Cellular and humoral immune response to a third generation hepatitis B vaccine

PreHevbrio: the first approved 3-antigen hepatitis B vaccine

INTRODUCTION

Hepatitis B remains a major cause of death and morbidity worldwide. Universal childhood immunization programs have been very successful, but many adults remain unprotected or are not optimally protected. PreHevbrio [Hepatitis B Vaccine (recombinant)] is a highly immunogenic 3-antigen (S/pre-S1/pre-S2) hepatitis B vaccine (3A-HBV) that recently received marketing authorization in the United States (2021), the European Union, United Kingdom (2022 - brand name PreHevbri), and Canada (2022- brand name PreHevbrio) for the prevention of infection caused by all known subtypes of the hepatitis B virus and the delta virus in adults 18 years and older.

AREAS COVERED

This review details the development of 3A-HBV and summarizes the results of the phase 3 clinical trials that support its immunogenicity and safety in adults.

EXPERT OPINION

3A-HBV is highly immunogenic in adults of all ages, including older adults and subgroups that respond sub-optimally to conventional single S-antigen hepatitis B vaccines (1A-HBV), such as those with obesity, type 2 diabetes, and smokers. 3A-HBV provides higher seroprotection rates after each vaccination compared to conventional 1A-HBV vaccines, allowing for more rapid protection. The higher overall immunogenicity is also reflected in more durable seroprotection years after vaccination, as supported by a follow-up study to one of the phase 3 studies.

Therapeutic vaccine BRII-179 restores HBV-specific immune responses in patients with chronic HBV in a phase Ib/IIa study

Background & Aims

Functional cure of chronic HBV infection (CHB) without life-long treatment requires the restoration of defective HBV-specific humoral and cellular immunity. Therapeutic vaccines based on the major structural and non-structural proteins have been tested in patients with CHB but have shown scarce immunogenicity. BRII-179, also known as VBI-2601, is a novel formulation comprised of all 3 HBV surface envelope proteins (Pre-S1, Pre-S2, and S). Safety, antiviral activity, and immunogenicity of BRII-179 admixed with co-adjuvant interferon (IFN)-α were assessed in patients with CHB.

Method

This randomized, open-label, controlled phase Ib/IIa study included 2 dose levels, 20 μg BRII-179 (Part 1, n = 25) and 40 μg BRII-179 (Part 2, n = 24). Patients, virally suppressed under nucleos(t)ide analogue (NA) therapy were randomized 1:2:2 into 3 cohorts in Part 1 and 1:1 into 2 cohorts in Part 2 to receive 4 monthly intramuscular injections of BRII-179 admixed with/without 3 MIU IFN-α. Antibody and cellular responses to HBsAg, as well as evolution of circulating HBsAg were monitored.

Results

Both 20 μg and 40 μg BRII-179 with/without IFN-α were well tolerated with no severe adverse events. BRII-179 induced anti-HBs responses in >30% patients in all treatment cohorts, however, moderate anti-Pre-S1 or anti-Pre-S2 antibody responses were only observed in patients receiving BRII-179 with IFN-α. BRII-179 also restored S-, Pre-S1-, Pre-S2-specific IFN-γ-producing T-cells in the majority of treated patients. Overall, no notable reduction of HBsAg was observed after BRII-179 treatment.

Conclusion

In patients with CHB under NA therapy, BRII-179 with/without IFN-α exhibited a good safety profile and induced HBV-specific B- and T-cell immune responses. These data support further clinical evaluation of BRII-179 in combination with other therapies.

Clinical Trial Number

ACTRN12619001210167.

Lay summary

BRII-179 is a therapeutic vaccine designed to improve the immune response in patients with chronic hepatitis B. In this study, BRII-179 alone or with a low dose of interferon-α was safe, well tolerated, and induced enhanced HBV-specific antibody and T-cell responses in patients with chronic hepatitis B. However, BRII-179 treatment alone had minimal effect on patient's virological status. The potential of BRII-179 to achieve a functional cure in conjunction with other agents is being evaluated in the clinic.

Rapid and high seroprotection rates achieved with a tri-antigenic Hepatitis B vaccine in healthy young adults: Results from a Phase IV study

BACKGROUND

Sci-B-Vac® is a tri-antigenic recombinant Hepatitis B vaccine (TAV) containing the small (s), medium (pre-S2) and large (pre-S1) hepatitis B surface (HBs) antigens. To comply with vaccine licensure, a new reference standard batch was qualified by characterizing the seroprotection rate (SPR) for anti-HBs titers ≥10 mIU/mL, following vaccination.

