Therapeutic vaccination of woodchucks against chronic woodchuck hepatitis virus infection

Cryptosporidium spp. CP15 and CSL protein-derived synthetic peptides' immunogenicity and in vitro seroneutralisation capability

Cryptosporidium spp. is a zoonotic intracellular protozoan and a significant cause of diarrhoea in humans and animals worldwide. This parasite can cause high morbidity in immunocompromised people and children in developing countries, livestock being the main reservoir. This study was aimed at performing preliminary tests on Swiss albino weaned mice (ICR) to evaluate the humoral immune response induced against peptides derived from Cryptosporidium parvum CP15 (15 kDa sporozoite surface antigen) and CSL (circumsporozoite-like antigen) proteins. Peptides were identified and characterised using bioinformatics tools and were chemically synthesised. The antibody response was determined and the neutralising effect of antibodies was measured in cell culture. Despite all peptides studied here were capable of stimulating antibody production, neutralising antibodies were detected for just two of the CP15-derived ones. Additional studies aimed at evaluating further the potential of such peptides as vaccine candidates are thus recommended.

Interleukin-17A Promotes Parietal Cell Atrophy by Inducing Apoptosis

BACKGROUND & AIMS

Atrophic gastritis caused by chronic inflammation in the gastric mucosa leads to the loss of gastric glandular cells, including acid-secreting parietal cells. Parietal cell atrophy in a setting of chronic inflammation induces spasmolytic polypeptide expressing metaplasia, a critical step in gastric carcinogenesis. However, the mechanisms by which inflammation causes parietal cell atrophy and spasmolytic polypeptide expressing metaplasia are not well defined. We investigated the role of interleukin-17A (IL-17A) in causing parietal cell atrophy.

METHODS

A mouse model of autoimmune atrophic gastritis was used to examine IL-17A production during early and late stages of disease. Organoids derived from corpus glands were used to determine the direct effects of IL-17A on gastric epithelial cells. Immunofluorescent staining was used to examine IL-17A receptors and the direct effect of signaling on parietal cells. Mice were infected with an IL-17A-producing adenovirus to determine the effects of IL-17A on parietal cells in vivo. Finally, IL-17A neutralizing antibodies were administered to mice with active atrophic gastritis to evaluate the effects on parietal cell atrophy and metaplasia.

RESULTS

Increased IL-17A correlated with disease severity in mice with chronic atrophic gastritis. IL-17A caused caspase-dependent gastric organoid degeneration, which could not be rescued with a necroptosis inhibitor. Parietal cells expressed IL-17A receptors and IL-17A treatment induced apoptosis in parietal cells. Overexpressing IL-17A in vivo induced caspase-3 activation and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling staining in parietal cells. Finally, IL-17A neutralizing antibody decreased parietal cell atrophy and metaplasia in mice with chronic atrophic gastritis.

CONCLUSIONS

These data identify IL-17A as a cytokine that promotes parietal cell apoptosis during atrophic gastritis, a precursor lesion for gastric cancer.

Therapeutic vaccination and immunomodulation in the treatment of chronic hepatitis B: preclinical studies in the woodchuck

Infection with hepatitis B virus (HBV) may lead to subclinical, acute or chronic hepatitis. In the prevaccination era, HBV infections were endemic due to frequent mother to child transmission in large regions of the world. However, there are still estimated 240 million chronic HBV carriers today and ca. 620,000 patients die per year due to HBV-related liver diseases. Recommended treatment of chronic hepatitis B with interferon-α and/or nucleos(t)ide analogues does not lead to satisfactory results. Induction of HBV-specific T cells by therapeutic vaccination or immunomodulation may be an innovative strategy to overcome virus persistence. Vaccination with commercially available HBV vaccines in patients with or without therapeutic reduction of viral load did not result in effective immune control of HBV infection, suggesting that combination of antiviral treatment with new formulations of therapeutic vaccines is needed. The woodchuck (Marmota monax) and its HBV-like woodchuck hepatitis virus are a useful preclinical animal model for developing new therapeutic approaches in chronic hepadnaviral infections. Several innovative approaches combining antiviral treatments using nucleos(t)ide analogues, with prime-boost vaccination using DNA vaccines, new hepadnaviral antigens or recombinant adenoviral vectors were tested in the woodchuck model. In this review, we summarize these encouraging results obtained with these therapeutic vaccines. In addition, we present potential innovations in immunostimulatory strategies by blocking the interaction of the inhibitory programmed death receptor 1 with its ligand in this animal model.

DNA prime-adenovirus boost immunization induces a vigorous and multifunctional T-cell response against hepadnaviral proteins in the mouse and woodchuck model

Induction of hepatitis B virus (HBV)-specific cytotoxic T cells by therapeutic immunization may be a strategy to treat chronic hepatitis B. In the HBV animal model, woodchucks, the application of DNA vaccine expressing woodchuck hepatitis virus (WHV) core antigen (WHcAg) in combination with antivirals led to the prolonged control of viral replication. However, it became clear that the use of more potent vaccines is required to overcome WHV persistence. Therefore, we asked whether stronger and more functional T-cell responses could be achieved using the modified vaccines and an optimized prime-boost vaccination regimen. We developed a new DNA plasmid (pCGWHc) and recombinant adenoviruses (AdVs) showing high expression levels of WHcAg. Mice vaccinated with the improved plasmid pCGWHc elicited a stronger WHcAg-specific CD8(+) T-cell response than with the previously used vaccines. Using multicolor flow cytometry and an in vivo cytotoxicity assay, we showed that immunization in a DNA prime-AdV boost regimen resulted in an even more vigorous and functional T-cell response than immunization with the new plasmid alone. Immunization of naïve woodchucks with pCGWHc plasmid or AdVs induced a significant WHcAg-specific degranulation response prior to the challenge, this response had not been previously detected. Consistently, this response led to a rapid control of infection after the challenge. Our results demonstrate that high antigen expression levels and the DNA prime-AdV boost immunization improved the T-cell response in mice and induced significant T-cell responses in woodchucks. Therefore, this new vaccination strategy may be a candidate for a therapeutic vaccine against chronic HBV infection.

