Abstract
Mannose-binding lectin (MBL), a mammalian lectin, is a pattern recognition molecule of the innate immune system and recognizes carbohydrates that are exposed on pathogens. In this study, we observed that fructose down regulates MBL-mediated innate immune mechanisms against both influenza A Virus (IAV) and Staphylococcus aureus. These mechanisms include the lectin complement pathway and coagulation enzyme-like activities on both pathogens. Furthermore, 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 immune 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.