Clinical and immunological efficacy of intradermal vaccine plus lamivudine with or without interleukin-2 in patients with chronic hepatitis B

Immunomodulatory and Antiviral Therapy Improved Functional Cure Rate in CHB Patients with High HBsAg Level Experienced NA

Background and Aims

A functional cure, or hepatitis B virus (HBV) surface antigen (HBsAg) loss, is difficult to achieve in patients with hepatitis B virus e antigen (HBeAg)-positive chronic hepatitis B. The HBV vaccine and granulocyte-macrophage colony-stimulating factor (GM-CSF) have been reported to help reduce HBsAg levels and promote HBsAg loss. In this prospective randomized trial, we evaluated HBsAg loss in patients receiving pegylated interferon-α2b (PEGIFN-α2b) and tenofovir disoproxil fumarate (TDF), with and without GM-CSF and HBV vaccination.

Methods

A total of 287 patients with HBeAg positive chronic hepatitis B and seroconversion after nucleot(s)ide analog treatment were assigned randomly to three treatment groups for 48 weeks, TDF alone (control), PEGIFN-α2b + TDF, and PEGIFN-α2b + TDF + GM-CSF + HBV vaccine. The primary endpoints were the proportions of patients with HBsAg loss and seroconversion at 48 and 72 weeks.

Results

The cumulative HBsAg loss rates in the control, PEGIFN-α2b + TDF, and PEGIFN-α2b + TDF + GM-CSF + HBV vaccine groups at week 48 were 0.0%, 28.3%, and 41.1%, respectively. The cumulative HBsAg seroconversion rates in these groups at week 48 were 0.0%, 21.7%, and 33.9%, respectively. Multivariate regression analysis showed that GM-CSF use plus HBV vaccination was significantly associated with HBsAg loss (p=0.017) and seroconversion (p=0.030).

Conclusions

In patients with HBeAg-positive chronic hepatitis B and seroconversion after nucleot(s)ide analog treatment, immunomodulatory/antiviral treatment regimens effectively improved HBsAg loss, and the regimen including GM-CSF and HBV vaccination was most effective.

HBV Infection and Host Interactions: The Role in Viral Persistence and Oncogenesis

Hepatitis B virus (HBV) is a major cause of chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. Despite the advent of vaccines and potent antiviral agents able to suppress viral replication, recovery from chronic HBV infection is still an extremely difficult goal to achieve. Complex interactions between virus and host are responsible for HBV persistence and the risk of oncogenesis. Through multiple pathways, HBV is able to silence both innate and adaptive immunological responses and become out of control. Furthermore, the integration of the viral genome into that of the host and the production of covalently closed circular DNA (cccDNA) represent reservoirs of viral persistence and account for the difficult eradication of the infection. An adequate knowledge of the virus-host interaction mechanisms responsible for viral persistence and the risk of hepatocarcinogenesis is necessary for the development of functional cures for chronic HBV infection. The purpose of this review is, therefore, to analyze how interactions between HBV and host concur in the mechanisms of infection, persistence, and oncogenesis and what are the implications and the therapeutic perspectives that follow.

Innovative Therapies Targeting the Virus and the Host for Treating Chronic Hepatitis B Virus Infection: From Bench to Bedside

Chronic hepatitis B (CHB) is a highly complicated pathological process in which the disease is initiated by the hepatitis B virus (HBV); however, host immune responses are primarily responsible for variable extents of liver damage. If the patients with CHB remain untreated, many CHB patients will eventually develop complications like cirrhosis of the liver (LC) and hepatocellular carcinoma (HCC). In 2019, an estimated 882,000 patients died due to HBV-related complications worldwide. Accordingly, several drugs with antiviral properties have been used to treat CHB patients during the last four decades. However, the treatment outcome is not satisfactory because viral suppression is not usually related to the containment of progressive liver damage. Although proper reconstruction of host immunity is essential in CHB patients, as of today, there is no acceptable immune therapeutic protocol for them. These realities have exposed new, novel, and innovative therapeutic regimens for the management of CHB patients. This review will update the scope and limitation of the different innovative antiviral and immune therapeutic approaches for restoring effective host immunity and containing the virus in CHB patients to block progression to LC and HCC.

Cellular and Molecular Mechanisms Underlying Scope and Limitation of Ongoing and Innovative Therapies for Treating Chronic Hepatitis B

Millions of people of the world suffer from chronic hepatitis B (CHB), a pathological entity in which the patients are chronically infected with hepatitis B virus (HBV) and express hepatitis B surface antigen (HBsAg) and HBV DNA, as well as evidence of liver damages. Considerable numbers of CHB patients develop cirrhosis of the liver and hepatocellular carcinoma if untreated. Two groups of drugs (interferons and nucleoside analogs) are used to treat CHB patients, but both are endowed with considerable adverse effects, increased costs, extended duration of therapy, and limited efficacy. Thus, there is a pressing need to develop new and innovative therapeutics for CHB patients, and many such drugs have been developed during the last four decades. Some of these drugs have inspired considerable optimism to be a game-changer for the treatment of CHB. Here, we first discuss why ongoing therapeutics such as interferon and nucleoside analogs could not stand the test of time. Next, we dissect the scope and limitation of evolving therapies for CHB by dissecting the cellular and molecular mechanisms of some of these innovative therapeutics.

Immune therapies against chronic hepatitis B

Patients with chronic hepatitis B (CHB) represent a living and permanent reservoir of hepatitis B virus (HBV). Millions of these CHB patients will eventually develop complications such as liver cirrhosis, hepatic failure, and hepatocellular carcinoma if they are not treated properly. Accordingly, several antiviral drugs have been developed for the treatment of CHB, but these drugs can neither eradicate all forms of HBV nor contain the progression of complications in most patients with CHB. Thus, the development of new and novel therapeutics for CHB remains a pressing need. The molecular and cellular mechanisms underlying the pathogenesis of CHB indicate that immune dysregulations may be responsible for HBV persistence and progressive liver damage in CHB. This provided the scientific and ethical basis for the immune therapy of CHB patients. Around 30 years have passed since the initiation of immune therapies for CHB in the early 1990s, and hundreds of clinical trials have been accomplished to substantiate this immune treatment. Despite these approaches, an acceptable regimen of immune therapy is yet to be realized. However, most immune therapeutic agents are safe for human usage, and many of these protocols have inspired considerable optimism. In this review, the pros and cons of different immune therapies, observed in patients with CHB during the last 30 years, will be discussed to derive insights into the development of an evidence-based, effective, and patient-friendly regimen of immune therapy for the treatment of CHB.

