Immunotherapy of chronic hepatitis B by anti HBV vaccine

Hepatitis B vaccination and immunotherapies: an update

World Health Organization (WHO) estimates that 257 million people were living with chronic hepatitis B virus (HBV) infection. Highest HBV prevalence was found in the WHO Western Pacific Region (6.2%) and in the WHO African Region (6.1%). The HBV vaccine is the best protection against chronic HBV infection and its complications. Globally, routine infant immunization against HBV has increased with an estimated coverage of 84% in 2017. Nevertheless, in many countries further efforts are needed to implement this coverage and ensure national immunization programs for people at major risk for HBV infection. Therapeutic vaccination in chronic HBV infected patients can cause anti-HBV immune responses able to remove and/or cure infected hepatocytes. It shows promising results in murine model and human trials, but these results need to be consolidated by further multicenter clinical studies. In particular, the efficacy of therapeutic vaccine seems to improve by combination therapies.

Therapeutic vaccination for chronic hepatitis B: A systematic review and meta-analysis

Therapeutic vaccines may be promising treatments for chronic hepatitis B (CHB), but their clinical efficacy and safety are unclear. We conducted a systematic review of the evidence for the efficacy and safety of therapeutic vaccines in CHB patients. We searched PubMed, EMBASE and Google Scholar from 1990 until present and abstracts from EASL, APASL and AASLD from 2012 to 2017 and selected randomized controlled trials of CHB patients, comparing therapeutic vaccines with no treatment or standard of care. The Cochrane Risk of Bias tool v2.0 and GRADE method were used. Analyses were stratified by hepatitis B e antigen (HBeAg) status and the comparator (therapeutic vaccines vs no treatment, or therapeutic vaccines + standard of care vs standard of care). Efficacy outcomes were HBeAg seroconversion, hepatitis B virus DNA reduction and hepatitis B virus surface antigen (HBsAg) loss, measured at the end of treatment or end of follow-up. Effects were reported as risk differences with 95% confidence intervals using a random effects model. Fifteen studies were included. A wide variety of therapeutic vaccines were tested. For HBeAg clearance at the end of follow-up, when comparing therapeutic vaccines vs no therapy, RD = 0.01, 95% CI -0.05 to 0.07, and when comparing therapeutic vaccines + standard of care vs standard of care, RD = 0.03, 95% CI -0.03 to 0.09. For HBVDNA reduction at the end of follow-up, when comparing therapeutic vaccines vs no therapy, RD = -0.03, 95% CI -0.08 to 0.02, and when comparing therapeutic vaccines + standard of care, RD = 0.15, 95% CI 0.02-0.28. There were only a few studies on HBsAg loss, and hence, the findings were inconclusive. The only efficacy finding was HBVDNA reduction at the end of follow-up for therapeutic vaccines + standard of care vs standard of care; otherwise, therapeutic vaccines do not appear to be efficacious for the treatment of CHB, but were limited by few RCTs, suboptimal therapeutic vaccines and patient selection.

Nanovaccine for immunotherapy and reduced hepatitis-B virus in humanized model

Chronic Hepatitis B Virus (HBV) infections are severe with weak antiviral immune responses. The lack of an appropriate small animal model for chronic hepatitis, a major hurdle for studying the immunotolerance and immunopathogenesis induced by hepatitis B viral (HBV) infection. In this study, for enhancing the antibody production efficiency the prepared polymeric HBsAg-loaded nanoparticles (nanovaccine) will be tested in immune-deficit mice, which suffer from chronic Hepatitis B virus. Vaccination of Balb/c mice by this prepared nanoparticles that were engrafted with peripheral blood mononuclear cells (PBMCs), which was already lethally irradiated and transplanted by the bone marrow of NOD (knockout mice) mice. In the present study, after the vaccination detected the high frequencies of immunoglobulin G (IgG)-secreting B cells and mitogen-responsive interferon-Y (IFN-Y) secreting T cells in serum, determined by specific ELISA technique. During the entire observation period, unvaccinated animals showed lower concentration of specific IgG secreting B cells and IFN-Y secreting T cells found in comparison to vaccinated mice group. Chronic HBV carrier PBMCs transplanted into the chimera failed to produce antigen and increased the antibodies production due to vaccination. Furthermore, another advantage was that the viral gene expression and viral DNA replication was no longer observed in vaccinated group. This prepared nanovaccine formulations is better for the cure of Hepatitis B viral infection carrier. Therefore, specific memory responses were elicited by vaccination with Hepatitis B virus surface (HBsAg) antigen of chimeric mice transplanted with PBMCs derived from HBV donors.

