PATHOGENESIS OF IDIOPATHIC LIVER DISEASE

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Hepatitis B virus is the most common cause of acute and chronic liver disease in the world. We have recently detected by monoclonal antibodies and recombinant DNA techniques, hepatitis B virus related antigens and genome inpatients with and without conventional serologic markers that include hepatitis B surface antigen, antibodies to hepatitis B surface antigen (anti-HBs), hepatitis B core antigen (anti-HBc) and hepatitis B e antigen (anti-HBe). These agents have been shown to be present in serum and are infectious since they will produce a long incubation hepatitis infection in chimpanzees. We wish to investigate these patients further and characterize such hepatitis viral agents in more detail at he molecular and antigenic level and to evaluate their significance in the pathogenesis of liver disease of unknown etiology. We plan to do the following: 1) Employ the polymerase chain reaction (PCR) to detect and amplify HBV related DNA sequences in serum and liver. For this procedure, we will first capture on a solid-phase support, HBV and related genome with different high affinity monoclonal anti-HBs antibodies that recognize all known subtypes of HBV and thus bind to different alpha domain epitopes. Next, we will amplify defined regions in the captured HBV genomes such as those conserved in all known hepadnaviruses (pre-core and core region) as well as those sequences in the more variable pre-S and S gene domains. Since the PCR developed in our laboratory in combination with monoclonal anti-HBs monoclonal antibodies will amplify and thus detect DNA sequences at a level of less than 10 viral particles per assay, we have the capability to clone amplify sequences directly through primary liners at the restriction enzyme site. 2) We have recently developed a new method of measuring heterogeneity in the HBV genome by restriction endonuclease fragment analysis. This approach will allow us to rapidly assess variations within the S region following amplification by the antibody capture-PCR technique. 3) We wish to determine nucleotide sequence variability of the surface antigen region which may be the molecular basis for different antigenic composition or immunologic reactivity. 4) Comparisons will be made to serologic findings that employ a newly developed monoclonal based second generation immunoradiometric assay (M2- IRMA). This assay detects as low as 10-15 pg/il of HBsAg associated epitopes. 4) Selected patient populations will be studied for the presence and significance of low level HBV related infection. In this regard, we will assess patients with acute and chronic liver disease and HBV serologic markers of previous infection (anti-HBc and/or anti-HBs or both). In addition, patients with acute and chronic liver disease without any HBV markers, including those classified as viral hepatitis of unknown etiology and idiopathic liver disease,k will be studied. Finally, we will evaluate HBV vaccine non-responders for the presence of low level HBV infection. Based on the preliminary data obtained thus far, we are optimistic that new information will be obtained on the characteristics of HBV and related agents. Low level HBV related genome will be identified and characterized at the molecular level. We believe that these agents may play a previously unrecognized role in the pathogenesis of acute and chronic liver disease of uncertain etiology.