Exploring evidence-based innovative therapy for the treatment of chronic HBV infection: experimental and clinical

With the advent of various vaccines and antimicrobial agents during the 20th century, the control and containment of infectious diseases appeared to be a matter of time. However, studies unveiled the diverse natures of microbes, their lifestyle, and pathogenetic potentials. Since the ground-breaking discovery of the hepatitis B virus (HBV) by Baruch Blumberg and the subsequent development of a vaccine in the early 1980s, the main task of the scientific community has been to develop a proper management strategy for HBV-induced chronic liver diseases. In the early 1980’s, standard interferon (IFN) induced a reduction of HBV DNA levels, followed by the normalization of serum transaminases (alanine aminotransferase, ALT), in some chronic hepatitis B (CHB) patients. However, in the course of time, the limitations of standard IFN became evident, and the search for an alternative began. In the late 1980’s, nucleoside analogs entered the arena of CHB treatment as oral drugs with potent antiviral capacities. At the beginning of the 21st century, insights were developed into the scope and limitations of standard IFN, pegylated-IFN as well as nucleoside analogs for treating CHB. Considering the non-cytopathic nature of the HBV, the presence of covalently closed circular DNA (cccDNA) in the nucleus of the infected hepatocytes and HBV-induced immune-mediated liver damages, a new field of CHB management was initiated by modulating the hosts’ immune system through immune therapy. This review will discuss the nature and design of innovative immune therapy for CHB.

Therapeutic vaccination for treatment of chronic hepatitis B

Chronic hepatitis B infection remains a serious global health threat, contributing to a large number of deaths through liver cirrhosis and hepatocellular carcinoma. Current treatment does not eradicate disease, and therefore new treatments are urgently needed. In acute hepatitis B virus (HBV) a strong immune response is necessary to clear the virus, but in chronic infection the immune response is weakened and dysfunctional. Therapeutic vaccination describes the process of inoculating individuals with a non‐infective form of viral antigen with the aim of inducing or boosting existing HBV‐specific immune responses, resulting in sustained control of HBV infection. In this review we outline the rationale for therapeutic vaccination in chronic HBV infection, discuss previous and ongoing trials of novel HBV therapeutic vaccine candidates and outline strategies to improve vaccine efficacy going forward.

Sequential combination therapy with interferon, interleukin-2 and therapeutic vaccine in entecavir-suppressed chronic hepatitis B patients: the Endeavor study

BACKGROUND

Switching from nucleos(t)ide analogues to interferon (IFN) improves hepatitis B surface antigen (HBsAg) loss. We aimed to evaluate whether combining immunomodulators such as interleukin-2 (IL-2) and therapeutic vaccine with IFN enhances HBsAg loss in entecavir (ETV)-suppressed patients.

METHODS

Ninety-four patients exhibiting virological suppression and hepatitis B e antigen (HBeAg) loss following ETV treatment were randomized 1:1:1 to receive ETV (group I) or IFN (group II) for 48 weeks, or IFN and vaccine for 48 weeks plus IL-2 for 12 weeks (group III). The primary endpoint was HBsAg loss at week 48. Peripheral natural killer (NK) cells and regulatory T cells (Treg) were measured as immune checkpoint indicators.

RESULTS

Mean HBsAg decline at week 48 was significantly greater in group III (0.85 log 10 IU/mL) and group II (0.74 log 10 IU/mL), than in group I (0.13 log 10 IU/mL). At week 48, 9.38%, 3.03%, and 3.70% of subjects in group III, II, and I, respectively, achieved HBsAg loss. Among patients with baseline HBsAg titers ranging from 100 to 1500 IU/mL, HBsAg loss rate was 27.3, 7.1, and 0% in group III, II, and I, respectively. Responders in group III showed a significantly higher increase in CD56^bright CD16^-NK cells from week 24 to 36, and a significant decline in Treg from week 12 to 24 than non-responders.

CONCLUSION

For ETV-suppressed patients, particularly those with low baseline HBsAg levels, combination therapy with IFN and other immunomodulators may enhance HBsAg loss, while successful response correlates with partial restoration of NK cells and Tregs.

Antiviral Therapy for AECHB and Severe Hepatitis B (Liver Failure)

This chapter describes the principles of antiviral therapy, treatment strategies, medications and recommendations for AECHB, HBV-ACLF, HBV-related liver cirrhosis, HBV-related HCC, and liver transplantation.

Severe exacerbation of chronic hepatitis B is closely related to continuous HBV replication. Therefore, inhibiting HBV replication to reduce viral load may block disease progression and improve the quality of life of these patients. ETV or TDF has been recommend first-line drug for the treatment of AECHB.

A hyperactive immune response due to continuous HBV replication is the main mechanism for development of severe hepatitis B. In addition to comprehensive treatment, early administration of potent nucleoside analogs can rapidly reduce HBV DNA concentration, relieve immune injury induced by HBV, and reduce liver inflammation and patient mortality. Antiviral agents have become important in the treatment of severe exacerbation of chronic hepatitis B.

Long-term antiviral treatment with nucleoside analogs can delay or reverse the progress of liver cirrhosis. Virologic response, viral resistance and adverse drug reactions should be closely monitored during treatment. The treatment should be optimized for maximum effect based on each patient’s responses.

Effective antiviral therapy can suppress HBV replication and reduce the incidence of HBV-related HCC. Patients with HBV-related HCC should receive individualized and optimal multidisciplinary comprehensive treatment. Anti-viral drugs with high efficacy, low resistance and low adverse drug reactions should be selected to improve the patient’s quality of life and prolong survival time.

Methods to prevent HBV reinfection after liver transplantation include passive immunization (HBIG), antiviral treatment (nucleoside analogs) and active immunization (hepatitis B vaccine).

Clinical trials involving sequential combination therapy with NUC and Peg-IFN have shown statistically significant decline in HBsAg levels on treatment and high rates of sustained post-treatment serologic response. Combination therapy with novel DAA and immunotherapeutic approach may hold promise to overcome both cccDNA persistence and immune escape, representing a critical step towards HBV cure.

Multiple doses of hepatitis B recombinant vaccine for chronic hepatitis B patients with low surface antigen levels: a pilot study

BACKGROUND

Seroclearance of hepatitis B surface antigen (HBsAg) has been rarely achieved in the treatment of chronic hepatitis B (CHB) patients. We administered HBsAg-based recombinant vaccine in patients with low HBsAg concentrations.