Therapeutic vaccination in chronic hepatitis B: preclinical studies in the woodchuck

Recommended treatment of chronic hepatitis B with interferon-α and/or nucleos(t)ide analogues does not lead to a satisfactory result. Induction of HBV-specific T cells by therapeutic vaccination or immunotherapies may be an innovative strategy to overcome virus persistence. Vaccination with commercially available HBV vaccines in patients did not result in effective control of HBV infection, suggesting that new formulations of therapeutic vaccines are needed. The woodchuck (Marmota monax) is a useful preclinical model for developing the new therapeutic approaches in chronic hepadnaviral infections. Several innovative approaches combining antiviral treatments with nucleos(t)ide analogues, DNA vaccines, and protein vaccines were tested in the woodchuck model. In this paper we summarize the available data concerning therapeutic immunization and gene therapy using recombinant viral vectors approaches in woodchucks, which show encouraging results. In addition, we present potential innovations in immunomodulatory strategies to be evaluated in this animal model.

The woodchuck: a model for therapeutic vaccination against hepadnaviral infection

Interferon-alpha and nucleoside analogues are available for the treatment of chronic hepatitis B virus (HBV) infection but do not lead to a satisfactory result. New findings about the immunological control of HBV during acute infection suggest the pivotal role of T-cell mediated immune responses. Several preclinical and clinical trials were undertaken to explore the possibility of stimulating specific immune responses in chronically infected animals and patients by vaccination. However, vaccination with commercially available HBV vaccines in patients and immunization in woodchucks with core or surface proteins of woodchuck hepatitis virus (WHV) did not result in effective control of HBV and WHV infection, suggesting that new formulations of therapeutic vaccines are needed. Some new approaches combining antiviral treatments with nucleoside analogues, DNA vaccines and protein vaccines were tested in the woodchuck model. It could be shown that therapeutic vaccinations are able to stimulate specific B- and T-cell responses and to achieve transient suppression of viral replication. These results suggest the great potential of therapeutic vaccination in combination with antivirals to reach an effective and sustained control of HBV infection.

Combination of an antiviral drug and immunomodulation against hepadnaviral infection in the woodchuck model

The essential role of multispecific immune responses for the control of hepatitis B virus (HBV) infection implies the need of multimodal therapeutic strategies for chronic HBV infection, including antiviral chemotherapy and immunomodulation. This hypothesis was tested in the woodchuck model by a combination of lamivudine pretreatment and subsequent immunizations of woodchucks chronically infected with woodchuck hepatitis virus. The immunizations were performed with DNA vaccines or antigen-antibody immune complexes (IC)/DNA vaccines. Immunizations with IC/DNA vaccines led to an anti-woodchuck hepatitis virus surface antibody response and significant reductions of viral load and antigenemia, suggesting that such a strategy may be effective against chronic HBV infection.

Therapeutic vaccination in chronic hepatitis B: preclinical studies in the woodchuck model

Interferon-alpha and nucleoside analogues are available for the treatment of chronic hepatitis B virus (HBV) infection but do not lead to a satisfactory result. New findings about the immunological control of HBV during acute infection suggest the pivotal role of T-cell mediated immune responses. Several preclinical and clinical trials were undertaken to explore the possibility of stimulating specific immune responses in chronically infected animals and patients by vaccination. However, vaccination with commercially available HBV vaccines in patients and immunization in woodchucks with core or surface proteins of woodchuck hepatitis virus (WHV) did not result in effective control of HBV and WHV infection, suggesting that new formulations of therapeutic vaccines are needed. Some new approaches combining antiviral treatments with nucleoside analogues, DNA vaccines and protein vaccines were tested in the woodchuck model. It could be shown that therapeutic vaccinations are able to stimulate specific B- and T-cell responses and to achieve transient suppression of viral replication. These results suggest the great potential of therapeutic vaccination in combination with antivirals to reach an effective and sustained control of HBV infection.

Cloning, expression and polyclonal antibody preparation of the asialoglycoprotein receptor of Marmota himalayan

The objective of this study is to express the carbohydrate recognition domain (CRD) of the asialoglycoprotein receptor (ASGPR) H1 and H2 subunits of Marmota himalayan in vitro, and develop polyclonal antibodies against the recombinant proteins. RT-PCR was used to amplify ASGPR CRDH1 and CRDH2 from the liver tissue of Marmota himalayan. The products of amplification were subcloned into prokaryotic expression vector pRSET-B, and expressed in E.coli BL21(DE3)plysS. The recombinant proteins were purified using Ni-NTA spin column. The purified proteins were inoculated into BALB/c mice to develop polyclonal antibodies. The sensitivity and specificity of antibodies were evaluated by enzyme-linked immunosorbent assay (ELISA), Western blotting and immunohistochemical staining (IHC). The polyclonal antibodies showed high sensitivity and specificity against both denaturated and native ASGPR proteins. We successfully amplified and expressed the ASGPR CRDs of Marmota himalayan. The nucleic sequences of ASGPR CRDH1 and CRDH2 of Marmota himalayan have been submitted to Genbank and the sequence ID are DQ 845465 and DQ845466, respectively. The proteins and antibodies prepared can be used for targeting gene therapy in a new animal model-Marmota Himalayan-for the research of infectious diseases of hepatitis viruses and liver cancer treatment.

