Therapeutic vaccination against chronic hepatitis B virus infection

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.

Hepatitis B surface antigen (HBsAg) and core antigen (HBcAg) combine CpG oligodeoxynucletides as a novel therapeutic vaccine for chronic hepatitis B infection

Hepatitis B virus infection is a non-cytopathic hepatotropic virus which can lead to chronic liver disease and hepatocellular carcinoma. Traditional therapies fail to provide sustained control of viral replication and liver damage in most patients. As an alternative strategy, immunotherapeutic approaches have shown promising efficacy in the treatment of chronic hepatitis B patients. Here, we investigated the efficacy of a novel therapeutic vaccine formulation consisting of two HBV antigens, HBsAg and HBcAg, and CpG adjuvant. This vaccine formulation elicits forceful humoral responses directed against HBsAg/HBcAg, and promotes a Th1/Th2 balance response against HBsAg and a Th1-biased response against HBcAg in both C57BL/6 and HBV transgenic mice. Vigorous cellular immune response was also detected in HBV transgenic mice, for a significantly higher number of HBs/HBc-specific IFN-γ secreting CD4+ and CD8+ T cells was generated. Moreover, vaccinated mice elicited significantly intense in vivo CTL attack, reduced serum HBsAg level without causing liver damage in HBV transgenic mice. In summary, this study demonstrates a novel therapeutic vaccine with the potential to elicit vigorous humoral and cellular response, overcoming tolerance in HBV transgenic mice.

Enhanced immune response to hepatitis B vaccination through immunization with a Pre-S1/Pre-S2/S vaccine

Efficacy and safety of recombinant yeast-derived hepatitis B vaccines for prevention of hepatitis B have been demonstrated unequivocally worldwide as reflected in reduction in HBsAg carrier rates and hepatocellular carcinoma. A new generation of recombinant HBV vaccines expressed in mammalian cells containing Pre-S/S epitopes has been developed in several countries. Such vaccines are useful in special risk groups, i.e., in non-responders to conventional HBV vaccines including older adults, obese people, health care workers, patients with renal failure and on dialysis, transplant patients, patients with HIV as well as travelers on short notice to HBV endemic regions. The future of such vaccines depends on their enhanced immunogenicity and cost profile. Sci-B-Vac™ is a mammalian cell-derived recombinant Pre-S1/Pre-S2/S hepatitis B vaccine which has been shown to be highly immunogenic, inducing faster and higher seroprotection rates against HBV with higher anti-HBs levels at lower HBsAg doses as compared to conventional yeast-derived vaccines. Recently, it has been suggested that such Pre-S/S vaccines against HBV might be efficacious not only for prevention but also for intervention in persistent HBV infection. Data obtained in a recent clinical trial conducted in Vietnam in patients with chronic hepatitis B suggest that repeated monthly i.m. injections of the Sci-B-Vac™ co-administered with daily oral lamivudine treatment can suppress HBV replication and lead to anti-HBs seroconversion in ~50 % of treated patients. Optimization of protocols and efficacy of such an intervention, intended to bypass T cell exhaustion and immune tolerance to HBV remains to be explored.

Anti-HBV DNA vaccination does not prevent relapse after discontinuation of analogues in the treatment of chronic hepatitis B: a randomised trial--ANRS HB02 VAC-ADN

OBJECTIVE

The antiviral efficacy of nucleos(t)ide analogues whose main limitation is relapse after discontinuation requires long-term therapy. To overcome the risk of relapse and virological breakthrough during long-term therapy, we performed a phase I/II, open, prospective, multicentre trial using a HBV envelope-expressing DNA vaccine.

DESIGN

70 patients treated effectively with nucleos(t)ide analogues for a median of 3 years (HBV DNA <12 IU/mL for at least 12 months) were randomised into two groups: one received five intramuscular injections of vaccine (weeks 0, 8, 16, 40 and 44) and one did not receive the vaccine. Analogues were stopped after an additional 48 weeks of treatment in patients who maintained HBV DNA <12 IU/mL with no clinical progression and monthly HBV DNA for 6 months. The primary endpoint was defined as viral reactivation at week 72 (HBV DNA >120 IU/mL) or impossibility of stopping treatment at week 48.