METHODS

Twenty hepatitis B e antigen-negative patients, with HBsAg < 1000 IU/ml, were enrolled. Vaccines were administered every 8 weeks for 48 weeks (seven doses). HBsAg levels and anti-HBs were assayed longitudinally until 48 weeks post-vaccination. HLA genotyping and cDNA microarray were performed to search for response predictors.

RESULTS

Nineteen patients completed the study. At the end of vaccination, HBsAg declined significantly (Δ = - 0.27 ± 0.49 log IU/ml, p = 0.0005). The annual decline rate was significantly greater than that of an age-, gender-, and baseline HBsAg-matched control group (Δ = - 0.18 ± 0.46 versus + 0.11 ± 0.42 log IU/ml/year; p = 0.0229). Two patients achieved HBsAg seroclearance. Fourteen had significant HBsAg decline (Δ = - 0.64 ± 0.88 log IU/ml). No significant adverse events occurred during the trial. cDNA microarray identified the top up- and down-regulated genes in responders as HLA-DQ and HLA-DMB, respectively. HLA genotyping identified HLA-DQB1*04, HLA-DRB1*04, and HLA-B*40 as predictors for non-response (p = 0.0499, 0.0152, and 0.0314, respectively).

CONCLUSIONS

In low-level HBsAg CHB patients, serial HBsAg-based vaccinations were safe, resulting in significant HBsAg decline. HLA gene expression and genotypes played a role in vaccine responsiveness (ClinicalTrials.gov Identifier: NCT01817725).

New treatments to reach functional cure: Rationale and challenges for emerging immune-based therapies

The landscape for chronic HBV therapy is rapidly evolving. The latest generation of antiviral drugs provide robust virus suppression with a high barrier to resistance that facilitates long-term treatment. However, low rates of HBsAg loss demonstrate that additional strategies are needed to consistency achieve a functional cure. The immune system can clear HBV and establish long-term control over the virus. Sufficiently boosting HBV immunity in chronic patients has been very difficult due to immune exhaustion, immune dysregulation, and inhibitory pathways suppressing the immune response. Therapeutic vaccines employing new technology, vectors and new immunomodulatory drugs that can elicit direct antiviral effects and cancel inhibitory mechanism may be able to overcome exhaustion. This review will discuss the justification for immunotherapy, lessons from previous trials and new vaccines/drugs in early stage clinical trials. The challenges of correlating immune responses induced by these drugs to clinical efficacy will also be addressed.

Novel insights into immunotherapy for hepatitis B patients

The possible use of immunotherapy for hepatitis B has emerged for two major reasons: (1) chronic hepatitis B (CHB) is an immune-mediated pathological condition, and (2) commercially available antiviral drugs are of limited efficacy. Although various immunomodulatory agents have been used to treat patients with CHB during the last three decades, there is currently no consensus among physicians and hepatologists regarding the suitability of immunotherapy for patients with CHB. However, new insights into immunotherapy for CHB have emerged; these may facilitate design of effective and tolerable immunotherapy regimens for these patients. This review provides a comprehensive overview of immunotherapy for CHB.

Immune therapy for hepatitis B

Although several antiviral drugs are now available for treatment of patients with chronic hepatitis B (CHB), sustained off-treatment clinical responses and containment of CHB-related complications are not achieved in majority of CHB patients by antiviral therapy. In addition, use of these drugs is endowed with substantial long term risk of viral resistance and drug toxicity. The infinite treatment regimens of antiviral drugs for CHB patients are also costly and usually unbearable by most patients of developing and resource-constrained countries. Taken together, there is a pressing need to develop new and innovative therapeutic approaches for CHB patients. Immune therapy seems to be an alternate therapeutic approach for CHB patients because impaired or distorted or diminished immune responses have been detected in most of these patients. Also, investigators have shown that restoration or induction of proper types of immune responses may have therapeutic implications in CHB. Various immunomodulatory agents have been used to treat patients with CHB around the world and the outcomes of these clinical trials show that the properties of immune modulators and nature and designing of immune therapeutic regimens seem to be highly relevant in the context of treatment of CHB patients. In this review, the general properties and specific features of immune therapy for CHB have been discussed for developing the guidelines of effective regimens of immune therapy for CHB.

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.

Circumventing failed antiviral immunity in chronic hepatitis B virus infection: triggering virus-specific or innate-like T cell response?

Therapeutic vaccination for the treatment of chronic hepatitis B has thus far been unsatisfactory. In this review, we discuss potential new therapeutic vaccination strategies and other immunotherapeutic approaches that aim to achieve efficient restoration of HBV immunity in chronically infected patients.

Designing immune therapy for chronic hepatitis B

Presently-available antiviral drugs may not be a satisfactory option for treatment of patients with chronic hepatitis B (CHB). In spite of presence of several antiviral drugs, sustained off-treatment clinical responses are not common in CHB patients treated with antiviral drugs. In addition, antiviral drug treatment may have limited effects on blocking the progression of HBV-related complications. However, substantial long-term risk of viral resistance and drug toxicity are related with maintenance antiviral therapy in CHB patients with presently-available antiviral agents. The infinite treatments with antiviral drugs for CHB patients are also costly and may be unbearable by most patients of developing and resource-constrained countries. In this situation, there is pressing need to develop new and innovative therapeutic approaches for patients with chronic hepatitis B virus (HBV) infection. Immune therapy has emerged as an alternate therapeutic approach for CHB patients because studies have shown that host immunity is either impaired or derailed or distorted or diminished in CHB patients compared to patients with acute resolved hepatitis B who contain the HBV replication and control liver damages. Both non antigen-specific immune modulators and HBV antigen-specific agents have been used in CHB patients during last three decades. However, similar to antiviral therapy, the ongoing regimens of immune therapeutic approaches have also been unable to show real promises for treating CHB patients. The concept of immune therapy for treating CHB patients seems to be rationale and scientific, however, concerns remain about suitable designs of immune therapy for CHB patients.

