Stability of peptide-HLA-I complexes and tapasin folding facilitation - tools to define immunogenic peptides

Only a small fraction of the peptides generated inside the cell end up being presented by HLA-I on the cell surface. High stability of peptide-HLA-I complexes and a low HLA-I tapasin-facilitation have been proposed to predict immunogenicity. We here set out to investigate if these parameters correlated and defined immunogenic peptides. Both peptide-HLA-B*08:01 and peptide-HLA-A*02:01 complexes showed small differences in tapasin-facilitation and larger differences in stability. This suggests that the stability of immunogenic peptide-HLA-I complexes vary above an HLA-I allomorph dependent lower limit (e. g. > 2 h for HLA-A*02:01), immunogenicity predicted by tapasin-facilitation may be defined by an equally allomorph unique upper value (e. g. tapasin-facilitation <1.5 for HLA-A*02:01), and variation above the stability-threshold does not directly reflect a variation in tapasin-facilitation. (C) 2012 Federation of European Biochemical Societies. Published by Elsevier B. V. All rights reserved

Tapasin discriminates peptide-human leukocyte antigen-A*02:01 complexes fromed with natural ligands

A plethora of peptides are generated intracellularly, and most peptide-human leukocyte antigen (HLA)-I interactions are of a transient, unproductive nature. Without a quality control mechanism, the HLA-I system would be stressed by futile attempts to present peptides not sufficient for the stable peptide-HLA-I complex formation required for long term presentation. Tapasin is thought to be central to this essential quality control, but the underlying mechanisms remain unknown. Here, we report that the N-terminal region of tapasin, Tpn(1-87), assisted folding of peptide-HLA-A*02:01 complexes according to the identity of the peptide. The facilitation was also specific for the identity of the HLA-I heavy chain, where it correlated to established tapasin dependence hierarchies. Two large sets of HLA-A*02:01 binding peptides, one extracted from natural HLA-I ligands from the SYFPEITHI database and one consisting of medium to high affinity non-SYFPEITHI ligands, were studied in the context of HLA-A*02:01 binding and stability. We show that the SYFPEITHI peptides induced more stable HLA-A*02:01 molecules than the other ligands, although affinities were similar. Remarkably, Tpn(1-87) could functionally discriminate the selected SYFPEITHI peptides from the other peptide binders with high sensitivity and specificity. We suggest that this HLA-I- and peptide-specific function, together with the functions exerted by the more C-terminal parts of tapasin, are major features of tapasin-mediated HLA-I quality control. These findings are important for understanding the biogenesis of HLA-I molecules, the selection of presented T-cell epitopes, and the identification of immunogenic targets in both basic research and vaccine design

Peptide‐MHC class I stability is a better predictor than peptide affinity of CTL immunogenicity

The past years have witnessed an increased use of applied games for developing and evaluating communication skills. These skills benefit from interpersonal interactions. Providing feedback to students practicing communication skills is difficult in a traditional class setting with one teacher and many students. This logistic challenge may be partly overcome by providing training using a simulation in which a student practices with communication scenarios. A scenario is a description of a series of interactions, where at each step the player is faced with a choice. We have developed a scenario editor that enables teachers to develop scenarios for practicing communication skills. A teacher can develop a scenario without knowledge of the implementation. This paper presents the implementation architecture for such a scenario-based simulation