Third component, HBeAg/3, of hepatitis B e antigen system, identified by three different double-diffusion techniques. (1/1024)

A third component, HB(e)AG/3, of the hepatitis B e antigen system has been detected, and it was consistently detected in three variations of the double-diffusion technique.  (+info)

Native display of complete foreign protein domains on the surface of hepatitis B virus capsids. (2/1024)

The nucleocapsid of hepatitis B virus (HBV), or HBcAg, is a highly symmetric structure formed by multiple dimers of a single core protein that contains potent T helper epitopes in its 183-aa sequence. Both factors make HBcAg an unusually strong immunogen and an attractive candidate as a carrier for foreign epitopes. The immunodominant c/e1 epitope on the capsid has been suggested as a superior location to convey high immunogenicity to a heterologous sequence. Because of its central position, however, any c/e1 insert disrupts the core protein's primary sequence; hence, only peptides, or rather small protein fragments seemed to be compatible with particle formation. According to recent structural data, the epitope is located at the tips of prominent surface spikes formed by the very stable dimer interfaces. We therefore reasoned that much larger inserts might be tolerated, provided the individual parts of a corresponding fusion protein could fold independently. Using the green fluorescent protein (GFP) as a model insert, we show that the chimeric protein efficiently forms fluorescent particles; hence, all of its structurally important parts must be properly folded. We also demonstrate that the GFP domains are surface-exposed and that the chimeric particles elicit a potent humoral response against native GFP. Hence, proteins of at least up to 238 aa can be natively displayed on the surface of HBV core particles. Such chimeras may not only be useful as vaccines but may also open the way for high resolution structural analyses of nonassembling proteins by electron microscopy.  (+info)

Hepatitis B virus (HBV)-transgenic mice as an investigative tool to study immunopathology during HBV infection. (3/1024)

An overview is given regarding the use of hepatitis B virus (HBV) transgenic mice as an animal model of the HBV-carrier state. Initially, we show how HBV-transgenic mice have contributed insights into the immunopathobiological processes during HBV infection and later, we show how this new information from the experiments with HBV-transgenic mice could be used to develop new methods to combat HBV infection. By microinjecting the full or selected parts of the HBV-genome into the fertilized eggs of inbred mice, different laboratories have developed different lines of HBV-transgenic mice, which express products of the HBV genome and also show signs of HBV replication. Studies in HBV-transgenic mice have provided insights into the process of destruction of hepatocytes, the critical role of cytokines in controlling HBV replication and gene expression, mechanisms underlying the immune response defect in chronic HBV-carriers and the critical role of antigen presenting cells (APC), especially that of antigen presenting dendritic cells in persistent HBV infection. All this new information has given us a better understanding about HBV immunopathobiology, and has led to the development of new therapeutic approaches to combat HBV infection.  (+info)

HBV-specific immune defect in chronic hepatitis B (CHB) is correlated with a dysregulation of pro- and anti-inflammatory cytokines. (4/1024)

The aim of this study was to examine the immunomodulating effects of rhIL-12 on the immune response induced by hepatitis B virus (HBV) antigens in clinical subgroups of patients with HBV infection. Peripheral blood mononuclear cells (PBMC) of 80 patients were stimulated with HBsAg, HBcAg, pre-S1Ag and tetanus toxoid in the absence or presence of IL-12 (0.01, 0.1 and 1 ng/ml). Stimulation by anti-CD3+ anti-CD28 and lipopolysaccharide (LPS) were used as controls. Proliferation and cytokine production were determined by 3H-thymidine uptake and ELISA after 72 h. After stimulation with HBV antigens only, production of tumour necrosis factor-alpha (TNF-alpha) or IL-10 was observed in all patients, while interferon-gamma (IFN-gamma) was detectable in only 27 patients. After costimulation with IL-12 and HBV antigens, however, large amounts of IFN-gamma were found in all patients, while HBV-induced IL-10 production remained mostly unchanged. When clinical subgroups including patients with compensated liver cirrhosis were compared, PBMC from patients with HBeAg+ hepatitis showed the lowest capacity to produce IFN-gamma after HBV antigen-positive IL-12. These data suggest that the ability of IL-12 to enhance IFN-gamma production against HBV antigens is correlated with the presence of HBeAg and is not impaired in patients with advanced liver disease. In addition, IL-12 and IL-10 production by antigen-presenting cells may be a critical factor that determines the efficacy of the immune response against the hepatitis B virus.  (+info)

Properties of monoclonal antibodies directed against hepatitis B virus polymerase protein. (5/1024)

