Improved immunogenicity in mice of a mammalian cell-derived recombinant hepatitis B vaccine containing pre-S1 and pre-S2 antigens as compared with conventional yeast-derived vaccines

CHO cells for virus-like particle and subunit vaccine manufacturing

Chinese Hamster Ovary (CHO) cells, employed primarily for manufacturing monoclonal antibodies and other recombinant protein (r-protein) therapeutics, are emerging as a promising host for vaccine antigen production. This is exemplified by the recently approved CHO cell-derived subunit vaccines (SUV) against respiratory syncytial virus (RSV) and varicella-zoster virus (VZV), as well as the enveloped virus-like particle (eVLP) vaccine against hepatitis B virus (HBV). Here, we summarize the design, production, and immunogenicity features of these vaccine and review the most recent progress of other CHO-derived vaccines in pre-clinical and clinical development. We also discuss the challenges associated with vaccine production in CHO cells, with a focus on ensuring viral clearance for eVLP products.

Hybrid large hepatitis B surface protein composed of two viral genotypes C and D induces strongly cross-neutralizing antibodies

Hepatitis B virus (HBV) vaccination is known to effectively decrease the risk of HBV infection. However, several issues need to be addressed in order to develop an improved HBV vaccine. Although the HBV vaccine has been shown to be effective, this vaccine needs to be more efficacious in defined groups, including non-responders (i.e., individuals who do not develop a protective response even after vaccination) and in health care workers and travelers who require rapid protection. Furthermore, it has been reported that universal HBV vaccination has accelerated the appearance of vaccine-escape mutants resulting from the accumulation of mutations altering the "a" determinant of the hepatitis B surface (HBs) protein. To address these problems, we have been focusing on the large HBs (LHBs) protein, which consists of three domains: pre-S1, pre-S2, and S (in N- to C-terminal order). To enhance the immunogenicity of LHBs, we developed a yeast-derived hybrid LHBs (hy-LHBs) antigen composed of the LHBs proteins from two distinct genotypes (Genotypes C and D). The levels of antibodies induced by hy-LHBs immunization were high not only against S, but also against the pre-S1 and pre-S2 domains. Additionally, hy-LHBs immunization induced significantly more strongly cross-reactive neutralizing antibodies than did small HBs (SHBs) or LHBs of any genotype alone. These findings suggested that hy-LHBs might serve as a candidate antigen for use in an improved prophylactic HBV 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.

Efficient cellular and humoral immune response and production of virus-neutralizing antibodies by the Hepatitis B Virus S/preS116-42 antigen

Despite the availability of improved antiviral therapies, infection with Hepatitis B virus (HBV) remains a3 significant health issue, as a curable treatment is yet to be discovered. Current HBV vaccines relaying on the efficient expression of the small (S) envelope protein in yeast and the implementation of mass vaccination programs have clearly contributed to containment of the disease. However, the lack of an efficient immune response in up to 10% of vaccinated adults, the controversies regarding the seroprotection persistence in vaccine responders and the emergence of vaccine escape virus mutations urge for the development of better HBV immunogens. Due to the critical role played by the preS1 domain of the large (L) envelope protein in HBV infection and its ability to trigger virus neutralizing antibodies, including this protein in novel vaccine formulations has been considered a promising strategy to overcome the limitations of S only-based vaccines. In this work we aimed to combine relevant L and S epitopes in chimeric antigens, by inserting preS1 sequences within the external antigenic loop of S, followed by production in mammalian cells and detailed analysis of their antigenic and immunogenic properties. Of the newly designed antigens, the S/preS1^16–42 protein assembled in subviral particles (SVP) showed the highest expression and secretion levels, therefore, it was selected for further studies in vivo. Analysis of the immune response induced in mice vaccinated with S/preS1^16–42- and S-SVPs, respectively, demonstrated enhanced immunogenicity of the former and its ability to activate both humoral and cellular immune responses. This combined activation resulted in production of neutralizing antibodies against both wild-type and vaccine-escape HBV variants. Our results validate the design of chimeric HBV antigens and promote the novel S/preS1 protein as a potential vaccine candidate for administration in poor-responders to current HBV vaccines.

Development, Production, and Characterization of Hepatitis B Subviral Envelope Particles as a Third-Generation Vaccine

Vaccination still represents the most efficient and inexpensive strategy in the control of hepatitis B virus (HBV) infection. However, about 10% of the population vaccinated with the current S yeast-derived vaccine fail to induce an adequate immune response. Our group has developed a new-generation hepatitis B vaccine candidate composed by the three surface proteins of the HBV. Here we describe the methods to develop and characterize a stable CHO-K1 recombinant cell line able to produce and secrete hepatitis B subviral envelope particles (HBV-SVPs) containing L and M glycoproteins in addition to S glycoprotein. In addition, Western blot and immunogold electron microscopy techniques to evaluate the size, morphology, and composition of the particles are explained. Finally, immunization protocols are described in order to study the immunogenicity of HBV-SVPs and the ability of the antibodies triggered by these particles to recognize the binding site of HBV with the hepatocyte.

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.

Characterization of hepatitis B virus surface antigen particles expressed in stably transformed mammalian cell lines containing the large, middle and small surface protein

Vaccination still represents the most efficient and inexpensive strategy in the control of hepatitis B virus (HBV) infection. However, about 10% of the population vaccinated with the current yeast derived vaccine, consisting of the non-glycosylated form of the small envelope protein (S) of the HBV, fail to display an adequate immune response. Therefore, there is a need for the development of new vaccines with enhanced immunogenicity. On this regard, new generation vaccines containing L and preS2-containing HBV surface proteins in addition to S, have proven to be able to bypass the lack of response of the standard vaccine. In this work, we describe the development of stable recombinant CHO-K1 and HEK293 cell lines able to produce and secrete hepatitis B subviral envelope particles (HBV-SVPs) composed by the three surface proteins of the HBV. In turn, we demonstrated that these particles induced a specific humoral immune response in experimental animals and triggered the production of antibodies with the ability to recognize the binding site of HBV with the hepatocyte. Thus, these HBV-SVPs represent a promising candidate as a new generation vaccine in order to enhance the immunogenicity of the conventional yeast derived HBV vaccine.

