Evaluation of B and T-cell responses in chimpanzees immunized with Hepagene, a hepatitis B vaccine containing pre-S1, pre-S2 gene products

Protective efficacy and hepatitis B virus clearance in mice enhanced by cell-mediated immunity with novel prime-boost regimens

In this study, anti-hepatitis B virus (HBV) immunity was evaluated in mice using several regimens of the HBV recombinant protein vaccine HBSS1 that expressed in CHO cells containing S (1-223 aa) and preS1 (21-47 aa) and recombinant adenovirus rAdSS1 vaccine. Further, the protective efficacy of these vaccine regimens was studied in a mouse model. High titres of antigen-specific antibodies and neutralizing activity were elicited in mice after vaccination. However, robust multi-antigen (preS1 and S)-specific cell-mediated immunity (CMI) was only detected in mice primed with HBSS1 and boosted with rAdSS1. Moreover, functional T-cell responses with high levels of cytokines and antigen-specific cytotoxic T-cell responses (CD107a⁺ CD8⁺ ) were also detected in the mice. Rapid clearance of hepatitis B surface antigen and HBV DNA in blood and significantly decreased hepatitis B envelope antigen levels were observed in mice immunized with the heterogeneous prime-boost vaccine after hepatitis B virus challenge by hydrodynamic injection (HI) of pCS-HBV1.3. The clearance of HBV correlated well with antigen-specific CMI (Th1 and CTL responses) and cytokine profiles (IFN-γ, TNF-α, IL-2) elicited by vaccination. Taken together, our results might contribute to the development of new human HBV vaccines and a better understanding of the mechanisms underlying immune protection and clearance of hepatitis B virus infection.

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.

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

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

Enhanced effect of DNA immunization plus in vivo electroporation with a combination of hepatitis B virus core-PreS1 and S-PreS1 plasmids

To develop a novel, effective HBV therapeutic vaccine, we constructed two HBV DNA immunogens that contained PreS1, HBSS1, and HBCS1. Several delivery methods, such as intramuscular (i.m.) injection, intramuscular injection plus electroporation (i.m.-EP), and intradermal injection plus electroporation (i.d.-EP) were used in a murine model to analyze and compare the immune responses that were induced by the DNA immunogens. We found that i.d.-EP accelerated specific antibody seroconversion and produced high antibody (anti-PreS1, anti-S, and anti-C antibody) titers after HBSS1 and HBCS1 immunization. Combining the HBSS1 and HBCS1 DNA immunogens with i.d.-EP produced the strongest multiantigen (PreS1, S, and C)-specific cellular immune response and the highest specific PreS1 antibody levels. The results indicated that DNA immunization using HBSS1 and HBCS1 might be an ideal candidate, with its ability to elicit robust B and T cell immune responses against multiantigen when combined with optimized delivery technology. The present study provides a basis for the design and rational application of a novel HBV DNA vaccine.

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.

Anti-preS responses influence the anti-HBs response in newborns after vaccination with the third generation Sci-B-Vac vaccine

We analysed the specificity and significance of the antibody response towards the linear preS1 sequence that has been shown to represent the "hepatocyte binding site" comprising amino acids preS1 (21-47) or the specific preS2 (131-140) antibody response to the "polymerised albumin receptor" in relation to the antibody response to hepatitis B surface antigen during immunisation of healthy children with the preS-containing Sci-B-Vac vaccine. Twenty-eight healthy newborns received three doses of the Sci-B-Vac vaccine according to a 0-, 1-, and 6-month scheme. Seventeen (61%) of the 28 newborns had detectable levels of anti-preS1 (21-47) antibodies and 14 (50%) were anti-preS2 (131-140) reactive at 6 and/or 9 months after initiation of the vaccination. The mean levels of anti-HBs were significantly higher in the anti-preS2 (131-140) non-reactive (24580+/-7815IU/l, mean+SEM) compared with the reactive sera (7287+/-2317IU/l, p<0.025). The highest anti-HBs levels were found in newborns who exhibited reactivity towards the aa 21-47 of the preS1 but lacked anti-preS2 (131-140) reactivity.

PreS1 epitope recognition in newborns after vaccination with the third-generation Sci-B-Vac vaccine and their relation to the antibody response to hepatitis B surface antigen

Background

Sci-B-Vac™ is a recombinant, hepatitis B vaccine derived from a mammalian cell line and containing hepatitis B surface antigen (HBsAg) as well as preS1 and preS2 antigens. Few studies have been performed on the antibody responses to preS1 in relation to the antibody to hepatitis B surface antigen (anti-HBs) response during immunisation of healthy children with preS-containing vaccines.

