Human Cathelicidin (LL-37), a Multifunctional Peptide, is Expressed by Ocular Surface Epithelia and has Potent Antibacterial and Antiviral Activity

Abstract

Purpose: 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 EC 50 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 (EC 50 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 μg/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 μM) 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.

Cathelicidin deficiency predisposes to eczema herpeticum

“…In our current study, we measured HSV replication by evaluating glycoprotein D gene expression using real-time RT-PCR. By directly measuring the virus activity rather than cellular proliferation, it provides a more direct and appropriate measurement of the anti-viral activity of LL-37 against HSV accounting for differences between our results and those of Yasin et al 15 Our observation is further supported by Gordon et al 16 who recently demonstrated that LL-37 exhibits anti-viral activity against HSV-1 in corneal and conjunctival epithelia.…”

“…AD skin is characterized by the over-expression of the Th2 cytokines IL-4 and IL-13. 16 Previously we demonstrated that Th2 cytokines down-regulate cathelicidin. 10 However, due to the difficulty in identifying ADEH patients and insufficient amounts of archived tissue, we were unable to investigate the levels of IL-4 and IL-13 in AD and ADEH patients for potential differences.…”

Antimicrobial peptides as new recognition molecules for screening challenging species

“…Although assays were less sensitive for VEE, detection limits for VEE in the AMP-based assays were similar to or better than those of competing cell-or antibodybased technologies [21,22,24,25]. Several groups have previously described the antiviral effects of various AMPs and their derivatives on vaccinia virus [26][27][28]. Most relevant to the present study is a cecropin Amagainin-2 hybrid peptide (CA (1-8)-MA(1-12)) which was shown to exhibit antiviral effects in other studies [26].…”

cAMP Stringently Regulates Human Cathelicidin Antimicrobial Peptide Expression in the Mucosal Epithelial Cells by Activating cAMP-response Element-binding Protein, AP-1, and Inducible cAMP Early Repressor

“…It has direct microbicidal activities against a wide range of bacteria, viruses, fungi, and protozoa in vitro (5)(6)(7)(8)(9)(10). In addition, its antimicrobial functions in vivo are significantly contributed by multiple immunomodulatory properties (11)(12)(13).…”