A synthetic peptide vaccine involving the product of the pre-S(2) region of hepatitis B virus DNA: protective efficacy in chimpanzees

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.

Identification of neutralizing epitopes in the preS2 domain of the hepatitis B virus

Hepatitis B virus (HBV) infection is a major public health problem. The sodium taurocholate cotransporting polypeptide (NTCP) has been identified as an essential HBV receptor. Human hepatocytes are infected with HBV via binding between the preS1 region of the HBV large envelope protein and the NTCP. However, the role of preS2 in HBV entry is not well understood. In this study, we induced anti-preS2 serum in mice by DNA immunization, and showed that the resulting antiserum neutralized HBV infectivity. Competition assays using overlapping peptides suggested that the neutralizing epitope is located in the N-terminal region of preS2. In addition, monoclonal antibodies targeting the N-terminal region of preS2 neutralized HBV infectivity, indicating that these domains are critical epitopes for viral neutralization. These findings provide new insights into the HBV entry machinery while suggesting a novel modality for the prevention and treatment of HBV infection.

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.

Molecular analysis of Hepatitis B virus sub-genotypes and incidence of preS1/preS2 region mutations in HBV-infected Egyptian patients from Mansoura

Hepatitis B virus (HBV) is one of the major causes of viral hepatitis worldwide. Despite the prevalence of HBV infection in Egypt, few studies have focused on sub-genotyping of the virus. Moreover, no studies are available regarding the mutational analysis of the preS1/preS2 region of the viral genome, or its impact on hepatocellular carcinoma (HCC) development in Egypt. In this study, we have analyzed the sub-genotypes and incidence of mutations in the preS1/preS2 region of HBV present in HBV-infected patients, from Mansoura city (located in the center of Nile Delta region of Egypt), via partial sequencing of this specific region. Moreover, we have investigated the impact of these mutations on HCC development by measuring serum alpha fetoprotein (AFP) level and abdominal ultrasound examination of the HBV-infected patients. According to our results, all samples were genotype D in which sub-genotype D1 was predominant. In addition, the results revealed mutations in the preS1/preS2 region, which could result in either immature preS1 protein or completely inhibit the translation of the preS2 protein. However, there was no incidence of HCC development in patients infected with mutated HBV in the preS1/preS2 region. In summary, for the first time our work has proved the predominance of sub-genotype D1 among HBV-infected Egyptian patients in Mansoura city, Nile Delta region, Egypt, and incidence of mutations in the preS1/preS2 region of HBV genome. This current study opens up research opportunities to discuss the impact of HBV mutations on the development of HCC in Egypt.

Sequence analysis and functional characterization of full-length hepatitis B virus genomes from Korean cirrhotic patients with or without liver cancer

This study aimed to identify and characterize mutations in the hepatitis B virus (HBV) genome associated with advanced liver diseases. The 3.2-kb HBV genome of the C2 subgenotype was amplified from sera of 18 cirrhotic Korean patients with (10) or without (8) hepatocellular carcinoma (HCC), and two clones per patient were characterized by transient transfection experiments in human hepatoma cells. While A1762T/G1764A core promoter mutations were highly prevalent in both groups, the G1896A precore mutation to abolish hepatitis B e antigen (HBeAg) expression was more common in HCC clones (55% vs. 20%). High replication capacity was mostly found in HCC clones and associated with core promoter mutations, whereas more non-HCC clones harbored a nonfunctional core gene (34% vs. 8%). Large in-frame deletions in the preS region were found in 60% of HCC clones and 38% of non-HCC clones. They removed the first 11 residues of large envelope protein or impaired small envelope protein expression, or deleted a neutralizing epitope in the preS2 domain. Additional point mutations prevented middle envelope protein expression, or caused nonsense mutations in the preS or S region to truncate large and/or small envelope protein. Consequently, many clones were unable to express or secrete hepatitis B surface antigen (HBsAg). In conclusion, mutations associated with the advanced stage of chronic HBV infection are complex and diverse. Host immune pressure most likely selected for mutations in the HBV genome to abolish or reduce HBeAg or HBsAg production, to enhance genome replication, or to escape neutralizing antibodies. Some of these mutations may contribute to liver cirrhosis or HCC development.

Antiviral effects of anti-HBs immunoglobulin and vaccine on HBs antigen seroclearance for chronic hepatitis B infection

BACKGROUND AND AIMS

Interferon and nucleotide/nucleoside analogues are the main treatments for chronic hepatitis B. These drugs effectively reduce serum hepatitis B virus (HBV) DNA titers but fail to sufficiently reduce hepatitis B surface antigen (HBsAg) levels. Following the recent identification of sodium taurocholate cotransporting polypeptide as a receptor for HBV entry, inhibition of HBV entry has become an attractive therapeutic target for chronic hepatitis B treatment. We therefore evaluated the antiviral effects of antibody to HBsAg (anti-HBs) immunoglobulin (HBIG), which can inhibit HBV entry, by in an vivo study and a clinical trial.

METHODS

In the in vivo study, HBV-infected mice were generated from human hepatocyte chimeric mice and treated with HBIG. A clinical trial evaluating HBIG therapy in patients was also performed.

RESULTS

In the mouse study, HBV DNA titers were reduced and serum HBsAg titers decreased to undetectable levels following high-dose HBIG injection. On the basis of this result, eight chronic hepatitis B patients, who had received long-term nucleotide analogue treatment, were treated with monthly HBIG injections as an additional treatment. After 1 year of treatment, an HBsAg level reduction of more than 1 log IU/mL was observed in four patients, and three patients became anti-HBs positive. No adverse events occurred during HBIG therapy.

CONCLUSION

These results suggest that monthly HBIG injection might benefit patients with chronic hepatitis B whose HBsAg titer becomes lower following long-term nucleotide/nucleoside analogue treatment.

