Development of a nasal vaccine for chronic hepatitis B infection that uses the ability of hepatitis B core antigen to stimulate a strong Th1 response against hepatitis B surface antigen

Feasibility study of inhaled hepatitis B vaccine formulated with tetradecylmaltoside

This study was designed to test the hypothesis that formulation of hepatitis B vaccine with tetradecyl-beta-maltoside (TDM) enhances the immune response after pulmonary administration in a rodent model. Commercially available recombinant hepatitis B vaccine (rHBV) was formulated with varying concentrations of TDM and administered intratracheally to anesthetized male Sprague-Dawley rats. rHBV administered intramuscularly at doses of 2 and 4 microg served as positive controls. All formulations were administered on days 0 and 14 and the immune response was evaluated for 28 days. Specific antibodies generated to HBsAg were analyzed by ELISA. Safety studies were carried out by measuring the levels of alkaline phosphatase (ALP), lactate dehydrogenase (LDH) and tumor necrosis factor alpha (TNF-alpha) in bronchoalveolar lavage (BAL) fluid. There was a significant increase in the immune response when the vaccine was administered intramuscularly at a dose of 4 microg. Only a modest increase in the immune response was observed when plain rHBV was administered intratracheally at the same dose. However, a pulmonary formulation of 4 microg rHBV plus 0.5% TDM produced a fourfold increase in the immune response compared to plain rHBV administered via the pulmonary route. No increase in immune response was observed for formulations containing rHBV plus 0.125% or 0.25% TDM. The levels of ALP and LDH in the BAL fluid suggest that the hepatitis B vaccine plus TDM formulations cause some injury to the lungs after the first intratracheal instillation of the formulation; however, the enzyme levels tended to be lower after the second instillation. The level of TNF-alpha in the BAL fluid of TDM-treated rats was substantially lower than that in rats treated with the positive control substance, sodium dodecyl sulfate. Overall, rHBV formulated with TDM increases the immune response after pulmonary administration, and pulmonary formulation of rHBV plus TDM could be used as an alternative to needle-based delivery of hepatitis B vaccine.

Therapeutic vaccination of chronic hepatitis B patients with virus suppression by antiviral therapy: a randomized, controlled study of co-administration of HBsAg/AS02 candidate vaccine and lamivudine

Induction of curative immune responses by therapeutic vaccination in chronic viral infections such as chronic hepatitis B (CHB) is expected to be facilitated by reduction of viral load by antiviral treatment. In this open label, controlled, randomized study, 195 patients with HBeAg positive CHB were randomized to receive 12 doses of HBsAg with AS02B adjuvant candidate vaccine plus lamivudine daily for 52 weeks or lamivudine daily alone. The combined administration of vaccine and lamivudine was safe and well tolerated, but did not improve the HBe seroconversion rate (18.8%) when compared to treatment with lamivudine alone (16.1%) (p=0.6824). Despite induction of a vigorous HBsAg-specific lymphoproliferative response, cytokine production and anti-HBs antibodies, therapeutic vaccination with an adjuvanted HBsAg vaccine administered concomitantly with lamivudine did not demonstrate superior clinical efficacy in HBeAg positive CHB patients as compared to lamivudine therapy alone.

Vaccine adjuvants revisited

The development of new adjuvants for human vaccines has become an expanding field of research in the last thirty years, for generating stronger vaccines capable of inducing protective and long-lasting immunity in humans. Instead of such efforts, with several adjuvant strategies approaching to requirements for their clinical application, limitations like adjuvant toxicity remain to be fully surpassed. Here we summarize the current status of adjuvant development, including regulatory recommendations, adjuvant requirements, and adjuvant categories like mineral salts, tensoactive compounds, microorganism-derived adjuvants, emulsions, cytokines, polysaccharides, nucleic acid-based adjuvants, and a section dedicated to particulate antigen delivery systems. The mechanisms of adjuvanticity are also discussed in the light of recent findings on Toll-like receptors' biology and their involvement on immune activation.

