Variable HIV peptide stability in human cytosol is critical to epitope presentation and immune escape
Estibaliz Lazaro, … , David Heckerman, Sylvie Le Gall
Estibaliz Lazaro, … , David Heckerman, Sylvie Le Gall
Published May 9, 2011
Citation Information: J Clin Invest. 2011;121(6):2480-2492. https://doi.org/10.1172/JCI44932.
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Research Article Virology

Variable HIV peptide stability in human cytosol is critical to epitope presentation and immune escape

Abstract

Induction of virus-specific CD8+ T cell responses is critical for the success of vaccines against chronic viral infections. Despite the large number of potential MHC-I–restricted epitopes located in viral proteins, MHC-I–restricted epitope generation is inefficient, and factors defining the production and presentation of MHC-I–restricted viral epitopes are poorly understood. Here, we have demonstrated that the half-lives of HIV-derived peptides in cytosol from primary human cells were highly variable and sequence dependent, and significantly affected the efficiency of cell recognition by CD8+ T cells. Furthermore, multiple clinical isolates of HLA-associated HIV epitope variants displayed reduced half-lives relative to consensus sequence. This decreased cytosolic peptide stability diminished epitope presentation and CTL recognition, illustrating a mechanism of immune escape. Chaperone complexes including Hsp90 and histone deacetylase HDAC6 enhanced peptide stability by transient protection from peptidase degradation. Based on empirical results with 166 peptides, we developed a computational approach utilizing a sequence-based algorithm to estimate the cytosolic stability of antigenic peptides. Our results identify sequence motifs able to alter the amount of peptide available for loading onto MHC-I, suggesting potential new strategies to modulate epitope production from vaccine immunogens.

Authors

Estibaliz Lazaro, Carl Kadie, Pamela Stamegna, Shao Chong Zhang, Pauline Gourdain, Nicole Y. Lai, Mei Zhang, Sergio A. Martinez, David Heckerman, Sylvie Le Gall

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Figure 1

Intracellular HIV epitope stability is variable and degradation is correlated with reduced epitope antigenicity.

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Intracellular HIV epitope stability is variable and degradation is corre...
(A) HLA-B57–restricted KF11 (diamonds), HLA-A03/11–restricted ATK9 (squares), and HLA-A03–restricted RK9 epitope (circles) were degraded in equal amounts of PBMC extracts (black or gray symbols) or buffer (open symbols). Aliquots of degradation products were analyzed and quantified by HPLC profile analysis after 2, 10, 30, 60, and 120 minutes. 100% represents the amount of peptide detected by HPLC at time 0 calculated as the surface under the peptide peak (2,487,757, 1,227,535, 1,614,506 for KF11, ATK9, and RK9, respectively). (B) Aliquots of purified degradation products were used to pulse HLA-matched 51Cr-labeled B cells. CTL responses against A03-RK9 (circles), A03/11-ATK9 (squares), and B57-KF11 (diamonds) were assessed by 51Cr release assay. (C) The percentage of peptide remaining at each degradation time point (same symbols as in A) is plotted versus the percentage of cell lysis for each experiment. Comparison by Spearman test is indicated. (D) Peptides A03-RK9, A03/A11-ATK9, or B57-KF11 were introduced by osmotic shock into HLA-A03+ or -B57+ cells that were pretreated or not with protease inhibitors (PI) and used as targets in a cytolysis assay with A03-RK9–specific or B57-KF11–specific CTL clones. Cells were stained for cell death markers annexin (V-PE, 7-ADD) 1–4 hours after osmotic shock (6.69% dead cells for untreated cells; 7.96% for peptide-loaded cells; average difference over 3 experiments, 0.84% ± 0.6%). Data represent the mean ± SD of 3 independent experiments.