Results

In this study 28 healthy newborns were randomly selected to receive either 2.5 ug or 5.0 ug of the Sci-B-Vac vaccine. Children received three doses of vaccine according to a 0-, 1-, 6-month scheme. Antibodies against the S-protein and three synthetic peptides mimicking three B-cell preS1 epitopes, (21–32 amino acid epitope), (32–47 amino acid epitope) and the C-terminal (amino acid epitope 94–117) were determined at 6 and 9 months. Fourteen (50%) of the 28 newborns had detectable levels of anti-preS1 (21–32) antibodies; 15 (54%) were anti-preS1 (32–47) reactive and 12 (43%) were anti-preS1 (94–117) reactive at 6 or 9 months after initiation of the vaccination. Significantly higher levels of anti-HBs were observed in the sera of patients with detectable anti-preS1 (32–47) reactivity (24 550 ± 7375 IU/L, mean ± SEM) as compared with the non-reactive sera (5991 ± 1530 IU/L, p < 0.05). The anti-HBs levels were significantly lower if none (p < 0.05) or one (p < 0.025) of the preS1 (21–32, 32–47, 94–117) peptides were recognised compared with the anti-HBs levels if two or three peptides were recognised.

Conclusion

Recognition of several preS1 epitopes, and in particular, the epitope contained within the second half of the hepatocyte binding site localised in the hepatitis B surface protein of the third-generation hepatitis B vaccine is accompanied by a more pronounced antibody response to the S-gene-derived protein in healthy newborns.

Overexpression and purification of PreS region of hepatitis B virus antigenic surface protein adr subtype in Escherichia coli

PreS domain of Hepatitis B virus (HBV) surface antigen is a good candidate for an effective vaccine as it activates both B and T cells besides binding to hepatocytes. This report deals with overexpression and purification of adr subtype of surface antigen that is more prevalent in Pakistan. PreS region, comprising 119 aa preS1 region plus a 55 aa preS2 region plus 11 aa from the N-terminal S region, was inserted in pET21a+ vector, cloned in E. coli DH5alpha cells and expressed in E. coli BL21 codon+ cells. The conditions for over expression were optimized using different concentrations of IPTG (0.01-5 mM), and incubating the cells at different temperatures (23-41 degrees C) for different durations (0-6 h). The cells were grown under the given optimized conditions (0.5 mM IPTG concentration at 37 degrees C for 4 h), lysed by sonication and the protein was purified by ion exchange chromatography. On the average, 24.5 mg of recombinant protein was purified per liter of culture. The purified protein was later lyophilized and stored at -80 degrees.

Expression and purification of the complete PreS region of hepatitis B Virus

AIM: To express the complete PreS region of HBV in E.coli with good solubility and stability, and to establish an effective method for purification of the recombinant PreS protein.

METHODS: The complete PreS region (PreS1 and PreS2) was fused into a series of tags including glutathione S-transferase (GST), dihydrofolate reductase (DHFR), maltose binding protein (MBP), 6×histidine, chitin binding domain (CBD), and thioredoxin, respectively. Expression of recombinant PreS fusion proteins was examined by SDS-PAGE analysis and confirmed by Western blot. Two fusion proteins, thio-PreS, and PreS-CBD, with desirable solubility and stability, were subjected to affinity purification and further characterization.

RESULTS: Recombinant PreS fusion proteins could be synthesized with good yields in E.coli. However, most of these proteins except for thio-PreS and PreS-CBD were vulnerable to degradation or insoluble as revealed by SDS-PAGE and Western blot. Thio-PreS could be purified by affinity chromatography with nickel-chelating sepharose as the matrix. However, some impurities were also co-purified. A simple freeze-thaw treatment yielded most of the thio-PreS proteins in solution while the impurities were in the precipitate. Purified thio-PreS protein was capable of inhibiting the binding of HBV virion to a specific monoclonal antibody against an epitope within the PreS1 domain.

CONCLUSION: Increased solubility and stability of the complete PreS region synthesized in E.coli can be achieved by fusion with the thioredoxin or the CBD tag. A simple yet highly effective method has been established for the purification of the thio-PreS protein. Purified thio-PreS protein likely assumes a native conformation, which makes it an ideal candidate for studying the structure of the PreS region as well as for screening antivirals.