METHODS

Ninety-one healthy adults aged 20-40 years were enrolled in an open label, single-arm phase IV study receiving three IM doses of 10 μg TAV at 0, 1 and 6 months. Immunogenicity was evaluated monthly and at 7, 9 and 12 months. The primary endpoint to qualify the reference standard was an SPR ≥95% by month 7. Secondary endpoints were proportion of high responders (anti-HBs titers ≥100 mIU/mL) and geometric mean concentrations (GMC) of HBs antibodies each month. Participants were followed for safety to month 12.

RESULTS

The primary endpoint was met 2 months after the second dose at month 3 [SPR 98.8%; 95% CI: 93.7%, 99.7%]. Proportion of high responders at months 3 and 7 were 81.4% and 97.6%, respectively. GMC at months 3 and 7 were 413.6 mIU/mL and 6799.9 mIU/mL, respectively. TAV was safe and well-tolerated.

CONCLUSIONS

The new reference standard batch of TAV was qualified successfully, demonstrating efficacy, a favorable safety profile and a rapid onset of seroprotection, including after two vaccine doses. Clinical trial registry: NCT04179786.

An Antigen-Free, Plasmacytoid Dendritic Cell-Targeting Immunotherapy To Bolster Memory CD8+ T Cells in Nonhuman Primates

The priming, boosting, and restoration of memory cytotoxic CD8⁺ T lymphocytes by vaccination or immunotherapy in vivo is an area of active research. Particularly, nucleic acid-based compounds have attracted attention due to their ability to elicit strong Ag-specific CTL responses as a vaccine adjuvant. Nucleic acid-based compounds have been shown to act as anticancer monotherapeutic agents even without coadministration of cancer Ag(s); however, so far they have lacked efficacy in clinical trials. We recently developed a second-generation TLR9 agonist, a humanized CpG DNA (K3) complexed with schizophyllan (SPG), K3-SPG, a nonagonistic Dectin-1 ligand. K3-SPG was previously shown to act as a potent monoimmunotherapeutic agent against established tumors in mice in vivo. In this study we extend the monoimmunotherapeutic potential of K3-SPG to a nonhuman primate model. K3-SPG activated monkey plasmacytoid dendritic cells to produce both IFN-α and IL-12/23 p40 in vitro and in vivo. A single injection s.c. or i.v. with K3-SPG significantly increased the frequencies of activated memory CD8⁺ T cells in circulation, including Ag-specific memory CTLs, in cynomolgus macaques. This increase did not occur in macaques injected with free CpG K3 or polyinosinic-polycytidylic acid. Injection of 2 mg K3-SPG induced mild systemic inflammation, however, levels of proinflammatory serum cytokines and circulating neutrophil influx were lower than those induced by the same dose of polyinosinic-polycytidylic acid. Therefore, even in the absence of specific Ags, we show that K3-SPG has potent Ag-specific memory CTL response-boosting capabilities, highlighting its potential as a monoimmunotherapeutic agent for chronic infectious diseases and cancer.

A virus-like particle of the hepatitis B virus preS antigen elicits robust neutralizing antibodies and T cell responses in mice

The preS antigen of hepatitis B virus (HBV) corresponds to the N-terminal polypeptide in the large (L) antigen in addition to the small (S) antigen. The virus-like particle (VLP) of the S antigen is widely used as a vaccine to protect the population from HBV infection. The presence of the S antigen and its antibodies in patient blood has been used as markers to monitor hepatitis B. However, there is very limited knowledge about the preS antigen. We generated a preS VLP that is formed by a chimeric protein between preS and hemagglutinin (HA), and the matrix protein M1 of influenza virus. The HBV preS antigen is displayed on the surface of preS VLP. Asn112 and Ser98 of preS in VLP were found to be glycosylated and O-glycosylation of Ser98 has not been reported previously. The preS VLP shows a significantly higher immunogenicity than recombinant preS, eliciting robust anti-preS neutralizing antibodies. In addition, preS VLP is also capable of stimulating preS-specific CD8⁺ and CD4⁺ T cell responses in Balb/c mice and HBV transgenic mice. Furthermore, preS VLP immunization provided protection against hydrodynamic transfection of HBV DNA in mice. The data clearly suggest that this novel preS VLP could elicit robust immune responses to the HBV antigen, and can be potentially developed into prophylactic and therapeutic vaccines.

