Gut microbiota in the innate immunity against hepatitis B virus - implication in age-dependent HBV clearance.

Hepatitis B virus (HBV) chronically infects 257 million people and is one of the most important liver diseases worldwide. A unique feature of HBV infection in humans is that viral clearance heavily depends on the age at exposure. Recent studies demonstrated that the virus takes advantage of immature innate immunity, especially hepatic macrophages, and not-yet-stabilized gut microbiota in early life to establish a chronic infection. The liver contains resident and infiltrating myeloid cells involved in immune responses to pathogens. They influence both innate and adaptive sectors of the immune system and their interplay with HBV has only been noticed recently. Here, we discuss how interactions between gut microbiota and hepatic macrophages influence the outcomes of HBV infection. Understanding the underlying mechanism would pave the way for the treatment of chronic HBV infection.