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.

Most humoral non-responders to hepatitis B vaccines develop HBV-specific cellular immune responses

About 10% of health care professionals vaccinated against hepatitis B virus (HBV) fail to develop protective antibodies. We tested the capacity of peripheral blood lymphocytes from 121 health care professionals, including 76 non-responders, to proliferate to four HBV vaccines, examined the proliferating cells' subset, production of IFN-gamma, IL-4 and IL-10, and for 22 subjects, the cytokine production genotype. Specific proliferative responses to at least one HBV antigen were noted in 75% humoral non-responders. These cells differed from the CD4+ strongly proliferating cells of responders. Non-responders frequently displayed a genotype of high TGF-beta and intermediate IL-10 secretion. Most humoral non-responders to HBV thus develop specific cellular immune responses, eventually liable to protect them against viral infection.

Construction and expression of eukaryotic vector bearing fusion gene of HBV PreS2S and Fc fragment

AIM: To construct and express a recombinant eukaryotic expression vector bearing fusion gene of HBV S2S and Fc fragment.

METHODS: The technique of splicing by overlapping extension and twice PCR were used, and fusion gene fragment was obtained and cloned into pGEM-T Easy TA cloning vector to get suited enzyme sites. Recombinant eukaryotic expression vector pcDNA3 S2S/Fc was constructed by double adhesive terminal ligation. Then the recombinant vector was transferred into SP2/0 cells by using Lipofectamine.

RESULTS: The recombinant vector was identified by digestion with restriction enzymes and confirmed by DNA sequencing analysis. And the vector bearing fusion gene could be expressed in eukaryotic cells detected by indirect immunofluotescence technique.

CONCLUSION: The relative efficient expression of the fusion gene in SP2/0 cells may provide an experimental basis for specific immunotherapy for HBV infection.

Hepatitis B vaccines

Yeast-derived hepatitis B vaccines, containing the small HBV envelope protein SHBAg, are immunogenic, safe and cost-effective in prevention of hepatitis B virus infection in neonates, children and adults. Newly developed pre-S/S hepatitis B vaccines may play a role in inducing fast and augmented seroconversion rates in special risk groups.

Recombinant hepatitis B triple antigen vaccine: Hepacare

Infection with hepatitis B virus is a public health problem throughout the world. Hepatitis B vaccines are now included in national immunization programmes of infants and/or adolescents in 129 countries. Current single antigen vaccines, that are plasma-derived or produced by recombinant DNA technology are highly effective, but between 5-10% or more of healthy immunocompetent subjects do not mount an antihepatitis B surface antibody protective response and others respond poorly (hyporesponders). The inclusion of pre-S1 and -S2 components of hepatitis B surface antigen in addition to the single antigen (triple antigen) in a novel vaccine, Hepacare, Medeva Pharma Plc, Speke, UK, overcomes nonresponsiveness and hyporesponsiveness in a significant number of individuals. The triple antigen is indicated for vaccination of nonresponders (and hyporesponders) to the current single antigen vaccines and for persons who require rapid protection against hepatitis B infection.

Chronic hepatitis B: current and future treatment options

Hepatitis B, a major viral infection that can lead to cirrhosis and hepatocellular carcinoma, is the ninth most common cause of death worldwide. Prevention of hepatitis B virus transmission is key to reducing the spread of this serious condition. Management of chronic hepatitis B requires significant knowledge of approved pharmacotherapeutic agents and their limitations. Today, agents approved by the Food and Drug Administration for this infection are interferon-alpha-2b and lamivudine. Newer agents are being developed and hold promise: adefovir, famciclovir, ganciclovir, lobucavir, entecavir, emtricitabine, L-deoxythymidine, clevudine, a therapeutic vaccine, and thymosin alpha-1. Therapeutic options for managing hepatitis infection after liver transplantation are also evolving. These include hepatitis B immunoglobulin and nucleoside analogues.

Detection of anti-preS1 antibodies for recovery of hepatitis B patients by immunoassay

AIM: To establish a convenient immunoassay method based on recombinant antigen preS1(21-119 aa) to detect anti-preS1 antibodies and evaluate the clinical significance of antibodies in hepatitis B.