RESULTS

Reactivation occurred in 97% of each group after a median 28 days without liver failure but with an HBV DNA <2000 IU/mL in 33%; 99% of adverse reactions were mild to moderate. Immune responses were evaluated by enzyme-linked immunosorbent spot and proliferation assays: there was no difference in the percentage of patients with interferon-γ secreting cells and a specific T-cell proliferation to HBcAg but not to HBsAg after reactivation in each group.

CONCLUSIONS

Although it is fairly well tolerated, the HBV DNA vaccine does not decrease the risk of relapse in HBV-treated patients or the rate of virological breakthrough, and does not restore the anti-HBV immune response despite effective viral suppression by analogues.

TRIAL REGISTRATION NUMBER

NCT00536627.

In vitro stimulation with HBV therapeutic vaccine candidate Nasvac activates B and T cells from chronic hepatitis B patients and healthy donors

Hepatitis B virus (HBV) chronic infections remain a considerable health problem worldwide. The standard therapies have demonstrated limited efficacy, side effects or need life-long treatments. Nowadays therapeutic vaccination is a promising option. Recently, we developed a new vaccine formulation called Nasvac, based on the combination of surface and core antigens from HBV. Clinical trials already performed showed good efficacy in virus control. However, the exact mode of action of Nasvac formulation remains unclear. So far the functional impairment of DCs during persistent HBV infection is a controversial issue. On the other hand, it is known that B cells may function as antigen presenting cells (APC) activating T cells. The hepatitis B core antigen contained in Nasvac vaccine is able to bind and activate a high frequency of naive human B cells. In the present study the surface expression of activation and exhaustion markers on B cells and the subsequent activation of T cells after in vitro stimulation with Nasvac antigens were evaluated in chronic HBV patients and healthy donors. B- and T-cell phenotype and proliferation were assessed by flow cytometry. Our results indicate that in contrast to exhaustions markers B cell activation markers were increased on both study groups after Nasvac stimulation. A shift toward an activation phenotype was observed for both B and T cells. The present work suggests that B cells could act as efficient APCs for Nasvac antigens in humans, which might suggest the use of activated B cells as immunotherapeutic strategy for chronic hepatitis B.

Results of a phase III clinical trial with an HBsAg-HBIG immunogenic complex therapeutic vaccine for chronic hepatitis B patients: experiences and findings

BACKGROUND & AIMS

Even though various experimental therapeutic approaches for chronic hepatitis B infection have been reported, few of them have been verified by clinical trials. We have developed an antigen-antibody (HBsAg-HBIG) immunogenic complex therapeutic vaccine candidate with alum as adjuvant (YIC), aimed at breaking immune tolerance to HBV by modulating viral antigen processing and presentation. A double-blind, placebo-controlled, phase II B clinical trial of YIC has been reported previously, and herein we present the results of the phase III clinical trial of 450 patients.

METHODS

Twelve doses of either YIC or alum alone as placebo were administered randomly to 450 CHB patients and they were followed for 24weeks after the completion of immunization. The primary end point was HBeAg seroconversion, and the secondary end points were decrease in viral load, improvement of liver function, and histology.

RESULTS

In contrast to the previous phase II B trial using six doses of YIC and alum as placebo, six more injections of YIC or alum resulted in a decrease of the HBeAg seroconversion rate from 21.8% to 14.0% in the YIC group, but an increase from 9% to 21.9% in the alum group. Decrease in serum HBV DNA and normalization of liver function were similar in both groups (p>0.05).

CONCLUSIONS

Overstimulation with YIC did not increase but decreased its efficacy due to immune fatigue in hosts. An appropriate immunization protocol should be explored and is crucial for therapeutic vaccination. Multiple injections of alum alone could have stimulated potent inflammatory and innate immune responses contributing to its therapeutic efficacy, and needs further investigation.

HBsAg, HBcAg, and combined HBsAg/HBcAg-based therapeutic vaccines in treating chronic hepatitis B virus infection

BACKGROUND

As the host immunity is diminished in patients with chronic hepatitis B (CHB), different approaches have been used to up-regulate their immune responses to produce therapeutic effects. But, cytokines, growth factors and polyclonal immune modulators could not exhibit sufficient therapeutic effects in these patients. Immune therapy with HBV-related antigens (vaccine therapy) has been used in CHB patients. But there is a paucity of information about the design of HBV antigen-based immune therapy in these patients.

DATA SOURCE

Preclinical and clinical studies on immune therapy with HBsAg-based vaccine, HBcAg and combination of HBsAg/HBcAg-based vaccines have been discussed.

