Genetic Diversity of NHE1, Receptor for Subgroup J Avian Leukosis Virus, in Domestic Chicken and Wild Anseriform Species

<div><p>J subgroup avian leukosis virus (ALV-J) infects domestic chicken, jungle fowl, and turkey and enters the host cell through a receptor encoded by <i>tvj</i> locus and identified as Na+/H+ exchanger 1 (NHE1). The resistance to ALV-J in a great majority of examined galliform species was explained by deletions or substitutions of the critical tryptophan 38 in the first extracellular loop of NHE1, and genetic polymorphisms around this site predict the susceptibility or resistance of a given species or individual. In this study, we examined the NHE1 polymorphism in domestic chicken breeds and documented quantitative differences in their susceptibility to ALV-J <i>in vitro</i>. In a panel of chicken breeds assembled with the aim to cover the maximum variability encountered in domestic chickens, we found a completely uniform sequence of NHE1 extracellular loop 1 (ECL1) without any source of genetic variation for the selection of ALV-J-resistant poultry. In parallel, we studied the natural polymorphisms of NHE1 in wild ducks and geese because of recent reports on ALV-J positivity in feral Asian species. In anseriform species, we demonstrate a specific and highly conserved critical ECL1 sequence without any homologue of tryptophan 38 in accordance with the resistance of duck cells to prototype ALV-J. Last, we demonstrated that the new Asian strains of ALV-J have not evolved their envelope glycoprotein to the entry the duck cells. Our results contribute substantially to the current discussion of possible heterotransmission of ALV-J and its spill-over into the wild ducks and geese.</p></div

Alignment of the left part of ECL1 and adjacent TM1 of NHE1 in the duck and goose species.

<p>The deduced amino-acid sequences of ECL1 and corresponding chNHE1 amino-acids 11 to 58 are compared and aligned. The border between ECL1 and putative transmembrane domain TM1 is depicted by horizontal arrow. The W38 amino-acid residue in chNHE1 is shown as a vertical arrow. Amino acids matching the consensus sequence of anseriforms are on a gray background.</p

Host range of new J subgroup RCAS vectors in avian species^a.

<p>Host range of new J subgroup RCAS vectors in avian species<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150589#t002fn001" target="_blank">^a</a>.</p

NHE1 allele in gray partridge contains deletion of W38 resembling the ALV-J resistant species in galliforms.

<p>The deduced gray partridge amino-acid sequence of ECL1 corresponding to chNHE1 amino-acids 23 to 104 are aligned to the sequences of eight galliform species analyzed previously (Kučerová et al., 2013). The susceptibility or resistance of galliform species is denoted (+) or (-), respectively. The borders between ECL1 and putative transmembrane domains TM1 and TM2 are shown. The W38 and P52 amino acid residues are denoted by vertical arrows. Amino acids matching the consensus sequence are on a gray background.</p

Differences in the susceptibility to ALV-J among embryo fibroblasts from inbred chicken lines.

<p>Infections were done with decreasing MOIs of RCAS(J)GFP and GFP+ cells were examined by FACS four d. p.i. MOIs of 0.1 (A) and 10 (B) are shown. The data represent a typical experiment done in one parallel for each inbred line and each time.</p