Immunotherapy With the PreS-based Grass Pollen Allergy Vaccine BM32 Induces Antibody Responses Protecting Against Hepatitis B Infection

Background

We have constructed and clinically evaluated a hypoallergenic vaccine for grass pollen allergy, BM32, which is based on fusion proteins consisting of peptides from the IgE binding sites of the major grass pollen allergens fused to preS (preS1 + preS2), a domain of the hepatitis B virus (HBV) large envelope protein which mediates the viral attachment and entry. Aim of this study was the characterization of the HBV-specific immune response induced by vaccination of allergic patients with BM32 and the investigation of the vaccines' potential to protect against infection with HBV.

Methods

Hepatitis B-specific antibody and T cell responses of patients vaccinated with BM32 were studied using recombinant preS and synthetic overlapping peptides spanning the preS sequence. The specificities of the antibody responses were compared with those of patients with chronic HBV infection. Furthermore, the capacity of BM32-induced antibodies, to inhibit HBV infection was investigated using HepG2-hNTCP cell-based in vitro virus neutralization assays.

Findings

IgG antibodies from BM32-vaccinated but not of HBV-infected individuals recognized the sequence motif implicated in NTCP (sodium-taurocholate co-transporting polypeptide)-receptor interaction of the hepatitis B virus and inhibited HBV infection.

Interpretation

Our study demonstrates that the recombinant hypoallergenic grass pollen allergy vaccine BM32 induces hepatitis B-specific immune responses which protect against hepatitis B virus infection in vitro.

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BM32 is a recombinant allergy vaccine consisting of the preS domain of the large envelope protein of hepatitis B virus (HBV) and allergen-derived peptides.

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Vaccination of allergic patients with BM32 induced preS-specific antibodies which inhibit hepatitis B infection in vitro.

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BM32 may be useful as therapeutic vaccine in HBV-infected patients.

Infection with HBV remains a major cause of morbidity and mortality worldwide. Conventional HBV vaccines, consisting of SHBs particles solely, do not elicit adequate antibody production in 5–10% of vaccines and there is a need for therapeutic HBV vaccines. We have engineered an allergy vaccine which consists of allergen-derived peptides fused to the preS domain of the large envelope protein of HBV. Here we show that vaccination of allergic patients with this vaccine induces antibodies which protect against HBV infection in vitro. The preS-containing allergy vaccine may thus be also useful for therapeutic vaccination of HBV-infected patients.

Sci-B-VacTM Vs ENGERIX-B Vaccines for Hepatitis B Virus in Patients with Inflammatory Bowel Diseases: A Randomised Controlled Trial

BACKGROUND AND AIMS

Response rate to second-generation hepatitis B virus vaccines is relatively low in patients with inflammatory bowel diseases compared with the general healthy population. We compared the efficacy and safety of a third- vs a second-generation hepatitis B virus vaccine in a group of patients with inflammatory bowel diseases treated with immunosuppressive medications.

METHODS

Prospective, randomised, single-blind, controlled study. Eligible patients were randomly assigned to receive one of two vaccines, ENGERIX-B or Sci-B-Vac. The vaccines were administered in three doses at 0, 1, and 6 months. The primary endpoint was defined as the titre of anti-hepatitis B S [HBs] antibodies following the standard three-dose hepatitis B virus vaccination schedule.

RESULTS

A total of 72 patients complied with study protocol [37 and 35 patients in the ENGERIX-B and Sci-B-Vac groups, respectively]. Overall, 75% of the cohort seroconverted. The primary endpoint was met in 81.1% in the ENGERIX-B group and 68.6% in the Sci-B-Vac group [p = 0.22]. Patients in the Sci-B-Vac group showed a statistically significant decreased seroconversion rate compared with the ENGERIX-B group, with use of tumour necrosis factor [TNF] alpha inhibitors [p = 0.03], and higher degree of disease activity [p = 0.03].

CONCLUSIONS

Overall seroconversion rate in our cohort was higher than in previous reports in the literature, possibly due to a low disease activity state in the majority of participants. Third-generation hepatitis B virus vaccines showed no apparent advantage over standard of care vaccine in this patient group.