Gene therapeutic approaches to inhibit hepatitis B virus replication

Acute and chronic hepatitis B virus (HBV) infections remain to present a major global health problem. The infection can be associated with acute symptomatic or asymptomatic hepatitis which can cause chronic inflammation of the liver and over years this can lead to cirrhosis and the development of hepatocellular carcinomas. Currently available therapeutics for chronically infected individuals aim at reducing viral replication and to slow down or stop the progression of the disease. Therefore, novel treatment options are needed to efficiently combat and eradicate this disease. Here we provide a state of the art overview of gene therapeutic approaches to inhibit HBV replication. We discuss non-viral and viral approaches which were explored to deliver therapeutic nucleic acids aiming at reducing HBV replication. Types of delivered therapeutic nucleic acids which were studied since many years include antisense oligodeoxynucleotides and antisense RNA, ribozymes and DNAzymes, RNA interference, and external guide sequences. More recently designer nucleases gained increased attention and were exploited to destroy the HBV genome. In addition we mention other strategies to reduce HBV replication based on delivery of DNA encoding dominant negative mutants and DNA vaccination. In combination with available cell culture and animal models for HBV infection, in vitro and in vivo studies can be performed to test efficacy of gene therapeutic approaches. Recent progress but also challenges will be specified and future perspectives will be discussed. This is an exciting time to explore such approaches because recent successes of gene therapeutic strategies in the clinic to treat genetic diseases raise hope to find alternative treatment options for patients chronically infected with HBV.

Immune modulator and antiviral potential of dendritic cells pulsed with both hepatitis B surface antigen and core antigen for treating chronic HBV infection

BACKGROUND

Commercially available prophylactic vaccines containing hepatitis B surface antigen (HBsAg), which are used to prevent HBV infections, are not as effective as a therapeutic immune modulator for treating patients with chronic hepatitis B (CHB). In this study, the immunogenicity of dendritic cells (DC) loaded with both HBsAg and hepatitis B core antigen (HBcAg) was tested in HBV transgenic mice (TM; 1.2HB-BS10) in vivo and in patients with CHB in vitro.

METHODS

Spleen DC from HBV TM were cultured with a vaccine containing both HBsAg and HBcAg to produce HBsAg/HBcAg-pulsed DC. HBV TM were immunized twice at an interval of 4 weeks with HBsAg/HBcAg-pulsed DC and other immune modulators. Antibody titres to HBsAg (anti-HBs) were measured in sera. Antigen-specific T-cells and cytotoxic T-lymphocytes (CTLs) in the spleen and liver were detected by lymphoproliferative and ELISPOT assays, respectively. HBsAg/HBcAg-pulsed human blood DC were cultured with autologous T-cells from CHB patients to assess their antigen-specific immune modulatory capacities.

RESULTS

Significantly higher levels of anti-HBs, HBsAg-specific and HBcAg-specific T-cells and CTLs were detected in the spleen and liver of HBV TM immunized with HBsAg/HBcAg-pulsed DC compared with those immunized with other vaccine formulations (P<0.05). HBsAg/HBcAg-pulsed human blood DC also induced HBsAg- and HBcAg-specific proliferation of autologous T-cells from CHB patients.

CONCLUSIONS

The immune modulatory capacities of HBsAg/HBcAg-pulsed DC in HBV TM in vivo, and in patients with CHB in vitro, inspire optimism about a clinical trial with this cell-based vaccine in patients with CHB.

Treatment of hepatitis B virus-infected patients: utility of therapeutic recommendations in developing countries

BACKGROUND

The treatment of individuals infected with hepatitis B virus (HBV) is a complex issue in practical settings, despite the explosion of new and effective antiviral agents.

OBJECTIVE

To assess the scope and limitations of ongoing treatment guidelines against HBV from a global perspective.

METHODS

Present therapeutic guidelines against HBV have been discussed with emphasis on their value in developing countries that harbor about 90% of the total number of global patients who are infected with HBV.

RESULTS/CONCLUSION

Treatment of HBV-infected patients should be appropriately followed up and healthcare delivery systems should be able to combat treatment-induced adverse side effects. Current therapeutic guidelines should be optimized based on the socio-economic conditions of developing countries.

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.

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.