Immunomodulation as an option for the treatment of chronic hepatitis B virus infection: preclinical studies in the woodchuck model

New therapeutic approaches for chronic hepatitis B virus infection based on immunomodulation are now under investigation. The woodchuck model for hepatitis B virus infection has emerged as a useful animal model for the evaluation of such approaches, after developing necessary assays and reagents for immunologic studies in this model. Conventional and novel vaccines such as DNA vaccines were tested in woodchucks for their ability to induce protective immune responses against challenge infection with the woodchuck hepatitis virus (WHV). Furthermore, immunotherapeutic approaches for the control of chronic hepadnaviral infection were evaluated in woodchucks. Immunizations with WHV proteins and DNA vaccines led to the development of antibodies to the WHV surface antigen and to a significant decrease of viral load in chronically WHV-infected woodchucks. Viral vector-mediated gene transfer was explored for the delivery of antiviral cytokines IFN-alpha in woodchucks and resulted in the decrease of viral replication. It is now generally accepted that a combination of antiviral treatment and immunization will be necessary to achieve successful immunomodulation with a long-term control of chronic hepatitis B virus infection.

Rapid emergence of a viral resistant mutant in WHV chronically infected woodchucks treated with lamivudine and a pre-S/S CHO-derived hepatitis B virus vaccine

To determine whether the addition of a pre-S/S human vaccine increases the antiviral activity of lamivudine, four woodchucks were treated with a daily dose of 100 mg/kg lamivudine and four 50 microg doses of CHO-derived pre-S/S human vaccine. WHV DNA titres decreased up to two logarithms in three woodchucks. At week 4, in three of the animals, the sequence analysis showed a predominant strain containing a nucleotide change from A to T at position 1696 of domain B of the WHV DNA polymerase. Vaccination did not further suppress WHV DNA, despite anti-HBs production in three animals. The woodchuck remains a useful model for characterising the biology and kinetics of the emergence of drug-resistant variants and could be used for pre-clinical studies of combinations of new antiviral drugs.

The woodchuck as an animal model for pathogenesis and therapy of chronic hepatitis B virus infection

This review describes the woodchuck and the woodchuck hepatitis virus (WHV) as an animal model for pathogenesis and therapy of chronic hepatitis B virus (HBV) infection and disease in humans. The establishment of woodchuck breeding colonies, and use of laboratory-reared woodchucks infected with defined WHV inocula, have enhanced our understanding of the virology and immunology of HBV infection and disease pathogenesis, including major sequelae like chronic hepatitis and hepatocellular carcinoma. The role of persistent WHV infection and of viral load on the natural history of infection and disease progression has been firmly established along the way. More recently, the model has shed new light on the role of host immune responses in these natural processes, and on how the immune system of the chronic carrier can be manipulated therapeutically to reduce or delay serious disease sequelae through induction of the recovery phenotype. The woodchuck is an outbred species and is not well defined immunologically due to a limitation of available host markers. However, the recent development of several key host response assays for woodchucks provides experimental opportunities for further mechanistic studies of outcome predictors in neonatal- and adult-acquired infections. Understanding the virological and immunological mechanisms responsible for resolution of self-limited infection, and for the onset and maintenance of chronic infection, will greatly facilitate the development of successful strategies for the therapeutic eradication of established chronic HBV infection. Likewise, the results of drug efficacy and toxicity studies in the chronic carrier woodchucks are predictive for responses of patients chronically infected with HBV. Therefore, chronic WHV carrier woodchucks provide a well-characterized mammalian model for preclinical evaluation of the safety and efficacy of drug candidates, experimental therapeutic vaccines, and immunomodulators for the treatment and prevention of HBV disease sequelae.

Treatment of chronic hepatitis B: efficacy of current drugs and prospects for the future

Chronic hepatitis B is an important clinical problem often leading to severe complications. In this review, the results obtained in the last few years with the use of current drugs, such as interferon and nucleo(t)side analogues, are summarized and the problems of obtaining a sustained remission, which is only achieved in a small number of patients, are discussed. The new approaches, such as the use of combinations of drugs, to optimize long-term tolerable treatment are also considered.

Bicistronic woodchuck hepatitis virus core and gamma interferon DNA vaccine can protect from hepatitis but does not elicit sterilizing antiviral immunity

The immunity elicited against nucleocapsid of hepatitis B virus (HBV) and closely related woodchuck hepatitis virus (WHV) has been shown to be important in resolution of hepatitis and protection from infection. Further, activity of gamma interferon (IFN-gamma), which may directly inhibit hepadnavirus replication, promotes antiviral defense and favors T helper cell type 1 (Th1) response, which is seemingly a prerequisite of HBV clearance. In this study, to enhance induction of protective immunity against hepadnavirus, healthy woodchucks were immunized with a bicistronic DNA vaccine carrying WHV core (WHc) and woodchuck IFN-gamma (wIFN-gamma) gene sequences. Three groups, each group containing three animals, were injected once or twice with 0.5 mg, 0.9 mg, or 1.5 mg per dose of this vaccine. In addition, four animals received two injections of 0.6 mg or 1 mg WHc DNA alone. All animals were challenged with WHV. The results showed that four of nine animals injected with the bicistronic vaccine and one of four immunized with WHc DNA became protected from serologically evident infection and hepatitis. This protection was not linked to induction of WHc antigen-specific antibodies or T-cell proliferative response and was not associated with enhanced transcription of Th1 cytokines or 2',5'-oligoadenylate synthetase. Strikingly, all animals protected from hepatitis became reactive for WHV DNA and carried low levels of replicating virus in hepatic and lymphoid tissues after challenge with WHV. This study shows that the bicistronic DNA vaccine encoding both hepadnavirus core antigen and IFN-gamma was more effective in preventing hepatitis than that encoding virus core alone, but neither of them could mount sterile immunity against the virus or prevent establishment of occult infection.

