Lipid microparticles for mucosal immunization against hepatitis B

HBV Vaccines: Advances and Development

Hepatitis B virus (HBV) infection is a global public health problem that is closely related to liver cirrhosis and hepatocellular carcinoma (HCC). The prevalence of acute and chronic HBV infection, liver cirrhosis, and HCC has significantly decreased as a result of the introduction of universal HBV vaccination programs. The first hepatitis B vaccine approved was developed by purifying the hepatitis B surface antigen (HBsAg) from the plasma of asymptomatic HBsAg carriers. Subsequently, recombinant DNA technology led to the development of the recombinant hepatitis B vaccine. Although there are already several licensed vaccines available for HBV infection, continuous research is essential to develop even more effective vaccines. Prophylactic hepatitis B vaccination has been important in the prevention of hepatitis B because it has effectively produced protective immunity against hepatitis B viral infection. Prophylactic vaccines only need to provoke neutralizing antibodies directed against the HBV envelop proteins, whereas therapeutic vaccines are most likely needed to induce a comprehensive T cell response and thus, should include other HBV antigens, such as HBV core and polymerase. The existing vaccines have proven to be highly effective in preventing HBV infection, but ongoing research aims to improve their efficacy, duration of protection, and accessibility. The routine administration of the HBV vaccine is safe and well-tolerated worldwide. The purpose of this type of immunization is to trigger an immunological response in the host, which will halt HBV replication. The clinical efficacy and safety of the HBV vaccine are affected by a number of immunological and clinical factors. However, this success is now in jeopardy due to the breakthrough infections caused by HBV variants with mutations in the S gene, high viral loads, and virus-induced immunosuppression. In this review, we describe various types of available HBV vaccines, along with the recent progress in the ongoing battle to develop new vaccines against HBV.

Solid Lipid Microspheres Decorated Nanoparticles As Drug Carriers

While Pickering emulsions have been known since 1906, where oil droplets are dispersed in aqueous media owing to nanoparticles decorating each oil droplet, no solid lipid microparticles decorated with nanoparticles have been described. These Solid-Pickering microparticles are surfactant-free micro-scale spherical active agent carriers composed of beeswax as a natural solid lipid with chitosan and starch nanoparticles embedded in the surface. Microparticles of this type were made by dispersing molten lipid in hot aqueous media containing dispersed nanoparticles to create microdroplets. Once the droplets are cooled below the melting point of the lipid, the microparticles of spherical form are obtained. The novel system allows encapsulation of active agents within a solid lipid core which is slowly released over time. It has been demonstrated through encapsulation of Ibuprofen and Lidocaine as a model poorly water-soluble drugs and an extended-release profile (for at least a week) was achieved. These Solid Pickering microparticles can be used in food, medicine, agriculture, and personal care products.

Microparticle fabricated from a series of symmetrical lipids based on dihydroxyacetone form textured architectures

We report the synthesis of a series of symmetrical lipids composed of dihydroxyacetone and even‑carbon fatty acids (eight to sixteen carbons), both components of the human metabolome, and characterize their formulation into porous microparticles through spontaneous emulsification without the use of additional porogens. Lipid hydrolysis products were identified by ¹H NMR to validate lipid degradation into the parent metabolic synthons. Microparticle architecture, as determined by scanning electron microscopy, was lipid-length dependent, with shorter alkyl chains forming tight structures and longer alkyl chains forming larger pores with plate-like lipid architectures. In all cases, the lipids formed organized patterns, not irregular shapes. As a demonstration of the potential use of these solid lipid-based microparticles, the release kinetics of a model drug (piroxicam) was quantified showing that release was more greatly influenced by microparticle porosity, and hence surface area, than by hydrophobicity of the lipids.

Spray congealed solid lipid microparticles as a sustained release delivery system for Gonadorelin [6-D-Phe]: Production, optimization and in vitro release behavior

Sustained release lipid microparticles for a potential veterinary application were produced by the means of spray congealing using saturated triglycerides with respective surfactants. The spray congealing process was optimized using unloaded and loaded microparticles, revealing the highest impact of the spray flow on material loss. Yield could be optimized by increasing the spray flow as well as a reduction of the melt temperature from 90 to 75 °C. For the delivery system developed in this study, a release of around 15 days was targeted. The release profile was in first hand determined with the use of model substances (aspartame and tryptophan), before incorporating the decapeptide Gonadorelin [6-D-Phe]. Release could be controlled between 2 and 28 d, which was dependent on stability of microparticles upon incubation, type and concentration of emulsifier, as well as the used triglyceride. Differential scanning calorimetry and X-ray powder diffraction confirmed the crystallization behavior of C14 and C16-triglycerides in combination with various emulsifiers in different modification without impact on release.