Immunotherapy for Chronic Hepatitis B using HBsAg-based Vaccine Formulations: From Preventive Commercial Vaccines to Therapeutic Approach Julio Cesar Aguilar

Despite the existence of effective prophylactic vaccines, hepatitis B virus (HBV) infections remain a major public health problem. It has been estimated that about 370 million people are chronically infected with this virus worldwide. These individuals act as a reservoir for viral spread and chronic infection also increases the risk of liver diseases, such as cirrhosis and hepatocellular carcinoma. Current antiviral therapies fail to control viral replication in the long term in most patients. Viral persistence has been associated with a defect in the development of HBV-specific cellular immunity. The limitations of the current available therapies underline the need for alternative therapies. Specific immunotherapeutic strategies target not only the induction or stimulation of CD4(+) and CD8(+) T-cell responses but also the induction of proinflammatory cytokines capable of controlling viral replication. Therapeutic vaccination has been extensively studied in chronic hepatitis B (CHB) based in the properties of hepatitis B surface antigen (HBsAg) and taking advantage of its previous use in preventive vaccination. In this sense, pioneer studies were carried out employing HBsAg-based vaccines, including prophylactic commercial vaccines and HBsAg-based formulations with novel adjuvants. The results and general knowledge coming from these studies are discussed in the present review. The decision on developing new generations of vaccines including new antigens or formulations should take into account the experience with HBsAg-based vaccine formulations in order to decide about changing the vaccine antigen or adding new antigens to improve the composition. How to cite this article: Aguilar JC, Lobaina Y. Immunotherapy for Chronic Hepatitis B using HBsAg-based Vaccine Formulations: From Preventive Commercial Vaccines to Therapeutic Approach. Euroasian J Hepato-Gastroenterol 2014;4(2):92-97.

New therapeutic vaccination strategies for the treatment of chronic hepatitis B

Chronic hepatitis B virus (CHB) is currently treated with either interferon-based or nucleot(s)ide-based antiviral therapies. However, treatment with pegylated interferon alpha results in a durable antiviral response in only about 30% patients and is associated with side effects. Most patients receiving nucleot(s)ide analogue treatment do not establish long-term, durable control of infection and have rebounding viremia after cessation of therapy. Thus, novel therapy strategies are necessary to achieve the induction of potent and durable antiviral immune responses of the patients which can maintain long-term control of viral replication. Therapeutic vaccination of HBV carriers is a promising strategy for the control of hepatitis B. Here the authors review new therapeutic vaccination strategies to treat chronic hepatitis B which may be introduced for patient treatment in the future.

Combination of DNA prime--adenovirus boost immunization with entecavir elicits sustained control of chronic hepatitis B in the woodchuck model

A potent therapeutic T-cell vaccine may be an alternative treatment of chronic hepatitis B virus (HBV) infection. Previously, we developed a DNA prime-adenovirus (AdV) boost vaccination protocol that could elicit strong and specific CD8⁺ T-cell responses to woodchuck hepatitis virus (WHV) core antigen (WHcAg) in mice. In the present study, we first examined whether this new prime-boost immunization could induce WHcAg-specific T-cell responses and effectively control WHV replication in the WHV-transgenic mouse model. Secondly, we evaluated the therapeutic effect of this new vaccination strategy in chronically WHV-infected woodchucks in combination with a potent antiviral treatment. Immunization of WHV-transgenic mice by DNA prime-AdV boost regimen elicited potent and functional WHcAg-specific CD8⁺ T-cell response that consequently resulted in the reduction of the WHV load below the detection limit in more than 70% of animals. The combination therapy of entecavir (ETV) treatment and DNA prime-AdV boost immunization in chronic WHV carriers resulted in WHsAg- and WHcAg-specific CD4⁺ and CD8⁺ T-cell responses, which were not detectable in ETV-only treated controls. Woodchucks receiving the combination therapy showed a prolonged suppression of WHV replication and lower WHsAg levels compared to controls. Moreover, two of four immunized carriers remained WHV negative after the end of ETV treatment and developed anti-WHs antibodies. These results demonstrate that the combined antiviral and vaccination approach efficiently elicited sustained immunological control of chronic hepadnaviral infection in woodchucks and may be a new promising therapeutic strategy in patients.

Chronic hepatitis B virus (HBV) infection is one of the major causes of liver cirrhosis and liver cancer worldwide. Recommended treatment regimens of chronic hepatitis B based on interferon alpha and nucleot(s)ide analogues do not lead to the satisfactory results. Over the last 20 years, continuous efforts have been undertaken to develop new immunotherapeutic approaches for the treatment of chronic hepatitis B, however, without satisfactory results. We proposed here that the combination of potent antivirals with a prime-boost vaccination protocol that is inducing appropriate virus-specific T-cell responses may restore immune control over HBV. To test this hypothesis we performed a proof-of-principle experiment using woodchucks, a widely accepted animal model of chronic HBV infection. We pretreated animals with entecavir to suppress viral replication and immunized them by a prime-boost regimen with DNA vaccines expressing woodchuck hepatitis virus (WHV) surface and core antigens and adenoviral vectors expressing WHV core antigen. Consistent with our hypothesis, the combination therapy achieved a stronger antiviral effect than the monotherapy alone, leading to sustained immunological control of chronic WHV infection and viral clearance in some animals. These data are encouraging and implicate the feasibility and usefulness of the immunotherapeutic strategies for the treatment of chronically HBV-infected patients.

Non-antigen-specific and antigen-specific immune therapies for chronic hepatitis B: evidences from laboratory benches and patient's bedsides

INTRODUCTION

Due to unsatisfactory therapeutic efficacy and considerable side effects of antiviral drugs in patients with chronic hepatitis B (CHB), immunotherapy has emerged as an alternative approach. CHB immunotherapy may be categorized into two main types: i) non-antigen-specific immune therapy and ii) hepatitis B virus (HBV) antigen-specific immune therapy. Although different immune modulators have been used in CHB patients for the last two to three decades, the nature and design of ongoing regimens of immunotherapeutic approaches need considerable modifications.

AREAS COVERED

In this review, the authors have outlined the relevant immunotherapies for CHB patients that have been used for the last two to three decades. The mechanisms underlying the limited therapeutic efficacy of available therapeutic agents for CHB patients have been discussed to aid in the development of an effective therapeutic approach for these patients.

EXPERT OPINION

Circumstantial evidence indicates that a better regimen of immunotherapy may be developed using different HBV-related antigens or combinations of two or more HBV-related antigens, or combinations of HBV-related antigens and antiviral drugs. However, the capacity of 'inducible immunity' by immune modulators to cure or block progression of liver diseases in CHB patients needs to be addressed.

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.