IFNgamma expression inhibits LHBs storage disease and ground glass hepatocyte appearance, but exacerbates inflammation and apoptosis in HBV surface protein-accumulating transgenic livers

BACKGROUND/AIMS

Interferon gamma (IFNgamma) controls hepatitis B virus replication. As systemic application may cause severe adverse effects, approaches of liver-directed IFNgamma gene therapy may represent an attractive alternative for treatment of chronic viral hepatitis B and thus needs testing in vivo in suitable animal models.

METHODS

We therefore crossbred Alb-1HBV transgenic mice overexpressing the large HBV surface protein (LHBs) in their livers and developing LHBs storage disease and ground glass hepatocyte appearance with SAP-IFNgamma transgenic animals previously shown to exhibit constitutive hepatic IFNgamma expression, and analyzed the resulting double-transgenic offspring.

RESULTS

We found that IFNgamma coexpression significantly reduced hepatic LHBs expression and thereby inhibited hepatocellular LHBs storage disease and ground glass hepatocyte appearance. The beneficial antiviral IFNgamma effects as observed in Alb1-HBV SAP-IFNgamma double-transgenic livers were associated with significantly elevated serum ALT concentrations, massive mononuclear cell infiltrates, appearance of Councilman bodies, and increased alpha-PARP (poly(ADP-ribose) polymerase cleavage).

CONCLUSIONS

Exacerbation of hepatic necroinflammation and increased hepatocellular apoptosis rate in IFNgamma-expressing Alb1-HBV transgenic livers suggest that special precautions be taken for testing approaches of liver-specific IFNgamma expression in patients with chronic hepatitis B.

Attempted therapeutic immunization in a chimpanzee chronic HBV carrier with a high viral load

BACKGROUND

We previously reported successful therapeutic immunization in a chimpanzee having a relatively low viral load, which was immunized with recombinant plasmid hepatitis B surface antigen (HBsAg) DNA and boosted with recombinant HBsAg encoding canarypox virus. In the present study, we attempted to confirm these findings in an animal with a high virus load.

METHODS AND RESULTS

We tested three immunization strategies successively over a 3-year period. In the first of these, we administered four monthly injections of DNA encoding HBsAg + PreS2 + hepatitis B core antigen (HBcAg) + DNA encoding interleukin (IL)-12, (given 3 days later), and boosted with canarypox expressing all of the above HBV genes 6 months after initial immunization. No reduction in viral load was observed. In the second trial, we administered lamivudine for 8 weeks, and then began monthly DNA-based immunization with plasmids expressing the above viral genes; however, viral loads rebounded 1 week after termination of lamivudine therapy. In a third trial, we continued lamivudine therapy for 30 weeks and immunized with vaccinia virus expressing the above viral genes 18 and 23 weeks after the start of lamivudine therapy. Again viral loads rebounded shortly after cessation of lamivudine treatment. Analysis of cell-mediated immune responses, and their avidity, revealed that DNA-based immunization produced the strongest enhancement of high avidity T-cell responses, while recombinant vaccinia immunization during lamivudine therapy enhanced low avidity responses only. The strongest low and high avidity responses were directed to the middle surface antigen.

CONCLUSIONS

Three strategies for therapeutic immunization failed to control HBV viremia in a chronically infected chimpanzee with a high viral load.

Immunization with the gene expressing woodchuck hepatitis virus nucleocapsid protein fused to cytotoxic-T-lymphocyte-associated antigen 4 leads to enhanced specific immune responses in mice and woodchucks

A number of options are available to modify and improve DNA vaccines. An interesting approach to improve DNA vaccines is to fuse bioactive domains, like cytotoxic-T-lymphocyte-associated protein 4 (CTLA-4), to an antigen. Such fusion antigens are expressed in vivo and directed to immune cells by the specific bioactive domain and therefore possess great potential to induce and modulate antigen-specific immune responses. In the present study, we tested this new approach for immunomodulation against hepadnavirus infection in the woodchuck model. Plasmids expressing the nucleocapsid protein (WHcAg) and e antigen (WHeAg) of woodchuck hepatitis virus (WHV) alone or in fusion to the extracellular domain of woodchuck CTLA-4 and CD28 were constructed. Immunizations of mice with plasmids expressing WHcAg or WHeAg led to a specific immunoglobulin G2a (IgG2a)-dominant antibody response. In contrast, fusions of WHcAg to CTLA-4 and CD28 induced a specific antibody response with comparable levels of IgG1 and IgG2a. Furthermore, the specific IgG1 response to WHcAg/WHeAg developed immediately after a single immunization with the CTLA-4-WHcAg fusion. Woodchucks were immunized with plasmids expressing WHeAg or the CTLA-4-WHcAg fusion and subsequently challenged with WHV. CTLA-4-WHcAg showed an improved efficacy in induction of protective immune responses to WHV. In particular, the anti-WHsAg antibody response developed earlier after challenge in woodchucks that received immunizations with CTLA-4-WHcAg, consistent with the hypothesis that anti-WHs response is dependent on a Th cell response to WHcAg. In conclusion, the use of fusion genes represents a generally applicable strategy to improve DNA vaccination.