Cancer Vaccines: Past, Present, and Future

Cancer is a common and potentially deadly disease. Some of the cancers may be difficult to treat by conventional means such as surgery, radiation, and chemotherapy, but may be controlled by the stimulation of the immune response of the body with the help of cancer vaccines. The use of vaccines for preventing infections by oncogenic viruses such as hepatitis B virus and human papilloma virus has been extremely successful in reducing the incidence of cancers resulting from these infections. The use of vaccines for treating cancers that are not due to viral infections and that are already established is currently the object of numerous clinical trials. Several types of cancer vaccines are being tried. These include antigen vaccines, tumor cell vaccines, dendritic vaccines, deoxyribonucleic acid vaccines, and viral vector vaccines. The development of these therapeutic vaccines is proving difficult with only 1 recent success. However, there is significant enthusiasm and optimism regarding the development of effective therapeutic vaccines stemming from the fact that our understanding regarding the cancer immunology is considerably enhanced in recent years. This expanded knowledge regarding the mechanisms that cancers use to escape the immune system is likely to open new avenues in modulating the immune response to cancer, thus enhancing the effectiveness of therapeutic cancer vaccines.

Donor- and recipient-derived immunity in ABO incompatible living-related liver transplantation

This report describes how donor- and recipient-derived immunity was influenced by immunosuppressive treatment of ABO incompatibility (rituximab and immunoadsorption/plasmaphereses) in the long-term. We present an 8-year course of Hepatitis B virus (HBV) immunity, isohemagglutinins and B cell numbers. Whereas cellular HBV immunity was transferred from the HBV vaccinated donor (blood group A1) to the HBV naïve recipient (blood group 0), humoral HBV specific immune transfer was lacking. Starting at month 17 after transplantation, the recipient was vaccinated six times against HBV. Anti-HBs did not appear until the sixth vaccination at month 44. Immunoadsorption prior to transplantation reduced anti-A1 IgG titers from 256 to 2. Titers after transplantation remained low (⩽64). B cell numbers were below standard values up to month 26, then normalized and exceeded normal values from year 7 to 8 post transplantation. In conclusion, donor-derived B cell immunity was lost but recipient-derived immunity persisted after ABO incompatible transplantation.

Ex vivo assessment of cellular immune function - applications in patient care and clinical studies

Cellular ex vivo assays have a broad range of applications in patient care and clinical studies, especially when they are standardized and highly sensitive. As compared to analyses by molecular genetics such as the single nucleotide polymorphism (SNP) testing, they are usually more global. These assays partly mimic the in vivo situation, relying on a complex interaction of various immune cells. For example, they can be used to determine modulation of alloresponses by treatment or underlying disease, diagnose and quantify primary and secondary cellular immunodeficiency, follow-up vaccination responses, measure adoptive transfer of virus-specific immunity via hematopoietic stem cell or liver transplantation, assess allergy, antimicrobial immunity and also rare effector/memory cells directed against tumor antigens. This review will first shortly describe various cellular in vitro methods and then present applications, summarizing some own studies performed within the last 18 years.

Lessons learned in the analysis of high-dimensional data in vaccinomics

The field of vaccinology is increasingly moving toward the generation, analysis, and modeling of extremely large and complex high-dimensional datasets. We have used data such as these in the development and advancement of the field of vaccinomics to enable prediction of vaccine responses and to develop new vaccine candidates. However, the application of systems biology to what has been termed "big data," or "high-dimensional data," is not without significant challenges-chief among them a paucity of gold standard analysis and modeling paradigms with which to interpret the data. In this article, we relate some of the lessons we have learned over the last decade of working with high-dimensional, high-throughput data as applied to the field of vaccinomics. The value of such efforts, however, is ultimately to better understand the immune mechanisms by which protective and non-protective responses to vaccines are generated, and to use this information to support a personalized vaccinology approach in creating better, and safer, vaccines for the public health.

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.

