Dual oxidase1/Lactoperoxidase Antimicrobial System Deplays Anti-Viral Effects in Cell-Free and Cell-Based in Vitro and Ameliorate Survival In Vivo during Influenza

Influenza virus infections cause severe morbidity and mortality, especially in high-risk patient populations. Broncho-epithelial cells orchestrate an oxidative antimicrobial system present in the airway liquid consisting of lactoperoxidase, the thiocyanate ion, and hydrogen peroxide. Dual Oxidase 1, an enzyme highly expressed in these cells, is the source of hydrogen peroxide, which in the presence of lactoperoxidase, catalyzes thiocyanate to hypo-thiocyanate ions with anti-viral properties.

Our objective was to demonstrate the effectiveness of this system using a cell-free and cell-based in vitro as well as in vivo. Our in vitro studies used a combination of both components of the system and assessed whether the full system has anti-viral effects. In a cell-based system, components were combined with the exception of hydrogen peroxide, which was expected to be generated by Dual Oxidase 1. Using a mouse adapted influenza strain PR8, we tested whether Dual oxidase 1 has a protective role in vivo using Dual oxidase 1 null mutants and wild type littermates mice. Our data demonstrate that the system has anti-viral effects in both cell-free and cell-based in vitro. While in vitro studies suggest an anti-viral properties of hypo thiocyanate, the in vivo effect of the system has never been addressed to our knowledge. Dual oxidase 1-deficient mice have significantly increased morbidity and mortality following influenza infection compared to controls. The characterization of infiltrated leukocyte subsets following infection revealed impaired natural killer cell recruitment in the lung of Dual oxidase 1-deficient animals.

In summary, we provide evidence of anti-viral effects of hypo-thiocyanate in vitro in cell-free and cell-based systems and demonstrate the in vivo antiviral role of Dual oxidase 1. All together, improving this system in vivo has the potential to provide novel treatment or prophylactic strategies against influenza and could be extended to other respiratory infections.