T cell immunopathogenesis and immunotherapeutic strategies for chronic hepatitis B virus infection

Hepatitis B is caused by the host immune response and T cells play a major role in the immunopathogenesis. More importantly, T cells not only destroy hepatocytes infected by hepatitis B virus (HBV), but also control HBV replication or eradicate HBV in a noncytolytic manner. Therefore, analysis of T cell immune response during acute and chronic HBV infection is important to develop a strategy for successful viral control, which could lead to immunotherapy for terminating persistent HBV infection. There have been many attempts at immunotherapy for chronic HBV infection, and some have shown promising results. High viral load has been shown to suppress antiviral immune responses and immunoinhibitory signals have been recently elucidated, therefore, viral suppression by nucleos(t)ide analogs, stimulation of antiviral immune response, and suppression of the immunoinhibitory signals must be combined to achieve desirable antiviral effects.

Design of therapeutic vaccines: hepatitis B as an example

Therapeutic vaccines are currently developed for chronic viral infections, such as human papillomavirus (HPV), human immunodeficiency virus (HIV), herpesvirus and hepatitis B (HBV) and C (HCV) virus infections. As an alternative to antiviral treatment or to support only partially effective therapy a therapeutic vaccine shall activate the patient's immune system to fight and finally control or ideally even eliminate the virus. Whereas the success of prophylactic vaccination is based on rapid neutralization of the invading pathogen by antibodies, virus control and elimination of infected cells require T cells. Therefore, induction of a multi-specific and multifunctional T-cell response against key viral antigens is a paradigm of therapeutic vaccination--besides activation of a humoral immune response to limit virus spread. In this review, we describe options to develop a therapeutic vaccine for chronic viral infections using HBV as a promising example.

Toll-like receptors signaling contributes to immunopathogenesis of HBV infection

Innate and adaptive immune systems have important role in the pathogenesis of acute and chronic infection with hepatitis B virus (HBV). These immune responses are mediated through complex interactions between the innate immune response and adaptive immune response. Toll-like receptors (TLRs) are a family of innate immune-recognition receptors that recognize the molecular patterns associated with microbial pathogens. So far, TLR1 to 13 were found in human or mice and investigated to detect the target molecules and the downstream mechanisms of these unique systems. Stimulation by their ligands initiates the activation of complex networks of intracellular signaling transduction and innate and adaptive immune-related cells (NK, NK-T, monocytes, dendritic cells, T cells, B cells, and Tregs, etc.). However, reports on such relationships between HBV and TLRs have been relatively rare in comparison to those on HCV and TLRs, but have recently been increasing. Thus, a review of TLRs involved in the pathogenesis of HBV infection may be needed toward better understanding of the immunopathogenesis of HBV infection.

Ubiquitin conjugation of hepatitis B virus core antigen DNA vaccine leads to enhanced cell-mediated immune response in BALB/c mice

BACKGROUND

Nearly 350 million persons worldwide are chronically infected with hepatitis B virus (HBV). Ubiquitin (Ub) is a highly conserved small regulatory protein, ubiquitous in eukaryotes, that usually serves as a signal for the target protein that is recognised and degraded in proteasomes . The Ub-mediated processing of antigens is rapid and efficient and stimulates cell-mediated immune responses. Accordingly, Ub-mediated processing of antigens has been widely used in chronic-infection and cancer studies to improve immune response.

OBJECTIVES

Many clinical trials have shown that DNA vaccine potency needs to be greatly enhanced. Here, we report a new strategy for designing an HBV DNA vaccine using the ubiquitin (Ub) sequence. The aim of this study was to investigate a novel DNA vaccination, based on the expression of HBV core antigen (HBcAg), fused to Ub to enhance DNA vaccine potency.

MATERIALS AND METHODS

Mouse ubiquitin fused to the HBcAg gene and cloned into the eukaryotic vector pcDNA3.1 (-). BALB/c mice were immunized with recombinant pUb-HBcAg or pHBcAg DNA vaccine. Lymphocyte proliferation assay, intracellular IFN-γ assay, CTL cytotoxicity assay, and antibody assay were performed to analyze the cellular and humoral immune responses to our DNA constructs.

RESULTS

HBcAg was expressed effectively in the COS-7 cells that were transiently transfected with pUb-HBcAg. Strong anti-HBc IgG responses were elicited in mice that were immunized with pUb-HBcAg. The endpoint titers of anti-HBc peaked at 1:656100 on the 42nd day after the third immunization. pUb-HBcAg stimulated greater lymphocyte proliferation and induced higher levels of IL-2 and IFN-γ and a greater percentage of HBcAg-specific CD8+ T cells in mice than pHBcAg. In the CTL assay, the specific lysis rate reached 56.5% at an effector:target ratio of 50:1 in mice that were immunized with pUb-HBcAg.

CONCLUSIONS

pUb-HBcAg elicits specific anti-HBc responses and induces HBc-specific CTL responses in immunized BALB/c mice. Our results imply that Ub can be used as a molecular adjuvant that enhances the potency of DNA vaccines.

Therapeutic vaccines and immune-based therapies for the treatment of chronic hepatitis B: perspectives and challenges

The treatment of chronic hepatitis B virus (HBV) infection has greatly improved over the last 10 years, but alternative treatments are still needed. Therapeutic vaccination is a promising new strategy for controlling chronic infection. However, this approach has not been as successful as initially anticipated for chronic hepatitis B. General impairment of the immune responses generated during persistent HBV infection, with exhausted T cells not responding correctly to therapeutic vaccination, is probably responsible for the poor clinical responses observed to date. Intensive research efforts are now focusing on increasing the efficacy of therapeutic vaccination without causing liver disease. Here we describe new approaches to use with therapeutic vaccination, in order to overcome the inhibitory mechanisms impairing immune responses. We also describe innovative strategies for generating functional immune responses and inducing sustained control of this persistent infection.

Partially randomized, non-blinded trial of DNA and MVA therapeutic vaccines based on hepatitis B virus surface protein for chronic HBV infection

BACKGROUND

Chronic HBV infects 350 million people causing cancer and liver failure. We aimed to assess the safety and efficacy of plasmid DNA (pSG2.HBs) vaccine, followed by recombinant modified vaccinia virus Ankara (MVA.HBs), encoding the surface antigen of HBV as therapy for chronic HBV. A secondary goal was to characterize the immune responses.

