Antiviral activity of hypothiocyanite produced by lactoperoxidase against influenza A and B viruses and mode of its antiviral action

摘要

Hypothiocyanitc (OSCN-) is a natural component of human saliva and is produced by the lactoperoxidase (LPO)/thiocyanate/hydrogen peroxide (H2O2) system. OSCN- has been previously shown to exhibit antiviral activity against influenza viruses (IFV) A/H1N1/2009 and A/H1N2/2009 in vitro as well as antimicrobial and antifungal activities. We elucidated the antiviral activity of OSCN- against both IFV types A and B and the mode of its antiviral action. OSCN- was produced constantly at 900 +/- 200 mu mol/l in Na3PO4 buffer solution containing NaSCN and LPO in the presence of H2O2 as an original OSCN- solution. In a plaque reduction assay, IFV A/PR/8/34 (H1N1), A/Fukushima/13/43 (H3N2), B/Singapore/222/97, and B/Fukushima/15/93 were exposed to various concentrations of OSCN- for 0 to 30 min before adsorption to MDCK cells, and plaque formation was examined. OSCN exhibited significant similar antiviral activities against all four viruses without cytotoxicity, and the EC50 values for them were from 57 +/- 16 to 148 +/- 27 mu mol/l regardless of the exposure times. The exposure of MDCK cells to OSCN before viral adsorption did not affect its anti-IFV activity (EC: more than 450 mu mol/l), but the exposure after viral adsorption affected it moderately (EC50: 380 +/- 40 mu mol/l). Moreover, the exposure of virus particles to OSCN at 450 mu mol/l did not affect the hemagglutinin activity of IFV in hemagglutination inhibition assay. These results suggest that the attachment of OSCN- to the viral envelope critically contributes to the mode of antiviral action of OSCN - without interfering with viral adsorption.