The chimpanzee model for hepatitis B virus infection

Even before the discovery of hepatitis B virus (HBV), it was known that chimpanzees (Pan troglodytes) are susceptible to human hepatitis viruses. The chimpanzee is the only primate animal model for HBV infections. Much like HBV-infected human patients, chimpanzees can develop acute and chronic HBV infections and consequent hepatitis. Chimpanzees also develop a cellular immune response similar to that observed in humans. For these reasons, the chimpanzee has proven to be an invaluable model for investigations on HBV-driven disease pathogenesis and also the testing of novel antiviral therapies and prophylactic approaches.

Hepatitis B virus preS1 deletion is related to viral replication increase and disease progression

AIM: To investigate the clinical implications of hepatitis B virus (HBV) preS1 deletion.

METHODS: We developed a fluorescence resonance energy transfer-based real-time polymerase chain reaction (RT-PCR) that can detect four genotypes (wild type, 15-bp, 18-bp and 21-bp deletion). The PCR method was used in two cohorts of Korean chronic HBV subjects with genotype C infections. Cohort I  included 292 chronic HBV subjects randomly selected from Cheju National University Hospital (Jeju, South Korea) or Seoul National University Hospital (Seoul, South Korea), and cohort II included 90 consecutive chronic HBV carriers recruited from Konkuk University Hospital (Seoul, South Korea); the cohort II patients did not have hepatocellular carcinoma or liver cirrhosis.

RESULTS: The method proposed in this study identified 341 of 382 samples (89.3%). Deletion variants were identified in 100 (29.3%) of the 341 detected samples. In both cohorts, the subjects with deletions had a significantly higher Hepatitis B virus e antigen (HBeAg)-positive seroprevalence [cohort I, wild (51.0%) vs deletion (75.0%), P < 0.001; cohort II, wild (69.2%) vs deletion (92.9%), P = 0.002] and higher HBV DNA levels [cohort I, wild (797.7 pg/mL) vs deletion (1678.9 pg/mL), P = 0.013; cohort II, wild (8.3 × 10⁸ copies/mL) vs deletion (2.2 × 10⁹ copies/mL), P = 0.049], compared to subjects with wild type HBV.

CONCLUSION: HBV genotype C preS1 deletion may affect disease progression in chronic HBV subjects through an extended duration of HBeAg seropositive status and increased HBV replications.

Monoclonal antibodies against hepatitis B viral surface antigens and epitope grouping

Monoclonal antibodies (MAbs) were generated against subtypes (ad/ad/rw) of the human hepatitis B viral surface antigen (HBsAg). Among dozens of antibodies that were generated, the majority was shown to commonly react with various ad/ay subtypes of the S protein. Epitope(s) of these antibodies were grouped by various immunoassay methods, and at least four distinct epitope regions were identified. Some of these antibodies were selected to formulate sandwich enzyme immunoassays for quantitative determinations of HBsAg in reconstituted specimens. Epitope-defined monoclonal antibodies with high affinity and specificity might be suitable for formulations as vaccines (containing a mixture of humanized monoclonal antibodies) for passive immunization in humans for immunoprophylaxis of HBV infection.

Male-specific hepatitis B virus large surface protein variant W4P potentiates tumorigenicity and induces gender disparity

Background

The underlying mechanisms of carcinogenesis and gender disparity in hepatitis B virus (HBV)-induced hepatocellular carcinoma (HCC) remain unclear. Recently, we reported a novel HCC-related W4P/R mutation in the large surface protein (LHB) of HBV genotype C, which was found exclusively in male HCC patients.

Methods

LHB sequences from a carrier (wild type; WT) and W4P variant LHB sequence from an HCC patient were cloned and used to generate NIH3T3 and Huh7 cell lines. Cell proliferation and in vitro tumorigenicity were assessed by cell growth and transformation assays. Male and female nude mice were injected with the cells to determine in vivo tumorigenicity. To confirm the effect of estrogen in W4P-mediated tumorigenicity, male mice were injected with estrogen and challenged with W4P-expressing cells. The serum levels of different cytokines from the mouse model and patients were analyzed by ELISA. A critical role of interleukin (IL)-6 signaling in W4P-mediated tumorigenicity was tested by inhibition of Jak2.

Results

Although both WT and W4P variant LHBs enhanced cell proliferation by regulating the cell cycle and facilitated cell colony formation, the W4P variant demonstrated significantly higher activity. NIH3T3 cells expressing variant LHB, but not the WT, induced tumor in a nude mouse model. Tumor masses produced by variant LHB were significantly larger in male than female mice, and significantly reduced by estrogen. IL-6, but not tumor necrosis factor-α, was elevated in male mice harboring W4P-induced tumor, and was reduced by estrogen. IL-6 levels of HCC patients with the W4P variant were significantly higher than those of patients with WT LHB. W4P LHB induced higher production of IL-6 than WT LHB in cell lines, and the level was reduced by estrogen. The ability to reduce cell proliferation and colony formation of W4P LHB was hampered by inhibition of IL-6 signaling.

Conclusions

This study suggests that the W4P mutation during the natural course of chronic hepatitis B infection may contribute to HCC development, particularly in male patients, in an IL-6-dependent manner.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0303-7) contains supplementary material, which is available to authorized users.

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.

