Toll Like Receptors in Chronic Viral Hepatitis – Friend and Foe

Abstract

Chronic viral hepatitis caused by Hepatitis B virus (HBV), Hepatitis C virus (HCV) and Hepatitis D virus (HDV) infection is among the most frequent causes for liver related morbidity and mortality worldwide. In recent years, it has become clear that not only the adaptive but also the innate immune system is involved in the pathogenesis of these infections. The innate immune system represents the initial line of host defense against invading pathogens. Germline-encoded pathogen recognition receptors (PRR), that are able to recognize specific structures of microorganisms, are an important component of this system. Amongst these, Toll like receptors (TLR) are a family of PRR perceiving a wide range of microorganisms, including bacteria, fungi, protozoa and viruses. Hepatitis viruses have evolved evading strategies to subvert the innate immune system of the liver which is of relevance for understanding the mechanisms that lead to chronicity of these infections and to develop novel therapeutic approaches based on these findings. Thus, recent studies suggested that TLR-based therapies may represent a promising approach in the treatment in viral hepatitis. This chapter focuses on the role of local innate immunity of the liver in the pathogenesis of chronic viral hepatitis.