Intrahepatic immune response in chronic viral hepatitis : an immunohistochemical study

The hepatitis B virus (HBV) is a 42 nm viral particle and belongs to a family of closely related DNA viruses called the hepadnaviruses. All the hepadnaviruses have similar hepatotropism and life cycles in their hosts. It is an enveloped small circular, partially double stranded DNA virus. The viral genome has a length of approximately 3200 base pairs that encodes four open reading frames (ORF). These are the pre-Surface (pre-S) and Surface (S) gene, the pre-Core (pre-C) and Core (C) gene, the X-gene and the Polymerase (P)-gene. The pre-S and pre-C genes are upstream regions of the S and C genes. The viral envelope encoded by the S gene contains three distinct configurations synthesized in all infected persons, termed the large, middle and major envelope proteins, which are produced by beginning transcription at, respectively, the pre-S1, pre-S2 or the S gene. The pre-S1 and pre-S2 represent two of the more immunogenic portions of hepatitis B surface antigen (HBsAg). The development of cellular and humoral immunity to HBsAg is protective, and recombinant HBsAg provides the basis for the HBV vaccines currently available. The hepatitis B core antigen (HBcAg) is the nucleocapsid that encloses the viral DNA. When HBcAg-derived peptides are presented by MHC-molecules present on the surface of hepatocytes, they can initiate a cellular immune response that is important for viral clearance.

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