Validation of cross-genotype neutralization by hepatitis B virus-specific monoclonal antibodies by in vitro and in vivo infection

Vaccines based on hepatitis B virus (HBV) genotype A have been used worldwide for immunoprophylaxis and are thought to prevent infections by non-A HBV strains effectively, whereas, vaccines generated from genotype C have been used in several Asian countries, including Japan and Korea, where HBV genotype C is prevalent. However, acute hepatitis B caused by HBV genotype A infection has been increasing in Japan and little is known about the efficacy of immunization with genotype C-based vaccines against non-C infection. We have isolated human monoclonal antibodies (mAbs) from individuals who were immunized with the genotype C-based vaccine. In this study, the efficacies of these two mAbs, HB0116 and HB0478, were analyzed using in vivo and in vitro models of HBV infection. Intravenous inoculation of HBV genotype C into chimeric mice with human hepatocytes resulted in the establishment of HBV infection after five weeks, whereas preincubation of the inocula with HB0116 or HB0478 protected chimeric mice from genotype C infection completely. Interestingly, both HB0116 and HB0478 were found to block completely genotype A infection. Moreover, infection by a genotype C strain with an immune escape substitution of amino acid 145 in the hepatitis B surface protein was also completely inhibited by incubation with HB0478. Finally, in vitro analysis of dose dependency revealed that the amounts of HB0478 required for complete protection against genotype C and genotype A infection were 5.5 mIU and 55 mIU, respectively. These results suggested that genotype C-based vaccines have ability to induce cross-genotype immunity against HBV 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.

Enhanced humanization and affinity maturation of neutralizing anti-hepatitis B virus preS1 antibody based on antigen-antibody complex structure

To improve a previously constructed broadly neutralizing hepatitis B virus (HBV)-specific preS1 humanized antibody (HzKR127), we further humanized it through specificity-determining residue (SDR) grafting. Moreover, we improved affinity by mutating two residues in heavy-chain complementarity-determining regions (CDR), on the basis of the crystal structure of the antigen-antibody complex. HzKR127-3.2 exhibited 2.5-fold higher affinity and enhanced virus-neutralizing activity compared to the original KR127 antibody and showed less immunogenic potential than HzKR127. Enhanced virus-neutralizing activity was achieved by the increased association rate, providing insights into engineering potent antibody therapeutics for HBV immunoprophylaxis. HzKR127-3.2 may be a good candidate for HBV immunoprophylaxis.

Male-specific W4P/R mutation in the pre-S1 region of hepatitis B virus, increasing the risk of progression of liver diseases in chronic patients

The issue of hepatitis B virus (HBV) mutations possibly leading to a gender disparity in the progression of liver diseases has not been explored. We aimed to elucidate the relationships of the novel pre-S1 mutations, W4P/R, with the progression of liver diseases and male predominance in a South Korean chronic cohort by use of a molecular epidemiologic study. We developed a fluorescence resonance energy transfer (FRET)-based real-time PCR (RT-PCR) assay for the detection of the W4P/R mutations and applied it to 292 chronic HBV patients. The pre-S1 mutations from 247 (84.6%) of a total of 292 patients were detected by this assay. W4P/R mutants were found to be significantly related to severe liver diseases (hepatocellular carcinoma [HCC] and liver cirrhosis, 12.4% [19/153] of patients, versus chronic hepatitis and asymptomatic carriage, 1.1% [1/94] of patients) (P < 0.001). All of the W4P/R mutants were found in males only. The novel HBV pre-S1 mutations, W4P/R, may be associated with disease severity in male patients chronically infected with HBV genotype C. The W4P/R mutations may provide in part an explanation for the relatively high ratio of male to female incidence in HCC generation in South Korean chronic HBV patients.

Removing N-terminal sequences in pre-S1 domain enhanced antibody and B-cell responses by an HBV large surface antigen DNA vaccine

Although the use of recombinant hepatitis B virus surface (HBsAg) protein vaccine has successfully reduced global hepatitis B infection, there are still a number of vaccine recipients who do not develop detectable antibody responses. Various novel vaccination approaches, including DNA vaccines, have been used to further improve the coverage of vaccine protection. Our previous studies demonstrated that HBsAg-based DNA vaccines could induce both humoral and CMI responses in experimental animal models. However, one form of the the HBsAg antigen, the large S antigen (HBs-L), expressed by DNA vaccine, was not sufficiently immunogenic in eliciting antibody responses. In the current study, we produced a modified large S antigen DNA vaccine, HBs-L(T), which has a truncated N-terminal sequence in the pre-S1 region. Compared to the original HBs-L DNA vaccine, the HBs-L(T) DNA vaccine improved secretion in cultured mammalian cells and generated significantly enhanced HBsAg-specific antibody and B cell responses. Furthermore, this improved HBsL DNA vaccine, along with other HBsAg-expressing DNA vaccines, was able to maintain predominantly Th1 type antibody responses while recombinant HBsAg protein vaccines produced in either yeast or CHO cells elicited mostly Th2 type antibody responses. Our data indicate that HBsAg DNA vaccines with improved immunogenicity offer a useful alternative choice to recombinant protein-based HBV vaccines, particularly for therapeutic purposes against chronic hepatitis infection where immune tolerance led to poor antibody responses to S antigens.

Viral deletions among healthy young Chinese adults with occult hepatitis B virus infection

To investigate the mechanism and prognosis of occult hepatitis B virus (HBV) infection (OBI) at a molecular level among healthy young adults, the presence of HBV DNA in 1176 sera samples collected from healthy young people after neonatal vaccination was assessed by nested polymerase chain reaction (PCR) using specific primers designed for the X and S regions of the HBV genome. Full-length HBV DNA from 9 patients with OBI (OB1-OB9) was cloned and sequenced. Deletions in the pre-S, basal core promoter (BCP), core (C) and polymerase (P) regions were observed. The data indicate that there is still a substantial risk of OBI in China despite neonatal vaccination. All deletions that were observed in the pre-S, BCP, C and P regions play a direct or indirect role in OBI. The presence of a deletion mutation in the pre-S1 region was considered to play a pivotal role in hepatocarcinogenesis and was found to increase the risk of hepatocellular carcinoma in the cohorts studied.

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.

