV-K) are primary causative pathogens of avian leukosis in chickens and continue to pose a persistent threat to poultry industry worldwide. Susceptibility or resistance of chicken cells to ALV-A and ALV-K is determined by the tva receptor gene. Indeed, six ALV-A resistant alleles (tva^r1-tva^r6) have been identified within the tva gene. However, whether these tva alleles confer resistance to ALV-K infection remains unclear. In this study, we identified five tva resistant alleles, namely tva^r2, tva^r3, tva^r4, tva^r5, and tva^r6, in Qingyuan partridge chickens (QYPC). In vitro analyses, including flow cytometry and quantitative real-time PCR, we demonstrated that the tva^r2 allele confers complete resistance to both ALV-A and ALV-K infection. In contrast, the tva^r3, tva^r4, tva^r5, and tva^r6 alleles each significantly reduced susceptibility to ALV-K. Furthermore, these in vitro observations were corroborated by in vivo infection experiments, which confirmed that the tva^r2 allele consistently conferred complete resistance to both ALV-A and ALV-K, while tva^r3, tva^r4, tva^r5, and tva^r6 alleles each resulted in a significant reduction in ALV-K susceptibility. Additionally, the tva^r2-tva^r6 alleles were broadly distributed across QYPC lines, with notably high frequencies of resistant genotypes observed in specific QYPC populations. Collectively, these findings not only expand our understanding of tva-mediated resistance to both ALV-A and ALV-K but also provide valuable genetic targets for selective breeding programs aimed at enhancing resistance to ALV-A and ALV-K in chickens.