Hepatitis Viruses and Hepatoma

Abstract

Overview Hepatitis is an inflammation of the liver, occurring as the result of a viral infection or the exposure of liver to toxic substances such as alcohol or aflatoxin B. Hepatitis viruses are the most common cause of hepatitis in the world, of which HBV and HCV can cause persistent liver infection, frequently resulting in chronic hepatitis, liver cirrhosis, and eventually hepatocellular carcinoma (HCC). HBV belongs to the genus Orthohepadnavirus of the Hepadnaviridae with a circular incomplete double‐stranded DNA genome, containing four overlapping open reading frames (ORFs) that encode the surface envelope protein (HBsAg), the core protein (HBcAg and HBeAg), a polymerase, and a multifunctional nonstructural protein termed X (HBx), respectively. HBV genotypes and subgenotypes have distinct geographical distributions. In East Asia, HBV genotypes B and C are endemic. Accordingly, any differences in its global incidence may be explained by differences in the HCV and HBV prevalence. It has been estimated that 57% of cirrhosis is attributable to either HBV (30%) or HCV (27%) and 78% of HCC is attributable to HBV (53%) or HCV (25%). In China, up to 80% of HCC cases are attributable to HBV, and approximately 20% of HCC patients test positive for HCV‐RNA. Besides the oncogenic function of HBV‐encoding protein, the HBV infection‐induced virus or host DNA mutation has been found contribution for HCC development. Unlike to HBV, HCV belongs to the genus Hepacivirus of the Flaviviridae family, with a single‐stranded positive‐sense RNA genome. There is no host genome integration, nor does HCV contain any known oncogenes. The major mechanisms of HCV‐induced hepatocarcinogenesis include the oncogenic effect of HCV viral proteins, steatosis and insulin resistance, chronic inflammation and fibrosis, oxidative stress, and chromosomal instability. This chapter exclusively focuses on hepatitis and hepatoma caused mainly by HBV and HCV infection, discussing epidemiologic considerations, construction and genotype, role of virus in performing HCC, and early diagnosis and prophylaxis. Still, viruses that selectively infect endemic host predispose patients to malignant hepatoma, to some extent, placing a burden on the healthcare worldwide. Therefore, an upturn in morbidity of hepatitis and hepatoma will be of great importance in public health.