RESULTS

HBsAg-based prophylactic vaccine was used as an immune therapeutic agent in CHB patients; however, monotherapy with HBsAg-based immune therapy could not lead to sustained control of HBV replication and/or liver damages. HBsAg-based vaccine was used as a combination therapy with cytokines, growth factors, and antiviral drugs. HBsAg-based vaccine was also used for cell-based therapy. However, satisfactory therapeutic effects of HBsAg-based vaccine could not be documented in CHB patients. In the mean time, evidences have supported that HBcAg-specific immunity is endowed with antiviral and liver protecting capacities in CHB patients. Recent data concentrate on the clinical use of combined HBsAg- and HBcAg-based vaccines in CHB patients.

CONCLUSION

Antigen-based immune therapy with HBV-related antigens may be an alternative method for the treatment of CHB patients but proper designs of antigens, types of adjuvants, dose of vaccinations, and routes of administration need further analyses for the development of an effective regimen of immune therapy against HBV.

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.

Hepatitis B surface antigen could contribute to the immunopathogenesis of hepatitis B virus infection

Various findings concerning the clinical significance of quantitative changes in hepatitis B surface antigen (HBsAg) during the acute and chronic phase of hepatitis B virus (HBV) infection have been reported. In addition to being a biomarker of HBV-replication activity, it has been reported that HBsAg could contribute to the immunopathogenesis of HBV persistent infection. Moreover, HBsAg could become an attractive target for immune therapy, since the cellular and humeral immune response against HBsAg might be able to control the HBV replication and life cycle. However, several reports have described the immune suppressive function of HBsAg. HBsAg might suppress monocytes, dendritic cells (DCs), natural killer (NK), and natural killer T (NK-T) cells by direct interaction. On the other hand, cytotoxic T lymphocytes (CTLs) and helper T (Th) cells were exhausted by high amounts of HBsAg. In this paper, we focused on the immunological aspects of HBsAg, since better understanding of the interaction between HBsAg and immune cells could contribute to the development of an immune therapy as well as a biomarker of the state of HBV persistent infection.

Synthetic DNA immunogen encoding hepatitis B core antigen drives immune response in liver

The prevalence of hepatitis B virus (HBV) infection in Asia and sub-Sahara Africa is alarming. With quarter of a billion people chronically infected worldwide and at risk of developing liver cancer, the need for a prophylactic or therapeutic vaccination approach that can effectively induce protective responses against the different genotypes of HBV is more important than ever. Such a strategy will require both the induction of a strong antigen-specific immune response and the subsequent deployment of immune response towards the liver. Here, we assessed the ability of a synthetic DNA vaccine encoding a recombinant consensus plasmid from genotype A through E of the HBV core antigen (HBcAg), to drive immunity in the liver. Intramuscular vaccination induced both strong antigen-specific T cell and high titer antibody responses systematically and in the liver. Furthermore, immunized mice showed strong cytotoxic responses that eliminate adoptively transferred HBV-coated target cells. Importantly, vaccine-induced immune responses provided protection from HBcAg plasmid-based liver transfection in a hydrodynamic liver transfection model. These data provide important insight into the generation of peripheral immune responses that are recruited to the liver-an approach that can be beneficial in the search for vaccines or immune-therapies to liver disease.

DNA immunization with fusion of CTLA-4 to hepatitis B virus (HBV) core protein enhanced Th2 type responses and cleared HBV with an accelerated kinetic

Background

Typically, DNA immunization via the intramuscular route induces specific, Th1-dominant immune responses. However, plasmids expressing viral proteins fused to cytotoxic T lymphocyte antigen 4 (CTLA-4) primed Th2-biased responses and were able to induced effective protection against viral challenge in the woodchuck model. Thus, we addressed the question in the mouse model how the Th1/Th2 bias of primed immune responses by a DNA vaccine influences hepatitis B virus (HBV) clearance.