METHODS

Firstly 32 HBV e antigen negative (eAg(-)) participants were randomly assigned to one of four groups: to receive vaccines alone, lamivudine (3TC) alone, both, or neither. Later 16 eAg(+) volunteers in two groups received either 3TC alone or both 3TC and vaccines. Finally, 12 eAg(-) and 12 eAg(+) subjects were enrolled into higher-dose treatment groups. Healthy but chronically HBV-infected males between the ages of 15-25 who lived in the western part of The Gambia were eligible. Participants in some groups received 1 mg or 2 mg of pSG2.HBs intramuscularly twice followed by 5×10(7) pfu or 1.5×10(8) pfu of MVA.HBs intradermally at 3-weekly intervals with or without concomitant 3TC for 11-14 weeks. Intradermal rabies vaccine was administered to a negative control group. Safety was assessed clinically and biochemically. The primary measure of efficacy was a quantitative PCR assay of plasma HBV. Immunity was assessed by IFN-γ ELISpot and intracellular cytokine staining.

RESULTS

Mild local and systemic adverse events were observed following the vaccines. A small shiny scar was observed in some cases after MVA.HBs. There were no significant changes in AST or ALT. HBeAg was lost in one participant in the higher-dose group. As expected, the 3TC therapy reduced viraemia levels during therapy, but the prime-boost vaccine regimen did not reduce the viraemia. The immune responses were variable. The majority of IFN-γ was made by antigen non-specific CD16(+) cells (both CD3(+) and CD3(-)).

CONCLUSIONS

The vaccines were well tolerated but did not control HBV infection.

TRIAL REGISTRATION

ISRCTN ISRCTN67270384.

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.

[Treatment of hepatitis B: new perspectives]

Despite the development of new anitiviral agents, the treatment of chronic hepatitis B remains a major clinical challenge. Major achievements have been made with the rationale use of antivirals exhibiting a complementary cross resistance profile to prevent antiviral drug resistance. The current concept of modern antiviral therapy of chronic hepatitis B relies on a precise virologic monitoring and early treatment adaptation to prevent drug resistance. The difficulty of achieving viral clearance and the risk of drug resistance development are major arguments to continue research in the field of antivirals and to identify new targets for therapy. The development of true combination therapy is highly desirable to fulfil the objective of long-term viral suppression, clearance of viral cccDNA and infected cells and ultimately cure of the disease.

Immunopathogenesis of hepatitis B persistent infection: implications for immunotherapeutic strategies

It has been shown that cellular immunity, especially by cytotoxic T lymphocytes (CTLs), NK cells and NK-T cells, plays a central role in the control of virus infection. In addition, CD4+ T cells facilitate both CTL and B-cell responses. Hyporesponsiveness of HBV-specific T cells in peripheral blood has been shown in patients with chronic HBV infection. Interferon and nucleos(t)ide analogs, such as lamivudine, adefovir, entecavir and tenofovir, are the currently available treatments. Unfortunately, the efficacy of nucleos(t)ide analogs is limited by viral reactivation by the emergence of escaped mutants in cases of prolonged treatment. Therefore, immunotherapy is one of the significant options to eradicate or control HBV replication without drugs. The aim of immunotherapies is to decrease the levels of viral replication and to eradicate infected hepatocytes. For this reason, new strategies for immunotherapies by vaccination target not only the induction or stimulation of CD4+ and CD8+ T cell responses, but also the induction of proinflammatory cytokines capable of controlling viral replication. We will review the immunopathogenesis of persistent HBV infection, especially focusing on the mechanisms of immune suppression. Then we will review the immunotherapy for HBV persistent infection.

Inhibition of woodchuck hepatitis virus gene expression in primary hepatocytes by siRNA enhances the cellular gene expression

Small interfering RNA (siRNA) has been shown to be active to inhibit the hepatitis B virus gene expression and replication in transient and stable transfection systems. Here in primary hepatocytes prepared from naturally woodchuck hepatitis virus (WHV)-infected woodchucks, four siRNAs targeting the WHV preS1, S, C, and X region led to a depletion of WHV transcripts and replicative intermediates with different kinetics and a decreased production of viral particles. Two siRNAs targeting WHV S and X region had the highest efficacy to deplete 70% of WHV transcripts and replicative intermediates. In addition, siRNA-mediated suppression of WHV enhanced the expression of cellular genes like MxA and MHC I. Specific siRNAs are able to inhibit the hepadnaviral replication and enhance the expression of cellular genes relevant for antiviral actions. Thus, siRNAs might be useful as novel antiviral agents for the treatment of chronic HBV infection.

Therapeutic vaccination of chronic hepatitis B patients with virus suppression by antiviral therapy: a randomized, controlled study of co-administration of HBsAg/AS02 candidate vaccine and lamivudine

Induction of curative immune responses by therapeutic vaccination in chronic viral infections such as chronic hepatitis B (CHB) is expected to be facilitated by reduction of viral load by antiviral treatment. In this open label, controlled, randomized study, 195 patients with HBeAg positive CHB were randomized to receive 12 doses of HBsAg with AS02B adjuvant candidate vaccine plus lamivudine daily for 52 weeks or lamivudine daily alone. The combined administration of vaccine and lamivudine was safe and well tolerated, but did not improve the HBe seroconversion rate (18.8%) when compared to treatment with lamivudine alone (16.1%) (p=0.6824). Despite induction of a vigorous HBsAg-specific lymphoproliferative response, cytokine production and anti-HBs antibodies, therapeutic vaccination with an adjuvanted HBsAg vaccine administered concomitantly with lamivudine did not demonstrate superior clinical efficacy in HBeAg positive CHB patients as compared to lamivudine therapy alone.

Failure of hepatitis B vaccination with conventional HBsAg vaccine in patients with continuous HBIG prophylaxis after liver transplantation

Hepatitis B vaccination after liver transplantation for hepatitis B-related liver disease has been investigated as an alternative strategy to reinfection prophylaxis with hepatitis B immunoglobulin (HBIG) with conflicting results. In most studies, HBIG treatment was discontinued before vaccination. An outstanding good response was achieved with vaccination under continuous HBIG administration using hepatitis B surface antigen (HBsAg)-based vaccine containing special adjuvants. Both, adjuvants and continuous HBIG administration have been discussed as crucial factors for good response. Twenty-four patients were vaccinated with conventional double dose recombinant vaccine containing 40 microg HBsAg up to 12 times at weeks 0, 2, 4 (cycle 1), 12, 14, 16 (cycle 2), 24, 26, 28 (cycle 3), and 36, 38, 40 (cycle 4). All patients received 2,000 IU HBIG every 6 weeks (4 times intravenously and 4 times intramuscularly). A significant response was defined as reconfirmed increase of anti-HBs-antigen (anti-HBs) unexplained by HBIG administration or lack of anti-HBs decrease below 100 IU/L after discontinuation of HBIG treatment after week 48. Only 2 of 24 patients (8.3%) responded significantly. Anti-HBs started to increase after the seventh vaccination (cycle 3, during intramuscular HBIG administration) in 1 patient and after 12th vaccination (cycle 4, during intravenous HBIG administration) in the other. Maximum anti-HBs levels were >1,000 IU/L in both patients and decreased significantly slower as compared to passive prophylaxis during follow-up. In conclusion, the conventional HBsAg vaccine failed to induce a significant humoral immune response in most patients despite continued HBIG treatment. Further studies should address the question, of whether the use of potent adjuvant systems results in higher response rates.