Critical overview and outlook: pathogenesis, prevention, and treatment of hepatitis and hepatocarcinoma caused by hepatitis B virus

Viral hepatitis B is an enigmatic disease in which the host's own immune response to persistent viral infection may bring about host destruction through antiviral inflammatory responses which might otherwise present as a benign or inapparent disease. The simple solution to the hepatitis B problem is by immunoprophylaxis using the vaccine licensed in 1981, which prevents both infection and the late sequelae of liver cirrhosis and hepatocarcinoma. Immunotherapeutic vaccines against persistent hepatitis B infection have not been successful and new explorations are being directed to therapies which include antisense, ribozymes, gene silencing by RNA interference (RNAi) and aptamer approaches. Limited benefits from nucleoside therapy and limitations in opportunity for liver transplantation have left a large void of curative treatments. Findings with respect to e antigen tolerance provide a basis for exploration to determine whether passively administered e antigen might suppress cell-mediated immunity, creating a commensal state in which virus persists but without pathologic damage to the host. Therapy of hepatocarcinoma by conventional chemotherapy, radiation, or surgical resection and ablation gives little hope for restoration of health unless the tumor is detected very early. The large engagement of the world medical science community to develop therapeutic vaccines against cancer is now in major clinical trials to determine the hope and credibility for the immunization approach. Vaccines based on tumor peptides which are linked to heat shock proteins and directed to host dendritic cells give reason for excitement and may be the "best show in town". A new era of tumor therapy will need to be based on new discoveries in immune function which are required to pursue immunotherapy on a more rational basis. The many facets of current hepatitis B virology, pathogenesis, immunoprophylaxis, immunotherapeusis, chemotherapy, and tumor pathogenesis and therapy are discussed here, in depth, but in keeping with needed brevity.

The lack of effect of therapeutic vaccination with a pre-S2/S HBV vaccine in the immune tolerant phase of chronic HBV infection

BACKGROUND/AIMS

Even if the results are controversial and preliminary, several reports suggest that the HBV vaccine might be effective in treating HBV infection. In this study, we aimed to evaluate the efficacy and safety of specific anti-HBV vaccination for the immune tolerance phase of chronic HBV infection in a randomized, controlled study.

PATIENTS AND METHODS

The 47 subjects included patients that were treatment-naive with hepatitis B e antigen positivity, active hepatitis B virus replication as measured by hepatitis B virus DNA levels, persistently normal alanine transaminase levels, and with minimal or absent disease activity by liver biopsy. Thirty patients were given three intramuscular injections of 20 micro g of a pre-S2/S vaccine (GenHevac-B) on days 0, 30, and 60, and the remaining 17 patients were included in the control group. The efficacy of vaccination was evaluated by testing for loss of serum HBV DNA or decrease in its level and for HBeAg seroconversion. A significant decrease in HBV DNA levels was accepted as a decrease of >50% of initial values. The complete response was defined as loss of HBV DNA in serum with HBeAg seroconversion. Postvaccination follow-up lasted 12 months after the first dose.

RESULTS

No significant effects were observed in the vaccination population in the reduction of HBV DNA to undetectable levels, or to <50% of prevaccination levels, in HBeAg/anti-HBe seroconversion, or in transaminase levels. There was an early clearance/decrease in HBV DNA levels in five vaccinated patients by 3 months, and none in controls (P = 0.143), and two of them had sustained responses later. At the end of follow-up, complete response is almost similar in study as well as control group (13% vs. 12%, P > 0.05). Disappearance of serum HBV DNA was more frequently observed in those patients who had pretreatment viremia of <100 pg/mL in both groups. The median levels of HBV DNA and alanine transaminase activity between baseline and 12 months did not differ significantly in both groups. All patients remained HBsAg positive and none developed anti-HBs. No serious adverse event was encountered in vaccinated patients, and the therapy was well tolerated. Follow-up lasted a median of 16 months (range 12-30 months) for the study group and 18 months (range 12-31months) for the control group.

CONCLUSIONS

Immunotherapy with specific anti-HBV vaccine in the immune tolerance phase of chronic HBV infection did not offer additional benefit. New immunotherapeutic strategies to control HBV infection by specific HBV vaccines in chronically infected subjects are needed.

Induction of antibodies to the PreS region of surface antigens of woodchuck hepatitis virus (WHV) in chronic carrier woodchucks by immunizations with WHV surface antigens

BACKGROUND/AIMS

One goal of therapeutic vaccinations against chronic hepatitis B virus infection is to stimulate the B-cell responses to viral surface antigens in chronic carriers. Here we investigated the induction of antibody responses to hepadnaviral surface antigens in the woodchuck model, with emphasis on the vaccination of woodchucks chronically infected with woodchuck hepatitis virus (WHV).

METHODS

Naive and chronically WHV-infected woodchucks were immunized with plasma-derived WHV surface antigens (p-WHsAg) containing the S and PreS sequences. Antibody responses to WHsAg and the WHV PreS region and viral load in immunized woodchucks were monitored.

RESULTS

After repeated immunizations with WHsAg, 17 of 18 chronic WHV carriers developed a persistent antibody response to WHsAg. These antibodies were mainly directed to epitopes within the PreS region and detectable by Western blotting. However, neither WHV DNA nor WHsAg concentrations in these woodchucks changed significantly by immunizations and during the follow up. Sequence analysis of WHV genomes showed that no WHV mutants emerged after the induction of anti-WHs/anti-WHpreS antibodies. No immunopathological changes in livers of immunized animals were recognized thus far.

CONCLUSIONS

Our study demonstrated that the immunological unresponsiveness of chronically WHV-infected woodchucks to WHsAg can be partially overcome by repeated immunizations with WHsAg.

The woodchuck interferon-alpha system: Cloning, family description, and biologic activity

Interferon-alpha (IFN-alpha) is a key element in the defense against viral infection because, in addition to a direct antiviral effect, it exhibits potent immunostimulatory activity. To investigate the function of this cytokine in the woodchuck model of chronic hepatitis B, the woodchuck IFN-alpha gene (IFNA) family was cloned and examined. The data indicate that this is a multigenic family from which 12 IFNA functional sequences and four pseudogene sequences were isolated. The overall identity of the amino acid sequence among the members of the woodchuck IFN-alpha family is 85%, and the identity with the IFN-alpha family from other species such as mice and humans is 50%. The analysis of hepatic expression of IFNA genes showed that wIFNA5a was the subtype transcribed preferentially in the woodchuck liver. The wIFNA genes transcribed in the liver were tested in an eukaryotic expression system and were found to enhance 2-5-oligoadenylate synthetase (2-5-OAS) mRNA levels and to posses a potent antiviral activity. Cloning of woodchuck IFNA genes will allow testing diverse forms of IFN-alpha delivery as well as different combination therapies in woodchuck hepatitis virus infection, thus providing useful information for the design of new strategies for the treatment of patients with chronic hepatitis B.

