The Big Picture Book of Viruses: Hepadnaviridae

Host: Virus infects vertebrates.

Genome: DNA. Partially double stranded and single stranded. Circular (but neither strand is a covalently closed circle); genomic nucleic acid in its full length strand negative sense, or positive sense (in the other strand that varies in length). Genome monopartite. Total genome 3020-3320 nucleotides long, or 1700-2800 nucleotides long (for the full and short length strand, respectively). Termini have sequences with cohesive ends (that match the uniquely located 5'-ends of the two strands which overlap by approximately 240 nucleotides and maintain the circular configuration of the DNA). Double stranded genome at unique site on full length negative strand. 50 nucleotides from 5' end of short positive strand, or 242 nucleotides from 5' end of short positive strand. Terminal repeats at the 3'-end 1 nucleotides long. Guanine + cytosine ratio 48 %. 5' terminus has a genome-linked protein (VPg) (on the long positive strand).

Morphology: Virions enveloped (with a detergent sensitive lipoprotein of 7 nm); slightly pleomorphic, or pleomorphic to pleomorphic and filamentous forms occur (most commonly, i.e. nucleic acid free HBsAg particles); spherical, or filamentous; 40-48 nm in diameter, or 22 nm in diameter (for the HBsAg particles). Surface projections of envelope not present. Capsids isometric. Nucleocapsids sometimes penetrated by stain. Nucleocapsids frequently with obvious regular surface structure (concentric rings); 30-35 nm in diameter. Symmetry icosahedral. 180 capsomers per nucleocapsid. Incomplete virus particles often present (that are the nucleic-acid free 22 nm lipoprotein particles (HBsAg) which are antigenically similar to the envelope and occur naturally in sera of infected patients).

(Note: for more information about the taxonomy and structure of this virus, see the ICTV database below.)

Hepadnaviridae Images:
Genus	EM Images	Example Virus Name	Description of Image
		Hepadnavirus	an example virus image from the ICTV
Orthohepadnavirus		Hepatitis B virus	(from Linda Stannard, of the Department of Medical Microbiology, University of Cape Town)
		another Hepatitis B virus	(from Linda Stannard, of the Department of Medical Microbiology, University of Cape Town)
		Hepatitis B virus	A group of hepatitis B virions with marked cores (from Linda Stannard, of the Department of Medical Microbiology, University of Cape Town)
		Hepatitis B virus	enlargements of the two exposed cores indicated by arrows in the image above (from Linda Stannard, of the Department of Medical Microbiology, University of Cape Town)
		Hepatitis B virus	Bar = 100 nm. From the NCID, of the CDC.
		Hepatitis B virus cartoon	A diagrammatic representation of the hepatitis B virion and the surface antigen components (from Linda Stannard, of the Department of Medical Microbiology, University of Cape Town).
Avihepadnavirus	N/A	Duck hepatitis B virus