Therapeutic vaccination in chronic hepatitis B virus carriers

Despite effective prophylactic vaccines against hepatitis B virus existing for over 20 years, more than 2.5 billion people worldwide have been exposed to the disease and approximately 370 million people are chronically infected with it. Chronic infection in more than two thirds of infected patients results in chronic liver disease, which may lead to cirrhosis, exposure to noncarcinomatous complications and hepatocellular carcinoma. Currently available therapies fail to allow complete control of viral replication in most patients. Viral persistence has been associated with a defect in the development of hepatitis B virus-specific cellular immunity. Immunomodulatory strategies to boost or to broaden the weak virus-specific T-cell response have been proposed to bypass the chronic hepatitis B infection, including hepatitis B virus envelope- and nucleocapsid-based vaccines, and new formulations for recombinant and DNA-based vaccines, which are currently being evaluated in clinical trials.

Potential effect of specific immunotherapy on chronic hepatitis B of vertical maternal-fetal transmission: an analysis of 23 cases

AIM: To study the efficacy of specific immuno-therapy in the treatment of patients with chronic hepatitis B (CHB) of vertical maternal-fetal transmission.

METHODS: HBsAg vaccine-loaded dendritic cells (DC, 10⁶) and HBIg (200 U) were injected respectively into 23 patients with CHB of vertical transmission. Six months were considered as one course, and there were two courses in total. At the end of treatment, liver function, HBV DNA level and HBV markers in the patients were measured.

RESULTS: Of the 9 patients with HBeAg(+) CHB, 1 case showed a complete response, and 7 showed partial responses. Of the 4 patients with HBeAg(-) CHB, partial responses occurred in 2 cases. No responses were observed in the 5 chronic HBV carriers. Of the 5 inactive HBsAg carriers, 1 case showed a complete response, while the rest showed no responses.

CONCLUSION: The specific immunotherapy is effective in the treatment of CHB transmitted from the mothers.

Efficacy of HBsAg vaccine-pulsed dendritic cells combined with hepatitis B immunoglobulin in treatment of chronic hepatitis B patients and hepatitis B virus carriers

AIM: To investigate the potential effect of HBsAg vaccine-pulsed dendritic cells (DC) combined with hepatitis B immunoglobulin (HBIg) on chronic hepatitis B (CHB) patients and hepatitis B virus (HBV) carriers.

METHODS: HBsAg vaccine-pulsed DC (10⁶) and HBIg (200 U) were injected into 66 CHB patients once a month, respectively. Six months were considered as one course, and there were two courses in total. At the end of treatment, liver function, HBV DNA level and HBV markers in the patients were measured.

RESULTS: Of the 27 patients with HBeAg(+) CHB, 7 showed complete responses, and 14 showed partial responses. Of the 15 patients with HBeAg(-) CHB, complete responses were observed in 4 patients, and partial responses were observed in 8 cases. Of the 13 chronic HBV carriers, complete responses occurred in 5 cases, and partial responses occurred in 2 cases. Of the 11 inactive HBsAg carriers, 2 cases showed complete responses.

CONCLUSION: HBsAg vaccine-pulsed DC with HBIg is effective in the treatment of CHB patients and HBV carriers.

Therapeutic vaccination against chronic hepatitis B virus infection

Chronic liver disease and hepatocellular carcinoma due to chronic hepatitis B virus (HBV) infection pose a major public health problem in highly endemic regions. Effective vaccines against HBV exist but more than 370 million people remain chronically infected with HBV For these patients there is a high risk to develop cirrhosis and hepatocellular carcinoma. Currently available therapies fail to control viral replication in the long term in most patients. Viral persistence has been associated with a defect in the development of HBV specific cellular immunity. Strategies to boost or to broaden the weak virus-specific T-cell response of patients with chronic hepatitis B have been proposed as a means of curing this persistent infection. HBV envelope- and nucleocapsid-based vaccines, new formulations for recombinant vaccines and DNA-based vaccines are currently being assessed in clinical trials. Improvements are clearly required, but vaccination is likely to be the cheapest and potentially most beneficial treatment.

Clinical safety and efficacy of a powdered Hepatitis B nucleic acid vaccine delivered to the epidermis by a commercial prototype device

This clinical delivery system bridging study evaluated the performance of a single-use disposable, commercial prototype device (designated ND 5.5) for particle-mediated epidermal delivery (PMED) of a nucleic acid vaccine against Hepatitis B virus (HBV). Healthy adults, previously immunized with licensed HBV vaccine, received a single boost vaccination of HBV nucleic acid vaccine administered by ND 5.5 or XR-1, the clinical research device used in previous clinical trials. Similar increases in anti-HBV surface antigen serum antibody titers and cell-mediated immune responses were produced by ND 5.5 and XR-1 when delivering comparable effective doses of the vaccine. The overall intensity of the immune response was lower in those subjects vaccinated with two, rather than 4 administrations of vaccine delivered by ND 5.5. Skin reactions at sites of vaccine administration were equivalent with both devices. This is the first clinical demonstration of the safe and effective PMED of a nucleic acid vaccine with the ND 5.5 device.

