Lentivirus-derived antimicrobial peptides: increased potency by sequence engineering and dimerization

We have previously described a family of cationic amphipathic peptides deri ved from lentivirus envelope proteins that have properties similar to those of naturally occurring antimicrobial peptides. Here, we explored the effec ts of amino acid truncations and substitutions on the antimicrobial potency and selectivity of the prototype peptide, LLP1. Removal of seven residues from the C-terminus of LLP1 had little effect on potency, but abrogated hae molytic activity. Replacement of the two glutamic acid residues of LLP1 wit h arginine resulted in a peptide with greater bactericidal activity. We dis covered that the cysteine-containing peptides spontaneously formed disulphi de-linked dimers, which were 16-fold more bactericidal to Staphylococcus au reus. Monomeric and dimeric LLP1 possessed similar alpha helical contents, indicating that disulphide formation did not alter the peptide's secondary structure. The dimerization strategy was applied to magainin 2, enhancing i ts bactericidal activity eightfold. By optimizing all three properties of L LP1, a highly potent and selective peptide, named TL-1, was produced. This peptide is significantly more potent than LLP1 against Gram-positive bacter ia while maintaining high activity against Gram-negative organisms and low activity against eukaryotic cells. In addition to new antimicrobial peptide s, these studies contribute useful information on which further peptide eng ineering efforts can be based.