Effect of hybrid peptides of cecropin A and melittin in an experimental model of bacterial keratitis.

Synthetic peptides, ranging from 12 to 18 residues, containing partial sequences from natural cecropin A and melittin were tested for activity in an experimental pseudomonas keratitis model in rabbits. In separate experiments, two Pseudomonas aeruginosa strains: (a) a clinical isolated strain, and (b) an American Type Culture Collection (ATCC) strain, were inoculated into the stroma of one cornea of each rabbit. Peptides were topically applied at 0.1% in phosphate-buffered saline (PBS) and compared with PBS alone and 0.3% gentamicin eye drops. Clinical evaluation, based on the McDonald-Shadduck scale, was performed during a > 48-h period after the bacterial inoculation. The peptide-treated animals showed significantly lower (p < 0.05) inflammatory signs and lower anterior-segment bacterial damage compared with PBS-treated animals, after the first 6 h. The antiinflammatory/antimicrobial activity was non significantly differnt (p > 0.05) from that in animals treated with gentamicin. We conclude that peptides keeping the sequence KWKLFKK from cecropin A and at least the sequence VLKVL from melittin show promise as novel agents in topical ocular therapy of bacterial keratitis.