Structure and Mechanism of ALV-J Epitope Presented by MHC Class Ⅰ Molecule BF2*0201
MHC B2 haplotype chickens are highly resistant to avian leukosis virus infection,and this resistance may be related to the activated T cell immune response stimulated by MHC molecule presented epitopes.This study aims to elucidate the structure and mechanism of ALV-J epitope presentation by the MHC class Ⅰ molecule BF2*0201.Peptides that can bind stably to MHC Ⅰ were screened by gel filtration chromatography.The complex crystals of the peptide and MHC Ⅰ were growninvitro using a crystal primary screening kit,and the crystal structure was resolved and analyzed using COOT,CCP4 and PYMOL.In this study,we identified two ALV-J CTL epitopes FVDFANRLI and SALQAFREV that bind stably to BF2*0201.We obtained a high quality crystal BF2*0201-SALQAFREV(SV9)grown under the conditions of 1.0 mol·L-1 succinic acid(pH 7.0),0.1 mol L-1 HEPES(pH 7.0),and 1％polyethylene glycol monomethyl ether 2000.We resolved the structure of the high-resolution(1.72 Å)BF2*0201-SV9 complex and found that the BF2*0201 antigen-binding groove exhibits weak electronegativity overall.Conserved residues were located at both ends of the antigen-binding groove,and specific amino acids gave BF2*0201 a medium-sized peptide-binding groove.The B,C,and F pockets played an important anchoring role.The residues in pockets and water molecules formed hydrogen bonds with the antigenic polypeptide to anchor it to the peptide-binding groove,and the antigenic polypeptide was in an"M"-shaped conformation.The conformational features of the prominent Gln-4 and Arg-7 residues in the SV9 epitope conformation suggested potential recognition of this site by specific TCRs.The crystal structure of BF2*0201-SV9 complex can help to elucidate the mechanism of ALV-J epitope presented by BF2*0201,which can help to explain the reason for the resistance of B2 haplotype chickens to ALV,and lay a theoretical foundation for the breeding of resistance to the disease.
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