Replicative homeostasis III: implications for antiviral therapy and mechanisms of response and non-response

While improved drug regimens have greatly enhanced outcomes for patients with chronic viral infection, antiviral therapy is still not ideal due to drug toxicities, treatment costs, primary drug failure and emergent resistance. New antiviral agents, alternative treatment strategies and a better understanding of viral pathobiology, host responses and drug action are desperately needed. Interferon (IFN) and ribavirin, are effective drugs used to treat hepatitis C (HCV), but the mechanism(s) of their action are uncertain. Error catastrophe (EC), or precipitous loss of replicative fitness caused by genomic mutation, is postulated to mediate ribavirin action, but is a deeply flawed hypothesis lacking empirical confirmation. Paradoxically ribavirin, a proven RNA mutagen, has no impact on HCV viraemia long term, suggesting real viruses, replicating in-vitro, as opposed to mathematical models, replicating in-silico, are likely to resist EC by highly selective replication of fit (~consensus sequence) genomes mediated, in part, by replicative homeostasis (RH), an epicyclic mechanism that dynamically links RNApol fidelity and processivity and other viral protein functions. Replicative homeostasis provides a rational explanation for the various responses seen during treatment of HCV, including genotype-specific and viral load-dependent differential response rates, as well as otherwise unexplained phenomena like the transient inhibition and rebound of HCV viraemia seen during ribavirin monotherapy. Replicative homeostasis also suggests a primarily non-immunological mechanism that mediates increased immune responsiveness during treatment with ribavirin (and other nucleos(t)ide analogues), explicating the enhanced second-phase clearance of HCV ribavirin promotes and, thus, the apparent immunomodulatory action of ribavirin. More importantly, RH suggests specific new antiviral therapeutic strategies.

Replicative homeostasis: a fundamental mechanism mediating selective viral replication and escape mutation

Hepatitis C (HCV), hepatitis B (HBV), the human immunodeficiency viruses (HIV), and other viruses that replicate via RNA intermediaries, cause an enormous burden of disease and premature death worldwide. These viruses circulate within infected hosts as vast populations of closely related, but genetically diverse, molecules known as "quasispecies". The mechanism(s) by which this extreme genetic and antigenic diversity is stably maintained are unclear, but are fundamental to understanding viral persistence and pathobiology. The persistence of HCV, an RNA virus, is especially problematic and HCV stability, maintained despite rapid genomic mutation, is highly paradoxical. This paper presents the hypothesis, and evidence, that viruses capable of persistent infection autoregulate replication and the likely mechanism mediating autoregulation - Replicative Homeostasis - is described. Replicative homeostasis causes formation of stable, but highly reactive, equilibria that drive quasispecies expansion and generates escape mutation. Replicative homeostasis explains both viral kinetics and the enigma of RNA quasispecies stability and provides a rational, mechanistic basis for all observed viral behaviours and host responses. More importantly, this paradigm has specific therapeutic implication and defines, precisely, new approaches to antiviral therapy. Replicative homeostasis may also modulate cellular gene expression.

Replicative homeostasis: a mechanism of viral persistence

Acute viral infection is characterised by high-level replication before prompt decline of viraemia and, commonly, viral clearance. This kinetic pattern is generally held to be due to immune control. However, infection with some viruses, notably hepatitis C (HCV), hepatitis B (HBV) and the human immunodeficiency virus (HIV), often results in chronic stable low-level spontaneously fluctuating viraemia, kinetics that are difficult to rationalize on this basis. The persistence of HCV, an RNA virus, is especially problematic and its stability, occurring despite rapid, genomic mutation is highly paradoxical. This paper outlines the hypothesis, and evidence, that viruses autoregulate replication and mutation and describes a mechanism--replicative homeostasis--explaining viral stability. Replicative homeostasis results in stable, but reactive, replicative equilibria that drive quasispecies expansion and immune escape and explain all observed viral behaviours and host responses. This paradigm implies new approaches to antiviral therapy and is broadly relevant to modulation of gene expression.

Efficacy of hepatitis B vaccination and interferon-alpha-2b combination therapy versus interferon-alpha-2b monotherapy in children with chronic hepatitis B

BACKGROUND

Although interferon (IFN) has been approved in the treatment of chronic hepatitis B in children, it is effective only in 30-40% of patients. In some studies it has been suggested that therapeutic use of anti-hepatitis B virus (HBV) vaccine may be beneficial in patients with chronic hepatitis B. The aim of the present study was to compare the efficacy of hepatitis B vaccination and IFN-alpha-2b in combination and IFN-alpha-2b monotherapy in children with chronic hepatitis B.

