Cytotoxic lymphocyte-inducing lipopeptides comprising a peptide part having between 10 and 40 amino acids approximately and comprising at least one tigenic determinant. The lipopeptides also comprise one or more chains derived from fatty acids and one or more modified steroid groups. Said lipopeptides may be used for immunizing the human or animal body against pathogenic agents such as viruses or parasites. The peptide part may, in particular, be a fragment of the protein encoded by the ENV gene, by the NEF gene or by the GAG gene of HIV viruses.