Principal Findings

Plasmids expressing HBV core protein (HBcAg) or HBV e antigen and HBcAg fused to the extracellular domain of CTLA-4 (pCTLA-4-HBc), CD27, and full length CD40L were constructed. Immunizations of these DNA plasmids induced HBcAg-specific antibody and cytotoxic T-cell responses in mice, but with different characteristics regarding the titers and subtypes of specific antibodies and intensity of T-cell responses. The plasmid pHBc expressing HBcAg induced an IgG2a-dominant response while immunizations of pCTLA-4-HBc induced a balanced IgG1/IgG2a response. To assess the protective values of the immune responses of different characteristics, mice were pre-immunized with pCTLA-4-HBc and pHBc, and challenged by hydrodynamic injection (HI) of pAAV/HBV1.2. HBV surface antigen (HBsAg) and DNA in peripheral blood and HBcAg in liver tissue were cleared with significantly accelerated kinetics in both groups. The clearance of HBsAg was completed within 16 days in immunized mice while more than 50% of the control mice are still positive for HBsAg on day 22. Stronger HBcAg-specific T-cell responses were primed by pHBc correlating with a more rapid decline of HBcAg expression in liver tissue, while anti-HBs antibody response developed rapidly in the mice immunized with pCTLA-4-HBc, indicating that the Th1/Th2 bias of vaccine-primed immune responses influences the mode of viral clearance.

Conclusion

Viral clearance could be efficiently achieved by Th1/Th2-balanced immune response, with a small but significant shift in T-cell and B-cell immune responses.

Kinetics of immune responses to hepatitis B virus infection

The pathogenesis of hepatitis B is mainly triggered by the host's cellular immune responses to hepatitis B virus (HBV) infection, and the immune responses against the virus depends on the interaction of various immune cells. Current research of immunity to hepatitis B infection mainly focuses on understanding the differences between patients who can control HBV infection and those with persistent infection. In this paper, we analyze how immunological events influence the development of innate and adaptive immunity needed to control HBV infection and explore the mechanisms by which high levels of viral antigens, CD4⁺ T cells, programmed death 1 (PD-1), the presence of regulatory T cells, and impaired dendritic cell functions maintain the HBV-specific immunological failure.

Lentivector expressing HBsAg and immunoglobulin Fc fusion antigen induces potent immune responses and results in seroconversion in HBsAg transgenic mice

Even though hepatitis B virus(HBV) vaccines effectively prevent new cases of HBV infection, with approximately 350 million patients worldwide, chronic HBV infection remains a major health problem because of the associated complications (such as liver cirrhosis and hepatocellular carcinoma) and the limited treatment options. Immunotherapy has the potential to effectively control HBV replication. In this current study, we found that recombinant lentivectors could induce potent HBV surface antigen (HBsAg) specific T cell responses and humoral immune responses. Tagging the HBsAg with immunoglobulin Fc fragment further substantially increased the HBsAg specific immune responses. Remarkably, the HBS-Fc-lv lentivector could effectively break immune tolerance and induce potent HBsAg specific adaptive immune responses in HBsAg transgenic (Tg) mice with low serum level of HBsAg. More importantly, the induction of HBsAg specific immune responses in Tg mice accompanied seroconversion from HBsAg to anti-HBsAg antibody (anti-HBsAb). Our study demonstrated the potential of utilizing lentivector to treat chronic HBV infection following reduction of viral load with antiviral drug therapy.

A critical role for virus-specific CD8(+) CTLs in protection from Theiler's virus-induced demyelination in disease-susceptible SJL mice

Theiler's murine encephalomyelitis virus (TMEV)-induced demyelinating disease (TMEV-IDD) is a relevant mouse model of multiple sclerosis. Infection of susceptible SJL/J mice leads to life-long CNS virus persistence and development of a chronic T cell-mediated autoimmune demyelinating disease triggered via epitope spreading to endogenous myelin epitopes. Potent CNS-infiltrating CD8(+) T cell responses to TMEV epitopes have previously been shown to be induced in both disease-susceptible SJL/J and resistant C57BL/6 mice, in which the virus is rapidly cleared. Specific tolerization of SJL CD8(+) T cells specific for the immunodominant TMEV VP3(159)(-)(166) epitope has no effect on viral load or development of clinical TMEV-IDD, but adoptive transfer of activated CD8(+) VP3(159)(-)(166)-specific T cell blasts shortly after TMEV infection to boost the early anti-viral response leads to clearance of CNS virus and protection from subsequent TMEV-IDD. These studies have important implications for vaccine strategies and treatment of chronic infections in humans.

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.

