Endocytosis of an HIV‐derived lipopeptide into human dendritic cells followed by class I‐restricted CD8+ T lymphocyte activation

• Published in: European journal of immunology 2000-11, Vol.30 (11), p.3256-3265
• Main Authors: Andrieu, Muriel, Loing, Estelle, Desoutter, Jean‐François, Connan, Francine, Choppin, Jeannine, Gras‐Masse, Hélène, Hanau, Daniel, Dautry‐Varsat, Alice, Guillet, Jean‐Gérard, Hosmalin, Anne
• Format: Article
• Language: English
• Subjects: Antigen Presentation; CD8+ T lymphocyte; CD8-Positive T-Lymphocytes - cytology; CD8-Positive T-Lymphocytes - immunology; Cell Communication - immunology; Cell Line; Dendritic cell; Dendritic Cells - cytology; Dendritic Cells - immunology; Endocytosis - immunology; Histocompatibility Antigens Class I - immunology; HIV; HIV Antigens - immunology; HIV Infections - immunology; HIV-1 - immunology; Humans; Lymphocyte Activation; MHC class I
• ISSN: 0014-2980; 1521-4141
• DOI: 10.1002/1521-4141(200011)30:11<3256::AID-IMMU3256>3.0.CO;2-H

CD8+ T lymphocytes, which are major immune effectors, require primary stimulation by dendritic cells (DC) presenting MHC class I molecule‐bound epitopes. Sensitization to exogenous protein epitopes that are not synthesized in DC, such as cross‐priming, is obtained through pathways leading to their association with MHC class I. To follow class I‐restricted pathways in human DC, we have tracked a lipopeptide derived from the conserved HLA‐A*0201‐restricted HIV‐1 reverse transcriptase 476‐484 epitope, by N‐terminal addition of an Nϵ‐palmytoyl‐lysine. Indeed, lipopeptides elicit cytotoxic responses from CD8+ T lymphocytes, whereas peptides without a lipid moiety do not. The lipopeptide and its parent peptide were labeled unequivocally by rhodamine to study their entry into immature monocyte‐derived human DC by confocal microscopy. The lipid moiety induced endocytosis of the lipopeptide, assessed by rapid entry into vesicles, colocalization with Dextran‐FITC and dependence on energy. Internalization occurred even when actin filaments were depolymerized by Cytochalasin B. This internalization induced functional stimulation of specific CD8+ T lymphocytes in IFN‐γ ELISPOT assays. The peptide alone was not visualized inside the DC and was presented through direct surface association to HLA‐A*0201. Therefore, lipopeptides are a unique opportunity to define precisely the pathways that lead exogenous proteins to associate with MHC class I molecules in DC. The results will also be useful to design lipopeptide vaccines.