Hepadnaviridae

A family of lipid-containing icosahedral DNA-containing viruses 42 mm in diameter whose genome consists of a single molecule of noncovalently closed, circular DNA that is partially single-stranded and partially double-stranded; associated with hepatitis in a number of animal species. The principal genus ortho Hepadnavirus is associated with hepatitis B in mammals and the genus Avihepadnavirus with disease in birds; persistant infection is common and is associated with chronic disease and liver cancer. [hepatitis + DNA + virus]

* * *

Hep·ad·na·vi·ri·dae (hep-ad″nə-virґĭ-de) [hepat- + DNA + virus] the hepatitis B–like viruses: a family of DNA viruses having a virion 42 nm in diameter consisting of a lipid-containing envelope (containing hepatitis B surface antigen, HBsAg) surrounding an icosahedral nucleocapsid (containing hepatitis B core antigen, HBcAg). The genome consists of a single circular molecule of DNA that contains a large single-stranded gap (size of fully double-stranded molecule 3.2 kbp). Viruses contain two major polypeptides comprising HBsAg, one comprising HBcAg, and a number of others comprising the e antigen (HBeAg); they are resistant to heat and organic solvents. Replication occurs in the nuclei of hepatocytes. HBsAg occurs in the cytoplasm and shedding of 22-nm HBsAg particles into the bloodstream produces antigenemia. Persistent infection is common and is associated with chronic disease and neoplasia. There are two genera, one (Orthohepadnavirus) containing species infecting mammals and the other (Avihepadnavirus) containing species infecting birds.