Recent Progress on the Versatility of Virus-Like Particles

Virus-like particles (VLPs) are multimeric nanostructures composed of one or more structural proteins of a virus in the absence of genetic material. Having similar morphology to natural viruses but lacking any pathogenicity or infectivity, VLPs have gradually become a safe substitute for inactivated or attenuated vaccines. VLPs can achieve tissue-specific targeting and complete and effective cell penetration. With highly ordered epitope repeats, VLPs have excellent immunogenicity and can induce strong cellular and humoral immune responses. In addition, as a type of nanocarrier, VLPs can be used to display antigenic epitopes or deliver small molecules. VLPs have thus become powerful tools for vaccinology and biomedical research. This review highlights the versatility of VLPs in antigen presentation, drug delivery, and vaccine technology.

Hepatitis B Virus (HBV) Subviral Particles as Protective Vaccines and Vaccine Platforms

Hepatitis B remains one of the major global health problems more than 40 years after the identification of human hepatitis B virus (HBV) as the causative agent. A critical turning point in combating this virus was the development of a preventative vaccine composed of the HBV surface (envelope) protein (HBsAg) to reduce the risk of new infections. The isolation of HBsAg sub-viral particles (SVPs) from the blood of asymptomatic HBV carriers as antigens for the first-generation vaccines, followed by the development of recombinant HBsAg SVPs produced in yeast as the antigenic components of the second-generation vaccines, represent landmark advancements in biotechnology and medicine. The ability of the HBsAg SVPs to accept and present foreign antigenic sequences provides the basis of a chimeric particulate delivery platform, and resulted in the development of a vaccine against malaria (RTS,S/AS01, Mosquirix^TM), and various preclinical vaccine candidates to overcome infectious diseases for which there are no effective vaccines. Biomedical modifications of the HBsAg subunits allowed the identification of strategies to enhance the HBsAg SVP immunogenicity to build potent vaccines for preventative and possibly therapeutic applications. The review provides an overview of the formation and assembly of the HBsAg SVPs and highlights the utilization of the particles in key effective vaccines.

Toward a Functional Cure for Hepatitis B: The Rationale and Challenges for Therapeutic Targeting of the B Cell Immune Response

The central role of the cellular immune response in the control and clearance of the hepatitis B virus (HBV) infection has been well-established. The contribution of humoral immunity, including B cell and antibody responses against HBV, has been investigated for a long time but has attracted increasing attention again in recent years. The anti-HBs antibody was first recognized as a marker of protective immunity after the acute resolution of the HBV infection (or vaccination) and is now defined as a biomarker for the functional cure of chronic hepatitis B (CHB). In this way, therapies targeting HBV-specific B cells and the induction of an anti-HBs antibody response are essential elements of a rational strategy to terminate chronic HBV infection. However, a high load of HBsAg in the blood, which has been proposed to induce antigen-specific immune tolerance, represents a major obstacle to curing CHB. Long-term antiviral treatment by nucleoside analogs, by targeting viral translation by siRNA, by inhibiting HBsAg release via nucleic acid polymers, or by neutralizing HBsAg via specific antibodies could potentially reduce the HBsAg load in CHB patients. A combined strategy including a reduction of the HBsAg load via the above treatments and the therapeutic targeting of B cells by vaccination may induce the appearance of anti-HBs antibodies and lead to a functional cure of CHB.

Immune Determinants in the Acquisition and Maintenance of Antibody to Hepatitis B Surface Antigen in Adults After First-Time Hepatitis B Vaccination

Global implementation of a birth‐dose hepatitis B (HB) vaccine has significantly reduced the prevalence of hepatitis B virus (HBV) carriers. Durable and sufficient titers of antibodies to hepatitis B surface antigen (anti‐HBs) are desirable for vaccinees to gain resistance to HBV exposure. However, the existence of primary nonresponders and vaccinees who lost anti‐HBs over time remains a challenge for the strategy of HBV elimination. We thus aim to clarify the mechanisms of acquisition and maintenance of vaccine‐induced anti‐HBs in healthy adults. We retrospectively analyzed the vaccination records of 3,755 first‐time HB‐vaccinated students and also traced the acquired antibody transition of 392 first‐time vaccinees for 10 consecutive years. To understand the cellular and humoral immune response, we prospectively examined peripheral blood from 47 healthy first‐time HB‐vaccinated students, 62 booster‐vaccinated health care workers, and 20 individuals who maintained their anti‐HBs. In responders, a significant increase of follicular helper T (Tfh) cells, activated plasmablasts, and plasma cells was observed in first‐time‐vaccinated but not booster‐vaccinated persons. We also discovered memory B cells and antibody‐secreting cells were more abundant in individuals who maintained anti‐HBs. According to vaccination records, higher anti‐HBs antibody titer acquisition was related to the longer term maintenance of anti‐HBs, the level of which was positively correlated with prevaccination levels of serum interferon‐γ and related chemokines. The second series of vaccination as a booster provided significantly higher anti‐HBs antibody titers compared to the initial series. Conclusion: Coordinated activation of Tfh and B‐cell lineages after HB vaccination is involved in the acquisition and maintenance of anti‐HBs. Our findings support the rationale of preconditioning the immune status of recipients to ensure durable vaccine responses.