Immunization with surface antigen vaccine alone and after treatment with 1-(2-fluoro-5-methyl-beta-L-arabinofuranosyl)-uracil (L-FMAU) breaks humoral and cell-mediated immune tolerance in chronic woodchuck hepatitis virus infection

Woodchucks chronically infected with the woodchuck hepatitis virus (WHV) were treated with the antiviral drug 1-(2-fluoro-5-methyl-beta-L-arabinofuranosyl)-uracil (L-FMAU) or placebo for 32 weeks. Half the woodchucks in each group then received four injections of surface antigen vaccine during the next 16 weeks. Vaccination alone elicited a low-level antibody response to surface antigen in most carriers but did not affect serum WHV DNA and surface antigen. Carriers treated first with L-FMAU to reduce serum WHV DNA and surface antigen and then vaccinated had a similar low-level antibody response to surface antigen. Following vaccinations, cell-mediated immunity to surface antigen was demonstrated in both groups, independent of serum viral and antigen load, but was significantly enhanced in woodchucks treated with L-FMAU and was broadened to include other viral antigens (core, e, and x antigens and selected core peptides). Cell-mediated immunity and antibody responses to surface antigen were observed after drug discontinuation in half of the carriers that received L-FMAU alone. Surface antigen vaccine alone or in combination with drug broke humoral and cell-mediated immune tolerance in chronic WHV infection, but the combination with drug was more effective. This suggested that a high viral and antigen load in carriers is important in maintaining immunologic tolerance during chronicity. The humoral and cellular immunity associated with the combination of L-FMAU and vaccine resembled that observed in self-limited WHV infection. Such combination therapy represents a potentially useful approach to the control of chronic hepatitis B virus infection in humans.

Management of viral hepatitis B

Hepatitis B virus (HBV) infection is a major global health concern and is the most common cause of chronic liver disease worldwide. The natural history and clinical outcomes of chronic HBV infection are determined by the viral replication cycle and the host immune responses. Treatment of chronic hepatitis B is directed at interrupting the natural history by suppressing HBV replication before development of any significant irreversible liver cell damage. Effective antiviral therapies should be followed by sustained suppression of HBV-DNA, normalization of transaminases levels and a stable stage of HBeAg seroconversion with persistence of circulating anti-HBeAg antibodies. Two major classes of antiviral therapeutic agents that have been approved for treatment of chronic hepatitis B are immunomodulating agents (i.e. interferon) and the nucleoside analogs (i.e. lamivudine). A 4-6 month course of interferon-alpha has resulted in improvement of survival in 20%-30% of patients with chronic hepatitis B who had elevated serum ALT levels without hepatic decompensation. Interferon-alpha therapy is associated with HBeAg seroconversion; normalization of ALT levels, reduced hepatic inflammation, and possibly reduced disease progression to cirrhosis and hepatocellular carcinoma. Interferon can also be used with caution in patients with early compensated cirrhosis. A 12-month course of lamivudine has been shown to be well tolerated and effective. Lamivudine can be used in decompensated cirrhosis and immunosuppressed patients and for prevention of recurrent HBV infection after liver transplantation. The response rates after 3 years of lamivudine therapy account for 40-65%. A major problem of antiviral treatment is the emergence of drug resistance conferred by mutations in the YMDD motif of HBV reverse transcriptase. The prevalence of YMDD mutations increases with longer durations of antiviral therapies and this has been detected in 20% of immunocompetent patients receiving lamivudine per year. Contentious issues remain when to stop the treatment if HBeAg seroconversion does not occur. Many new immunomodulatory therapies and antiviral agents are in various stages of clinical development and have shown some promise. Among newer HBV antivirals, adefovir dipivoxil, entecavir, emtricitabine, DAPD and clevudine appear to be at least as potent as lamivudine in suppressing HBV replication. In vitro studies have shown that YMDD mutations confer cross-resistance between lamivudine and emtricitabine. However, adefovir, dipivoxil, lobucavir, DAPD and possibly clevudine suppress replications of both YMDD mutants and wild types of HBV. Immunomodulatory approaches for treatment of chronic hepatitis B are conceptually attractive, but newer agents used to date (thymosin-alpha, interleukin-12, therapeutic vaccines) have not demonstrated sufficient efficacy for widespread use. Combinations of an immunomodulatory agent and nucleoside analog may improve the therapeutic efficacy and reduce the emergence of drug resistance. Nevertheless, combinations of interferon and lamivudine therapies do not confer such additional benefits. The next challenge for HBV treatment is to use antivirals in combination and/or in cyclical therapy to minimize the emergence of drug resistance and increase efficacy, particularly to achieve sustainable post-treatment suppression of HBV. Randomized prospective control trials of combined antiviral therapies given simultaneously or sequentially are needed to establish safe and effective combined regimens that can be recommended for future treatment strategies.

