Important roles played by TGF-β in hepatitis B infection

Hepatitis B virus (HBV) which includes, fulminant, acute, chronic, asymptomatic, and occult HBV infection is the most prevalent virus that leads to human liver diseases. Chronic, asymptomatic, and occult infection can induce further sever diseases such as hepatocellular carcinoma (HCC) and cirrhosis of the liver. The underlying mechanisms that allow progression of the prolonged forms of the infection and subsequent HCC or cirrhosis of the liver are yet to be clarified. However, many researchers have suggested that immunological and genetic parameters may play important roles in the etiology of hepatitis B. Transforming growth factor beta (TGF-β) is an important cytokine with dual regulatory functions in the immune system and in the responses against viral infections. However, the pathways and mechanisms controlling these are not fully understood. The crucial roles of TGF-β in the development of Th17 and T regulatory lymphocytes, the main cell types involved in autoimmunity and destructive immune related diseases, have been documented and this provides insights into TGF-β function during hepatitis infection and subsequent HCC and cirrhosis of the liver. Recent findings also confirm that TGF-β directly alters hepatocyte function during hepatitis B, hence, the aim of this review is to address the current data regarding the association and status of TGF-β with hepatitis B infection and its related disorders including HCC and cirrhosis of the liver.