Comparative purification and characterization of hepatitis B virus-like particles produced by recombinant vaccinia viruses in human hepatoma cells and human primary hepatocytes

This study describes the comparative expression and purification of hepatitis B surface antigen (HBsAg) particles produced upon infection of human primary hepatocytes and human hepatoma cell lines (HuH-7 and HepG2) with recombinant vaccinia viruses. The highest levels of HBsAg expression were found in HuH-7 hepatoma cells following infection with recombinant vaccinia viruses, which contain the S gene under control of a 7.5 k-promoter. Four different methods for purification of the HBsAg particles were examined: isopycnic ultracentrifugation, sucrose cushion sedimentation, isocratic column gel filtration, and binding to anti-HBs-coated microparticles. The highest degree of purity of HBsAg particles was reached by the method based on anti-HBs-coated microparticles. The resulting product was >98% pure. Biochemical analysis and characterization of purified HBsAg particles were performed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), western blotting, and electron microscopy. The HBsAg, purified from human hepatoma cell lines and from human primary hepatocytes, consisted of both the non-glycosylated (p25) and the glycosylated (gp27) form and assembled into typical 22-nm particles, and thus may be of great interest and importance for research, diagnostics, and medical treatments.

Hepatitis B virus subgenotype F3 reactivation with vaccine escape mutations: A case report and review of the literature

Hepatitis B represents a global health threat because its chronic course and sequelae contribute to a high morbidity and mortality. Hepatitis B virus (HBV) infection can be controlled by vaccines, antiviral treatment, and by interrupting transmission. Rare vaccine escape mutants are serious because they eliminate vaccine protection. Here, we present a 74-year-old vaccinated patient with HBV reactivation 11 years after kidney transplantation. The patient was HBV-positive but HBsAg-negative prior to vaccination 6 years before transplantation. The reactivated virus was HBV genotype F3 with vaccine escape mutations G145R, P120Q, and Q129P. The patient was successfully treated with entecavir. The epidemiological reasons for this subgenotype, which is extremely rare in Western Europe, were unclear. This case illustrates that second-generation vaccines are not always effective in a specific group of patients.

A randomized, controlled clinical trial to evaluate the immunogenicity of a PreS/S hepatitis B vaccine Sci-B-Vac™, as compared to Engerix B®, among vaccine naïve and vaccine non-responder dialysis patients

BACKGROUND

Dialysis patients have a suboptimal response to hepatitis B (HBV) vaccination. This study aimed to compare the immunogenicity of two vaccines: the third-generation Sci-B-Vac™ vs. the second-generation Engerix B^®. The cohort included two groups of dialysis patients: naïve and previously vaccinated non-responders. Primary endpoints were antibody titers ≥10 IU/L at 3 and 7 month post-vaccination. Secondary objectives were seroprotection rates in vaccine-naïve patients and in previously vaccinated non-responders.

METHODS

Eighty-six patients were assigned to vaccine (Sci-B-Vac™ or Engerix B^®) using computer-generated randomization, stratified by age, gender, diabetes, and previous HBV vaccination. Sci-B-Vac™ was administered in three doses, 10 μg, at 0, 1, and 6 months in naïve patients; or 20 μg in previously vaccinated non-responders. Engerix B^® included four doses, 40 μg at 0, 1, 2, and 6 months.

RESULTS

Each group had 43 patients. Seroconversion was 69.8% with Engerix B^® vs. 73.2% with Sci-B-Vac™. Antibody titers at 7 months were higher with Sci-B-Vac™ (266.4 ± 383.9, median 53.4) than with Engerix^® (193.2 ± 328.9, median 19). However, these differences were not significant, perhaps due to a suboptimal sample size.

CONCLUSIONS

This study suggests comparable immunogenicity for both vaccines. Thus, we cannot reject the null hypothesis that there is no difference in seroconversion by vaccine type. It is noteworthy that naïve patients were vaccinated with a standard dose of Sci-B-Vac™, while Engerix B^® was administered at a double dose. Similarly, although mean antibody titer levels in the Sci-B-Vac™ group were higher than in the Engerix^® group, this difference did not reach significance. Consequently, a future clinical trial should recruit a larger cohort of patients, using a standard double-dose protocol in both groups.

Low Immunogenicity of Recombinant Hepatitis B Vaccine Derived from Hansenula polymorpha in Adults Aged Over 40 Years

The Brazilian recombinant hepatitis B vaccine (VrHB-IB) is based on the expression of the recombinant antigen in Hansenula polymorpha yeast cells. Currently, data on the immunogenicity of this vaccine in older adults are nonexistent. This study aimed to evaluate the immunogenicity of VrHB-IB in adults over 40 years of age. From May to October 2011, 235 rural settlers between 2 and 93 years of age from the State of Goias in Brazil were eligible for vaccination. Of these, 180 accepted the first dose of the vaccine and 106 (58.9%) completed the vaccination schedule. Multivariate analysis revealed that individuals ≥ 40 years of age responded significantly less well to vaccination than younger adults. Also, a greater proportion of male nonresponders was observed (versus women; P = 0.02). These results point to the need for better evaluation of the immunogenicity of VrHB-IB in older adults.