METHODS: The expression plasmid pET-28a-preS1 was constructed, and a large quantity of preS1(21-119 aa) fragment of the large HBsAg protein was obtained. The preS1 fragment purified by Ni²⁺-IDA affinity chromatography was used as coated antigen to establish the indirect ELISA based on streptavidin-biotin system for detection of the anti-preS1 antibodies in sera from HBV-infected patients. For follow-up study, serial sera were collected during the clinical course of 21 HBV-infected patients and anti-preS1 antibodies, preS1 antigen, HBV-DNA and other serological HBV markers were analyzed.

RESULTS: preS1(21-119 aa) fragment was highly expressed from the plasmid pET-28a-preS1 in a soluble form in E. coli (30 mg•L⁻¹), and easily purified to high purity over 90% by one step of Ni²⁺-IDA-sepharose 6B affinity chromatography. The purity and antigenicity of the purified preS1(21-119 aa) protein was determined by 150 g•L⁻¹ SDS-PAGE, Western blot and a direct ELISA. Recombinant preS1(21-119 aa) protein was successfully applied in the immunoassay which could sensitively detect the anti-preS1 antibodies in serum specimens of acute or chronic hepatitis B patients. Results showed that more than half of 19 acute hepatitis B patients produced anti-preS1 antibodies during recovery of the disease, however, the response was only found in a few of chronic patients. In the clinical follow-up study of 11 patients with anti-preS1 positive serological profile, HBsAg and HBV-DNA clearance occurred in 6 of 10 acute hepatitis B patients in 5-6 mo, and seroconversion of HBeAg and disappearance of HBV-DNA occurred in 1 chronic patients treated with lavumidine, a antiviral agent.

CONCLUSION: The high-purity preS1(21-119 aa) coated antigen was successfully prepared by gene expression and affinity chromatography. Using this antigen, a conveniently detective system of anti-preS1 antibodies in sera was established. Preliminarily clinical trial the occurrence of anti-preS1 antibodies in acute hepatitis B patients suggests the clearance of HBV from serum in a short-term time, and anti-preS1 positive in chronic patients means health improvement or recovery from the disease.

A multi-center controlled study of rapid hepatitis B vaccination using a novel triple antigen recombinant vaccine

Hepatitis B vaccines have been available for 20 years, however, the disease still remains a global problem. Clearly, the protection of at-risk groups could be improved if a more potent vaccine with a shorter vaccination regimen were available. Hepacare is new recombinant vaccine, which contains three of the surface antigens of the HB virus and has higher immunogenicity than present single antigen (HBsAg only) vaccines. This study evaluates the potential for developing seroprotection rapidly and the viability of a 1 month/two dose regimen. A total of 400 adult subjects were vaccinated using either the present accelerated 2 month/three dose regimen of Engerix-B or a 1 month/two dose regimen of a novel triple antigen vaccine (Hepacare). Both vaccines were well tolerated. Four weeks after a single dose, the seroprotective rates for Engerix-B and the triple antigen vaccine were 5 and 17%, respectively. By month 2, 4 weeks after two doses of vaccine, it was 38 and 61%. Finally by month 3, 4 weeks after a third dose of Engerix-B or placebo, respectively, the seroprotection rates were 71 and 82%. The geometric mean titres (GMTs), of these responders was then 119 and 120 IU/l, respectively. Both vaccines were well tolerated. At all points up to and including 3 months after beginning vaccination, the novel 1 month/two dose regimen of Hepacare was significantly more effective in producing seroporotective titres than the 2 month/three dose regimen of Engerix-B (P = 0.001).

Comparison of a triple antigen and a single antigen recombinant vaccine for adult hepatitis B vaccination

