Anti-adenoviral Effects of Human Cationic Antimicrobial Protein-18/LL-37, an Antimicrobial Peptide, by Quantitative Polymerase Chain Reaction

PURPOSE: Antimicrobial peptides have an important role in self-protection of the ocular surface. Human cationic antimicrobial protein (hCAP)-18 is a linear, alpha-helical peptide that consists of a conserved pro-sequence called a cathelin-like domain and a C-terminal peptide named LL-37. We investigated the in vitro anti-adenoviral activity of hCAP-18/LL-37 in several adenovirus types, inducing keratoconjunctivitis. METHODS: A549 cells were used for viral cell culture, and human adenovirus (HAdV) types 3 (HAdV3, species B), 4 (species E), 8, 19a, and 37 (species D) were used. The cytotoxicity of LL-37 was evaluated by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay to obtain 50% cytotoxic concentration. After pretreatment of A549 cells with serial dilutions of LL-37 for 24 hours, adenovirus was cultured for seven days, and adenoviral DNA was quantitatively measured by real-time polymerase chain reaction (PCR). RESULTS: The 50% effective concentration of LL-37 obtained by real-time PCR ranged between 118 and 270 microM. LL-37 showed a significant inhibitory effect on adenoviral proliferation in all adenovirus types except HAdV4 in a dose-dependent manner. CONCLUSIONS: LL-37 has significant inhibitory activity against HAdV3, 8, and 19, which induce keratoconjunctivitis. These results indicate that hCAP-18/LL-37 may be a possible candidate for the treatment of HAdV keratoconjunctivitis.

In vitro antiviral activity of antimicrobial peptides against herpes simplex virus 1, adenovirus, and rotavirus

Peptides with broad-spectrum antimicrobial activity, known as antimicrobial peptides, have been isolated from distinct organisms. This paper describes the in vitro evaluation of the cytotoxicity and antiviral activity of nine peptides with different structures and origins against herpes simplex virus type 1, human adenovirus respiratory strain, and rotavirus SA11. Most of the evaluated peptides presented antiviral activity but they were only active near cytotoxic concentrations. Nevertheless, these results seem promising, and further modifications on the peptide's structures may improve their selectivity and reduce their cytotoxicity.