Human cathelicidin (LL-37), a multifunctional peptide, is expressed by ocular surface epithelia and has potent antibacterial and antiviral activity.
OBJECTIVE
This study determined whether LL-37 (cathelicidin) is expressed by conjunctival and corneal epithelia as part of ocular host defense. The antimicrobial activity of LL-37 was also assessed in vitro against Pseudomonas aeruginosa (PA), Staphylococcus aureus (SA), Staphylococcus epidermidis (SE), herpes simplex virus type 1 (HSV-1), and adenovirus (Ad).


METHODS
Expression of LL-37/hCAP 18 mRNA and LL-37 protein was determined by reverse transcription-polymerase chain reaction (RT-PCR) and immunoblotting, respectively, in scraped human corneal epithelium and primary cultured human corneal and conjunctival epithelial cells. The EC50 values for three strains of PA and one each of SA and SE were determined for LL-37. LL-37 antiviral inhibition of HSV-1 and adenovirus was assessed by direct inactivation assays. Toxicity of LL-37 to A549 cells was evaluated by a MTT assay.


RESULTS
LL-37/hCAP18 mRNA and LL-37 peptide were expressed by human corneal and conjunctival epithelial cells. Antibacterial activity for LL-37 was demonstrated (EC50 values for the three PA strains were 2.8 +/- 1.3, 1.9 +/- 0.3, and 3.6 +/- 2.1; for SA: 1.6 +/- 1.5; for SE: 1.3 +/- 1.9 microg/ml). LL-37 produced a significant reduction (p < 0.001 ANOVA) in HSV-1 and Ad19 viral titers with distinctly different time-kill curves (p < 0.001). LL-37 (up to 111 microM) produced no toxicity in A549 cells.


CONCLUSIONS
Corneal and conjunctival epithelia express LL-37 as part of mucosal innate immunity to protect against bacterial and viral ocular infections.
Gordon
Y Jerold
YJ
The Charles T. Campbell Ophthalmic Microbiology Laboratory, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
Huang
Ling C
LC
Romanowski
Eric G
EG
Yates
Kathleen A
KA
Proske
Rita J
RJ
McDermott
Alison M
AM
D000256:Adenoviridae / Q000187:drug effects; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000235:genetics* / Q000494:pharmacology*; D000998:Antiviral Agents / Q000494:pharmacology*; D018929:Cell Culture Techniques; D003228:Conjunctiva / Q000166:cytology / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism; D019573:Epithelium, Corneal / Q000378:metabolism*; D015870:Gene Expression; D018259:Herpesvirus 1, Human / Q000187:drug effects; D006801:Humans; D015151:Immunoblotting; D011550:Pseudomonas aeruginosa / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013211:Staphylococcus aureus / Q000187:drug effects; D013212:Staphylococcus epidermidis / Q000187:drug effects; D054804:Cathelicidins
D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D000998:Antiviral Agents; D012333:RNA, Messenger; D054804:Cathelicidins