Induction of a robust T- and B-cell immune response in non- and low-responders to conventional vaccination against hepatitis B by using a third generation PreS/S vaccine

Non-responsiveness to conventional hepatitis B vaccines in individuals at high risk of exposure to hepatitis B virus (HBV) is an important public health problem and of particular relevance in health care providers. Yeast-derived conventional HBsAg vaccines fail to induce protective antibody titers in up to 10% of immune competent vaccinees. Therefore, a third generation HBV vaccine, Sci-B-Vac™, was developed which contains in addition to the small S antigen the PreS1 and PreS2 antigens. This vaccine proved to induce a highly potent cellular and humoral immune response in healthy individuals as well as protective antibody levels in non- and low-responders to conventional HBV vaccines. The aim of the study was to examine whether Sci-B-Vac™ triggers cellular and humoral immunity in individuals who failed immunization with conventional vaccines. We immunized 21 volunteers (15 non- and 6 low-responders) according to the standard vaccination schedule (0, 4 and 24 weeks), determined the cellular immunity by proliferation assay and interferon (IFN)-γ ELISpot and measured the anti-HBs antibody titers prior to each vaccination and four weeks after the third vaccine dose. Following three vaccinations, PreS/S-specific T-cell proliferation was detected in 8 out of 15 non-responders and 5 out of 6 low-responders. Specific IFN-γ responses were measured in 2 out of 15 non-responders and 4 out of 6 low-responders. All but one (20/21) study participants developed anti-HBs titers ≥10IU/l after three vaccinations. Anti-HBs ≥100IU/L were detected in 12 out of 15 non-responders and in 6 out of 6 low-responders. Anti-HBs ≥10IU/l and <100IU/l were found in 2 non-responders. These results indicate that Sci-B-Vac™ induces cellular immunity as well as protective anti-HBs antibody titers in non- and low-responders. In conclusion, these results confirm that Sci-B-Vac™ should be administered to non-responders to conventional HBV vaccines and patients with impaired immune function.

DNA vaccine cocktail expressing genotype A and C HBV surface and consensus core antigens generates robust cytotoxic and antibody responses in mice and Rhesus macaques

There are well over a quarter of a billion chronic hepatitis B virus (HBV) carriers across the globe. Most carriers are at high risk for development of liver cirrhosis and subsequent progression to hepatocellular carcinoma. It is therefore imperative to develop new approaches for immunotherapy against this infection. Antibodies and cytotoxic T cells to different HBV antigens are believed to be important for reducing viral load and clearing HBV-infected cells from the liver. Some of the major challenges facing current vaccine candidates have been their inability to induce both humoral and cellular immunity to multiple antigenic targets and the induction of potent immune responses against the major genotypes of HBV. In this study, highly optimized synthetic DNA plasmids against the HBV consensus core (HBc) and surface (HBs) antigens genotypes A and C were developed and evaluated for their immune potential. These plasmids, which encode the most prevalent genotypes of the virus, were observed to individually induce binding antibodies to HBs antigens and drove robust cell-mediated immunity in animal models. Similar responses to both HBc and HBs antigens were observed when mice and non-human primates were inoculated with the HBc-HBs cocktails. In addition to the cytotoxic T lymphocyte activities exhibited by the immunized mice, the vaccine-induced responses were broadly distributed across multiple antigenic epitopes. These elements are believed to be important to develop an effective therapeutic vaccine. These data support further evaluation of multivalent synthetic plasmids as therapeutic HBV vaccines.

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.

Allergen-specific immunotherapy: towards combination vaccines for allergic and infectious diseases

IgE-mediated allergies affect more than 25% of the population. Allergen-specific immunotherapy (SIT) is an antigen-specific and disease-modifying form of treatment. It is based on the therapeutic administration of the disease-causing allergens to allergic patients. However, the fact that only allergen extracts of insufficient quality are currently available and the possible occurrence of side effects during treatment limit the broad use of SIT and prophylactic vaccination is has not yet been performed. In the last 20 years the DNA sequences of the most common allergens have been isolated and the corresponding allergens have been produced as recombinant allergens. Based on the progress made in the field of allergen characterization it is possible to improve the quality and safety of allergy vaccines and to develop new, more effective strategies for a broad application of SIT and even for prophylactic treatment. Here we discuss the development of combination vaccines for allergy and infectious diseases. This approach is based on the selection of allergen-derived peptides with reduced IgE- and T cell reactivity in order to minimize IgE- and T cell-mediated side effects as well as the potential of the vaccine to induce allergic sensitization. These peptides are fused by recombinant technology onto a viral carrier protein to obtain a combination vaccine which induces protective immunity against allergy and viral infections. The application of such combination vaccines for therapy and prophylaxis of allergy and infectious diseases is discussed.

