Jenny Waters

Cytotoxic T-cell responses to the nucleocapsid proteins of HBV in chronic hepatitis: evidence that antibody modulation may cause protracted infection

The nucleocapsid antigens (HBc and HBe) are present on the membranes of HBV-infected hepatocytes from HBV carriers. In autologous cytotoxicity experiments we demonstrate that cytotoxic T cells sensitised to the nucleocapsid proteins of hepatitis B are present in HBe antigen-positive HBV carriers with chronic hepatitis and can be blocked by monoclonal anti-HBc and anti-HBe. Passive immunisation of chimpanzees with monoclonal anti-HBc and anti-HBe offers no protection against HBV infection but in both cases leads to an unusually prolonged hepatitis probably by modulation of HBc and HBe antigen display on the hepatocytes. High-titre anti-HBc in the circulation of HBe antigen-positive patients probably modulates the former protein making HBe the important target antigen for cytotoxic T cells mediating liver damage in chronic carriers. These data also support the hypothesis that passive transfer of IgG anti-HBc across the placenta may be one major factor promoting development of persistent infection in neonates infected from carrier mothers.

Effect of human immunodeficiency virus (HIV) infection on chronic hepatitis B hepatic viral antigen display

Immunofluorescent and immunoperoxidase monoclonal antibody-based techniques were used to demonstrate hepatitis B e antigen (HBeAg) and hepatitis B c antigen (HBcAg) display in the liver biopsy specimens of 45 chronic hepatitis B virus (HBV) carriers. Anti-human immunodeficiency virus (anti-HIV)-positive HBV carriers had many more HBe- and HBc-positive hepatocyte nuclei than anti-HIV-negative carriers (P less than 0.0003 and less than 0.02, respectively), and HBV-DNA levels were slightly, but not significantly, increased in the positive subjects. The number of HBe- and HBc-positive nuclei were positively correlated with serum HBV-DNA levels (P less than 0.05 comparing high serum HBV-DNA levels of greater than 2880 pg/ml and levels of 1-480 pg/ml), and were negatively correlated with disease activity (P less than 0.05 comparing those with severe chronic active hepatitis (CAH) and those with mild CAH and chronic persistent hepatitis (CPH]. These results indicate that male homosexual HBV carriers, positive for anti-HIV, may be immunosuppressed before there are clinical signs of immunodeficiency, and this allows an increased level of replication of at least one other virus (HBV).

A rapid one-step radiometric assay for hepatitis b surface antigen utilising monoclonal antibodies.

A two-site antigen assay for HBsAg has been developed that employs 3 monoclonal antibodies. The antibodies were selected for their high affinity and their particular epitope specificity to establish an assay with a sensitivity for the antigen comparable with that of a conventional assay with heterologous antisera. In addition, by selecting a monoclonal antibody for use as a tracer which does not compete for antigenic binding sites with the solid-phase monoclonal antibodies, it has been possible to perform a two-site assay in a single 1 h incubation step, achieving the same degree of sensitivity. This principle of using monoclonal antibodies in a one-step assay therefore gives advantages of speed and simplicity over assays using heterologous antisera and would be applicable to a variety of antigen assays for which appropriate monoclonal antibodies are available.

Virus-neutralizing Antibodies to Hepatitis B Virus: The Nature of an Immunogenic Epitope on the S Gene Peptide

Using a murine monoclonal antibody (RF-HBs-1) which has been shown to be capable of neutralizing both ad and ay subtypes of hepatitis B virus (HBV), we have devised a competitive inhibition assay to measure the presence of virus-neutralizing antibodies in the sera of patients who have recovered from acute type B hepatitis. The majority of patients have this antibody in their serum. We also show that this antibody inhibits the binding of polymerized human serum albumin (pHSA) to the pHSA receptor site of the HBV particle, which has been proposed as an important site for the entry of HBV into liver cells. We have demonstrated that the epitope recognized by this antibody is dependent on the linkage of 24,000 and 28,000 mol. wt. polypeptides via a disulphide bond. This conformational determinant in the coat of the virus which is part of or near to the pHSA binding site is important in evoking a virus-neutralizing response.

Hepatitis B Surface Antigen Variant with Multiple Mutations in the a Determinant in an Agammaglobulinemic Patient

ABSTRACT A patient with agammaglobulinemia developed acute hepatitis that progressed to chronic liver disease with high levels of hepatitis B virus (HBV) DNA in the absence of detectable HBsAg. Sequencing of the a determinant region of HBsAg revealed multiple amino acid substitutions that, unusually, also included a substitution at position 122 that defines subtype specificity. All of these mutations had a profound effect on the antigenicity of this region, which led to the complete failure of variant detection by commercially available routine diagnostic assays or laboratory-based monoclonal antibody assays.

A recombinant vaccinia virus expressing hepatitis A virus structural polypeptides: characterization and demonstration of protective immunogenicity.

A recombinant vaccinia virus containing most of the P1 region of hepatitis A virus (HAV) was constructed. Cell lysates of cultures infected with the virus contained HAV proteins detectable by radioimmunoassay. Western blot analysis revealed the presence of a single protein of Mr 60K to 62K, bearing epitopes from structural polypeptides VP4, -3 and -2, and the N terminus of VP1. The size of the protein suggests that at least some of the vaccinia virus thymidine kinase is also expressed. Inoculation of tamarin monkeys with the recombinant virus resulted in the development of a specific anti-HAV immune response which was protective against challenge with a virulent strain of HAV. Recombinant viruses expressing the above region of HAV or the proteins expressed by such viruses may be useful in the development of a vaccine suitable for use in man.