Protective efficacy, immunotherapeutic potential, and safety of hepatitis B vaccines

Hepatitis B vaccines are highly effective and safe and have been incorporated into national immunization programs in over 150 countries. The major humoral immune response is to the common a determinant of the surface antigen protein of the virus. Approximately 5-10% of healthy immunocompetent subjects do not mount an antibody response (anti-HBs). Non-response is associated with different HLA-DR alleles and impaired Th cell response, among other factors such as route of injection, age, gender, body mass, and other factors. Important hepatitis B surface antigen variants have also been identified, which may have a potential impact on immunization and routine screening of blood, blood products and tissues, and organs for transplantation. Strategies for hepatitis B immunization are reviewed. Over 1,000 million doses of hepatitis B vaccine have been used with an outstanding record of safety. There is no evidence of an association between hepatitis B vaccines and the sudden infant death syndrome, chronic fatigue syndrome, and multiple sclerosis (MS). Several studies are in progress on treatment of chronic hepatitis B infection by immunization with multiple antigenic components, combination of vaccine with antiviral drugs and cytokines, T cell vaccines, DNA vaccines alone or with DNA encoded immunomodulatory cytokines, and direct genetic manipulation of antigen presenting cells.

Immunomodulatory therapy for chronic hepatitis B virus infection

Hepatitis B virus (HBV) is one of the most prevalent viral pathogens of man with around 350 million chronically infected patients. It has been postulated that in persistently infected individuals the HBV-specific immune response is too weak to eliminate HBV from all infected hepatocytes, but sufficiently strong to continuously destroy HBV-infected hepatocytes and to induce chronic inflammatory liver disease. The primary aim in the treatment of chronic hepatitis B is to induce sustained disease remission and prevent serious complications like liver failure and/or hepatocellular carcinoma. The recent emergence of drug-resistant HBV mutants and post-treatment relapse as a consequence of nucleoside analogue monotherapy emphasizes that the principal goal should be to stimulate a successful immune response. In this paper we will focus on the immune response to HBV and we will review reported data on immunotherapeutic strategies like immunomodulatory drugs (cytokines and Thymic derivates) and vaccine therapies using currently available recombinant anti-HBV vaccines, lipopeptide-based T cell vaccine and newly developed genetic vaccines.

Traitement des infections chroniques dues au virus de l’hépatite B par vaccination thérapeutique

Chronic liver disease and hepatocellular carcinoma associated with chronic hepatitis B virus (HBV) infection are among the most serious human health problems in highly endemic regions. Despite the existence for many years of effective vaccines against HBV, more than 370 million people remain persistently infected with HBV today. Currently available therapies fail to provide long-term control of viral replication in most patients. Viral persistence has been associated with a defect in the development of HBV-specific cell-mediated immunity. Strategies to boost or to broaden the weak virus-specific T-cell response of patients with chronic hepatitis B have been proposed as a means of terminating this persistent infection. The immunogenicity of HBV envelope- or capsid-based vaccines, new formulations for recombinant vaccines as well as DNA-based vaccines are currently under investigation in clinical trials. Although improvements are still required, vaccination would be the therapeutic procedure with the lowest cost and the potentially greatest benefit.

Emerging treatments in chronic hepatitis B

Although the management of chronic hepatitis B has improved over the last decade, none of the available therapeutic agents, IFN-alpha, lamivudine and adefovir dipivoxil, can achieve sustained off-therapy responses in most cases. Therefore, several newer, mainly antiviral and immunomodulatory agents, are being evaluated. Pegylated IFN-alpha(2a) has been shown to be more effective than lamivudine or standard IFN-alpha monotherapy in achieving post-therapy biochemical and virological responses, and is expected to be licensed soon for the treatment of chronic hepatitis B. Newer antiviral agents, such as entecavir and telbivudine, appear to be quite effective initially, but their sustained off-therapy response rates remain unknown. The preliminary data of monotherapies with immunomodulatory agents, or of combination therapies, have been rather disappointing. Long-term maintenance treatment with antiviral agent(s) with good safety and tolerability profiles and low resistance rates appears to be the most realistic future therapeutic option for most chronic hepatitis B patients.

ELISPOT cell rescue

The enzyme-linked immunospot (ELISPOT) assay is a highly sensitive and reproducible method for quantifying T cell-mediated immune responses, and has been used to measure antigen-specific responses post-vaccination. While there are several advantages of the ELISPOT assay for use in field settings for large-scale vaccination trials, blood draw volumes are often limited, and the number of antigen-specific responses that can be measured is constrained by the limited cell number. We reasoned that it should be possible to salvage and rescue viable cells from a completed ELISPOT assay post-incubation, to use for further experimentation. Here, we show that cells rescued from an ELISPOT plate after assay are viable, and may be used in a second cytokine-producing assay, in a proliferation assay, or to provide a source of DNA for genetic studies such as human leukocyte antigen (HLA) typing. Rescue of cells after an ELISPOT assay will be particularly useful for increasing sample utility and maximizing data collection from T cell assays in vaccine trials.

Therapeutic vaccines for chronic infections

Therapeutic vaccines aim to prevent severe complications of a chronic infection by reinforcing host defenses when some immune control, albeit insufficient, can already be demonstrated and when a conventional antimicrobial therapy either is not available or has limited efficacy. We focus on the rationale and challenges behind this still controversial strategy and provide examples from three major chronic infectious diseases- human immunodeficiency virus, hepatitis B virus, and human papillomavirus-for which the efficacy of therapeutic vaccines is currently being evaluated.

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.

HLA and cytokine gene polymorphisms are independently associated with responses to hepatitis B vaccination

Variable immune responses to hepatitis B virus (HBV) infection and recombinant HBV vaccines have been associated with polymorphisms in several genes within the human leukocyte antigen (HLA) complex. Analyses of polymerase chain reaction (PCR)-based genotyping data from 164 North American adolescents vaccinated with recombinant HBV products confirmed that HLA-DRB1*07 (relative odds [RO] = 5.18, P <.0001) and human immunodeficiency virus type 1 (HIV-1) infection (RO = 3.91, P <.001) were both associated with nonresponse to full-dose vaccination. Further associations were observed with single nucleotide polymorphisms (SNPs) at the IL2 and IL4 loci along with insertion/deletion variants at the IL12B locus (P =.003-.01). Host genetic associations were independent of one another as well as other HLA (A, B, C, and DQB1) and cytokine gene (IL4R, IL6, IL10, and TNF) variants. Statistical adjustments for nongenetic factors (gender, ethnicity, age, HIV-1 infection, and vaccination protocols) did not substantially alter the strengths of the genetic relationships. The overall distribution pattern of genetic variations was similar between the analyzed vaccinees and additional adolescents (n = 292) from the same cohort. In conclusion, DRB1*07 (or a closely linked allele) and immunoregulatory cytokine gene polymorphisms correlate with variable immune response to recombinant HBV vaccines.