Safety and efficacy of a recombinant yeast-derived pre-S2 + S-containing hepatitis B vaccine (TGP-943): phase 1, 2 and 3 clinical testing

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.

Subcutaneous vaccine administration - an outmoded practice

Subcutaneous vaccine (SC) administration is an outmoded practice which complicates vaccine administration recommendations. Local adverse events following immunization (AEFIs) are a recognized determinant of vaccine hesitancy/refusal which can lead to an increased prevalence of vaccine-preventable disease.

This extensive narrative review provides high-grade evidence that intramuscular (IM) administration of all vaccine types [adjuvanted, live virus and non-adjuvanted (inactivated whole cell, split cell and subunit)] significantly reduces the likelihood of local adverse events. This, combined with moderate grade evidence that IM injection generates significantly greater immune response compared with SC injection, allows a strong recommendation to be made for the IM injection of all vaccines except BCG and Rotavirus.

This will simplify vaccination practice, minimize the inadvertent misadministration of vaccines and potentially improve public trust in vaccination.

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.

Immune Evasion Strategies during Chronic Hepatitis B and C Virus Infection

Both hepatitis B virus (HBV) and hepatitis C virus (HCV) infections are a major global healthcare problem with more than 240 million and 70 million infected, respectively. Both viruses persist within the liver and result in progressive liver disease, resulting in liver fibrosis, cirrhosis and hepatocellular carcinoma. Strikingly, this pathogenesis is largely driven by immune responses, unable to clear an established infection, rather than by the viral pathogens themselves. Even though disease progression is very similar in both infections, HBV and HCV have evolved distinct mechanisms, by which they ensure persistence within the host. Whereas HCV utilizes a cloak-and-dagger approach, disguising itself as a lipid-like particle and immediately crippling essential pattern-recognition pathways, HBV has long been considered a "stealth" virus, due to the complete absence of innate immune responses during infection. Recent developments and access to improved model systems, however, revealed that even though it is among the smallest human-tropic viruses, HBV may, in addition to evading host responses, employ subtle immune evasion mechanisms directed at ensuring viral persistence in the absence of host responses. In this review, we compare the different strategies of both viruses to ensure viral persistence by actively interfering with viral recognition and innate immune responses.

Plant–derived vaccines: a look back at the highlights and a view to the challenges on the road ahead

The sobering reality is that each year, 33 million children remain unvaccinated for vaccine-preventable diseases. Universal childhood vaccination would have profound effects on leveling the health inequities in many parts of the world. As an alternative to administration of vaccines by needle and syringe, oral vaccines offer significant logistical advantages, as the polio eradication campaign has demonstrated. Over the past decade, the expression of subunit vaccine antigens in plants has emerged as a convenient, safe and potentially economical platform technology, with the potential to provide a novel biotechnological solution to vaccine production and delivery. As this technology has come of age, many improvements have been made on several fronts, as a growing number of research groups worldwide have extensively investigated plants as factories for vaccine production. This review attempts to highlight some of the achievements over the past 15 years, identify some of the potential problems and discuss the promises that this technology could fulfill.

Virus-like particles production in green plants

Viruses-like particles (VLPs), assembled from capsid structural subunits of several different viruses, have found a number of biomedical applications such as vaccines and novel delivery systems for nucleic acids and small molecules. Production of recombinant proteins in different plant systems has been intensely investigated and improved upon in the last two decades. Plant-derived antibodies, vaccines, and microbicides have received great attention and shown immense promise. In the case of mucosal vaccines, orally delivered plant-produced VLPs require minimal processing of the plant tissue, thus offering an inexpensive and safe alternative to more conventional live attenuated and killed virus vaccines. For other applications which require higher level of purification, recent progress in expression levels using plant viral vectors have shown that plants can compete with traditional fermentation systems. In this review, the different methods used in the production of VLPs in green plants are described. Specific examples of expression, assembly, and immunogenicity of several plant-derived VLPs are presented.

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.

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.

A novel, recombinant triple antigen hepatitis B vaccine (Hepacare)

Infection with hepatitis B virus (HBV) continues to be a major problem in the human population. There remains a specific requirement for HBV vaccines capable of circumventing the non-responder/inadequate responder status of some vaccinees. Hepacare has been primarily developed to (1) improve anti-SHBs antibody titres in low responders, to conventional SHBsAg vaccinees, (2) overcome difficulties of non-compliance seen with existing SHBsAg vaccine regimens. Hepacare is a novel recombinant particle produced in eukaryotic cells, consisting of pre-S1, pre-S2 and S proteins of HBV and is adjuvanted with alhydrogel. It has been demonstrated to be highly immunogenic for both B and T cells in mice, chimpanzees and humans and induces higher anti-S 'a' determinant antibody titres than SHBsAg vaccines in mice and humans. Hepacare has proven to be at least as efficacious as current SHBsAg vaccines in chimpanzees. Clinical trials in both Europe and the USA have clearly demonstrated its superior ability to induce anti-SHBs antibody seroconversion in low-responder groups, compared with SHBsAg vaccines.

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.