METHODS

Fifty treatment-naive children with chronic hepatitis B infection were randomly assigned to receive either 5 million units/m(2) recombinant IFN-alpha-2b subcutaneously three times per week for 9 months, and pre-S2/S vaccine at the beginning and 4 and 24 weeks after initiation of IFN therapy (n = 25) or recombinant IFN-alpha-2b (5 million units/m(2) subcutaneously thrice weekly) alone for 9 months (n = 25). Children were followed for at least 6 months after the end of therapy.

RESULTS

There was no statistically significant difference in the mean alanine aminotransferase levels, histologic activity index and fibrosis scores between combination and IFN monotherapy groups at the end of the therapy and end of the follow-up period. When combination and monotherapy groups were compared, the mean HBV-DNA values were significantly reduced in combination group at the end of the therapy (P = 0.004), but no statistically significant difference was found at the end of the follow up. Sustained HBeAg seroconversion with clearance of HBV-DNA was obtained in 13 of 25 children (52%) treated with combination therapy, and in eight of 25 patients (32%) treated with IFN monotherapy (P = 0.251).

CONCLUSION

Although the difference was statistically insignificant, the sustained response rates were better in the combination therapy group than in the monotherapy group. The potential benefit of combining IFN and hepatitis B vaccine should be investigated in further studies with different regimens of combination therapy.

Late failure of combined recombinant hepatitis B vaccine and lamivudine in treatment of a patient with chronic hepatitis B

We report the first case of a woman having chronic hepatitis B treated with a combination therapy of recombinant hepatitis B vaccine and lamivudine for 18 months. The main aims of such a combined therapy were to assess whether the concomitant anti-hepatitis B virus (HBV) vaccination might prevent the emergence of a mutant HBV and lead to sustained hepatitis B e antigen seroconversion with undetectable serum HBV DNA. The data from the present case demonstrated that combination of anti-HBV vaccine and lamivudine did not eliminate viral DNA despite prolonged treatment and did not have any effect on preventing resistant-type HBV. Although the combined therapy failed to reach the therapeutic endpoints, it concerned a single and unique patient. Hepatitis B vaccine and lamivudine for HBV treatment should be further investigated in randomized controlled trials.

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.

Vaccines for viral diseases with dermatologic manifestations

Vaccines against infectious diseases have been available since the 1800s, when an immunization strategy against smallpox developed by Jenner gained wide acceptance. Until recently, the only vaccination strategies available involved the use of protein-based, whole killed, and attenuated live virus vaccines. These strategies have led to the development of effective vaccines against a variety of diseases with primary or prominent cutaneous manifestations. Effective and safe vaccines now used worldwide include those directed against measles and rubella (now commonly used together with a mumps vaccine as the trivalent MMR), chickenpox, and hepatitis B. The eradication of naturally occurring smallpox remains one of the greatest successes in the history of modern medicine, but stockpiles of live smallpox exist in the United States and Russia. Renewed interest in the smallpox vaccine reflects concerns about a possible bioterrorist threat using this virus. Yellow fever is a hemorrhagic virus endemic to tropical areas of South America and Africa. An effective vaccine for this virus has existed since 1937, and it is used widely in endemic areas of South America, and to a lesser extent in Africa. This vaccine is recommended once every 10 years for people who are traveling to endemic areas. Advances in immunology have led to a greater understanding of immune system function in viral diseases. Progress in genetics and molecular biology has allowed researchers to design vaccines with novel mechanisms of action (eg, DNA, vector, and VLP vaccines). Vaccines have also been designed to specifically target particular viral components, allowing for stimulation of various arms of the immune system as desired. Ongoing research shows promise in prophylactic and therapeutic vaccination for viral infections with cutaneous manifestations. Further studies are necessary before vaccines for HSV, HPV, and HIV become commercially available.

Therapeutic vaccination against chronic viral infections

Chronic viral infections such as those caused by hepatitis B virus, human papilloma virus, herpes simplex virus, and HIV, in theory, present logical targets of active specific immunotherapy. Indeed, immunological mechanisms are involved in several aspects of their pathogenesis and natural course, such as virus persistence, destruction of infected cells and control of viral replication. Therapeutic vaccination could therefore be an adequate replacement for, or adjunct to, existing therapies. Almost all approaches to therapeutic vaccination have been evaluated in those four disease areas. Despite encouraging results in animals none of these attempts has, so far, been completely successful in the human setting. However, with a better understanding of the immunological mechanisms involved in the control of disease successful therapeutic vaccines, used alone or in combination with other therapies, are an achievable goal.