Transfusion of autologous cytokine-induced killer cells inhibits viral replication in patients with chronic hepatitis B virus infection

Adoptive immune transfer plays an important role in clearance of hepatitis B virus (HBV) in chronic hepatitis B (CHB) patients. However, it is unclear whether cytokine-induced killer (CIK) cells could suppress HBV replication in CHB patients, especially if drug resistance develops. In this study, functional CIK cells were efficiently generated from 21 CHB patients and were transfused in an autologous manner. We found that CIK cells from the CHB patients displayed substantial proliferation and function. Administration of the CIK cells closely correlated with the decrease in the serum HBV load and improvement in liver function in some patients. The virological response rate in patients with baseline serum alanine aminotransferase (ALT) levels of >40 U/L was higher than that in patients with baseline serum ALT levels of < or = 40 U/L. Moreover, patients who had HBeAg loss or showed seroconversion generally had baseline serum ALT levels of >40 U/L. No serious side effects were observed. This protocol represents an alternative immune therapeutic strategy for the disease.

In vitro use of autologous dendritic cells improves detection of T cell responses to hepatitis B virus (HBV) antigens

T lymphocyte responses to hepatitis B virus (HBV) core antigen (HBcAg) are vigorous and easily detectable in vitro during recovery from acute hepatitis B but significantly weaker in patients with chronic HBV infection. In contrast, T cell responses to hepatitis B surface antigen (HBsAg) are almost undetectable during infection and even in a substantial fraction of subjects receiving vaccination with HBsAg. The aim of this study was to investigate whether the use of dendritic cells (DCs) in an in vitro assay could increase the detection of HBV-specific T cells in these conditions. Autologous monocyte-derived DCs, compared to direct HBsAg addition to the cultures, increased the stimulation of HBs- specific T cells. These were detected in 73% of healthy subjects who had recently received hepatitis B vaccine and in 43% of patients recovering from acute hepatitis B. Likewise, proliferation in response to DC-presented HBcAg was detected in both CD4(+) and CD8(+) T cells from the majority of chronic hepatitis B patients. A longitudinal evaluation of HBc-specific T cell responses during and after a 1-year treatment with pegylated interferon (IFN)-alpha showed that HBc-specific CD4(+) T cell responses had no correlation with sustained virus suppression whereas CD8(+) T cell responses were more frequently detected in patients able to control HBV replication after therapy interruption. The use of autologous DCs as antigen-presenting cells appears applicable to clinically relevant in vitro evaluation of T cell responses, particularly in those conditions characterized by low frequency of circulating antigen-specific cells and suboptimal in vivo activation.

Pre-clinical evaluation of a novel nanoemulsion-based hepatitis B mucosal vaccine

BACKGROUND

Hepatitis B virus infection remains an important global health concern despite the availability of safe and effective prophylactic vaccines. Limitations to these vaccines include requirement for refrigeration and three immunizations thereby restricting use in the developing world. A new nasal hepatitis B vaccine composed of recombinant hepatitis B surface antigen (HBsAg) in a novel nanoemulsion (NE) adjuvant (HBsAg-NE) could be effective with fewer administrations.

METHODOLOGY AND PRINCIPAL FINDINGS

Physical characterization indicated that HBsAg-NE consists of uniform lipid droplets (349+/-17 nm) associated with HBsAg through electrostatic and hydrophobic interactions. Immunogenicity of HBsAg-NE vaccine was evaluated in mice, rats and guinea pigs. Animals immunized intranasally developed robust and sustained systemic IgG, mucosal IgA and strong antigen-specific cellular immune responses. Serum IgG reached > or = 10(6) titers and was comparable to intramuscular vaccination with alum-adjuvanted vaccine (HBsAg-Alu). Normalization showed that HBsAg-NE vaccination correlates with a protective immunity equivalent or greater than 1000 IU/ml. Th1 polarized immune response was indicated by IFN-gamma and TNF-alpha cytokine production and elevated levels of IgG(2) subclass of HBsAg-specific antibodies. The vaccine retains full immunogenicity for a year at 4 degrees C, 6 months at 25 degrees C and 6 weeks at 40 degrees C. Comprehensive pre-clinical toxicology evaluation demonstrated that HBsAg-NE vaccine is safe and well tolerated in multiple animal models.

CONCLUSIONS

Our results suggest that needle-free nasal immunization with HBsAg-NE could be a safe and effective hepatitis B vaccine, or provide an alternative booster administration for the parenteral hepatitis B vaccines. This vaccine induces a Th1 associated cellular immunity and also may provide therapeutic benefit to patients with chronic hepatitis B infection who lack cellular immune responses to adequately control viral replication. Long-term stability of this vaccine formulation at elevated temperatures suggests a direct advantage in the field, since potential excursions from cold chain maintenance could be tolerated without a loss in therapeutic efficacy.

