Comparative study of HLA-B27 peptide binding specificity by in vitro refolding assay

Abstract

HLA-B27 is strongly associated with predisposition to ankylosing spondylitis and reactive arthritis, but the mechanism of pathogenesis remains a mystery. There are experimental evidences supporting the hypothesis of an a??arthritogenica?? peptide which induces an anti-self response. In this study, we used an in vitro refolding assay to reconstitute the HLA-B27/peptide complex to precisely define the effects of variability at the C-terminal anchor residue of a synthetic nonapeptide on its binding affinity to HLA-B27 subtypes. Out results showed that among the 20 variants of the nonapeptide, non-polar amino acid is clearly preferred at the C-terminal anchor. The disease associated subtypes B*2702, B*2704 and B*2705 bound C-terminal tyrosine strongly, while B*2706 and B*2709 which are negatively associated with disease displayed poor affinity for C-terminal tyrosine. Overall, the pattern of in vitro refolded HLA-B27/peptide complexes showed remarkable agreement with known data derived from mass spectrometry analysis of recovered naturally bound peptide ligands.