Lipopeptides are chemically synthetized peptides, bearing HIV epitopes, covalently bound to a fatty acid moiety, a monopalmtoyl chain in this case. This lipid chain produces internalization of the lipopeptide into the cytoplasm of the antigen presenting cells. Combinations of several lipopeptides containing sequences from different HIV proteins are used in vaccination trials in order to increase polyepitopic responses. Lipopeptides have been synthetized by the French National Agency for Research on AIDS and Viral Hepatitis (ANRS) preventive program by the group of Helen Gras following a long and meticulous work of epitope screening performed by the team of Jean-Gérard Guillet at the Cochin Institute in Paris. The epitopes were selected on the basis of their strong affinity for HLA class I molecule, on their ability to form a stable complex with these molecules, and on the capacity of these epitopes to be recognized by T cells. The selected peptides are those containing the richest array of epitopes and those most frequently recognized by HIV infected patients. Each peptide has a length of 23 to 32 amino acids (AA).