Nanoimmunoliposome delivery of superparamagnetic iron oxide markedly enhances targeting and uptake in human cancer cells in vitro and in vivo

To circumvent the problem of reduction of the supermagnetic properties of superparamagnetic iron oxide (SPIO) nanoparticles after chemical modification to conjugate targeting molecules, we have adapted a tumor-targeting nanoimmunoliposome platform technology (scL) to encapsulate and deliver SPIO (scL-SPIO) in vitro and in vivo without chemical modification. Scanning probe microscopy, confocal microscopy, and Prussian blue staining were used to analyze the scL-SPIO and assess intracellular uptake and distribution of SPIO in vitro. In vivo targeting and tumor-specific uptake of scL-SPIO was examined using fluorescent-labeled SPIO. We demonstrated that SPIO encapsulation in the scL complex results in an approximately 11-fold increase in SPIO uptake in human cancer cells in vitro, with distribution to cytoplasm and nucleus. Moreover, the scL nanocomplex specifically and efficiently delivered SPIO into tumor cells after systemic administration, demonstrating the potential of this approach to enhance local tumor concentration and the utility of SPIO for clinical applications.

Enhancing therapeutic vaccination by blocking PD-1-mediated inhibitory signals during chronic infection

Therapeutic vaccination is a potentially promising strategy to enhance T cell immunity and viral control in chronically infected individuals. However, therapeutic vaccination approaches have fallen short of expectations, and effective boosting of antiviral T cell responses has not always been observed. One of the principal reasons for the limited success of therapeutic vaccination is that virus-specific T cells become functionally exhausted during chronic infections. We now provide a novel strategy for enhancing the efficacy of therapeutic vaccines. In this study, we show that blocking programmed death (PD)-1/PD-L1 inhibitory signals on exhausted CD8⁺ T cells, in combination with therapeutic vaccination, synergistically enhances functional CD8⁺ T cell responses and improves viral control in mice chronically infected with lymphocytic choriomeningitis virus. This combinatorial therapeutic vaccination was effective even in the absence of CD4⁺ T cell help. Thus, our study defines a potent new approach to augment the efficacy of therapeutic vaccination by blocking negative signals. Such an approach may have broad applications in developing treatment strategies for chronic infections in general, and perhaps also for tumors.

Heplisav™: a new hepatitis B vaccine

Heplisav™ is a vaccine comprising recombinant hepatitis B surface antigen mixed with a synthetic oligonucleotide containing CpG motifs, which stimulates innate immunity. A clinical study demonstrated that Heplisav was significantly more immunogenic compared with Engerix-B in terms of an earlier seroprotection (78.9 vs 11.8%) 4 weeks after the first dose, and 100 versus only 64% seroprotection 4 weeks after the second dose. Geometric mean concentrations also peaked earlier in the Heplisav group. A similar finding was confirmed in a Phase III study in an older (aged >40 years) vaccine-naive population, with 100 versus 73.1% seroprotection in Heplisav versus Engerix-B recipients, respectively, 4 weeks after the third injection. The main adverse events were injection-site reactions, but these were usually mild and self-limiting. In conclusion, Heplisav, a vaccine containing a CpG adjuvant mixed with hepatitis B surface antigen, was more immunogenic and produced earlier seroprotection compared with an existing vaccine, Engerix-B.

Efficacy of hepatitis B virus (HBV) vaccination in treating lamivudine-resistant HBV reactivation following hepatitis B surface antigen seroconversion

BACKGROUND

HBsAg vaccination might help to control HBV replication following nucleos(t)ide analog therapy. We tested HBsAg vaccine in a patient who developed lamivudine resistance.

PATIENT AND RESULTS

An HBeAg negative HBV chronically-infected patient developed HBsAg seroconversion after 3 years of treatment by lamivudine. However, the control of HBV replication was transient and HBV DNA could be detected in the serum one year after lamivudine was stopped. Concurrently, the anti-HBs antibodies (HBsAb) titre had decreased from more than 100 IU/L to 23 IU/L. Due to the presence of rtM204V resistance mutation, lamivudine was not reintroduced and the patient was treated by HBsAg vaccination. After three injections, HBV DNA was no more detectable and the HBsAb titre reached more than 200 IU/L.