Primary and secondary prevention of liver cancer caused by HBV

Primary cancer of the liver (hepatocellular carcinoma, HCC) is one of the most common cancers worldwide; HBV is the major cause of HCC. A vaccine that protects against HBV infection was invented in 1969 and is now one of the most commonly used vaccines. National vaccination programs have dramatically reduced the prevalence of HBV infection and carriers, with a concomitant decrease in the incidence of HCC in the vaccine-impacted populations. HBV vaccine is the first widely used cancer prevention vaccine; a second that protects against papilloma virus and cancer of the cervix has recently been introduced. Appropriate treatment of HBV carriers with antivirals can reduce the titers of HBV in their blood and thereby greatly reduce the risk of HCC and chronic liver disease. Further data are required to establish criterion for treatment to enable protocols for medical and prevention programs. There are other viral caused cancers and an understanding of their pathogenesis is an important future direction for research to reduce the human burden of cancer.

T3098C and T53C mutations of HBV genotype C is associated with HBV infection progress

OBJECTIVE

To analyze the association between mutation(s) in preS region of HBV and hepatitis B disease progress in Chinese patients with genotype C chronic HBV infection.

METHODS

Ninety-three patients with chronic genotype C HBV infection, including 24 asymptomatic carriers (ASC), 26 patients with chronic hepatitis B (CHB), 22 patients with liver cirrhosis (LC) and 21 HCC patients were investigated. Levels of HBV DNA, HBeAg, alanine aminotransferase (ALT), asparate transaminase (AST) were measured. HBV preS region was analyzed by PCR direct sequencing.

RESULTS

The prevalence of preS T3098C and T53C mutations of genotype C HBV was significantly higher in LC and HCC patients than ASC and CHB patients. The rate of T3098C mutation in ASC, CHB, LC, and HCC patients were 0.00% (0/24), 3.85% (1/26), 9.09% (2/22), and 30.77% (8/22), respectively (P=0.0015), while the rate of T53C mutation was 12.50% (3/24), 3.85% (1/26), 40.91% (9/22), and 42.31% (11/26), respectively (P=0.0012).

CONCLUSION

The frequency of genotype C HBV preS T3098C and T53C mutations is associated with hepatitis B infection progression

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.

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.

Mutations in preS genes of genotype C hepatitis B virus in patients with chronic hepatitis B and hepatocellular carcinoma

BACKGROUND

Hepatitis B virus (HBV) preS mutations are frequently isolated from patients with severe forms of liver disease. Meanwhile, genotype C has been shown to cause more serious liver disease than genotype B. This study assesses the frequency of preS mutation in Chinese patients with genotype C chronic HBV infection and its relation to liver damage.

METHODS

Seventy-nine persistently infected patients (25 asymptomatic carriers, 28 with chronic hepatitis, and 26 with hepatocellular carcinoma) with genotype C HBV were analyzed. Levels of HBV DNA, hepatitis B e antigen (HBeAg), alanine aminotransferase, and aspartate transaminase and mutations in the preS region were determined.

RESULTS

The correlations of preS deletion with disease progression were distinct: preS deletion mutations were more commonly found in the hepatocellular carcinoma (HCC) group than in the chronic hepatitis B (CHB) or asymptomatic carrier (ASC) groups, with the frequencies of 38.46% (10/26) in the HCC, 7.14% (2/28) in the CHB, and 4.00% (1/25) in the ASC (P = 0.001) groups. The HBeAg-positive rate and HBV DNA levels were comparable between patients with the preS mutation and those without.

CONCLUSIONS

PreS deletion mutations of genotype C HBV might play a role in HBV-related hepatocarcinogenesis.

Viral and cellular determinants involved in hepadnaviral entry

Hepadnaviridae is a family of hepatotropic DNA viruses that is divided into the genera orthohepadnavirus of mammals and avihepadnavirus of birds. All members of this family can cause acute and chronic hepatic infection, which in the case of human hepatitis B virus (HBV) constitutes a major global health problem. Although our knowledge about the molecular biology of these highly liver-specific viruses has profoundly increased in the last two decades, the mechanisms of attachment and productive entrance into the differentiated host hepatocytes are still enigmatic. The difficulties in studying hepadnaviral entry were primarily caused by the lack of easily accessible in vitro infection systems. Thus, for more than twenty years, differentiated primary hepatocytes from the respective species were the only in vitro models for both orthohepadnaviruses (e.g. HBV) and avihepadnaviruses (e.g. duck hepatitis B virus [DHBV]). Two important discoveries have been made recently regarding HBV: (1) primary hepatocytes from tree-shrews; i.e., Tupaia belangeri, can be substituted for primary human hepatocytes, and (2) a human hepatoma cell line (HepaRG) was established that gains susceptibility for HBV infection upon induction of differentiation in vitro. A number of potential HBV receptor candidates have been described in the past, but none of them have been confirmed to function as a receptor. For DHBV and probably all other avian hepadnaviruses, carboxypeptidase D (CPD) has been shown to be indispensable for infection, although the exact role of this molecule is still under debate. While still restricted to the use of primary duck hepatocytes (PDH), investigations performed with DHBV provided important general concepts on the first steps of hepadnaviral infection. However, with emerging data obtained from the new HBV infection systems, the hope that DHBV utilizes the same mechanism as HBV only partially held true. Nevertheless, both HBV and DHBV in vitro infection systems will help to: (1) functionally dissect the hepadnaviral entry pathways, (2) perform reverse genetics (e.g. test the fitness of escape mutants), (3) titrate and map neutralizing antibodies, (4) improve current vaccines to combat acute and chronic infections of hepatitis B, and (5) develop entry inhibitors for future clinical applications.