Hepatitis B and its sequelae are a major public health problem. Vaccines have been available for almost 20 years; however the disease still remains a global problem. Many factors contribute to the failure to control hepatitis B, including the limited nature of the vaccination programs implemented initially. Only relatively recently has mass childhood vaccination begun to be implemented and vaccination of high-risk groups, other than healthcare workers, is still not general policy. Additional factors contributing to continued persistence of hepatitis B in the developed world are that the present vaccines are not fully used by those recommended to be vaccinated and even when vaccination is carried out appropriately, there remain some who fail to achieve adequate protection. Clearly, the protection of at-risk groups who have inadequate response to current vaccines, and those who are unwilling or unable to comply with protracted multi-dose vaccine regimens, could be improved if there were a more potent vaccine and/or a shorter vaccination regimen available. Adults who had never been vaccinated against hepatitis B were randomised to receive a vaccination course of either a present single antigen (S) vaccine (Recombivax-HB) or a novel triple antigen (S, pre-S1, and pre-S2) recombinant vaccine (Hepacare Medeva Pharma plc). Doses were given at baseline and 1 month and 6 months later. Hepatitis B surface antibody (anti-HBs) levels were measured at 2, 4, 6, and 7 months after beginning vaccination. The primary efficacy parameter was the degree of protection, measured as the percentage of subjects with anti-HBs titres > or = 10 IU/L, 6 or 7 months (26 +/- 2 weeks) after beginning vaccination. A total of 303 adult subjects entered the study and were vaccinated. Of these, 11 failed to complete the study (4 on Hepacare and 7 on Recombivax-HB); however all but 2 (1 to receive the triple antigen vaccine and 1 to receive Recombivax-HB) were included in the intent-to-treat population for efficacy evaluation. Treatment randomisation was stratified at entry based on age (above and below 40 years old) and gender. The standard three-dose/6-month vaccination regimen of the single antigen vaccine protected 83% of subjects by 7 months after starting vaccination whereas the triple antigen vaccine as a two-dose/1-month regimen protected 88% within 6 months and as a three-dose/6-month regimen protected 97% by 7 months after starting vaccination. Thus the protection rate provided by the shortened (0, 1) regimen of the novel vaccine was "essentially equivalent" (i.e., not statistically inferior) to that provided by the full (0, 1, and 6) regimen of today's vaccine (88% vs. 81%, P < 0.001), and the protection rate provided by a three-dose/6-month (0, 1, and 6) regimen of the new vaccine was significantly superior to that provided by present vaccines (97% vs. 83% P < 0.001). The percentage of subjects protected increases with time after beginning vaccination and at all time points up to and including 6 months was significantly greater with the two-dose regimen of the triple antigen vaccine than with the single antigen vaccine regimen. In adults at risk for a reduced response to hepatitis B vaccination [i.e., older adults (>/=40), the obese, males, and smokers], the triple antigen vaccine produced a significantly greater percentage of protected subjects (P < 0.001) and higher geometric mean titre (P < 0.001). Indeed as a three-dose/6 month regimen, the triple antigen vaccine raised the level of protection in these vulnerable subgroups to that seen when a single antigen vaccine is used in the optimal younger adult group. Both vaccines were well tolerated and had similar safety profiles. The most frequently (> or = 10%) reported adverse events with the use of either vaccine were pain at the site of injection (38% vs. 41% vs. 20% for the two-dose Hepacare regimen, the three-dose Hepacare regimen, and the three-dose Recombivax-HB regimen, respectively), infections at the site of injection (1% vs. 14% vs. 9%), headache (9% vs. 13% vs. 11%), and nausea (7% vs. 11% vs. 3%). It is concluded that in healthy normal adults, a triple antigen hepatitis B vaccine that contained S and pre-S antigens produced an enhanced immunological response. This was exemplified by the novel vaccine's ability to overcome factors such as advancing age (> or = 40 years), obesity, and smoking, each of which is known to reduce the potential for protection with present recombinant S only vaccines. A two-dose/1-month (0 and 1) regimen of this triple antigen vaccine was as effective as the standard three-dose/6 month (0, 1, and 6) regimen of present single antigen vaccines. (c) 2001 Wiley-Liss, Inc.

Physicochemical and immunological characterization of hepatitis B virus envelope particles exclusively consisting of the entire L (pre-S1 + pre-S2 + S) protein

The hepatitis B virus (HBV) envelope (env) protein is composed of three regions; the 108- or 119-residue pre-S1 region involved in the direct interaction with hepatocytes, the 55-residue pre-S2 region associated with the polymerized albumin-mediated interaction, and the major 226-residue S protein region. Thus, to improve the immunogenic potency of conventional HB vaccines, development of a new vaccine containing the entire pre-S1 region in addition to pre-S2 and S is desired. We previously reported the efficient production of the HBV env L (pre-S1 + pre-S2 + S) protein in the recombinant yeast cells [J Biol Chem 267 (1992) 1953]. In this study, the HBV env L protein produced as nano-particles in yeast has been purified and characterized. By equilibrium sedimentation, an average molecular weight of L particle was estimated to be approximately 6.4 x 10(6), indicating that about 110 molecules of L proteins are assembled into an L particle. By atomic force microscopy in a moist atmosphere, the L particles were observed as large spherical particles with a diameter of 50-500 nm. The L particles were stable on short-time heating at a high temperature and long-time storage at a low temperature but rather unstable on repeated freezing and thawing and treatment with dithiothreitol. When immunized in mice, L particles elicited efficiently and simultaneously the anti-S, anti-pre-S2, and anti-pre-S1 antibodies. The ED(50) values in mice for the anti-S and anti-pre-S2 antibodies were similar to those elicited by the M (pre-S2 + S) particles. Furthermore, the anti-pre-S1 rabbit antibodies were found to recognize various segments of the pre-S1 region, including the pre-S1 (21-47) segment. These results show the high ability of L particles to induce all antibodies against HBV env proteins, hence promising the future application of L particles for the next generation HB vaccine.