Induction of strong hepatitis B virus (HBV) specific T helper cell and cytotoxic T lymphocyte responses by therapeutic vaccination in the trimera mouse model of chronic HBV infection

Humanized BALB/c mice (termed trimera mice) conditioned by lethal total body irradiation and bone marrow transplantation from SCID mice have been described to support rapid engraftment of human peripheral blood mononuclear cells (PBMC) and the induction of strong B and T cell responses after immunization in vivo. Moreover, these mice can be infected with the hepatitis B and C viruses (HBV, HCV). The current study employed this model to study therapeutic vaccination approaches against the HBV. Thus, strong primary Th cell responses against the HBV core (HBc) and the Borrelia burgdorferi control antigen were induced by transfer of antigen-loaded dendritic cells together with autologous PBMC from HBV-naive donors as well as by vaccination with high doses of antigen or a DNA plasmid encoding for HBcAg. Moreover, primary peptide-specific CTL responses against the immunodominant epitope HBc(18 - 27) were induced by HBc particle or DNA vaccination of chimera engrafted with HBV-naive PBMC. Finally, strong HBc-specific Th cell and antibody responses were induced by HBc or DNA vaccination of mice reconstituted with PBMC from a chronic HBV patient. Thus, since HBc represents the immunodominant antigen in self-limited HBV infection, HBc particles or DNA vectors are good candidates for therapeutic vaccination, that will be further studied in our model and clinical studies.

Comparison of in vivo fate and immunogenicity of hepatitis B surface antigen incorporated in cationic and neutral liposomes

To compare cationic liposomes (CatL) and neutral liposomes (NeuL), as a vaccine carrier, the in vivo fate and immunogenicity of hepatitis B surface antigen (HBsAg), incorporated in CatL and NeuL, were investigated. CatL, composed of phosphatidyl choline (PC) and stearyl amine (SA) with a molar ratio of 9:1, showed a 2.5-fold higher incorporating efficiency of HBsAg than NeuL composed of PC alone. Most of HBsAg incorporated in both liposomes existed in an antibody-available form on the outer surface of liposomes. After intramuscular injection to rats, HBsAg in CatL resided at the injection site for a longer period than that in NeuL with terminal half lives of 52.5 and 42.9 h, respectively. However, HBsAg in NeuL was more efficiently taken up by the lymphatic organs and spleen than that in CatL. Furthermore, the group treated with HBsAg in NeuL showed earlier sero-conversion with higher anti-HBsAg titre than the group treated with HBsAg in CatL. Sero-conversion rates (SCRs) in both CatL- and NeuL-treated animals were 100% after every injection carried out, except the primary injection of CatL. These results demonstrate that CatL can enhance the retention of incorporated antigen at the injection site, compared with NeuL. However, the production of antibody by HBsAg in NeuL is more effective than that by HBsAg in CatL, probably due to the higher lymphatic targeting ability of NeuL. Thus, NeuL appears to be a better carrier for HBsAg than CatL.

Reduced hepatitis B virus surface antigen-specific Th1 helper cell frequency of chronic HBV carriers is associated with a failure to produce antigen-specific antibodies in the trimera mouse

In chronic hepatitis B virus (HBV) infection weak antiviral immune responses are associated with viral persistence. We studied possible immune deficits underlying the lack of serum antibodies of such patients against the HBV surface antigen (HBsAg) in a novel human/mouse chimeric model. A hepatitis B surface antigen (HBs) vaccination of Balb/c mice engrafted with peripheral blood mononuclear cells (PBMC) of naturally HBV-immunized donors induced high frequencies of human HBsAg-specific B and T helper 1 (Th1) cells. These responses were associated with high serum anti-HBs antibody levels of the subclasses immunoglobulin G1 (IgG1) and IgG2 that are driven by interleukin-2 (IL-2) and interferon-gamma (IFN-gamma). In contrast, PBMC of chronic HBV carriers transplanted into the chimera failed to produce anti-HBs antibodies after vaccination with HBsAg and exhibited a deficit of antigen-specific Th1 cells. A possible influence of HBsAg or viremia was excluded by the lack of viral replication in such chimera. The observed T-cell defect was specific for HBsAg, as the B- and T-cell responses to tetanus toxoid (TT) were fully retained. Thus, our study shows that viral persistence in chronic HBV carriers is associated with an HBsAg-specific Th1 cell defect, which likely is responsible for the insufficient neutralizing anti-HBs-antibody response and is not reversed by HBs vaccination. Alternative approaches to induce HBs-specific Th1 cell responses might represent a future therapeutic option.