Oral immunogenicity of potato-derived HBsAg middle protein in BALB/c mice

The antibodies to preS2 synthetic peptides have been probed to neutralize hepatitis B virus (HBV), and also the addition of preS2 sequence could enhance the antibody response compared with a conventional vaccine in the non- and low responders. Previously, we generated transgenic potatoes expressing middle protein, which contains additional 55 amino acid preS2 region at the N-terminus of the S protein, of HBV to determine the feasibility of developing a plant-delivered HBV vaccine. In this study, we monitored the immune response after induction of immunoglobulin by boosting and assessed the efficacy of the mucosal immune response with regard to generate IgA antibodies. The HBsAg middle protein expressed in our transgenic potatoes was well immunized at low antigenic quantities in mice and the induced anti-S or anti-preS2 antibodies were sustained for the whole period without decrease. Orally delivery of plant-derived HBsAg middle protein to mice resulted in fecal anti-S or anti-preS2 as well as serum IgG. In addition, we used antibodies induced from the immunized mice with the potato-derived rHBsAg in competition assay as competitors to confirm the binding ability of preS2 antibodies to surface antigen of hepatitis virus. Anti-preS2 antibodies induced from immunized mice with transgenic potatoes effectively competed with anti-preS2 murine antibody H8 as expected. From these results, the inclusion of preS2 antigen to HBV plant vaccine may provide additional protective immunity in the HBV prevention.

Solution conformation of an immunodominant epitope in the hepatitis B virus preS2 surface antigen

We have determined the solution conformation of the major B cell epitope (residues 123-145, adrl23 hereafter) in the preS2 region of hepatitis B virus known to be associated with infection neutralization. The adrl23 shows an "L" shaped helix-turn-helix topology with two beta-turns formed by residues Ala(130)-Asp(133) and Asp(133)-Val(136) intervening the N- and C-terminal helices. The N-terminal alpha-helix consists of residues Ser(124)-Gln(129) whereas the C-terminal 3(10) helix is formed by residues Val(136)-Tyr(140). The beta-turns overlap partially with the putative "conformational" epitope. The overall topology of adrl23 is primarily maintained by hydrophobic interactions involving Phe(127), Leu(131), Leu(132), Val(136), and Tyr(140) that are clustered on one side of the molecule. An additional hydrophobic stabilization comes from Phe(141) that is buried inside the concave side of the molecule. A network of hydrogen bonds formed among Thr(125), His(128), and Arg(137) further contribute to the "boomerang-shaped" architecture of adrl23. The N-terminus of adrl23 is immobile due to a hydrogen bond between the N-terminal amide proton of Asn(123) and the hydroxyl oxygen of Thr(126). The side chains of Asp(133), Arg(135), Val(136), Leu(139), and Tyr(140) that were shown to be important for binding to a monoclonal antibody H8 mAb are surface exposed.

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.

Virus-like particle expression and assembly in plants: hepatitis B and Norwalk viruses

Expression of vaccine antigens in plants and delivery via ingestion of transgenic plant material has shown promise in numerous pre-clinical animal studies and in a few clinical trials. A number of different viral antigens have been tested, and among the most promising are those that can assemble virus-like particles (VLP), which mimic the form of authentic virions and display neutralizing antibody epitopes. We have extensively studied plant expression, VLP assembly, and immunogenicity of hepatitis B surface antigen (HBsAg) and Norwalk virus capsid protein (NVCP). The HBsAg small protein (S protein) was found by TEM to assemble tubular membrane complexes derived from endoplasmic reticulum in suspension cultured cells of tobacco and soybean, and in potato leaf and tuber tissues. The potato material was immunogenic in mice upon delivery by ingestion. Here we describe the plant expression and immunogenicity of HBsAg middle protein (M protein or pre-S2 + S) which contains additional 55 amino acid pre-S2 region at N-terminus of the S protein. Plant-derived recombinant M protein provoked stronger serum antibody responses against HBsAg than did S protein when injected systemically in mice. We discuss implications for use of fusion proteins for enhanced immunogenicity and mucosal targeting of HBsAg, as well as delivery of heterologous fused antigens. NVCP expressed in plants assembled 38 nm virion-size icosahedral (T = 3) VLP, similar to those produced in insect cells. The VLP stimulated serum IgG and IgA responses in mice and humans when they were delivered by ingestion of fresh potato tuber. Here we show that freeze-drying of transgenic NVCP tomato fruit yielded stable preparations that stimulated excellent IgG and IgA responses against NVCP when fed to mice. However, the predominant VLP form in tomato fruit was the small 23 nm particle also observed in insect cell-derived NVCP.

Structure of pre-S2 N- and O-linked glycans in surface proteins from different genotypes of hepatitis B virus

The middle-sized (M) surface proteins of hepatitis B virus (HBV) and other orthohepadnaviruses contain a conserved N-glycan in their pre-S2 domain, which is essential for the secretion of viral particles. Recently, we also found O-glycans in the pre-S2 domain of M protein from woodchuck hepatitis virus (WHV) and HBV genotype D. Since the O-glycosylation motif is not conserved in all genotypes of HBV, the glycosylation patterns of HBV genotypes A and C were analysed. Pre-S2 (glyco)peptides were released from HBV-carrier-derived HBV subviral particles by tryptic digestion, purified by reversed-phase HPLC and identified by amino acid and amino-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 all genotypes examined. Pre-S2 O-glycans were characterized by on-target sequential exoglycosidase digestions in combination with MALDI-TOF-MS. The pre-S2 domain of M protein and, to a minor extent, of L (large) protein from HBV genotype C and D was partially O-glycosylated by Neu5Ac(alpha2-3)Gal(beta1-3)GalNAcalpha- or Gal(beta1-3)GalNAcalpha-units at Thr-37 within a conserved sequence context. Genotype A, containing no Thr at position 37 or 38, was not O-glycosylated. Analytical data further revealed that M protein is mostly amino-terminally acetylated in all examined genotypes and that the terminal methionine is partially oxidized. The findings may be relevant for the secretion and the immunogenicity of HBV.

