HBV is an enveloped DNA virus that infects hepatocytes, causing hepatitis B (Blum et al. 1983). It is a member of the Hepadnaviridae family, which includes the genera Orthohepadnavirus (infecting mammals) and Avihepadnavirus (infecting birds). The hepadnaviruses have a characteristic partially double-stranded DNA genome,which is held in a circular conformation by a short, cohesive overlap between the 5′ ends of the two strands (Ganem and Schneider 2001). The HBV genome codes for seven proteins: viral DNA polymerase, the core protein (HBcAg), the precore protein, the X protein, and three viral envelope (surface antigen) proteins, large (L), middle (M), and small (S) (NTP 2003). The virion has an icosahedral nucleocapsid, composed of core protein enclosing the viral genome. The nucleocapsid is surrounded by an envelope 42 nm in diameter, which contains (in order of decreasing abundance) the L, M, and S proteins. L is thought to specify the virus’s host range, by recognizing cell surface receptors, and S is the immunodominant component of the envelope. The functions of the precore and X proteins are unknown. However, it has been proposed that X affects a variety of cell processes, which may in turn significantly affect hepatocyte gene expression, cell survival, and viral replication. The precore protein is cleaved to form a soluble protein (HBeAg), which is secreted from infected cells and may be detected in the blood of infected individuals (Seeger and Mason 2000, Ganem and Schneider 2001).
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Food and Drug Administration (FDA)
Regulations have been established to guard against the spread of hepatitis B through donation of
blood, serum, and human immune globulin, including requirements for donor screening, product
testing, and product labeling. Each donation of blood, plasma, or serum to be used in preparing a biological product shall be tested for the presence of hepatitis B surface antigen.
21 CFR 1270 and 1271 prescribe procedures, including donor screening and tissue testing, to ensure
that tissues intended for human transplant or other human cells, tissues, and cellular and tissuebased
products are free of hepatitis B.
Occupational Safety and Health Administration (OSHA)
Comprehensive regulations have been developed for employers to develop and adhere to exposure control plans for bloodborne pathogens.
Carcinogenicity
Hepatitis B virus (HBV) is known to be a human carcinogen based on sufficient evidence from studies in humans.