Hepadnavirus polymerases are multifunctional enzymes that play critical roles during the viral life cycle but have been difficult to study due to a lack of a well-defined panel of monoclonal antibodies (MAbs). We have used recombinant human hepatitis B virus (HBV) polymerase (Pol) expressed in and purified from baculovirus-infected insect cells to generate a panel of six MAbs directed against HBV Pol protein. Such MAbs were subsequently characterized with respect to their isotypes and functions in analytical and preparative assays. Using these MAbs as probes together with various deletion mutants of Pol expressed in insect cells, we mapped the B-cell epitopes of Pol recognized by these MAbs to amino acids (aa) 8 to 20 and 20 to 30 in the terminal protein (TP) region of Pol, to aa 225 to 250 in the spacer region, and to aa 800 to 832 in the RNase H domain. Confocal microscopy and immunocytochemical studies using various Pol-specific MAbs revealed that the protein itself appears to be exclusively localized to the cytoplasm. Finally, MAbs specific for the TP domain, but not MAbs specific for the spacer or RNase H regions of Pol, appeared to inhibit Pol function in the in vitro priming assay, suggesting that antibody-mediated interference with TP may now be assessed in the context of HBV replication.  (+info)

Intracellular retention of hepatitis B virus surface proteins reduces interleukin-2 augmentation after genetic immunizations. (6/1024)

We have previously shown that hepatitis B virus (HBV) surface antigens (HBsAgs) are highly immunogenic after genetic immunization. Compared to the secreted middle HBV surface proteins (MHBs) or small HBV surface proteins (SHBs), the nonsecreted large HBV surface protein (LHBs), however, induced significantly weaker humoral and cellular immune responses that could not be augmented by genetic coimmunizations with cytokine expression plasmids. In order to understand the mechanisms underlying this phenomenon, we examined the effect of coimmunizations with an interleukin-2 (IL-2) DNA expression plasmid on the immunogenicity at the B- and T-cell level of nonsecreted wild-type LHBs, a secreted mutant LHBs, wild-type SHBs, and a nonsecreted mutant SHBs. Coimmunizations of mice with plasmids encoding wild-type SHBs or the secreted mutant LHBs and IL-2 increased anti-HBs responses, helper T-cell proliferative activity and cytotoxic T-lymphocyte killing. By contrast, coimmunizations of plasmids encoding wild-type LHBs or nonsecreted mutant SHBs and IL-2 had no significant effects on immune responses. Interestingly, mice immunized with cytokine expression plasmids 14 days after the injection of the wild-type LHBs plasmid showed augmented immune responses compared to animals simultaneously injected with both expression constructs. Anti-HBs responses in mice injected with plasmids encoding secreted forms of HBsAgs were detectable about 10 days earlier than those in mice immunized with plasmids encoding nonsecreted forms of HBsAgs. Based on these observations, we conclude that cytokines produced by DNA plasmids at the initial site of antigen presentation cannot augment LHBs specific immune responses because LHBs is not produced at high enough levels or is not accessible for uptake by antigen-presenting cells.  (+info)

A mathematical model predicting anti-hepatitis B virus surface antigen (HBs) decay after vaccination against hepatitis B. (7/1024)

The determination of serum levels of antibodies against hepatitis B virus surface antigen (anti-HBs) after hepatitis B vaccination is currently the only simple test available to predict the decay of protection and to plan the administration of booster doses. A total of 3085 vaccine recipients of plasma-derived and recombinant vaccine have been followed for 10 years to determine the kinetics of anti-HBs production and to construct a mathematical model which could efficiently predict the anti-HBs level decline. The anti-HBs peak level was reached 68 days after the last dose of recombinant vaccine and 138 days after the last dose of plasma-derived vaccines. The age of vaccinees negatively influenced the anti-HBs levels and also the time necessary to reach the anti-HBs peak. A bilogarithmic mathematical model (log10 level, log10 time) of anti-HBs decay has been constructed on a sample of recombinant vaccine recipients and subsequently validated on different samples of recombinant or plasma-derived vaccine recipients. Age, gender, type of vaccine (recombinant or plasma-derived), number of vaccine doses (three or four) did not influence the mathematical model of antibody decay. The program can be downloaded at the site: http:@www2.stat.unibo.it/palareti/vaccine.htm . Introducing an anti-HBs determination obtained after the peak, the program calculates a prediction of individual anti-HBs decline and allows planning of an efficient booster policy.  (+info)

Viral clearance without destruction of infected cells during acute HBV infection. (8/1024)

Viral clearance during hepatitis B virus (HBV) infection has been thought to reflect the destruction of infected hepatocytes by CD8(+) T lymphocytes. However, in this study, HBV DNA was shown to largely disappear from the liver and the blood of acutely infected chimpanzees long before the peak of T cell infiltration and most of the liver disease. These results demonstrate that noncytopathic antiviral mechanisms contribute to viral clearance during acute viral hepatitis by purging HBV replicative intermediates from the cytoplasm and covalently closed circular viral DNA from the nucleus of infected cells.  (+info)