The potential of retro-inverso peptides as synthetic vaccines

Retro-inverso peptides, also known as all-D-retro or retro-enantio peptides, are composed of D-amino acids assembled in the reverse order from that of the parent L-sequence. Since the orientation of the side-chains in a retro-inverso analogue is very similar to that in the parent L-peptide, this leads to a high level of antigenic cross-reactivity between the two peptides. The potential of retro-inverso peptides as synthetic vaccines has been investigated in the case of foot-and-mouth disease. A single inoculation of retro-inverso peptide corresponding to residues 141-159 of the VP1 protein of foot-and-mouth disease virus induced longer-lasting and higher antibody titres in immunised animals than the corresponding L-peptides. The antibodies cross-reacted strongly with virus particles and with L-peptides and conferred substantial protection in guinea-pigs challenged with the cognate virus. Retro-inverso peptides have considerable potential as synthetic vaccines, since their increased resistance to proteases may overcome one of the major drawbacks of classical L-peptide vaccines.