Analysis of the relationship between immunogenicity and immunity for viral subunit vaccines

The prevention of viral infection by vaccination relies on stimulating an appropriate immune response in order to reduce the probability with which a virus can establish an infection. Post-vaccination antibody responses have therefore been associated with reducing the probability with which an individual can be infected (i.e., the vaccine's "impact"). Quantifying this relationship is essential in evaluating new vaccines, especially since comparisons between vaccines, and vaccine licensure, may be dependent on antibody responses alone. In this paper two principal questions are identified which need to be addressed in the evaluation of subunit vaccines: i) how do specific antibody levels relate to complete protection from infection or disease and ii) how do antigenic subunits interact in developing protection when combined together in a single vaccine. The aim is to identify explicitly certain assumptions that are frequently made implicitly in the discussion of vaccine action. First, antibody levels are related to levels of protection through a novel statistical analysis of incidence data from a published hepatitis B vaccine trial. The antibody response observed after influenza A virus infection is discussed in relation to the selection of neutralisation escape variants. Finally, by way of example, a theoretical situation is examined and three simple models of subunit vaccine action are constructed in order to describe how antibody levels may be related to population level phenomena such as the elimination of an infection by mass vaccination.

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.

Perinatal transmission of hepatitis B virus and its prevention

In order to prevent liver cirrhosis and hepatocellular carcinoma in later life, it is essential to prevent HBV infection in infants. If the mother is chronically infected with HBV and is also positive for HBeAg, 80-90% of the newborns become chronically infected, whereas if the mother is positive for anti-HBe, only some newborns will develop acute hepatitis or fulminant hepatitis. It is necessary to screen pregnant women for HBsAg and prevent mother-to-infant infection of HBV, treating the infant with hepatitis B hyperimmune globulin at birth, followed by HBV vaccination. In highly endemic areas of HBV, universal HBV vaccination of all newborns is advisable.

Vaccines for prevention of viral hepatitis

At the end of the 20th century active immunization against hepatitis A and B has been introduced into routine medical practice. Therefore, patients at risk, and especially those with coagulation disorders, should be immunized at the earliest age possible. In contrast, development of an efficacious vaccine against hepatitis C remains an important goal for the next decade.

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

Approximately 5-10% of healthy young adults receiving the commercially available hepatitis B vaccine (either serum derived or recombinant) fail to mount an adequate immune response. This nonresponder rate has prompted the demand for more immunogenic vaccines. An alternative to the currently licensed hepatitis B vaccines is Hepagene, a novel recombinant hepatitis B vaccine containing S, pre-S1 and pre-S2 antigenic components, produced in the mouse C127I clonal cell line after transfection of the cells with genes encoding the three antigens. In this study, chimpanzees were immunized with Hepagene to study the humoral and cellular immune responses to this vaccine. Two out of the three animals immunized with this vaccine seroconverted 4 weeks after their first injection and all of the animals elicited high anti-HBs levels that were maintained for at least 28-30 weeks after their third immunization. The anti-HBs levels elicited in these animals protected them against an experimental challenge with HBV. Peripheral blood mononuclear cells (PBMCs) obtained from immunized animals could be stimulated in vitro by rHBsAg and peptides representing regions within all three of the viral envelope proteins. Additionally, an anti-id that mimics the a determinant in the S-region of HBsAg could also stimulate in vitro proliferation of PBMCs from these immune animals. These results indicate that this new recombinant HBV vaccine encoding all three of the surface antigen proteins is highly immunogenic is that it can stimulate strong cellular and humoral immune responses.

-Vaccination against hepatitis B-

Although relatively uncommon among French children, hepatitis B virus infection is a major problem of public health which deserves coordinated strategies of prevention and immunization, in order to eliminate chronic carriers among groups at risk. The participation of pediatricians to these strategies is essential, knowing that transmission of hepatitis B virus from asymptomatic carrier mothers to their newborns contributes to new generation of chronic carriers who will be exposed to cirrhosis and hepatocellular carcinoma. Four hepatitis B vaccine are presently available in France with equal good efficiency and tolerance. These vaccines allow a protection against hepatitis B in 90 to 95% of the vaccinated subjects. Active search for new vaccines, particularly DNA vaccines, is in progress to extend the protection to the 5-10% non or low responders. The current recommended strategy of immunization in France associates immunizations of infants, preadolescents and groups at risk. In addition newborns from carrier mothers must receive combined passive and active immunization at birth.

Hepatitis B vaccine containing surface antigen and selected preS1 and preS2 sequences. 1. Safety and immunogenicity in young, healthy adults

The safety and immunogenicity of a yeast-derived recombinant hepatitis B virus (HBV) vaccine containing surface antigen (S) and selected preS1 and preS2 sequences (S-L*) were compared with those of a vaccine prepared with S alone (Engerix-B). S-L* consisted of composite particles containing S and L* at a ratio of 70/30. L* encompassed amino acid residues 12-52 of preS1 residues 133-145 of preS2, and the entire S domain. A total of 100 healthy, HBV-seronegative, young adults were randomized to receive 20 micrograms/dose of either S-L* or Engerix-B under double-blind conditions according to a 0-, 1-, 2-, 12-month schedule. In vivo humoral and in vitro lymphoproliferative responses to S and preS regions were monitored. Addition of the selected preS sequences to S did not enhance the in vivo humoral anti-HBs response but improved the in vitro stimulating capacity of the antigen (L*) in S-L* primed subjects.

