ICTV Virus Taxonomy Profile: Hepadnaviridae

Abstract

The family Hepadnaviridae comprises small enveloped viruses with a partially double-stranded DNA genome of 3.0-3.4 kb. All family members express three sets of proteins (preC/C, polymerase and preS/S) and replication involves reverse transcription within nucleocapsids in the cytoplasm of hepatocytes. Hepadnaviruses are hepatotropic and infections may be transient or persistent. There are five genera: Parahepadnavirus, Metahepadnavirus, Herpetohepadnavirus, Avihepadnavirus and Orthohepadnavirus. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Hepadnaviridae, which is available at ictv.global/report/hepadnaviridae.

Keywords: Hepadnaviridae; ICTV Report; hepatitis B virus; taxonomy.

Fig. 1.

Negative-contrast electron micrographs of hepatitis B virus virions (left) and virus-associated particles (right; spheres are 17–22 nm in diameter), together with their SDS-PAGE protein profile. LHBs, MHBs and SHBs refer to large, middle and small hepatitis B virus surface proteins, respectively. HBc, hepatitis B virus core proteins. GP, glycoprotein; P, protein. (Courtesy of W. Gerlich).

Fig. 2.

Genome organization of hepatitis B virus genotype A (X02763). The outer circle represents the relaxed circular negative-sense viral DNA found within virions that has a terminal redundancy. Coloured arrows indicate the position of ORFs together with their start and termination coordinates numbered from a unique EcoR1 restriction site. M, 5E and 3E are regulatory elements required for genome circularization; DR1 and DR2 are direct repeats; plus-strand DNA synthesis is initiated at DR2.