OR43 Four DRβ1 amino acids mediate preferential binding of citrullinated peptides and collagen

Abstract

Aim Several polymorphic amino acids within the peptide-binding groove of the DR β 1 molecule correlate with rheumatoid arthritis disease susceptibility and resistance. We have previously demonstrated through assessment of peptide binding to 97 HLA class II alleles on Luminex beads that susceptible alleles exhibit a preference for citrullinated peptides over native. In this study, we assess the importance of these amino acids in binding and T cell responses to potentially arthritogenic peptides to alleles containing mutations in the peptide binding groove. Methods We measured binding of native and citrullinated forms of vimentin66–78 and α-enolase11–25 and non-citrullinated type II collagen259–273, to DRβ1*04:01, DRβ1*04:02 and DRβ1*08:01 wild type alleles and DRβ1*04:01 with the following mutations: L67I, L67F, Q70D, K71E, K71R, A74L and G86V. We also measured T cell hybridoma responses to type II collagen259–273 when presented on the aforementioned alleles. Results The most susceptible allele, DRβ1*04:01, preferred citrullinated vimentin66–78 and citrullinated α-enolase11–25 over the native forms. Resistant alleles DRβ1*04:02 and *08:01 exhibited either no preference or preferred the native forms of these peptides. Similarly, collagen259–273 bound to DRβ1*04:01, but not to *04:02 or *08:01. Individually mutating susceptible DRβ1*04:01 at positions 70, 71, 74 and 86 to the corresponding resistance residues in DRβ1*04:02 or *08:01 dramatically reduced the specificity for citrullinated peptides and collagen. T cell hybridomas responded to collagen259–273 presented on DRβ1*04:01 and DRβ1*04:01 with mutations at position 67. However, despite binding being conserved among some mutations, negatively charged amino acids at positions 70 and 71 eliminated the T cell response to collagen. Conclusions These observations suggest that Q70, K71, A74 and G86 in DRβ1 mediate binding preference of both citrullinated and non-citrullinated arthritogenic peptides and are important for T cell responses. Download : Download full-size image