16. HEPATITIS B VIRUS

Abstract

This chapter discusses the molecular virology, natural history and treatment options for hepatitis B virus (HBV). HBV is a DNA virus belonging to the Hepadnaviridae family, and is similar genetically to viruses that infect primates, squirrels, woodchucks and ducks. There are seven genotypes and four subtypes of HBV, with various insertions or deletions of nucleotides defining the genotypes, but with less than 10% variation overall between them. The genotypes (A–G) have pathogenic differences, with C and D causing more severe disease generally, and being less responsive to interferon therapy. Evaluation of HBV includes serologic evaluation and assessment for other viruses. Hepatitis C virus (HCV) and HIV should be checked in all patients that have potential risk factors, along with HDV. Treatment of HBV has undergone rapid change over the past several years and with the advent of newer nucleoside/nucleotide analog agents, this evolution will continue. The primary goal of any therapy is to suppress replication of virus, and ideally to clear virus. The hope with this strategy is to also normalize biochemical and histologic parameters. There are currently three FDA approved agents which are indicated for chronic HBV, usually for patients with an abnormal aminotransferases (ALT).