Age-dependent decrease of anti-HBs titers and effect of booster doses using 2 different vaccines in Palestinian children vaccinated in early childhood

Immunization against hepatitis B virus (HBV) has proven to be highly effective and led to significant reduction of new infections worldwide. However, protective immunity measured by anti-HBs titers may decrease to critical levels in the years after basal immunization, particularly in case of exposure to HBV variants different from the vaccine strain. We tested 400 Palestinian children between one and 19 years of age for their anti-HBs titer, challenged the immune memory of those with low or absent anti-HBs with 2 types of hepatitis B vaccines and determined thereafter the anti-HBs titer. At the age of one, 92.2% of the children presented with protective anti-HBs titers (≥ 10 mIU/ml) with the majority having ≥ 100 mIU/ml. Protective immunity was still high at ages 2 (87.5%) and 4 (95%), declining by age 5 and 6 (from 69.2% to 66.7%) and down to an average of 39.8% between the ages of 7 and 19. 160 children with a nonprotective or low immune response challenged with either the yeast-derived Engerix-B or the mammalian cell-derived preS1-containing Sci-B-Vac vaccine showed an anamnestic immune response. 92.4% and 85.9% of the children challenged with one dose Sci-B-Vac and Engerix-B presented with anti-HBs titers >100 mIU/ml respectively. Our results reveal that vaccine-induced protective anti-HBs titers against HBV decrease rapidly beyond the age of 6 in Palestinian children, but can be strongly enhanced with a single booster vaccine dose, independent of brand and antigen composition. Our data suggest that a booster vaccine dose against HBV during school years may be useful.

Novel Perspectives on the Hepatitis B Virus Vaccine in the Chronic Kidney Disease Population

Background

The prevalence and incidence rates of hepatitis B virus (HBV) among patients undergoing maintenance dialysis in developed countries have declined over the last 2 decades thanks to the implementation of numerous infection control procedures in dialysis units, including the hepatitis B vaccine. It is well known that the immune response against HBV vaccine is unsatisfactory in the chronic kidney disease (CKD) population. The seroprotection rate after the HB vaccine schedule is low and the anti-HB titers are reduced, falling logarithmically over time.

Purpose

We did an extensive review of the medical literature on the mechanisms underlying the reduced response rate towards the HBV vaccine in patients with CKD. The efficacy and safety of HBV vaccines for use in the CKD population was also evaluated.

Results

Currently available vaccines against HBV are mostly plasma-derived or manufactured by recombinant DNA technology (yielding the S protein of the HBV envelope). The most promising strategy to enhance the immune response toward the HBV vaccine in the dialysis population is given by adjuvanted vaccines. Second-generation recombinant HB vaccines provided with a novel adjuvant (AS04, made of 3- O-4′-desacyl-monophosphoryl lipid A adsorbed on aluminum phosphate) demonstrated improved immunogenicity but a number of patients with an unsatisfactory response still occurs. Additional second-generation vaccines containing nonaluminum-based adjuvant systems such as AS02 (3- O-desacyl-4′-monophoshoryl lipid A and QS21) or 1018 (a Toll-like receptor 9 agonist) have shown higher immunogenicity and acceptable safety in the CKD population. The evidence in patients with end-stage renal disease is extremely limited on the use of third-generation vaccines, recombinant HBV vaccines expressed in mammalian cells containing S/Pre-S antigens.

Conclusions

The immunogenicity of HBV vaccines in patients with CKD is suboptimal but novel technologies promise to give better results in the near future.

Applications of human hepatitis B virus preS domain in bio- and nanotechnology

Human hepatitis B virus (HBV) is a member of the family Hepadnaviridae, and causes acute and chronic infections of the liver. The hepatitis B surface antigen (HBsAg) contains the large (L), middle (M), and small (S) surface proteins. The L protein consists of the S protein, preS1, and preS2. In HBsAg, the preS domain (preS1 + preS2) plays a key role in the infection of hepatocytic cells by HBV and has several immunogenic epitopes. Based on these characteristics of preS, several preS-based diagnostic and therapeutic materials and systems have been developed. PreS1-specific monoclonal antibodies (e.g., MA18/7 and KR127) can be used to inhibit HBV infection. A myristoylated preS1 peptide (amino acids 2-48) also inhibits the attachment of HBV to HepaRG cells, primary human hepatocytes, and primary tupaia hepatocytes. Antibodies and antigens related to the components of HBsAg, preS (preS1 + preS2), or preS1 can be available as diagnostic markers of acute and chronic HBV infections. Hepatocyte-targeting delivery systems for therapeutic molecules (drugs, genes, or proteins) are very important for increasing the clinical efficacy of these molecules and in reducing their adverse effects on other organs. The selective delivery of diagnostic molecules to target hepatocytic cells can also improve the efficiency of diagnosis. In addition to the full-length HBV vector, preS (preS1 + preS2), preS1, and preS1-derived fragments can be useful in hepatocyte-specific targeting. In this review, we discuss the literature concerning the applications of the HBV preS domain in bio- and nanotechnology.

Induced immunity against hepatitis B virus

Prevention of hepatitis B virus (HBV) infection with its consequent development of HBV chronic liver disease and hepatocellular carcinoma is a global mandatory goal. Fortunately, safe and effective HBV vaccines are currently available. Universal hepatitis B surface antigen HBV vaccination coverage is almost done. Growing knowledge based upon monitoring and surveillance of HBV vaccination programs has accumulated and the policy of booster vaccination has been evaluated. This review article provides an overview of the natural history of HBV infection, immune responses and the future of HBV infection. It also summarizes the updated sources, types and uses of HBV vaccines, whether in the preclinical phase or in the post-field vaccination.

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.

Old and new adjuvants for hepatitis B vaccines

The safety and immunogenicity profiles of currently available recombinant hepatitis B vaccines are excellent. However, it remains a real challenge to induce protective immunity in the target groups that respond poorly or not at all to conventional vaccines. Ideally, a hepatitis B vaccine can be developed that conveys lifelong protection against infection rapidly after the injection of a single dose. Although this goal is far from being reached, important improvements have been made. Novel vaccine adjuvants have been developed that enhance the immunogenicity of recombinant hepatitis B vaccines while maintaining a good safety profile. The different adjuvants and adjuvant systems that are discussed herein have all been thoroughly evaluated in clinical trials and some have reached or are close to reach the market.