Structure of pre-S2 N- and O-linked glycans in surface proteins from different genotypes of hepatitis B virus

The middle-sized (M) surface proteins of hepatitis B virus (HBV) and other orthohepadnaviruses contain a conserved N-glycan in their pre-S2 domain, which is essential for the secretion of viral particles. Recently, we also found O-glycans in the pre-S2 domain of M protein from woodchuck hepatitis virus (WHV) and HBV genotype D. Since the O-glycosylation motif is not conserved in all genotypes of HBV, the glycosylation patterns of HBV genotypes A and C were analysed. Pre-S2 (glyco)peptides were released from HBV-carrier-derived HBV subviral particles by tryptic digestion, purified by reversed-phase HPLC and identified by amino acid and amino-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 all genotypes examined. Pre-S2 O-glycans were characterized by on-target sequential exoglycosidase digestions in combination with MALDI-TOF-MS. The pre-S2 domain of M protein and, to a minor extent, of L (large) protein from HBV genotype C and D was partially O-glycosylated by Neu5Ac(α2–3)Gal(β1–3)GalNAcα- or Gal(β1–3)GalNAcα-units at Thr-37 within a conserved sequence context. Genotype A, containing no Thr at position 37 or 38, was not O-glycosylated. Analytical data further revealed that M protein is mostly amino-terminally acetylated in all examined genotypes and that the terminal methionine is partially oxidized. The findings may be relevant for the secretion and the immunogenicity of HBV.

In vivo neutralization of hepatitis B virus infection by an anti-preS1 humanized antibody in chimpanzees

Previously, we generated a murine monoclonal antibody (mAb), KR127, that recognizes amino acids (aa) 37-45 of the preS1 of hepatitis B virus (HBV). In this study, we have constructed a humanized version of KR127 and evaluated its HBV-neutralizing activity in chimpanzees. A study chimpanzee was given a single intravenous dose of the humanized antibody, followed by intravenous challenge with adr subtype of wild type HBV, while a control chimpanzee was only challenged with the virus. The result showed that the study chimpanzee did not develop HBV infection during 1 year, while the control chimpanzee was infected, indicating that the humanized antibody exhibited in vivo virus-neutralizing activity and thus protected the chimpanzee from HBV infection. In addition, the humanized antibody bound to the preS1 of all subtypes of HBV. We first demonstrate that an anti-preS1 mAb can neutralize HBV infection in vivo. This humanized antibody will be useful for the immunoprophylaxis of 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.

Pre-s1 antigen-dependent infection of Tupaia hepatocyte cultures with human hepatitis B virus

The susceptibility of the tree shrew Tupaia belangeri to human hepatitis B virus (HBV) has been demonstrated both in vivo and in vitro. In this study, we show that purified HBV infects primary T. belangeri hepatocyte cultures in a very specific manner, as detected by HBV covalently closed circular DNA, mRNA, HBV e antigen, and HBsAg production. A monoclonal antibody (MAb), MA18/7, directed against the pre-S1 domain of the large HBs protein, which has been shown to neutralize infectivity of HBV for primary human hepatocytes, also blocked infection of primary Tupaia hepatocytes. MAbs against the pre-S2 domain of HBs inhibited infection only partially, whereas an S MAb and polyvalent anti-HBs antibodies neutralized infection completely. Thus, both pre-S1 and S antigens are necessary for infection in the tupaia. Using subviral particles, >70% of primary Tupaia hepatocytes are capable of specific binding of pre-S1-rich HBsAg, showing localization in distinct membrane areas. The data show that the early steps of HBV infection in Tupaia hepatocyte cultures are comparable to those in the human system.

Mutations within the hepatitis B virus genome among chronic hepatitis B patients with hepatocellular carcinoma

Chronic hepatitis B infection is a major cause of hepatocellular cancer (HCC). The pathogenesis of the carcinogenesis is not fully understood. Viral proteins such as the X protein and the truncated middle S protein have been implicated to be transactivators. In order to investigate whether any mutations within relevant parts of the hepatitis B virus (HBV) genome could be associated with the development of HCC, the genomes of 16 HBV strains from chronic HBV carriers with HCC were studied. Serum samples were subjected to PCR and the HBV DNA sequenced subsequently. Genotypes A-D were represented. The sequence analysis showed that an especially high proportion, 50% (CI 95%, 25-75%), of the patients with HCC carried HBV mutants with deletions or insertions in the N-terminal half of the pre-S2 region or had a point mutation in the start codon of pre-S2 compared with controls with chronic HBV infection, 21% (CI 95%, 3-39%). A high proportion (69%) also had mutations at position 1762 (A --> T) and/or 1764 (G --> A) in the core promoter region, but the proportion of core promoter mutations was no different from what was found in a control group of HBV carriers without HCC (68%). The pre-S2 variants, which involve deletions of immunogenic regions, may have a survival advantage as they are mostly found in long-standing HBV infection. There were no other mutations found frequently within the region coding for the X protein.

Influence of hepatitis B virus genotypes on the development of preS deletions and advanced liver disease

Hepatitis B virus (HBV) mutants with deletions in the preS region have not been evaluated for association with viral genotypes. In a case-control study, HBV DNA samples collected from 80 each of carriers infected with HBV genotype B or C were examined for preS deletions. PreS deletion mutants were found in a total of 37 of 160 (23%) HBV carriers. Carriers with preS deletion mutants were older (56.0 +/- 12.7 vs 49.3 +/- 16.9 years, P < 0.05), were infected more frequently with HBV genotype C (84% vs 40%, P < 0.05), and had more advanced disease, such as liver cirrhosis and hepatocellular carcinoma (54% vs 31%; P < 0.05), than did those without such mutants. In a multivariate analysis, genotype C (odds ratio [OR] = 9.3, P < 0.001) and advanced liver disease (OR = 3.1, P < 0.01) were the most significant variables in association with preS deletions. A direct repeat sequence (TCAGG) was found at the start or at the end of preS1 deletions in 6 of the 20 (30%) cases examined, and preS2 deletions in these cases were clustered over the 5'-terminal half of this region. These results indicate that the development of preS deletion mutants depends on HBV genotypes and that it may be associated with progressive liver disease.