Influence of aluminum-based adjuvant on the immune response to multiantigenic formulation

Several adjuvants have been described and tested in humans. However, the aluminum-based adjuvants remain the most widely used component in vaccines today. Emerging data suggest that aluminum phosphate and aluminum hydroxide adjuvants do not promote a strong commitment to the helper T cell type 2 (Th2) pathway when they are coadministered with some Th1 adjuvants. In this regard, subtle differences between both aluminum-based adjuvants have been demonstrated. We have previously shown that subcutaneous immunization, in aluminum phosphate, of a mixture comprising the surface and core antigens of hepatitis B virus (HBV) and the multiepitopic protein CR3 of human immunodeficiency virus type 1 elicits a CR3-specific Th1 immune response. In these experiments, the antigens were adjuvated at the same time. As the final selection of the best adjuvant should be based on experimental evidence, we asked whether aluminum hydroxide allows a better Th1 immune deviation than aluminum phosphate. We also studied several ways to mix the antigens and the impact on CR3-specific interferon (IFN)-gamma secretion. Our findings indicate that aluminum hydroxide allows better Th1 immunodeviation than aluminum phosphate adjuvant for the mixture of HBV antigens and CR3. In addition, CR3-specific IFN-gamma secretion of the various formulations tested was the same irrespective of the order in which the antigens were combined.

Phase I clinical trial in healthy adults of a nasal vaccine candidate containing recombinant hepatitis B surface and core antigens

BACKGROUND

The nasal vaccine candidate (NASVAC), comprising hepatitis B virus (HBV) surface (HBsAg) and core antigens (HBcAg), has been shown to be highly immunogenic in animal models.

METHODS

A phase I double-blinded, placebo-controlled randomized clinical trial was carried out in 19 healthy male adults with no serologic markers of immunity/infection to HBV. This study was aimed at exploring the safety and immunogenic profile of nasal co-administration of both HBV recombinant antigens. The trial was performed according to Good Clinical Practice guidelines. Participants ranged in age from 18 to 45 years and were randomly allocated to receive a mixture of 50 microg HBsAg and 50 microg HBcAg or 0.9% physiologic saline solution, as a placebo, via nasal spray in a five-dose schedule at 0, 7, 15, 30, and 60 days. A total volume of 0.5 ml was administered in two dosages of 125 microl per nostril. Adverse events were actively recorded 1 h, 6 h, 12 h, 24 h, 48 h, 72 h, 7 days and 30 days after each dose. Anti-HBs and anti-HBc titers were evaluated using corresponding ELISA kits at days 30 and 90.

RESULTS

The vaccine candidate was safe and well tolerated. Adverse reactions included sneezing (34.1%), rhinorrhea (12.2%), nasal stuffiness (9.8%), palate itching (9.8%), headache (9.8%), and general malaise (7.3%). These reactions were all self-limiting and mild in intensity. No severe or unexpected events were recorded during the trial. The vaccine elicited anti-HBc seroconversion in 100% of subjects as early as day 30 of the immunization schedule, while a seroprotective anti-HBs titer (>or=10 IU/l) was at a maximum at day 90 (75%). All subjects in the placebo group remained seronegative during the trial.

CONCLUSION

The HBsAg-HBcAg vaccine candidate was safe, well tolerated and immunogenic in this phase I study in healthy adults. To our knowledge, this is the first demonstration of safety and immunogenicity for a nasal vaccine candidate comprising HBV antigens.

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.

Coinoculation with hepatitis B surface and core antigen promotes a Th1 immune response to a multiepitopic protein of HIV-1

It has been defined that strong and multispecific cellular immune responses correlate with a better prognosis during the course of chronic diseases. A cross-enhancing effect on the resulting immune response obtained by the coadministration of recombinant hepatitis B virus (HBV) surface and core Ag was recently observed. With the objective of studying the effect of such Ag on the immune response to coinoculated heterologous Ag and vice versa, several formulations containing the recombinant HBV Ag and a multiepitopic protein (CR3) composed by CTL and Th epitopes from HIV-1 were evaluated by s.c. and mucosal administration. Combinations of two and three Ag were evaluated for cellular and humoral immune responses. The results showed that the best Ag combination for nasal immunization was the mixture comprising the CR3 recombinant HIV protein and both HBV Ag. Similarly, it was also the best formulation for s.c. immunization in aluminium phosphate adjuvant. In conclusion, it is possible to induce a Th1 stimulation of the cellular immune response specific for a HIV-based recombinant protein by formulating this Ag with the recombinant HBV Ag.