Chylomicron mimicking solid lipid nanoemulsions encapsulated enteric minicapsules targeted to colon for immunization against hepatitis B

The oral route is one of the most convenient routes for drug and/or vaccine delivery. Yet variable nature of gastrointestinal tract due to transient changes in pH, physiology, and flora throughout the gut together with hostile nature of peptide drugs/vaccines when given by this route results in limited success. Colon targeting is a recent area of interest for most of the research among which hard gelatin coated capsules is one such important and useful contrivance. The present study assesses the mucosal immunization with HBsAg loaded lyophilized nanoparticles delivered in the colonic region using enteric coated minicapsules. Designed minicapsules offers better compliance and oral vaccine antigen delivery to the colonic region which involving mucosal exposure thus mimicking the natural pathogen entry in the body. The present study is an extension of our reported work where nanoparticles were administered to the colon through the rectal route. Lyophilized nanoparticles were characterized for particle size, in-vitro release and antigen integrity along with cell uptake study. Particles had ~241 ± 32 nm sizes, flattened yet spherical in morphology. Enteric coated minicapsules were evaluated for size, coating thickness, and dissolution profile. In-vivo immune response assured its immunogenic potential with profound IgG (485 ± 41 mIU/ml) and IgA (885 ± 126 mIU/ml) antibody production as compared to marketed recombinant hepatitis B antigen formulation (Gene Vac-B®) which induce IgG and IgA titer; 1027 ± 62 mIU/ml and 220 ± 11 mIU/ml respectively following well established immunization protocol. Former induced significant mucosal immunity due to the involvement of Common Mucosal Immune System (CMIS). The study supports the workable novel approach for immune protection against hepatitis B.

Lipid A adjuvanted Chylomicron Mimicking Solid Fat Nanoemulsions for Immunization Against Hepatitis B

Traditional parenteral recombinant hepatitis B virus (HBV) vaccines have effectively reduced the disease burden despite being able to induce seroprotective antibody titers in 5-10% vaccinated individuals (non-responders). Moreover, an estimated 340 million chronic HBV cases are in need of treatment. Development of safe, stable, and more effective hepatitis B vaccine formulation would address these challenges. Recombinant hepatitis B surface antigen (rHBsAg) entrapped solid fat nanoemulsions (SFNs) containing monophosphoryl lipid A (MPLA) that was prepared and optimized by quality by design (QbD) using response surface methodology (RSM), i.e., central composite design (CCD). Its immune potential was evaluated with preset immunization protocol in a murine model. Dose escalation study revealed that formulation containing 1 μg of rHBsAg entrapped SFNs with MPLA-induced significant higher humoral, and cellular response compared to the marketed vaccine (Genvac B) administered intramuscularly. SFNs with nanometric morphology and structural similarity with chylomicrons assist in improved uptake and processing to lymphatics. Moreover, the presence of an immunogenic component in its structure further augments delivery of rHBsAg to immune cells with induction of danger signals. This multi-adjuvant based approach explores new prospect for the dose sparing. Improved cellular immune response induced by this vaccine formulation suggests that it could be tested as an immunotherapeutic vaccine as well.

Development of Adjuvanted Solid Fat Nanoemulsions for Pulmonary Hepatitis B Vaccination

Pulmonary vaccination is one of the most promising routes for immunization owing to its noninvasive nature and induction of strong mucosal immunity and systemic response. In the present study, recombinant hepatitis B surface antigen loaded solid fat nanoemulsions (SFNs) as carrier system and monophosphoryl lipid A as an adjuvant-carrier system was prepared and evaluated as multiadjuvanted vaccine system for deep pulmonary vaccination. Deposition and clearance from the deep lung of rats were determined by gamma scintigraphy. Biodistribution of SFNs was determined by the live animal imaging system. SFNs dispersion showed slower clearance as compared with sodium pertechnetate control solution (^∗∗∗p <0.001) from the pulmonary region due to the virtue of particulate and hydrophobic nature of formulations. Humoral (sIgA and IgG) and cellular (IL-2 and IF-γ) immune responses were found to be significant (^∗∗∗p <0.001) when compared with naïve antigen (recombinant surface antigen without any excipient) solution. Data indicate that deep pulmonary immunization offers a stronger immune response with balanced humoral, mucosal, and cellular immunization, which further needs to be tested in higher animals to support this hypothesis for clinical translation of this so far neglected yet potential target tissue for immunization.