Cloning, expression, and purification of histidine-tagged preS domains of hepatitis B virus

The preS domains of the hepatitis B virus are hydrophilic polypeptides that have been implicated, among other functions, in the binding of the virus to hepatocytes and in the induction of virus-neutralizing antibodies. A method of overproducing the preS domains of two different subtypes, adw and ayw, has been developed by adding a 6x His tag at the carboxy-terminal end of the polypeptides. Codons for the 6x His were added in reverse primers used to amplify the corresponding cDNAs. The polymerase chain reaction products were cloned into the expression vectors pET-3d (subtype ayw) and pT7-7 (subtype adw), under the control of the inducible bacteriophage T7 RNA polymerase promoter. Upon induction with isopropyl-beta-d-thiogalactopyranoside, proteins were overexpressed and purified by affinity chromatography on a Ni-nitrilotriacetic acid agarose column. This method yielded 20-40 mg of highly pure and very stable proteins per liter of cell culture. Circular dichroism and fluorescence spectroscopy of isolated preS-his-ayw and preS-his-adw, as well as their ability to bind polymerized human serum albumin, indicate that the 6x His tag does not modify the native-like conformation and, therefore, they may be considered as useful tools to study the function of these viral polypeptide regions.

Expression and characterization of chimeric hepatitis B surface antigen particles carrying preS epitopes

Many studies have provided evidence that hepatitis B surface antigen (HBsAg) including preS1 and preS2 sequences could be an ideal candidate for a new hepatitis B virus (HBV) vaccine with higher efficacy. However, the large (L) protein containing the entire preS region expressed in mammalian cells is not efficiently assembled into particles and secreted. Here we report an alternative approach to include the dominant epitopes of preS1 and preS2 to the small (S) protein as fusion proteins by the recombinant DNA technology. Three fusion proteins containing preS2(120-146) and preS1(21-47) at the N-terminus and/or truncated C-terminus of S protein were expressed using the recombinant vaccinia virus system. All these fusion proteins were efficiently secreted in the particulate form, and displayed S, preS1 and/or preS2 antigenicity. Further analysis showed that these chimeric HBsAg particles elicited strong antibody responses against S, preS1 and preS2 antigens in BALB/c mice, suggesting that they could be promising candidates for a new recombinant vaccine to induce broader antibody response required for protection against hepatitis B viral infection.

Analysis of the pre-S2 N- and O-linked glycans of the M surface protein from human hepatitis B virus

The surface antigen of hepatitis B virus comprises a nested set of small (S), middle (M), and large (L) proteins, all of which are partially glycosylated in their S domains. The pre-S2 domain, present only in M and L proteins, is further N-glycosylated at Asn-4 exclusively in the M protein. Since the pre-S2 N-glycan appears to play a crucial role in the secretion of viral particles, the M protein may be considered as a potential target for antiviral therapy. For characterization of the pre-S2 glycosylation, pre-S2 (glyco)peptides were released from native, patient-derived hepatitis B virus subviral particles by tryptic digestion, separated from remaining particles, purified by reversed-phase high performance liquid chromatography, and identified by amino acid and N-terminal sequence analysis as well as matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Pre-S2 N-glycans were characterized by anion exchange chromatography, methylation analysis, and on target sequential exoglycosidase digestions in combination with MALDI-TOF-MS, demonstrating the presence of partially sialylated diantennary complex-type oligosaccharides. In addition, the pre-S2 domain of M protein, but not that of L protein, was found to be partially O-glycosylated by a Gal(beta1-3)GalNAcalpha-, Neu5Ac(alpha2-3)Gal(beta1-3)GalNAcalpha-, or GalNAcalpha-residue. The respective O-glycosylation site was assigned to Thr-37 by digestion with carboxypeptidases in combination with MALDI-TOF-MS and by quadrupole time-of-flight electrospray mass spectrometry. Analytical data further revealed that about 90% of M protein is N-terminally acetylated.