Hepatitis B vaccine containing surface antigen and selected preS1 and preS2 sequences. 2. Immunogenicity in poor responders to hepatitis B vaccines

The immunogenicity of a yeast-derived recombinant hepatitis B virus (HBV) vaccine containing surface antigen (S) and selected preS1 and preS2 sequences (S-L*) was compared with that of a vaccine containing S alone (Engerix-B) in 32 healthy adults with a previous history of poor response (anti-HBs < 10 mIU ml-1) after at least three consecutive monthly doses of hepatitis B vaccines. The poor responders were randomized to receive three additional 20-microgram doses of either S-L* or Engerix-B in a double-blind fashion according to a 0-, 1-, 2-month schedule. In vivo humoral and in vitro lymphoproliferative responses to the S and preS regions were monitored. Although the addition of the selected preS sequences to S did not enhance the in vivo humoral anti-HBs response, the administration of the three additional vaccine doses, irrespective of their preS content, induced seroprotective anti-HBs levels in most vaccinees (29/32, 91%). In vitro proliferative responses to HBV surface antigens were only observed in subjects displaying anti-HBs titers > 1000 mIU ml-1 after the third additional vaccine dose.

Efficacy of a high and accelerated dose of hepatitis B vaccine in alcoholic patients: a randomized clinical trial

PURPOSE

A randomized, double-blind trial was conducted to compare the efficacy of a high-dose versus standard-dose hepatitis B vaccine in alcoholic patients.

PATIENTS AND METHODS

One hundred ten alcoholic patients were randomized to either receive the standard dose (20 micrograms at 0.1, and 6 months) or a high dose (40 micrograms at 0, 1, 2, and 6 months) of recombinant hepatitis B vaccine (Engerix-B). Patients were monitored for relapse of drinking using self-report, serial serum carbohydrate deficient transferrin, and collateral verification. The final titer of antibody to hepatitis B surface antigen (anti-HBs) was obtained 12 months after the first vaccine dose; a seroconversion was defined as a titer greater than 10 mlU/ml.

RESULTS

One hundred subjects completed the study; 10 of these had clinical or pathological evidence of cirrhosis. Thirty-six out of 48 (75%) of patients administered the high-dose regimen seroconverted compared with 24 of 52 (46%) in the standard dose group (P < 0.005). The mean anti-HBs titer of the high dose group was significantly greater than of the standard dose group (76.4 versus 39.4 mlU/ml, P < 0.01). Logistic regression demonstrated a significant effect on seroconversion for the vaccine dose (P < 0.005) and serum albumin (P = 0.05) but not for the other variables such as race, age, drinking during the study, serum creatinine, arm muscle circumference, and cirrhosis.

CONCLUSIONS

A high- and accelerated-dose regimen of hepatitis B improves the serological response in alcoholic patients. This regimen (currently recommended for hemodialysis patients) should now also be considered for patients with a history of alcoholism.

Contribution of human leukocyte antigens to the antibody response to hepatitis B vaccination

We present here the analysis of 86 individuals who were true antibody nonresponders to a vaccine containing hepatitis B surface antigen. The HLA type of these individuals and of 248 controls were determined by serology for HLA class I and by molecular typing for the HLA class II loci DRB1 and DQB1. Subsequent analysis of the results revealed that HLA-DRB1*0701 and HLA-DQB1*02 were significantly associated with antibody non-response to the "S"-containing vaccine compared with the HLA control population. Further, we found that the antibody non-response was also significantly associated with the above antigens when found in linkage disequilibrium on the HLA haplotype DRB1*0701; DQB1*0202. The hepatitis B surface antigen vaccine antibody nonresponder group, comprising 86 individuals, were revaccinated with a novel vaccine Hep B-3, containing both preS1- and preS2-derived proteins in addition to hepatitis B surface antigen, to circumvent their previous nonresponsiveness. The hepatitis B surface antigen antibody results from this group of patients show that 30 of the 86 individuals remained antibody non-responders and that 24 individuals (80%) expressed the HLA-DQB1*02 and that 21 individuals (70%) expressed HLA-DRB1*0701. Our results indicate that antibody nonresponse to the Hep B-3 vaccine is significantly associated with an extended HLA haplotype B44; DRB1*0701; DQB1*0202. A possible indication of these results is that antibody nonresponse to Hep B-3 vaccine is linked with the HLA allele DQB1*0202. These findings may have an important impact on future vaccine design.

Nonresponse to hepatitis B vaccines and the kinetics of anti-HBs production

No empirical data are available for the anti-HBs title required for protection against infection with the hepatitis B virus (HBV), but nonresponders to hepatitis B vaccines remain susceptible to infection. There may be an unexplained qualitative difference between hyporesponders and true nonresponders, but there is a clear association with HLA haplotypes. There is no evidence for silent infection with HBV in nonresponders.