Abstract
Aim Class I HLA reveal virus-derived peptide ligands to cytotoxic T lymphocytes (CTL) whose function is to eliminate infected cells. The Los Alamos National Laboratory (LANL) database reports numerous HIV-1 CTL epitopes characterized by various methods. To date, none have elicited protective immunity when tested in a vaccine. Our aim was to gather HLA-A*11:01 from HIV infected cells to identify viral ligands presented directly by HLA. An HLA-based view of HIV ligand presentation to CTL might enhance therapies directed against HIV. Methods Soluble class I HLA-A*11:01 (sHLA) was gathered from HIV-1 (NL4-3)-infected human CD4+ SUP-T1 cells. sHLA harvested from infected cells was immunoaffinity purified, then bound ligands were recovered, fractionated by RP-HPLC and mapped by tandem mass spectrometry. A*11:01 peptide maps from HIV-1 infected cells were compared to maps from uninfected as well as to maps of LANL’s 15 best characterized HLA-A11-restricted ligands. Results The HLA-A*11:01 of HIV-infected cells bound seven viral peptides. Three ligands (2 HIV Nef; 1 HIV polymerase) were previously reported in the LANL’s A*11:01 CTL target database. However, twelve LANL-reported HIV epitopes are definitively absent from the A*11:01 of infected SUP-T1 cells. Beyond what has been previously reported, we detect two Gag variants with partial homology to LANL sequences, a Nef 10mer variant, and a novel Nef-derived epitope not previously reported. Conclusions This is the first study to identify HIV/HLA peptides isolated from infected cells. An HLA-centric approach shows that class I HLA samples a handful of HIV ligands for presentation to CTL. New ligands found by our method provide a view of HIV infection not available using other approaches, and absence of most LANL ligands suggests that not all CTL targets are presented by infected cells. Identification of HIV ligands consistently displayed by HLA class I can improve vaccine strategies, and HLA-based methods are available to detect these promising targets.
Published Version
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