Prophylactic vaccination against hepatitis B: achievements, challenges and perspectives

Large-scale vaccination against hepatitis B virus (HBV) infection started in 1984 with first-generation vaccines made from plasma of chronic carriers containing HBV surface antigen (HBsAg). Thereafter, it was replaced in most countries by second-generation vaccines manufactured in yeast cells transformed with gene S encoding HBsAg. Both generations of vaccines have been applied for universal neonate and early childhood vaccination worldwide and have led to a 70-90 % decrease in chronic HBV carrier rates. However, 10-30% of newborns from HBsAg/HBeAg-positive mothers cannot be protected by passive/active vaccination alone and become chronic HBV carriers themselves. Asymptomatic occult HBV infections are frequent even in those who have protective levels of anti-HBs. Suboptimal protection may be due to heterologous HBsAg subtypes that are present in 99% of HBV carriers worldwide. Second-generation vaccines contain partially misfolded HBsAg and lack preS1 antigen that carries the major HBV attachment site and neutralizing epitopes. Third-generation vaccines produced in mammalian cells contain correctly folded HBsAg and neutralizing epitopes of the preS antigens, induce more rapid protection, overcome nonresponse to second-generation vaccines and, most importantly, may provide better protection for newborns of HBV-positive mothers. PreS/S vaccines expressed in mammalian cells are more expensive to manufacture, but introduction of more potent HBV vaccines should be considered in regions with a high rate of vertical transmission pending assessment of health economics and healthcare priorities. With optimal vaccines and vaccination coverage, eradication of HBV would be possible.

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.

Analytical platform for glycomic characterization of recombinant erythropoietin biotherapeutics and biosimilars by MS

Background: Erythropoietin is a therapeutic glycoprotein that stimulates red blood cell production. The quality, safety and potency of recombinant erythropoietins are determined largely by their glycosylation. Small variations in cell culture conditions can significantly affect the glycosylation, and therefore the efficacy, of recombinant erythropoietins. Thus, detailed glycomic analyses are necessary to assess biotherapeutic quality. We have developed a platform for qualitative and quantitative glycomic analysis of recombinant erythropoietins. Results: The platform was used to profile native N-glycans from three production batches of darbepoetin alfa (also known as NESP), a common form of recombinant erythropoietin. Darbepoetin alfa was found to contain an abundance of large, multi-antennary N-glycans with high levels of sialylation, O-acetylation and dehydration. Results were verified by independent orthogonal analysis with both MALDI-TOF and nano-LC/Q-TOF MS. Conclusion: This platform may be applied to QC and batch analysis of not only recombinant erythropoietin, but also other complex, glycosylated biotherapeutics and biosimilars.

The twenty-year story of a plant-based vaccine against hepatitis B: stagnation or promising prospects?

Hepatitis B persists as a common human disease despite effective vaccines having been employed for almost 30 years. Plants were considered as alternative sources of vaccines, to be mainly orally administered. Despite 20-year attempts, no real anti-HBV plant-based vaccine has been developed. Immunization trials, based on ingestion of raw plant tissue and conjugated with injection or exclusively oral administration of lyophilized tissue, were either impractical or insufficient due to oral tolerance acquisition. Plant-produced purified HBV antigens were highly immunogenic when injected, but their yields were initially insufficient for practical purposes. However, knowledge and technology have progressed, hence new plant-derived anti-HBV vaccines can be proposed today. All HBV antigens can be efficiently produced in stable or transient expression systems. Processing of injection vaccines has been developed and needs only to be successfully completed. Purified antigens can be used for injection in an equivalent manner to the present commercial vaccines. Although oral vaccines require improvement, plant tissue, lyophilized or extracted and converted into tablets, etc., may serve as a boosting vaccine. Preliminary data indicate also that both vaccines can be combined in an effective parenteral-oral immunization procedure. A partial substitution of injection vaccines with oral formulations still offers good prospects for economically viable and efficacious anti-HBV plant-based vaccines.

Use of pre-S protein-containing hepatitis B virus surface antigens and a powerful adjuvant to develop an immune therapy for chronic hepatitis B virus infection

A hepatitis B virus (HBV) vaccine has been developed using a new adjuvant and HBV surface antigens produced from a CHO cell line. The purified HBV surface antigens are composed of L protein, M protein, and S protein in a mixture of 20- and 40-nm-diameter particles and filamentous forms. This HBV surface antigen, formulated with L-pampo, a proprietary adjuvant, induced 10 times more antibody than the same antigen with alum and was capable of inducing strong immune responses in three different HBV transgenic mice. In spite of the presence of a large amount of HBV antigen in the blood, no antibody against HBV surface antigen was normally detected in these transgenic mice. After immunization, the HBV antigen was also cleared from the blood.

Viral nanoparticles and virus-like particles: platforms for contemporary vaccine design

Current vaccines that provide protection against infectious diseases have primarily relied on attenuated or inactivated pathogens. Virus‐like particles (VLPs), comprised of capsid proteins that can initiate an immune response but do not include the genetic material required for replication, promote immunogenicity and have been developed and approved as vaccines in some cases. In addition, many of these VLPs can be used as molecular platforms for genetic fusion or chemical attachment of heterologous antigenic epitopes. This approach has been shown to provide protective immunity against the foreign epitopes in many cases. A variety of VLPs and virus‐based nanoparticles are being developed for use as vaccines and epitope platforms. These particles have the potential to increase efficacy of current vaccines as well as treat diseases for which no effective vaccines are available. WIREs Nanomed Nanobiotechnol 2011 3 174–196 DOI: 10.1002/wnan.119

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Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease

Expression of hepatitis B virus surface antigen determinants in Lactococcus lactis for oral vaccination