Protection against woodchuck hepatitis virus (WHV) infection by gene gun coimmunization with WHV core and interleukin-12

Woodchuck hepatitis virus (WHV) and hepatitis B virus (HBV) are closely similar with respect to genomic organization, host antiviral responses, and pathobiology of the infection. T-cell immunity against viral nucleocapsid (HBcAg or WHcAg) has been shown to play a critical role in viral clearance and protection against infection. Here we show that vaccination of healthy woodchucks by gene gun bombardment with a plasmid coding for WHcAg (pCw) stimulates proliferation of WHcAg-specific T cells but that these cells do not produce significant levels of gamma interferon (IFN-gamma) upon antigen stimulation. In addition, animals vaccinated with pCw alone were not protected against WHV inoculation. In order to induce a Th1 cytokine response, another group of woodchucks was immunized with pCw together with another plasmid coding for woodchuck interleukin-12 (IL-12). These animals exhibited WHcAg-specific T-cell proliferation with high IFN-gamma production and were protected against challenge with WHV, showing no viremia or low-level transient viremia after WHV inoculation. In conclusion, gene gun immunization with WHV core generates a non-Th1 type of response which does not protect against experimental infection. However, steering the immune response to a Th1 cytokine profile by IL-12 coadministration achieves protective immunity. These data demonstrate a crucial role of Th1 responses in the control of hepadnavirus replication and suggest new approaches to inducing protection against HBV infection.

T-helper cell response to woodchuck hepatitis virus antigens after therapeutic vaccination of chronically-infected animals treated with lamivudine

BACKGROUND/AIMS

Immunotherapy of patients chronically-infected with hepatitis B virus (HBV) may have the risk of fulminant hepatitis. This risk might be diminished if immunotherapy was carried out under conditions of low viremia.

METHODS

Five woodchucks chronically-infected with woodchuck hepatitis virus (WHV), a virus closely related to HBV, were treated with lamivudine for 23 weeks. At week 10, when viremia had decreased by 3-5 logs, three woodchucks were vaccinated with woodchuck hepatitis virus surface antigen (WHsAg) plus the T-helper determinant FISEAIIHVLHSR.

RESULTS

It was found that the administration of lamivudine only, had no effect on the T-helper response against WHV antigens. By contrast, vaccination induced T-helper responses against WHV antigens, shifting the cytokine profile from Th2 to Th0/Th1, but was without effect on viremia, WHsAg levels, or anti-WHs antibodies. Analysis of liver biopsies showed that lamivudine administration may have reduced hepatic inflammation. By contrast, vaccination clearly enhanced hepatic inflammation. After lamivudine withdrawal, viremia returned to high levels.

CONCLUSIONS

These results suggest that therapeutic vaccination of chronically-infected woodchucks under conditions of low viremia shifts the cytokine profile against viral antigens towards Th0/Th1. This shift may prevent the efficient induction of anti-WHs antibodies.

Efficacy and limitations of a specific immunotherapy in chronic hepatitis B

BACKGROUND/AIMS

This controlled study aimed to evaluate the efficacy and potential side effects of hepatitis B virus (HBV) vaccination as active immunotherapy in HBV-related chronic hepatitis.

METHODS

The 118 included patients were 'naive' subjects who had never received any previous anti-HBV therapy, showed detectable serum HBV DNA and had biopsy-proven chronic hepatitis. In a 12-month follow-up they were given either five intramuscular injections of 20 microg of a preS2/S (GenHevac B, Pasteur-Mérieux) (n = 46) or an S vaccine (Recombivax Merck & Co.) (n = 34) or no treatment as a control (n = 37). The efficacy of vaccination was evaluated by testing for serum HBV DNA negativation using a standard liquid hybridization assay.

RESULTS

Three months after the first three vaccine injections, the percentage of serum HBV DNA negativation was higher in the vaccine groups (16.3%) than in the control group (2.7%) (P = 0.033, by the chi2 Pearson test) and was more frequently observed in patients who had pretreatment viremia >200 pg/ml (none in the control group vs. 16.7% in the vaccinated groups) (P = 0.025). After 12 months follow-up and five vaccine injections, there was no difference in the rate of serum HBV DNA negativation between vaccinated and unvaccinated subjects but HBV vaccines significantly decreased the HBV viral load between the sixth and twelfth months (P = 0.04) in contrast with the control group. The rate of HBe/anti-HBe seroconversion after 6 months of follow-up occurred only in eight (13.3%) vaccinated patients and in one (3.6%) of the controls. Disappearance of serum HBsAg was not observed in any of the patients.

CONCLUSIONS

This controlled study offers direct evidence that the HBV vaccine may decrease HBV replication in chronic hepatitis B patients. It also emphasizes the need for reinforced immunization strategies as well as combination therapies.

Hepatitis B infection in China

Chronic HBV infection is a serious health threat in the Asian-Pacific region. The introduction of lamivudine has greatly improved the hope of these patients and is undoubtly a milestone in the management of chronic HBV infection. The combination of lamivudine with another nucleotide or nucleoside analogue or immunomodulatory agent to improve its therapeutic efficacy further must be investigated. Also, the use of lamivudine to prevent HBV reactivation on withdrawal of immunosuppressive therapy should be explored.

Use of immunomodulatory therapy (other than interferon) for the treatment of chronic hepatitis B virus infection

Chronic hepatitis B virus (HBV) infection is a major health threat in Asia. In order to design a better therapeutic regimen, the underlying mechanism of HBV viral persistence must be understood. Immunological studies have found that impaired HBV virus-specific T cell reactivity is the major cause of chronic infection, whereas strong and multispecific T cell responses to HBV are associated with long-term control, but not elimination of the virus. Furthermore, in the serological clearance of hepatitis B surface antigen (HBsAg) in allogeneic haematopoietic cell transplantation, HBsAg seroconversion is associated with activation of the donor's hepatitis B core antigen-specific CD4+ T lymphocytes. This suggests that the donor's hepatitis B core antigen-specific CD4+ T cells provide 'intermolecular T cell help' for the HBsAg seroconversion. These findings are relevant to the future development of therapeutic vaccines or DNA vaccine as immunotherapy for chronic hepatitis B. Apart from interferon-alpha, thymosin alpha1 (Talpha1) has been investigated for treatment of chronic hepatitis B. Meta-analysis of 4 randomized controlled studies investigating the safety and efficacy of Talpha1 monotherapy for the treatment of chronic hepatitis B showed that 6 months treatment with Talpha1 (1.6 mg twice weekly) almost doubles the sustained response rate (36%) compared with controls (19%; P=0.04). However, more specific immunological approaches are being developed; notably, hepatitis B core antigen-based therapeutic vaccine was found to induce T cell proliferative responses in chronically infected hepatitis B patients to the T helper epitope included in the construct. However, the cytokine profile observed suggested the induction of a T helper 0/T helper 2 CD4+ T cell response rather than T helper 1 response. Thus, its combination with interferon-gamma or interleukin-12, which might reverse the CD4+T cell response, should be considered. In the future, it is likely that different types of combination therapy may have to be tailor-made for chronic HBV infection with different virological and immunological profiles and different degrees of liver damage.