Targeted destruction of the polymerized human serum albumin binding site within the preS2 region of the HBV surface antigen while retaining full immunogenicity for this epitope

The 55-amino acid (a.a.) preS2 region of the hepatitis B virus (HBV) envelope protein is highly immunogenic, and antibodies against this epitope confer seroprotection against HBV infections. Accordingly, various experimental and clinical studies for developing and evaluating HBV vaccines that include this particular epitope have been reported. However, a pitfall in using preS2 epitopes as part of a vaccinating antigen is that polymerized human serum albumin (pHSA), which is a normal constituent of the human serum, binds to and makes complexes with this particular region. Consequently, it is most likely that the antigen epitope is masked by serum pHSA and subsequently not detected by the immune system. To overcome these limitations, a novel single a.a substitute of the preS2 region was designed that corresponds to a tyrosine to serine exchange at position 140 of preS2. Competitive enzyme-linked immunosorbent assay showed that this substitution completely abolishes pHSA-binding activities in the mutated preS2 peptide, and CD spectra analysis revealed that this property might have been induced by slight conformational changes in its secondary structure. Nevertheless, the original B-cell epitope was still preserved in the mutated preS2 as determined by experimental immunization in mice. In this regard, the preS2(120-145/Y140S) sequence may be an HBV vaccine where epitopes, with intrinsic properties have been deleted without affecting the immunogenicity of the epitope itself. It is expected that the inclusion of this point mutated preS2 epitope will improve the efficacy of conventional preS2-containing HBV vaccines.

Characterization of complex B cell epitopes on woodchuck hepatitis virus surface antigens by using plasmids encoding chimeric proteins and DNA immunization

The conformational nature of the B cell epitopes on the hepadnavirus surface antigens makes its characterization difficult. Here, a new approach by DNA vaccination with plasmids expressing chimeric hepadnavirus surface antigens was explored to determine B cell epitopes on the surface antigens of woodchuck hepatitis virus (WHsAg). A series of chimeric genes consisting of complementary fragments of WHsAg and hepatitis B virus surface antigens (HBsAg) was constructed. These plasmids expressed the following: (i) middle chimeric surface antigens (MCSAgs), including pre-S2 region and small surface antigens; (ii) small chimeric surface antigens (CSAgs); (iii) a mutated WHsAg with two amino acid substitutions, the Leu 136 to Thr and Ala 140 to Asp, within the central immunogenic region. The mutated region from amino acid 135 to 143 within WHsAg mimics the second loop of the HBsAg a-determinant. MCSAgs and CSAgs were expressed in transiently transfected mammalian cells and were reactive to anti-HBsAg and anti-WHsAg, as shown by indirect immunofluorescence staining and ELISA. Vaccination with plasmids encoding MCSAgs induced strong antibody responses to the pre-S2 region. Anti-pre-S2 antibodies were directed to a linear, immunodominant region within the amino-terminal region of the pre-S2 region and were able to precipitate serum WHsAg. Vaccinations with the plasmids expressing the CSAgs led to the conclusion that an extended region aa 116-169 of WHsAg, analogous to the HBsAg a-determinant, was sufficient for the induction of anti-WHsAg antibodies. The mutated WHsAg with the second loop of the HBsAg a-determinant efficiently induced anti-WHsAg antibodies, but also a low titer of anti-HBsAg. Thus, multiple B cell epitopes of a linear and conformational nature are present on WHsAg. We presented an efficient and broadly applicable strategy for analysis of complex immunogenic determinants of natural or mutated viral antigens.

Fine-mapping of the B-cell epitope domain at the N-terminus of the preS2 region of the hepatitis B surface antigen

In this study, we report the exact localization and substitutional characterization of a B-cell epitope domain at the N-terminus of the preS2 region of the hepatitis B surface antigen. A set of deletion variants containing preS2 sequences of different length was generated on the basis of frCP as a carrier. It was found after Western blot analysis that three monoclonal antibodies (MAbs) (2-11B1, 3-11C2, HB.OT10) recognized the linear preS2 sequence within the amino acid (aa) stretch 3-WNSTTFHQTLQDP-13. The importance of each aa residue of the epitope was proved by comparison of antibody binding to alanine-substituted peptides in both free-peptide and Pepscan variants.

Hypermodification and immune escape of an internally deleted middle-envelope (M) protein of frequent and predominant hepatitis B virus variants

Naturally occurring deletions within the human hepatitis B virus (HBV) preS2 region have frequently been identified in patients with hepatocellular carcinoma (HCC), while chronic carriers without cirrhosis and HCC contain no detectable preS2 deletion variants. We have characterized two different preS2 internal deletion variants from two patients. In addition to several weak phenotypes, our study revealed three unexpected strong phenotypes: (1) a paradoxical "hypermodification" phenomenon was observed with significantly increased size heterogeneity and molecular weights of the secreted middle (M) envelope proteins containing a preS2 internal deletion. This phenomenon was observed in transient transfection with a human hepatoma Huh7 cell line as well as in stable transfection with a rodent hepatoma cell line 7777. (2) A significantly increased intracellular accumulation of all three envelope proteins (large, middle, and small) was detected by both Western blot analysis and immunofluorescence microscopy. (3) The middle envelope proteins with a preS2 internal deletion were not recognized in vitro by a putative neutralizing antiserum, suggesting that these variants can evade immune recognition in vivo. To our knowledge, this is the first identification and characterization of the M deletion variant protein in HBV natural infection.

Prevalence of vaccine-induced escape mutants of hepatitis B virus in the adult population in China: a prospective study in 176 restaurant employees

BACKGROUND AND AIM

Hepatitis B virus (HBV) variants with mutations in the S gene would pose a substantial risk to the community as current HBV vaccines are not effective in preventing infection with them. The majority of such vaccine escape mutants so far reported have been found while studying vertical transmission of HBV; the vaccine failure rate in connection with vaccine escape mutants in adults is not clear at the moment. The purpose of this study was to evaluate the efficacy of immunization against HBV in the adult population by analysis using polymerase chain reaction (PCR) to detect HBV-DNA, and also to elucidate the type of mutation encountered in vaccine failure cases.

