Antimicrobial defensin peptides of the human ocular surface

Abstract

Background/aims: The antimicrobial activity of the tear film exceeds the activity of its known constituents. The authors postulate that this excess activity is the result of antimicrobial peptides called defensins, and they aimed to look for defensins in the human eye. Methods: Evidence of defensin production was sought by reverse transcriptase polymerase chain reaction (RT-PCR). Intron spanning primers were designed for β defensins 1 and 2, and α defensins 5 and 6. RT-PCR was performed on cornea, conjunctiva, and lacrimal gland samples, and reaction products were size fractionated and sequenced to confirm their identity. A monoclonal antibody was utilised for the detection of a defensins 1, 2, and 3 in tissue sections and in immunoblots of tears. Results: RT-PCR revealed β defensin 1 message in samples of conjunctiva, cornea, and lacrimal gland. β Defensin 2 message was detected in the conjunctiva and cornea but was absent from the lacrimal gland. α Defensin 5 and 6 message was absent in these tissues but a defensins 1, 2, and 3 were detected in normal tears, lacrimal gland, and inflamed conjunctiva by immunochemistry. Conclusion: The data suggest the human eye innately produces a spectrum of antimicrobial defensin peptides. Defensins hold therapeutic potential in ocular infections as they have a broad spectrum of antimicrobial activity (bacteria fungi and viruses) and accelerate epithelial healing.