title: Biochemical and structural impact of natural polymorphism in the HLA-A3 superfamily.
abstract: Class I alleles of the HLA-A3 superfamily (-A*0301, -A*1101, -A*3101, -A*3301, and -Aw*6801) share largely overlapping peptide repertoires. Cross-reactive T cell responses between HLA-A3-like molecule/peptide complexes have been demonstrated in vitro and during natural diseases. In spite of this immune relatedness, HLA-A3-like molecules exhibit noticeable differences in their antigen-selecting and -presenting properties. Identifying molecular and structural features responsible for these differences is important for understanding how natural polymorphism leads to functional divergence within the HLA-A3 superfamily. Towards this goal, we used an approach that combines thermal stability data on recombinant, soluble HLA-A3-like molecules complexed with a nonamer and decamer HIV-1 peptide, together with a detailed structural analysis of these HLA-A3-like molecule/peptide complexes based on crystal and molecular model structures. Our studies revealed the importance of residues 9 and 67 for modulating peptide selection within the B pocket; of residue 97 for modulating peptide selection within the F pocket interdependently with the presence (or absence) of a middle, secondary anchor residue; and of residues 70, 73, 97, 152, and 156 for modulating peptide presentation in the central region of the groove that leads to altered antigenic surfaces. Overall, our detailed assessment of the biochemical and structural impact of natural polymorphism within the HLA-A3 superfamily has permitted to understand how HLA-A3-like molecules differ at the level of their primary and secondary anchor pockets causing fine differences in their peptide-selecting and -presenting properties. A better understanding of the molecular immunological properties of HLA-A3-like molecules is significantly important for the rationale design of broad peptide-based vaccines.
authors.affiliation: School of Pharmacy, University of Connecticut, 372 Fairfield Road U-92, Storrs, CT 06269, USA. bouvier@uconnvm.uconn.edu
authors.forename: Lenong
authors.initials: L
authors.lastname: Li
authors.forename: Marlene
authors.initials: M
authors.lastname: Bouvier
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D017951:Antigen Presentation; D001665:Binding Sites; D003001:Cloning, Molecular; D003429:Cross Reactions; D018076:DNA, Complementary / Q000235:genetics; D005805:Genes, MHC Class I; D015791:HLA-A3 Antigen / Q000737:chemistry* / Q000235:genetics*; D006801:Humans; D066298:In Vitro Techniques; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011110:Polymorphism, Genetic; D011487:Protein Conformation; D011489:Protein Denaturation; D011948:Receptors, Antigen, T-Cell / Q000737:chemistry; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D017386:Sequence Homology, Amino Acid; D013696:Temperature
chemical_list: D018076:DNA, Complementary; D015791:HLA-A3 Antigen; D011948:Receptors, Antigen, T-Cell; D011994:Recombinant Proteins