PMID: 19789338

Authors:

van Stipdonk MJ, Badia-Martinez D, Sluijter M, Offringa R, van Hall T, Achour A

Title:

Design of agonistic altered peptides for the robust induction of CTL directed towards H-2Db in complex with the melanoma-associated epitope gp100.

Journal:

Cancer Res. 2009 Oct 1;69(19):7784-92. Epub 2009 Sep 29.

Abstract:

Immunogenicity of tumor-associated antigens (TAA) is often weak because many TAA are autoantigens for which the T-cell repertoire is sculpted by tolerance mechanisms. Substitutions at main anchor positions to increase the complementarity between the peptide and the MHC class I (MHC-I) binding cleft constitute a common procedure to improve binding capacity and immunogenicity of TAA. However, such alterations are tailored for each MHC-I allele and may recruit different CTL specificities through conformational changes in the targeted peptides. Comparative analysis of substituted melanoma-differentiation antigen gp100 in complex with H-2D(b) revealed that combined introduction of glycine and proline residues at the nonanchor positions 2 and 3, respectively, resulted in an agonistic altered peptide with dramatically enhanced binding affinity, stability, and immunogenicity of this TAA. Peptide vaccination using the p2Gp3P-altered peptide version of gp100 induced high frequencies of melanoma-specific CTL in the endogenous CD8+ repertoire. Crystal structure analysis of MHC/peptide complexes revealed that the conformation of the modified p2Gp3P-peptide was similar to the wild-type peptide, and indicated that this mimotope was stabilized through interactions between peptide residue p3P and the tyrosine residue Y159 that is conserved among most known MHC-I molecules throughout mammalian species. Our results may provide an alternative approach to enhance MHC stabilization capacity and immunogenicity of low-affinity peptides for induction of robust tumor-specific CTL.