Mechanism of action of vaccine therapy in murine hepatitis B virus carriers: vaccine-induced activation of antigen presenting dendritic cells

BACKGROUND/AIMS

Vaccine therapy in which vaccine containing hepatitis B surface antigen (HBsAg) is injected has shown therapeutic activity (vaccine therapy) in some human and murine chronic hepatitis B virus (HBV)-carriers. Using HBV-transgenic mice (HBV-Tg), an animal model of the HBV-carrier state, the mechanism underlying the antiviral and immune modulatory capacity of vaccine therapy was studied.

METHODS

Placebo-controlled, double-blind trials of vaccine therapy were conducted in HBV-Tg; some HBV-Tg responded to the therapy, whereas others were non-responders. The titers of HBV-markers, the functions of lymphocytes and antigen presenting dendritic cells were compared between vaccine responders and vaccine non-responders.

RESULTS

The prevaccinated titers of HBsAg, hepatitis B e-antigen (HBeAg), HBV DNA and the responses of lymphocytes to polyclonal mitogens were almost unchanged between responders and non-responders, but the levels of proliferation of HBsAg-specific lymphocytes from non-responders was significantly lower than responders (p<0.05). The capacity of dendritic cells to induce proliferation of T cells and production of antibody to HBsAg (anti-HBs) was significantly higher in responders compared with non-responders (p<0.05). Injection with HBsAg resulted in upregulation of MHC class II and CD86 antigens (p<0.05) on dendritic cells and increased production of IL-12, IL-2 and TNF-alpha in cultures (p<0.05) in vaccine responders but not in non-responders.

CONCLUSIONS

The activation of dendritic cells following injection with vaccine containing HBsAg is the vital factor underlying the therapeutic potentiality of vaccine therapy in HBV carriers.

Prognostic importance of antigen-presenting dendritic cells during vaccine therapy in a murine hepatitis B virus carrier

As, the outcome of vaccine therapy was extremely heterogeneous in both human and murine hepatitis B virus (HBV)-carriers, the experiments presented here were performed to find out a prognostic marker of vaccine therapy using an animal model of HBV-carrier state, HBV-transgenic mice (Tg). Neither the prevaccinated titres of viral markers, such as hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg) or HBV DNA, nor the function of lymphocytes prior to vaccination, had significant influence on the outcome of vaccine therapy. Two independent, placebo-controlled, trials of vaccine therapy for 12 months, one in 17 HBV-Tg and the other in 26 HBV-Tg (total, n=43) showed that the eight of 17 and 15 of 26 HBV-Tg that had potent dendritic cell (DC) function at the start of vaccine therapy became completely negative for HBsAg, HBeAg and reduced HBV DNA, whereas all 19 HBV-Tg that had poor DC function at the start of vaccine therapy became complete non-responders, although, the prevaccinated titres of HBsAg, and HBeAg were similar in all 43 HBV-Tg. Further study to find the mechanism underlying this revealed that there was up-regulation of major histocompatibility complex (MHC) class II, CD86 antigens on DC and increased production of interleukin-12 (IL-12) by DC and of IL-2, and tumour necrosis factor-alpha (TNF-alpha) in DC/T-cell cultures when vaccine containing HBsAg was injected in HBV-Tg with potent DC function but not in HBV-Tg with poor DC function. This is the first report on the prognostic importance of DC during an immune therapy. Degree of activation of DC following vaccination would possibly help to predict the outcome of vaccine therapy in human HBV-carriers. These data also provide the scientific and logical basis to up-regulate the function of the DC before an immune therapy.

Hepatitis B virus and liver transplantation: concepts in antiviral prophylaxis

Liver transplantation remains problematic in patients with end-stage liver disease secondary to chronic hepatitis B virus (HBV) infection. Recurrent hepatitis is almost universal in those patients who are HBV DNA-positive prior to transplantation. Prophylactic hepatitis B immune globulin can be given to reduce the rate of hepatitis B recurrence in patients who are HBV DNA-negative prior to transplantation. More recently novel antiviral drugs such as lamivudine or famciclovir have been used specifically to inhibit hepatitis B viral replication. However, the development of drug-resistant viral mutants have been observed. Further studies are needed to investigate these drugs more extensively, particularly to assess whether combination therapy may be a more effective means of controlling viral recurrence in patients transplanted for chronic HBV infection.