Lactococcus lactis with non-pathogenic and non-colonizing properties is an attractive candidate for delivering biologically active proteins by mucosal routes. In this report we described recombinant L. lactis applicable for the development of live mucosal vaccine against hepatitis B virus (HBV). The PreS region of the HBV surface antigen alone or combined with "a" determinant of S region (PreSa) was cloned and expressed in the food grade bacterium L. lactis using a nisin-controlled expression (NICE) system. Western blot analysis indicated that both PreS and PreSa fusion proteins were successfully expressed in L. lactis after nisin induction. Oral immunization of BALB/c mice with PreS and PreSa-producing strains induced both mucosal (intestinal IgA) and systemic (serum IgG) immune responses against HBV at the same magnitude. Two additional groups of mice given L. lactis expressing human interferon-alpha 2b as an adjuvant with the PreS or PreSa-producing strains produced higher IgG but not IgA antibody responses. These results indicated that the lactococci-derived vaccines could be promising candidates as alternative HBV vaccines for preventing hepatitis B.

The global impact of vaccination against hepatitis B: a historical overview

Hepatitis B virus (HBV) infection is a world wide public health problem of major concern. HBV infection may lead to chronic liver disease, including cirrhosis and hepatocellular carcinoma (HCC). Vaccination is the most effective measure to control and prevent hepatitis B and its long-term serious sequelae on global scale, both in terms of cost-effectiveness and benefit-cost ratios. According to the WHO recommendations, universal vaccination has been currently implemented in 168 countries world wide with an outstanding record of safety and efficacy. The effective implementation of such programmes of vaccination has resulted in a substantial decrease in disease burden, in the carrier rate and in hepatitis B-related morbidity and mortality. A future challenge is to overcome the social and economic hurdles which still hamper the introduction of hepatitis B vaccination on a global scale.

Nanotechnology in vaccine delivery

With very few adjuvants currently being used in marketed human vaccines, a critical need exists for novel immunopotentiators and delivery vehicles capable of eliciting humoral, cellular and mucosal immunity. Such crucial vaccine components could facilitate the development of novel vaccines for viral and parasitic infections, such as hepatitis, HIV, malaria, cancer, etc. In this review, we discuss clinical trial results for various vaccine adjuvants and delivery vehicles being developed that are approximately nanoscale (< 1000 nm) in size. Humoral immune responses have been observed for most adjuvants and delivery platforms while only viral vectors, ISCOMs and Montanide™ ISA 51 and 720 have shown cytotoxic T cell responses in the clinic. MF59 and MPL® have elicited Th1 responses, and virus-like particles, non-degradable nanoparticles and liposomes have also generated cellular immunity. Such vaccine components have also been evaluated for alternative routes of administration with clinical successes reported for intranasal delivery of viral vectors and proteosomes and oral delivery of a VLP vaccine.

Serum levels of preS antigen (HBpreSAg) in chronic hepatitis B virus infected patients

Background

Hepatitis B virus (HBV) infection is a serious health problem worldwide. Treatment recommendation and response are mainly indicated by viral load, e antigen (HBeAg) seroconversion, and ALT levels. The S antigen (HBsAg) seroconversion is much less frequent. Since HBeAg can be negative in the presence of high viral replication, preS antigen (HBpreSAg) might be a useful indicator in management of chronic HBV infection.

Results

A new assay of double antibody sandwich ELISA was established to detect preS antigens. Sera of 104 HBeAg-negative and 50 HBeAg-positive chronic hepatitis B patients have been studied and 23 HBeAg-positive patients were enrolled in a treatment follow-up study. 70% of the HBeAg-positive patients and 47% of the HBeAg-negative patients showed HBpreSAg positive. Particularly, in the HBeAg-negative patients, 30 out of 47 HBpreSAg positive patients showed no evidence of viral replication based on HBV DNA copies. A comparison with HBV DNA copies demonstrated that the overall accuracy of the HBpreSAg test could reach 72% for active HBV replication. HBpreSAg changes were well correlated with changes of HBsAg, HBV DNA and ALT levels during the course of IFN-α treatment and follow-up. HBeAg positive patients responded well to treatment when reduction of HBpreSAg levels was more pronounced.

Conclusion

Our results suggested that HBpreSAg could be detected effectively, and well correlated with HBsAg and HBV DNA copies. The reduction of HBpreSAg levels in conjunction with the HBV DNA copies appears to be an improved predictor of treatment outcome.

Virus-like particles: passport to immune recognition

Virus-like particles (VLPs) are formed by the self-assembly of envelope and/or capsid proteins from many viruses. In many cases such VLPs have structural characteristics and antigenicity similar to the parental virus, and some have already proven successful as vaccines against the cognate virus infection. The structural components of some VLPs have also proven amenable to the insertion or fusion of foreign antigenic sequences, allowing the production of chimeric VLPs exposing the foreign antigen on their surface. Other VLPs have been used as carriers for foreign antigens, including non-protein antigens, via chemical conjugation. This review outlines some of the advantages, disadvantages, and technical considerations for the use of a wide range of VLP systems in vaccine development.

Immune responses to recombinant Mycobacterium smegmatis expressing fused core protein and preS1 peptide of hepatitis B virus in mice

Attenuated strains of bacteria have been developed as potential live vectors to express homologous or heterologous antigens of many pathogens for inducing protective immune responses. The non-pathogenic and rapidly growing Mycobacterium smegmatis can be transformed effectively by genes for pathogenic antigens, and has been used as a valuable vector for the development of live vaccines. However, little is known on whether M. smegmatis could be transformed with the genes for HBV antigens and could express those genes, and whether vaccination with recombinant M. smegmatis could induce humoral and cellular immune responses in vivo. Both the core protein and preS1 peptide of the hepatitis B virus (HBV) are immunogenic and can induce cellular and humoral immune responses. This made them ideal platform for the development of new vaccines. In the present study, both recombinant M. smegmatis and DNA vaccines were generated to express the CS1 antigen, a fusion protein that comprises truncated core protein (amino acids 1-155) and preS1 peptide (amino acids 1-55) of HBV. Following vaccination of BALB/c mice with the live recombinant M. smegmatis, the CS1-based DNA vaccine, or controls, antigen-specific humoral and cellular immune responses were characterized. Vaccination with live recombinant M. smegmatis induced a stronger cellular immune response and a longer period of humoral immune response than with the DNA vaccination. These results indicate that the recombinant M. smegmatis can express efficiently immunogenic CS1 antigen of HBV in vivo, and may be used for the prevention of HBV infection.

