Extension of HLA-A*0201-restricted minimal epitope by N-epsilon-palmitoyl-lysine increases the life span of functional presentation to cytotoxic T cells

The delineation of the minimal requirements for efficient delivery of funct ional cytotoxic epitopes into APC could be a step toward the definition of "minimal length" lipopeptides for the modulation of CTL activity, Several a nalogues of the HLA-A*0201-restricted HIV-1 polymerase (pol(476-484)) minim al cytotoxic epitope were obtained by modifying P0, P1, or P10 positions by a single N-epsilon-palmitoyl-lysine residue, The use of fluorescent deriva tives confirmed the cell-permeating activities and suggested that a P0-and a P1-modified lipopeptide possessing ionizable extremities fulfills the str uctural requirements for MHC loading. The expressions of HLA-peptide comple xes at the surface of TAP-deficient cells incubated with the parent epitope or lipopeptide derivatives were compared, in terms of intensity and stabil ity, Both lipopeptides induced a considerably prolonged expression of confo rmationally correct complexes, which were dependent on the integrity of the exocytosis pathway, suggesting a dynamic mechanism of formation or reloadi ng of the complexes from an intracellular pool, The agonistic activities of the different HLA-peptide complexes were evaluated using two independent T cell lines from HIV-infected donors. We report that a lipodecapeptide obta ined by N-terminal addition of a N-epsilon-palmitoyl-lysine to the pol(476- 484) epitope was able to increase the life span of functional presentation to cytotoxic T cells specific far the parent peptide.