Hepatitis B virus surface antigen (HBsAg) and antibody (anti-HBs) forming immune complexes in fulminant hepatitis

This paper reports an unusual pattern of serological HBV markers and the presence of HBsAg/anti-HBs immune complexes in serum samples from two patients with fulminant hepatitis from the Brazilian Western Amazon Basin. The diagnosis was made by both serologic tests and demonstration of antigen/antibody complexes by transmission electron microscopy. Concurrent Delta virus superinfection is also discussed.

Histological changes during clearance of chronic hepatitis B virus infection by adoptive immunity transfer

BACKGROUND

Serological clearance of hepatitis B surface antigen (HBsAg) has been described after reception of hepatitis B surface antibody positive marrow, via allogeneic bone marrow transplantation (BMT). Histological changes during the clearance of HBsAg are unknown.

METHODS AND RESULTS

We described two chronic hepatitis B carriers (both hepatitis B e antigen negative), who cleared HBsAg after allogeneic bone marrow transplantation. Both received hepatitis B surface and core antibody positive human leucocyte antigen identical donors' marrow and had serological clearance of HBsAg 15 and 7 weeks after allogeneic BMT, respectively. Both events were preceded by hepatic flare. Both patients were also treated with famciclovir for the prevention of hepatitis B reactivation after BMT. Histological examination during the flare showed only mild necroinflammatory activity with multiple foci of confluent necrosis, associated with moderate lymphocytic infiltration. The majority of these lymphocytes were cluster of differentiation (CD) 8 positive. Using immunohistochemistry, there was no detectable hepatic expression of hepatitis B core antigen. However, HBsAg was positive, mainly in the area of confluent necrosis. Using in situ hybridization, hepatitis B virus (HBV) DNA was detected in the nucleus of 5% of hepatocytes, but not in the cytoplasm.

CONCLUSIONS

At their last follow up, 22 and 16 months after BMT, the serum of both patients remained HBsAg negative, hepatitis B surface antibody positive and HBV-DNA negative by branched DNA assay.

Treatment of chronic hepatitis B virus infection: an Asia-Pacific perspective

Chronic hepatitis B infection is a serious health threat in the Asia-Pacific area. A consensus meeting on the treatment of chronic hepatitis B infection was conducted in Hong Kong, in August 1997. It was generally agreed that treatment of chronic hepatitis B infection should be based on the understanding of the natural history of chronic hepatitis B infection. To date, interferon alpha is the only Food and Drug Administration (FDA)-approved form of therapy for chronic hepatitis B infection. The overall response in Asian patients is unsatisfactory: approximately 15-20% will clear hepatitis B e antigen, but less than 5% will clear hepatitis B surface antigen. Newer immunomodulatory therapies are under trial. In contrast, nucleoside analogues, such as lamivudine (pending FDA approval) and famciclovir, have been shown to be potent suppressors of hepatitis B viral replication; however, their role as monotherapy in the treatment of chronic hepatitis B infection remains to be defined. Also, the issues of resistance to nucleoside analogues and withdrawal rebound need to be carefully studied. The future direction of therapy in chronic hepatitis B infection is probably a combination of nucleoside analogues or nucleoside analogues with immunomodulatory therapy.

Immunization of woodchucks with plasmids expressing woodchuck hepatitis virus (WHV) core antigen and surface antigen suppresses WHV infection

DNA vaccination can induce humoral and cellular immune response to viral antigens and confer protection to virus infection. In woodchucks, we tested the protective efficacy of immune response to woodchuck hepatitis core antigen (WHcAg) and surface antigen (WHsAg) of woodchuck hepatitis virus (WHV) elicited by DNA-based vaccination. Plasmids pWHcIm and pWHsIm containing WHV c- or pre-s2/s genes expressed WHcAg and WHsAg in transient transfection assays. Pilot experiments in mice revealed that a single intramuscular injection of 100 microgram of plasmid pWHcIm DNA induced an anti-WHcAg titer over 1:300 that was enhanced by boost injections. However, two injections of 100 microgram of pWHcIm did not induce detectable anti-WHcAg in woodchucks. With an increase in the dose to 1 mg of pWHcIm per injection, transient anti-WHcAg response and WHcAg-specific proliferation of peripheral mononuclear blood cells (PMBCs) appeared in woodchucks after repeated immunizations. Four woodchucks vaccinated with pWHcIm were challenged with 10(4) or 10(5) of the WHV 50% infective dose. They remained negative for markers of WHV replication (WHV DNA and WHsAg) in peripheral blood and developed anti-WHs in week 5 after challenge. In contrast, woodchucks not immunized or immunized with the control vector pcDNA3 developed acute WHV infection. Two woodchucks immunized with 1 mg of pWHsIm developed WHsAg-specific proliferative response of PBMCs but no measurable anti-WHsAg response. A rapid anti-WHsAg response developed during week 2 after virus challenge. Neither woodchuck developed any signs of WHV infection. These data indicate that DNA-based vaccination with WHcAg and WHsAg can elicit immunity to WHV infection.