Expression, purification and characterization of the Hepatitis B virus entire envelope large protein in Pichia pastoris

The current HBsAg vaccine has performed a vital role in preventing the transmission of HBV during the past 20 years. However, a number of individuals still show no response or a low response to the vaccine. In the present study, the HBV envelope large protein gene was cloned into the eukaryotic expression vector pPIC9k and was subsequently expressed in the yeast Pichia pastoris. The HBV large protein (L protein) was produced and secreted into the medium, where some of the L protein formed particles. The soluble L protein and particles were purified by column chromatography and sucrose density gradient centrifugation. Western blot analysis demonstrated that the particle was composed of both HBV L and S protein. To compare the antigenicity of the L protein and HBsAg, rabbits were immunized with the soluble L protein and the commercially available HBV vaccine and the increasing level of antibodies was determined by ELISA. The results showed that the anti-HBsAg antibody, from rabbits injected with the L protein at a dose of 2 and 10microg, was detected on day 14, whereas rabbits vaccinated with 10 and 2microg HBsAg did not develop antibodies until day 21 and 28, respectively. The antibody level in groups inoculated with the L protein was approximately 50% higher than in the group injected with HBsAg using the same dose. Furthermore, 2microg L protein induced a significant and rapid anti-HBsAg antibody response than 10microg HBsAg. Therefore, we suggest that the L protein is an ideal candidate for a new generation HB vaccine to protect people from HBV infection.

Molecular characterization of recombinant Hepatitis B surface antigen from Chinese hamster ovary and Hansenula polymorpha cells by high-performance size exclusion chromatography and multi-angle laser light scattering

The molecular weight and size of recombinant Hepatitis B surface antigen (HBsAg) derived from Chinese hamster ovary (CHO) and the Hansenula polymorph have been characterized by high-performance size exclusion chromatography with multi-angle laser light scattering (HPSEC-MALLS). The average molecular weight of CHO-derived HBsAg particle (CHO-rHBsAg) (4921 kDa) was higher than that of H. polymorpha yeast strain (Hans-rHBsAg) (3010 kDa). The size of CHO-rHBsAg (22.1 nm) is nearly the same as that of native HBsAg compared to 18.1 nm for Hans-rHBsAg. The average monomer numbers were found to be 155 for CHO-rHBsAg and 86 for Hans-rHBsAg, respectively. The data obtained support the assumption that the higher immunogenicity of CHO-derived HBsAg is related to its more favorable macromolecular assembly structure.

Expression of Hepatitis B Virus S Gene in Pichia pastoris and Application of the Product for Detection of Anti-HBs Antibody

Antibody to hepatitis B surface antigen (HBsAb) is the important serological marker of the hepatitis B virus (HBV) infection. Conventionally, the hepatitis B surface antigen (HBsAg) obtained from the plasma of HBV carriers is used as the diagnostic antigen for detection of HBsAb. This blood-origin antigen has some disadvantages involved in high cost, over-elaborate preparation, risk of infection, et al. In an attempt to explore the suitable recombinant HBsAg for the diagnostic purpose, the HBV S gene was expressed in Pichia pastoris and the product was applied for detection of HBsAb. Hepatitis B virus S gene was inserted into the yeast vector and the expressed product was analyzed by sodium dodecyl sulphate polyacrolamide gel electrophoresis (SDS-PAGE), immunoblot, electronic microscope and enzyme linked immunosorbent assay (ELISA). The preparations of synthesized S protein were applied to detect HBsAb by sandwich ELISA. The S gene encoding the 226 amino acid of HBsAg carrying a hexa-histidine tag at C terminus was successfully expressed in Pichia pastoris. The His-Tagged S protein in this strain was expressed at a level of about 14.5 % of total cell protein. Immunoblot showed the recombinant HBsAg recognized by monoclonal HBsAb and there was no cross reaction between all proteins from the host and normal sera. HBsAb detection indicated that the sensitivity reached 10 mIu (micro international unit)/ml and the specificity was 100 % with HBsAb standard of National Center for Clinical Laboratories. A total of 293 random sera were assayed using recombinant S protein and a commercial HBsAb ELISA kit (produced by blood-origin HBsAg), 35 HBsAb positive sera and 258 HBsAb negative sera were examined. The same results were obtained with two different reagents and there was no significant difference in the value of S/CO between the two reagents. The recombinant HBV S protein with good immunoreactivity and specificity was successfully expressed in Pichia pastoris. The reagent for HBsAb detection prepared by Pichia pastoris-derived S protein showed high sensitivity and specificity for detection of HBsAb standard. And a good correlation was obtained between the reagent produced by recombinant S protein and commercial kit produced by blood-origin HBsAg in random samples.

