Antiadenoviral effects of N-chlorotaurine in vitro confirmed by quantitative polymerase chain reaction methods

PURPOSE: Adenoviral keratoconjunctivitis is recognized as one of the major pathogens of ophthalmological nosocomial infection worldwide. N-Chlorotaurine (Cl–HN–CH(2)–CH(2)–SO(3)H, NCT) is the N-chloro derivative of the amino acid taurine, which is an oxidant produced by human granulocytes and monocytes during inflammatory reactions. Using conventional viral plaque assay, it was previously shown that NCT causes inactivation of several human adenovirus (HAdV) serotypes. In this study, we evaluated the antiadenoviral effect of NCT by quantitative polymerase chain reaction (PCR) methods. METHODS: A549 cells were used for viral cell culture, and HAdV serotypes 3, 4, 8, 19, and 37 were used. After calculating 50% cytotoxic concentration (CC(50)) of NCT by MTS (3-(4,5- dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) method, HAdV was cultured with NCT for 7 days, and extracted adenoviral DNA was quantitatively measured by real-time PCR. RESULTS: A statistically significant (P < 0.05) dose-dependent inhibition was indicated for all serotypes except HAdV type 4 (HAdV4), which was maximally inhibited by only ~50%. Among the serotypes, NCT was particularly effective against HAdV8, HAdV19a, and HAdV37. The 50% effective concentration (EC(50)) obtained by real-time PCR of NCT ranged between 49 and 256 μM. EC(50) of NCT against HAdV3 was slightly higher than that against serotypes of species D. The selective index (CC(50)/EC(50)) ranged between 41 and 60 except for HAdV4 (11.5). CONCLUSIONS: These results show that NCT has an antiviral effect against most serotypes of human HAdV inducing keratoconjunctivitis, indicating its possible therapeutic use.