CONCLUSION

This observation suggests that a regular follow up of patients presenting HBsAg seroconversion following lamivudine therapy is necessary. In these patients, a low titre of HBsAb may not prevent from lamivudine-resistant HBV reactivation. Evaluation of HBsAg vaccination to maintain HBsAb at a high titre in these patients deserves further studies.

Vaccines and immunotherapies against hepatitis B and hepatitis C viruses

Both hepatitis B and hepatitis C viruses (HBV and HCV) cause chronic infections worldwide that are associated with development of liver diseases ranging from mild liver inflammation to hepatocellular carcinomas. While efficient preventive vaccines are available for HBV, efforts are ongoing to develop one in case of HCV. Yet, both infections share the fact that therapeutic agents available to treat already established infections are yet poorly efficient, toxic or associated with development of resistance. Thus, novel immune-based therapies are actively being developed to complement or replace standard antiviral treatments. Among those, development of therapeutic vaccines represents a major effort. Peptide-, recombinant protein- or viral vector-based vaccines have been engineered and tested at preclinical and clinical levels. Means to adjuvant these vaccines are being pursued, including approaches based on combining vaccines of different nature. This review will outline major advances in the field of both HBV and HCV therapeutic vaccine development with a particular focus on candidates presented at the 12th International Symposium on Viral Hepatitis and Liver Disease (July 2006, Paris, France).

Coimmunization with RANTES plasmid polarized Th1 immune response against hepatitis B virus envelope via recruitment of dendritic cells

Induction of T help cell type 1 (Th1) response seems to be a prerequisite of HBV clearance. DNA vaccines have shown its potential to elicit Th1-biased immune response. However, its immunogenicity needs to be improved. Regulated upon activation normal T cell expressed and secreted (RANTES) is an inflammatory chemokine that promotes the accumulation and activation of CD4+, CD8+ T cells, and dendritic cells (DCs), which would favor antiviral immunity. In this study, the efficacy of a DNA vaccine encoding hepatitis B virus (HBV) preS2 plus S protein was enhanced through co-injection of a plasmid encoding RANTES in a BALB/c model. Co-injection of RANTES gene resulted in a moderate increase in the HBV specific humoral and cellular immune responses and a significant increase following an HBsAg booster vaccination compared to DNA encoding HBsAg alone. This enhancement was due to an enrichment of DCs in the draining lymph node and an up-regulation of DCs maturation by RANTES. More importantly, RANTES polarized the specific immunity towards a dominant Th1 profile and even converted an established Th2 response to a Th1 phenotype. Our study suggested the feasibility of using a plasmid-encoded RANTES as a modulatory Th1 adjuvant in genetic vaccination.

In vivo kinetics and biodistribution of HB-110, a novel HBV DNA vaccine, after administration in Mice

This study investigated the pharmacokinetic profile and biodistribution of HB-110, a novel HBV therapeutic vaccine candidate, in mice. HB-110 was rapidly degraded in the blood after i.v. injection with a half-life of 1.9+/-0.083 min, and was no longer detected at 60 min except in one individual near the detection limit. In the i.m. injection, plasmid DNA was detectable at the injection site until 11 days after administration, but the amounts were just above the detection limit. The blood concentration of HB-110 showed a maximum of 604 pg/mL at 15 min after i.m. injection, which was followed by degradation to undetectable levels at 90 min. The plasmid DNA in tissues peaked at 90 min after administration. The highest concentration of plasmid DNA was detected in the liver (24.172 pg/mg tissue), and considerable amounts were also observed in the lung (9.467 pg/mg tissue) and spleen (7.688 pg/mg tissue). The amount of plasmid DNA in tissues was 2 to 3 orders of magnitude lower than in the injection site at the same time points. The HB-110 concentration in tissues, including gonads, decreased rapidly and was undetectable 24 h after administration.

Comparison of vesicle based antigen delivery systems for delivery of hepatitis B surface antigen

