Peptide vaccine that is a mixture of different peptide species, where each species has a number of fixed amino acid residues and a number of randomized residues. The fixed resides are the same amino acid residues at the corresponding positions in each species of the mixture while the randomized residues are randomly any available candidate amino acids chosen by design. The degree of randomization may be also been chosen according to the design under a particular situation. This type of peptide vaccines have shown to be able to induce highly specific antibodies against epitopes that are otherwise difficult to induce antibodies in vitro, for example the GPG triplet in the V3 of HIV-1 gpl20.
