Synthesis of Glycopeptides from Type II Collagen-Incorporating Galactosylated Hydroxylysine Mimetics and Their Use in Studying the Fine Specificity of Arthritogenic T Cells

Five analogues of the bovine type II collagen (bCII) immunodominant glycopeptide [β-D-Gal-(5R)-5-Hyl264]CII(256–270) (1) carrying diverse modifications at the critical hydroxylysine (Hyl) 264 side chain were designed and synthesised, to explore the fine specificity of bCII-reactive T cells involved in the initiation and/or regulation of collagen-induced arthritis (CIA), a mouse model for rheumatoid arthritis (RA). β-D-Galactosyl-(5R)-5-hydroxy-L-lysine (19) and corresponding mimetics (22–25), conveniently protected for solid-phase synthesis, were all obtained by a divergent route involving enantiopure 5-hydroxylated 6-oxo-1,2-piperidinedicarboxylates as the key intermediates. All three bCII-specific T hybridomas used, as well as a recurrent pathogenic CD4+T-cell clone isolated from bCII-immunised DBA/1 mice, recognised the galactosylated form 1 of the immunodominant bCII (256–270) epitope. These cells were extremely sensitive to changes at the e-amino group of Hyl264, but differed in their pattern of recognition of analogues with a Hyl264 side chain modified at C-5 (i.e. inversion of stereochemistry, methylation). These data further document the importance of collagen post-translational modifications in autoimmunity and in the CIA model in particular, and provide a new insight into the molecular interaction between glycopeptide 1 and the TCR of pathogenic T cells.