There is a clinical need for a more effective vaccine against hepatitis B, and in particular vaccines that may be suitable for therapeutic administration. This study assesses the potential of cationic surfactant vesicle based formulations using two agents; the cationic amine containing [N-(N',N'-dimethylaminoethane)-carbamoyl] cholesterol (DC-Chol) or dimethyl dioctadecylammonium bromide (DDA) with hepatitis B surface antigen (HBsAg). Synthetic mycobacterial cord factor, trehalose 6,6'-dibehenate (TDB) has been used as an adjuvant and the addition of 1-monopalmitoyl glycerol (C16:0) (MP) and cholesterol (Chol) to DDA-TDB is assessed for its potential to facilitate formation of dehydration-rehydration vesicles (DRV) at room temperature, and the effect of this on immune responses. A DRV formulation is directly compared to an adsorbed formulation of the same composition and preparation protocol (MP:dioleoyl phosphoethanolamine (DOPE):Chol:DC-Chol) and the direct substitution of MP with phosphatidylcholine (PC) is also compared in DRV antigen-entrapped formulations. MP and Chol were shown to facilitate the use of DDA-TDB in DRV formulations prepared at room temperature, whilst there was marginal alteration of immunogenicity (a reduction in HBsAg-specific IL-2). The HBsAg adsorbed DRV formulation was not significantly different from the HBsAg entrapped DRV formulation. Overall, DDA formulations incorporating TDB showed markedly increased antigen specific splenocyte proliferation and elicited cytokine production concomitant with a strong T cell driven response, delineating formulations that may be useful for further evaluation of their clinical potential.

Phase I clinical trial in healthy adults of a nasal vaccine candidate containing recombinant hepatitis B surface and core antigens

BACKGROUND

The nasal vaccine candidate (NASVAC), comprising hepatitis B virus (HBV) surface (HBsAg) and core antigens (HBcAg), has been shown to be highly immunogenic in animal models.

METHODS

A phase I double-blinded, placebo-controlled randomized clinical trial was carried out in 19 healthy male adults with no serologic markers of immunity/infection to HBV. This study was aimed at exploring the safety and immunogenic profile of nasal co-administration of both HBV recombinant antigens. The trial was performed according to Good Clinical Practice guidelines. Participants ranged in age from 18 to 45 years and were randomly allocated to receive a mixture of 50 microg HBsAg and 50 microg HBcAg or 0.9% physiologic saline solution, as a placebo, via nasal spray in a five-dose schedule at 0, 7, 15, 30, and 60 days. A total volume of 0.5 ml was administered in two dosages of 125 microl per nostril. Adverse events were actively recorded 1 h, 6 h, 12 h, 24 h, 48 h, 72 h, 7 days and 30 days after each dose. Anti-HBs and anti-HBc titers were evaluated using corresponding ELISA kits at days 30 and 90.

RESULTS

The vaccine candidate was safe and well tolerated. Adverse reactions included sneezing (34.1%), rhinorrhea (12.2%), nasal stuffiness (9.8%), palate itching (9.8%), headache (9.8%), and general malaise (7.3%). These reactions were all self-limiting and mild in intensity. No severe or unexpected events were recorded during the trial. The vaccine elicited anti-HBc seroconversion in 100% of subjects as early as day 30 of the immunization schedule, while a seroprotective anti-HBs titer (>or=10 IU/l) was at a maximum at day 90 (75%). All subjects in the placebo group remained seronegative during the trial.

CONCLUSION

The HBsAg-HBcAg vaccine candidate was safe, well tolerated and immunogenic in this phase I study in healthy adults. To our knowledge, this is the first demonstration of safety and immunogenicity for a nasal vaccine candidate comprising HBV antigens.

Gene therapy for viral hepatitis

Hepatitis B and C infections are two of the most prevalent viral diseases in the world. Existing therapies against chronic viral hepatitis are far from satisfactory due to low response rates, undesirable side effects and selection of resistant viral strains. Therefore, new therapeutic approaches are urgently needed. This review, after briefly summarising the in vitro and in vivo systems for the study of both diseases and the genetic vehicles commonly used for liver gene transfer, examines the existing status of gene therapy-based antiviral strategies that have been employed to prevent, eliminate or reduce viral infection. In particular, the authors focus on the results obtained in clinical trials and experimental clinically relevant animal models.

Nanotechnology: intelligent design to treat complex disease

The purpose of this expert review is to discuss the impact of nanotechnology in the treatment of the major health threats including cancer, infections, metabolic diseases, autoimmune diseases, and inflammations. Indeed, during the past 30 years, the explosive growth of nanotechnology has burst into challenging innovations in pharmacology, the main input being the ability to perform temporal and spatial site-specific delivery. This has led to some marketed compounds through the last decade. Although the introduction of nanotechnology obviously permitted to step over numerous milestones toward the development of the "magic bullet" proposed a century ago by the immunologist Paul Ehrlich, there are, however, unresolved delivery problems to be still addressed. These scientific and technological locks are discussed along this review together with an analysis of the current situation concerning the industrial development.