Immunological evaluation of colonic delivered Hepatitis B surface antigen loaded TLR-4 agonist modified solid fat nanoparticles

Hepatitis B is one of the leading liver diseases and remains a major global health problem. Currently available vaccines provide protection but often results in weaker/minimal mucosal immunity. Thus the present study is devoted to the development and in-vivo exploration of the colonically delivered biomimetic nanoparticles which capably enhance humoral as well as cellular immune response. In present work, Hepatitis B surface antigen (HBsAg) entrapped nanoparticles containing Monophosphoryl lipid A (MPLA) (HB+L-NP) were prepared by solvent evaporation method and characterized for particle size (~210nm), shape, zeta potential (-24mV±0.68), entrapment efficiency (58.45±1.68%), in-vitro release and antigen integrity. Dose escalation study was done to confirm prophylactic immune response following defined doses of prepared nanoparticulate formulations with or without MPLA. Intramuscular administered alum based marketed HBsAg (Genevac B) was used as standard (10μg) and were able to induce significant systemic (IgG) but remarkably low mucosal immune (IgA) response. Notably, HB+L-NP (0.5ml-10μg) induced strong systemic and robust mucosal immunity (510 and 470 mIU/ml respectively, p<0.001) from which mucosal was more significant due to the involvement of Common Mucosal Immune System (CMIS). Likewise, significant cellular immune response was elicited by HB+L-NP through T-cell activation (mixed Th1 and Th2) as confirmed by significantly increased cytokines level (IL-2 and Interferon-γ) in spleen homogenates. This study supports that delivery of HBsAg to the colon may open new vista in designing oral vaccines later being one of most accepted route for potential vaccines in future.

Intranasal and oral vaccination with protein-based antigens: advantages, challenges and formulation strategies

Most pathogens initiate their infections at the human mucosal surface. Therefore, mucosal vaccination, especially through oral or intranasal administration routes, is highly desired for infectious diseases. Meanwhile, protein-based antigens provide a safer alternative to the whole pathogen or DNA based ones in vaccine development. However, the unique biopharmaceutical hurdles that intranasally or orally delivered protein vaccines need to overcome before they reach the sites of targeting, the relatively low immunogenicity, as well as the low stability of the protein antigens, require thoughtful and fine-tuned mucosal vaccine formulations, including the selection of immunostimulants, the identification of the suitable vaccine delivery system, and the determination of the exact composition and manufacturing conditions. This review aims to provide an up-to-date survey of the protein antigen-based vaccine formulation development, including the usage of immunostimulants and the optimization of vaccine delivery systems for intranasal and oral administrations.

Nanocarriers: a versatile approach for mucosal vaccine delivery

Infectious agents generally use mucosal surfaces as entry port to the body thereby necessitating the need of development of mucosal vaccine as vaccination is important for disease avoidance and suppression. Vaccination through mucosal route is a promising strategy to elicit efficient immune response as parentally administered vaccines induce poor mucosal immunity in general. Safety, economy and stability are highly desired with vaccines and this can be achieved with use of delivery cargos. This review focuses on challenges related with mucosal vaccines and use of nanocarriers as suitable cargos to cater the antigen effectively to the desired site. The review also includes different factors which are to be considered regarding the performance of the nanocarriers and clinical status of these systems.

First in vivo evaluation of particulate nasal dry powder vaccine formulations containing ovalbumin in mice

In this study three different dry powder vaccine formulations containing the model antigen ovalbumin were evaluated for their immune effects after nasal administration to C57Bl/6 mice in an adoptive cell transfer model. The formulations were chitosan nanoparticles in a mannitol matrix, chitosan microparticles and agarose nanoparticles in a mannitol matrix. Dry powder administration to mice was well tolerated and did not result in any adverse reactions. No translocation of the dry powder formulations to the lung could be detected. The local cellular immune response in the cervical lymph nodes was modest and only for the chitosan microparticles and the agarose nanoparticles was there a significant difference compared to s.c. injection of ovalbumin in alum. No humoral response could be measured after nasal administration. The results provide some evidence that nasal administration of dry powder formulations can stimulate an immune response, but the response was modest. This is probably due to a low antigen dose and low immunogenicity of the formulations. Further studies will aim at enhancing the antigen load and improving adjuvant activity.

Administration strategies for proteins and peptides

Proteins are a vital constituent of the body as they perform many of its major physiological and biological processes. Recently, proteins and peptides have attracted much attention as potential treatments for various dangerous and traditionally incurable diseases such as cancer, AIDS, dwarfism and autoimmune disorders. Furthermore, proteins could be used for diagnostics. At present, most therapeutic proteins are administered via parenteral routes that have many drawbacks, for example, they are painful, expensive and may cause toxicity. Finding more effective, easier and safer alternative routes for administering proteins and peptides is the key to therapeutic and commercial success. In this context, much research has been focused on non-invasive routes such as nasal, pulmonary, oral, ocular, and rectal for administering proteins and peptides. Unfortunately, the widespread use of proteins and peptides as drugs is still faced by many obstacles such as low bioavailability, short half-life in the blood stream, in vivo instability and numerous other problems. In order to overcome these hurdled and improve protein/peptide drug efficacy, various strategies have been developed such as permeability enhancement, enzyme inhibition, protein structure modification and protection by encapsulation. This review provides a detailed description of all the previous points in order to highlight the importance and potential of proteins and peptides as drugs.