Humoral response and genetic stability of recombinant BCG expressing hepatitis B surface antigens

The Bacille Calmette Guerin (BCG), long valued for its role as a live vaccine for the prevention of tuberculosis, is being used as a recombinant delivery vehicle for foreign antigens, principally, for inducing long-lived specific humoral and cellular immunity. Hepatitis B and its sequelae are major public health problems. Although vaccines have been available for over 20 years the disease remains a significant global problem. Many factors contribute to vaccine failure to control hepatitis B, including attaining of adequate immune protection. In this study, a novel rBCG delivery system is described using non-integrative plasmids harboring hepatitis B surface antigen genes. This rBCG was able to elicit an anti-HBs response in BALB/c mice. The titres of anti-HBs response obtained using rBCG was relatively lower than that of the commercial vaccine used as positive control. In vivo or in vitro stability assays showed that the vector used to generate rBCG is stable in spite of being a non-integrative plasmid. In addition, the HBsAg proteins expression profiles were almost similar to those obtained using an Escherichia coli expression system.

Efficient inhibition of hepatitis B virus infection by acylated peptides derived from the large viral surface protein

The lack of an appropriate in vitro infection system for the major human pathogen hepatitis B virus (HBV) has prevented a molecular understanding of the early infection events of HBV. We used the novel HBV-infectible cell line HepaRG and primary human hepatocytes to investigate the interference of infection by HBV envelope protein-derived peptides. We found that a peptide consisting of the authentically myristoylated N-terminal 47 amino acids of the pre-S1 domain of the large viral envelope protein (L protein) specifically prevented HBV infection, with a 50% inhibitory concentration (IC50) of 8 nM. The replacement of myristic acid with other hydrophobic moieties resulted in changes in the inhibitory activity, most notably by a decrease in the IC50 to picomolar concentrations for longer unbranched fatty acids. The obstruction of HepaRG cell susceptibility to HBV infection after short preincubation times with the peptides suggested that the peptides efficiently target and inactivate a receptor at the hepatocyte surface. Our data both shed light on the molecular mechanism of HBV entry into hepatocytes and provide a basis for the development of potent hepadnaviral entry inhibitors as a novel therapeutic concept for the treatment of hepatitis Beta.

Improved immunogenicity of a novel third-generation recombinant hepatitis B vaccine in patients with end-stage renal disease

Hepatitis B (HBV) infection remains a significant epidemiological problem in the end-stage renal disease (ESRD) population. Vaccination programs using second-generation vaccines lead to effective seroprotection in only 50-60% of these patients. The purpose of this case series was to describe our experience with a novel third-generation vaccine, Bio-Hep-B, in ESRD patients who had not developed protective anti-HBs titers following a second-generation HBV vaccination protocol. Twenty-nine ESRD patients who had not responded in the past to a standard second-generation HBV vaccination protocol were included in this series. Each patient received 10 microg of Bio-Hep-B) intramuscularly at 0, 1 and 6 months. A month after completion of the vaccination protocol, anti-HBs antibody levels were measured. Following immunization, 25 of 29 patients (86%) developed seroprotective anti-HBs levels > or =10 mIU/ml. There was a significant difference in the titers of anti-HBs antibodies prior to and following vaccination (p < 0.0001). Statistical analysis of the variables age, gender, diagnosis, dialysis mode, weight, hemoglobin, albumin, and KT/V failed to detect predictors of antibody response. A retrospective analysis of the results of a second-generation vaccination program for the years 1999-2001 in our department showed that 19 of 36 (56.4%) ESRD patients developed seroprotection. In conclusion, the results of this study show that the third-generation HBV vaccine Bio-Hep-B is highly immunogenic in the population of ESRD patients who did not respond in the past to a second-generation vaccine. This enhanced seroprotection offers hope that the new vaccine will reduce the rate of non-responders and help to eliminate HBV infection from dialysis centers.

Induction of oral immune regulation towards liver-extracted proteins for treatment of chronic HBV and HCV hepatitis: results of a phase I clinical trial

BACKGROUND

Anti-viral immunity can be modulated via oral feeding of viral proteins. Hepatitis B and C viral (HBV, HCV)-associated hepatocellular injury is mediated by a defective host anti-viral immune response.

AIMS

To determine the effect of oral administration of a mixture of liver-extracted proteins with HBV/HCV proteins, on viral load, liver injury, and the anti-viral T-cell response of chronic HBV/HCV patients.

METHODS

Fourteen patients with chronic HBV and 15 patients with chronic HCV were treated orally with hepatocyte-extracted proteins and HBV or HCV viral proteins for 24 weeks, and followed for an additional 26 weeks. Patients were monitored for HBV-DNA or HCV-RNA levels, liver enzymes and liver histology. Viral-directed T-cell immunity was assessed by IFNgamma and IL10 ELISPOT, viral-specific T-cell proliferation, cytotoxicity, and cytokines assays, and followed for peripheral natural killer T-cell (NKT) number.

RESULTS

In both chronic HBV and HCV patients, oral administration of a mixture of selected liver-extracted proteins and viral proteins induced a favorable increase in viral-specific T-cell proliferation, and IFNgamma-secreting clones, along with a significant decrease in the anti-viral IL10-secreting T-cell clones. However, the effects of modulation of the anti-viral immunity differed between the HBV and HCV patients. In both groups, no major adverse events were noted. In chronic HBV patients, a significant decrease in viral load was observed in 5/14 (35.7%) of patients. HB surface antigen/HB nucleocapsid antigen scores on liver biopsy improved in 46.1% and 50%, respectively, and the histological necroinflammatory score improved in 4/13 (30.7%). Forty percent of the patients with elevated liver enzymes showed a favorable biochemical response. In contrast, an improvement in the histological necroinflammatory score was observed in only 2/12 (17%) of the chronic HCV patients. No significant decrease in HCV RNA was noted in any of these patients.

CONCLUSIONS

Immune regulation of the anti-HBV/HCV immune response via oral administration of a mixture of liver-extracted and viral proteins significantly altered the viral-specific immunity. This effect was associated with clinical and virological improvements in chronic HBV patients.