METHOD

A total of 176 adult restaurant employees in China, who had been vaccinated according to the food epidemic law, were enrolled in a standard vaccination program. Their serum HBV-DNA was determined before and 1 year after the completion of the vaccination program. In those infected with HBV, despite having received the HBV vaccine, direct sequencing within the S gene of the amplified samples was conducted.

RESULTS

Although only two cases were found to be hepatitis B surface antigen (HBsAg) positive 1 year after the completion of the vaccination program, six subjects (3.4%) were found to be HBV-DNA positive assessed by a nested PCR. Four out of these six cases had a point mutation within the 'a' determinant; they were Gly-145-Ala, and Ile/Thr-126-Asn/Ser.

CONCLUSION

The HBV vaccine failure rate assessed by using PCR analysis was 3.4% (six of 176) in the Chinese adult population undergoing the HBV vaccination program. Hepatitis B virus variants with missense mutation within the 'a' determinant were responsible in most cases.

Antibody responses to preS components after immunization of children with low doses of BioHepB

BioHepB is a recombinant, hepatitis B vaccine derived from a mammalian cell line and containing HBs as well as preS1 and preS2 antigens, in their glycosylated and non-glycosylated forms. The vaccine was administered intramuscularly to 18 children aged 5 months to 11 years at 0, 1 and 6 months. One hundred percent seroconversion and seroprotection rates were achieved after primary and secondary immunization with the 2.5 microg doses of BioHepB. Ten out of the 18 children (56%) responded with the appearance of anti-preS1 and/or anti-preS2 antibodies in circulation, when analyzed 1, 2, 6, 7 and 12 months after the initiation of vaccination. In comparison with the emergence of the anti-HBs response, early (month 2, after two injections) or late (month 7, after three injections) peak responses were noted for the kinetics of anti-preS1 and anti-preS2 production during the course of immunization, demonstrating that the anti-preS1 and anti-preS2 responses are differently regulated, compared with the anti-HBs response. At month 6, just prior to the final injection, BioHepB caused significantly higher anti-HBs responses (GMT) in preS1-reactive children than in children without preS1 antibodies (P<0.005). Moreover, a significantly higher, anti-HBs response in GMT was also noted for anti-preS2-reactive children compared with anti-preS2-negative children (P<0.05). These findings demonstrated that recognition of the preS epitopes contained in the experimental preS1/preS2/S vaccine is accompanied by a more rapid onset and pronounced antibody response to the S-gene-derived protein in healthy children.

A mimotope of pre-S2 region of surface antigen of viral hepatitis B screened by phage display

To acquire the phage-displayed mimotopes which mimic the specificity of hepatitis B virus surface antigen (HBsAg), a random peptide library expressing linear peptide with 12 amino acids in length were used to screen with the serum from a hepatitis B virus infected patient in the recovery phase. After 3 rounds of biopanning, the positive phages were confirmed by competitive ELISA using HBsAg/P33. Two phagotopes were identified and one of them was confirmed as mimotope by competition experiment. Based on the mimotpe, a multiple antigenic peptide with four branches was synthesized by solid phase peptide synthesis. The antiginicity and specificity of the synthesized antigen was tested in BALB/c mice compared with the native epitope-based antigen. The results showed that the mimotope-based antigen could evoke higher titer of antibodies with the same specificity of the epitope-based antigen. Those findings indicate mimotopes can be used in antigen and vaccine design.

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.

Purification and structural analysis of the hepatitis B virus preS1 expressed from Escherichia coli

The preS1 of hepatitis B virus (HBV) is located at the outermost part of the envelope protein and possesses several functionally important regions such as hepatocyte receptor-binding site and virus-neutralizing epitopes. As the first step to understand the structure-function relationship for the preS1 antigen, we have purified the preS1 and performed its structural characterization by circular dichroism (CD) spectroscopy. The preS1 was purified to near homogeneity from bacterially expressed glutathione S-transferase (GST)-preS1 fusion protein by two-step purification, affinity chromatography on glutathione-agarose column, and cation-exchange chromatography on Mono S column. The CD analysis showed that the purified preS1, which was largely unstructured in aqueous solution, acquired a significant (16%) alpha-helical structure when analyzed in 50% trifluoroethanol or 20 mM SDS. The results suggest that the preS1 assumes a mainly unstructured conformation and may form induced secondary structures upon binding to target proteins or under hydrophobic environment.

Rapid seroprotection against hepatitis B following the first dose of a Pre-S1/Pre-S2/S vaccine

BACKGROUND/AIMS

Will immunization with an experimental Pre-S1/Pre-S2/S hepatitis B vaccine (Bio-Hep-B) induce faster seroprotection using fewer doses as compared with a yeast derived S vaccine (Engerix B).

METHODS

Healthy volunteers, n = 36, mean age 23 y, randomized to receive 2 or 3 doses of both vaccines given months 0 and 6, or 0, 1 and 6.

RESULTS

Following primary immunization, seroprotection occurred in 6, 39, 53 and 60% in the Bio-Hep-B group at weeks 1, 2, 3 and 4, compared with 0, 12, 18 and 12.5% in the Engerix-B vaccinees, respectively. Six months following injection of the first dose, seroprotection was 70 and 25% in Pre-S/S and S vaccinees respectively. Area under the curve in vaccinees of Bio-Hep-B; versus Engerix-B showed mean anti-HBs level of 365 +/- 166 and 85 +/- 48 mIU/ml x day respectively (P = 0.012). At month 7, 100% seroprotection was achieved in both groups while anti-HBs rose from 81 to 28,800 mIU/ml and from 12 to 923 mIU/ml in recipients of Bio-Hep-B and Engerix-B respectively (P < 0.025).

CONCLUSIONS

Bio-Hep-B induces rapid seroprotection against hepatitis B in 60-70% of vaccinees, within 4-24 weeks after the first dose. Two instead of the conventional three doses of the Pre-S/S vaccine may be sufficient to induce adequate seroprotection.