Hepatitis B virus is a small DNA-containing virus that causes persistent noncytopathic infections of the liver. Infected hepatocytes continually secrete viral specific particles that accumulate to high levels (1013/ml) in the blood. These particles (Figure 1) are of two types: i) noninfectious particles consisting of excess viral coat protein (HBsAg) and containing no nucleic acid, and ii) lower amounts (1010/ml) of infectious, DNA-containing particles (Dane particles) consisting of a 27 nm nucleocapsid core (HBcAg) around which is assembled an envelope containing the major viral coat protein, carbohydrate, and lipid. The DNA genome is about 3000 nucleotides in length, is circular (1) and partly single stranded, containing an incomplete plus strand (2) (Figure 1). The incomplete plus strand is complexed with a DNA polymerase in the virion which, under appropriate in vitro conditions, can elongate it using the complete minus strand as the template. These morphological and structural features distinguish hepatitis B viruses from all known classes of DNA-containing viruses.
KeywordsViral Coat Protein Minus Strand Woodchuck Hepatitis Virus Dane Particle Strand Polarity
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