The present invention relates to an immunogenic composition comprising an antigenic peptide of formula (I) below Nt-S-X1-X2-X3-K-X4-Ct (I) [SEQ ID N°1], wherein - Nt consists of a peptide having from 0 to 50 amino acids in length, - Ct consists of a peptide having from 0 to 50 amino acids in length, - each of X1 to X4 consists of an amino acid residue, wherein: - (i) X1 means the specific amino acid W or (ii) X1 means any amino acid residue excepted W, - (i) X2 means the specific amino acid S or (ii) X2 means any amino acid residue excepted S, - (i) X3 means the Specific amino acid N or (ii) X3 means any amino acid residue excepted N, - (i) X4 means the specific amino acid S or (ii) X4 means any amino acid residue excepted S, with the proviso that - three out of the four amino acid residues X1, X2, X3 and X4 mean the specific amino acid defined in their respective meaning (i) above, and - the remaining amino acid residue among X1 to X4 means any amino acid residue excepted the specific amino acid residue defined in its meaning (i), for preventing and/or treating an infection of an individual with an HIV-1 virus.
