Dietary sugars inhibit biologic functions of the pattern recognition molecule, mannose-binding lectin

Abstract

Mannose-binding lectin (MBL), a mammalian lectin, is a pattern recognition molecule of the innate immune system and recognizes carbo-hydrates that are exposed on pathogens. In this study, we observed that fructose down regu-lates MBL-mediated innate immune mechanisms against both influenza A virus (IAV) and Staphy-lococcus aureus. These mechanisms include the lectin complement pathway and coagulation enzyme-like activities on both pathogens. Fur-thermore, fructose also reduces MBL-mediated phagocytosis of S. aureus and IAV and MBL- mediated IAV infection to epithelial cells. In contrast, sucrose inhibits MBL-mediated im-mune mechanisms against S. aureus but not IAV. Together, our studies show that dietary sugars, in particular fructose, negatively regulate the innate immunity against viral and bacterial pathogens.