Immune responses to duck hepatitis B virus infection.

The duck hepatitis B virus (DHBV) was the first hepatitis B virus identified from an avian host. It is a member of the Hepadnaviridae family of viruses. All members of this family display similar genomic organization and replication strategies and cause species-specific infections that result in either transient (acute) or persistent infection. Hepadnavirus infection occurs primarily in hepatocytes in the liver with release of infectious virions and non-infectious 'empty' surface antigen particles into the bloodstream. Hepadnavirus replication is non-cytopathic and immune responses to viral antigens are thought to be responsible for the liver damage seen in both transient and persistent infection and for the clearance of virus from infected cells. This has provided the basis for the use of vaccines and prophylactic treatments for individuals at high risk of human hepatitis B virus (HBV) infection. It follows that detailed understanding of the immune responses induced during transient and persistent infection may well facilitate the development of more effective approaches to immunotherapy in patients with persistent infection and may also provide a means of reducing the liver damage associated with this infection, without reducing the effectiveness of the immunity required to eliminate the virus. Immune responses to hepadnavirus infection have been studied primarily in humans, following natural infection with HBV, but studies have also been performed with the woodchuck hepatitis virus (WHV) and the DHBV models. This manuscript reviews the recent studies of immune responses to DHBV infection.