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Hepatitis B virus (HBV) is a DNA virus with an envelope, its membrane protein gene preS/S have three parts-preS1, preS2 and S, there is a translation initiation codon ATG in each of them. By different ATG, the membrane protein gene can be translated into three kinds of products, i.e. the large protein ( preS1 + preS2 + S ), medium ( preS2 + S) and small (S) (also called primary protein). In patients with acute hepatitis B, PreS antigen occurred together with other HBV markers and parallels the level of HBV DNA. Disappearance of PreS antigen predicts a benig n outcome[1]. Its presence in chronic hepatitis B is somewhat correlated with HBsAg, the ratio of PreS1/HBsAg antigen titers can reflect the level of DNA replication[2]. Meanwhile, the PreS domain in the membrane prote in include the binding sites for hepatocyte receptor and a number of epitopes of B cells and T cells. The PreS domain possesses very strong immunogenicity in mouse and man. In mice with consanguinity, the PreS domain can induce broad-spectrum protective antibodies and overcome their nonresponsiveness to protein S. In human body, it has been proved the PreS domain is an effective immunogen at both B and T cell levels. The antibodies directing against synthetic peptides (PreS: 21-47 ) mimicking receptor-binding sites can protect chimpanzee from HBV infection[3]. During the disease course appearance of antibody against PreS1 is considered an early marker for elimination of HBV infection[4,5]. Therefore PreS antigen/ antibody is a pair of important indexes for diagnosis of hepatitis B. As one part of a research project granted by the EC Foundation, we have prepared a recombinant PreS protein with high purity, a polyclonal anti -PreS antibody and established the ELISA method for detection of PreS antigen, preliminary clinical studies had been carried out. |