A hypoallergenic cat vaccine based on Fel d 1-derived peptides fused to hepatitis B PreS

BACKGROUND

Allergen-specific immunotherapy is clinically effective for the treatment of cat allergy but shows a high rate of side effects.

OBJECTIVE

We sought to engineer recombinant fusion proteins for cat immunotherapy that allow reducing both IgE-mediated and T cell-mediated side effects.

METHODS

Fusion proteins consisting of the hepatitis B virus-derived PreS domain and 2 nonallergenic Fel d 1-derived peptides were expressed in Escherichia coli and purified. IgE reactivity and allergenic activity of Fel d 1 and the fusion proteins were compared by using IgE-binding assays and basophil activation tests in patients with cat allergy. Mice and rabbits were immunized subcutaneously with Fel d 1 and the fusion proteins to investigate the allergenicity of the vaccines and the development of Fel d 1-specific IgG antibodies.

RESULTS

The recombinant fusion proteins showed no relevant IgE reactivity and exhibited more than 1000-fold reduced allergenic activity in basophil activation tests. On immunization of mice and rabbits, the fusion proteins induced Fel d 1-specific IgG antibodies that inhibited the binding of allergic patients' IgE to the allergen without allergic sensitization to Fel d 1.

CONCLUSION

The described recombinant fusion proteins exhibit strongly reduced IgE-mediated allergenic activity, contain less than 40% of the Fel d 1 sequence, and thus lack many of the specific T-cell epitopes. Therefore they should represent safe vaccines for the treatment of cat allergy.

Different effect of HBV vaccine after liver transplantation between chronic HBV carriers and non-HBV patients who received HBcAb-positive grafts

BACKGROUND

Combination of nucleos(t)ide analogue and anti-HBs immunoglobulin (HBIg) is the standard protocol for prevention of HBV reactivation after liver transplantation, but because of the extremely high cost of HBIg, HBV vaccine is tried as a much cheaper and potentially safer substitute. Here we show the different effect of HBV vaccine between chronic HBV carrier and non-HBV patients who received grafts from HBc antibody-positive donors.

METHODS

Fifteen chronic HBV carriers and 6 non-HBV patients who received grafts from HBc antibody-positive donors were included in this study. These patients received double dose of pre-S-containing HBV vaccine every month from later than 12 months after liver transplantation. Successful vaccination was defined as HBsAb >100 IU/l without HBIg administration for 3 months.

RESULTS

None of the 15 chronic HBV carriers succeeded in maintaining high enough HBsAb titers. In contrast, 5 of 6 non-HBV patients with HBcAb-positive donors achieved HBsAb >100 IU/l without HBIg coadministration. Recipient HBV status (HBV carrier/non-HBV) was considered to have a stronger effect on vaccine success (p < 0.001) though recipient age (p = 0.006) was also selected as a significant factor.

CONCLUSIONS

Recipient HBV status seems to be the most important factor affecting success of HBV vaccine after liver transplantation. In non-HBV patients who received grafts from HBcAb-positive donors, HBV vaccination is an effective, cost-saving, and safe method for prevention of HBV reactivations. In contrast in chronic HBV patients, response rate was quite poor, so some modifications such as combination with adjuvant or modification of administration schedules should be considered.

Profiles of B and T cell immune responses elicited by different forms of the hepatitis B virus surface antigen

Gene-based hepatitis B virus (HBV) vaccines have been proposed as a novel approach to improve the immunogenicity toward non-responders and to allow for protection against potential viral escape mutants. Furthermore, there is significant interest in using DNA or viral vector vaccines to serve as therapeutic agents to treat chronic HBV infections that are resistant to existing drug therapies. However, the key protective antigen of HBV, the surface protein (HBsAg), can be expressed in three different sizes due to its multiple translational initiation sites: small, middle, and large forms of HBsAg. It is not clear whether the immunogenicity of these HBsAg is same, especially their ability to elicit HBsAg-specific B cell and T cell immune responses in addition to the traditional serum HBsAg-specific antibody responses. In the current study, the immunogenicity of three forms of HBsAg DNA vaccines was analyzed individually in a mouse model. Our results indicated that different forms of the HBsAg have unique immunogenicity profiles and this information is useful for the selection of optimal gene-based HBV vaccines for further improved prophylactic and therapeutic applications.