Pulmonary vaccine delivery

This review will discuss developments in the field of pulmonary vaccine delivery. The possibilities of adopting aerosol-generation technology and specific pharmaceutical formulations for the purpose of pulmonary immunization are described. Aerosol-generation systems might offer advantages with respect to vaccine stability and antigenicity. Adjuvants and their inclusion in vaccine-delivery systems are described. Other formulation components, such as surfactants, particulate systems and dispersion of the aerosols are detailed in this paper. The noninvasive, relatively safe and low-cost nature of pulmonary delivery may provide great benefits to the public health vaccination campaign.

Recent advances in nanocarrier-based mucosal delivery of biomolecules

This review highlights the recent developments in the area of nanocarrier-based mucosal delivery of therapeutic biomolecules and antigens. Macromolecular drugs have the unique power to tackle challenging diseases but their structure, physicochemical properties, stability, pharmacodynamics, and pharmacokinetics place stringent demands on the way they are delivered into the body (e.g., inability to cross mucosal surfaces and biological membranes). Carrier-based drug delivery systems can diminish the toxicity of therapeutic biomolecules, improve their bioavailability and make possible their administration via less-invasive routes (e.g., oral, nasal, pulmonary, etc.). Thus, the development of functionalized nanocarriers and nanoparticle-based microcarriers for the delivery of macromolecular drugs is considered an important scientific challenge and at the same time a business breakthrough for the biopharmaceutical industry. In order to be translated to the clinic the nanocarriers need to be biocompatible, biodegradable, stable in biological media, non-toxic and non-immunogenic, to exhibit mucoadhesive properties, to cross mucosal barriers and to protect their sensitive payload and deliver it to its target site in a controlled manner, thus increasing significantly its bioavailability and efficacy.

Lipid nanoparticles as delivery vehicles for the Parietaria judaica major allergen Par j 2

Parietaria pollen is one of the major causes of allergic reaction in southern Europe, affecting about 30% of all allergic patients in this area. Specific immunotherapy is the only treatment able to modify the natural outcome of the disease by restoring a normal immunity against allergens. The preparation of allergen-solid lipid nanoparticles as delivery vehicles for therapeutic proteins, P. judaica major allergen Par j 2, was investigated. The Par j 2 allergen was expressed in a large amount in Escherichia coli and purified to homogeneity. Its immunological properties were studied by western blotting and enzyme-linked immunosorbent assay inhibition. Solid lipid nanoparticles were obtained by water-in-oil-in-water multiple emulsion method and characterized in terms of mean size and surface charge. These systems (approximately 250 nm diameter and negative surface charge) incorporated recombinant Par j 2 with 40% or greater efficiency. Moreover, the endotoxin level and anaphylactic activity of the empty solid lipid nanoparticles and recombinant Par j 2-loaded solid lipid nanoparticles were evaluated by looking at the overexpression of CD203c marker on human basophils. These results demonstrate that recombinant Par j 2-nanoparticles could be proposed as safe compositions for the development of new therapeutic dosage forms to cure allergic reactions.

Delivery of antigens used for vaccination: recent advances and challenges

Pasteur’s principle ‘isolate, inactivate, inject’ was the starting point for the successful development of many vaccines, but now, new ways for antigen discovery and vaccine administration present a challenge. Whereas vaccines against polio, measles and influenza are common for many parts of the world, the development of thermostable vaccines not being injected would ease vaccine distribution in developing countries. This review summarizes the general principles of vaccination and looks at common and novel vaccination targets. It also gives a rationale for using other routes than parenteral administration, such as mucosal or transdermal vaccination, and focuses on novel vaccination vehicles, as well as their formulation and stability aspects. Additionally, the review looks at novel application devices for the administration of vaccines.

Preparation and characterization of catalase-loaded solid lipid nanoparticles protecting enzyme against proteolysis

Catalase-loaded solid lipid nanoparticles (SLNs) were prepared by the double emulsion method (w/o/w) and solvent evaporation techniques, using acetone/methylene chloride (1:1) as an organic solvent, lecithin and triglyceride as oil phase and Poloxmer 188 as a surfactant. The optimized SLN was prepared by lecithin: triglyceride ratio (5%), 20-second + 30-second sonication, and 2% Poloxmer 188. The mean particle size of SLN was 296.0 ± 7.0 nm, polydispersity index range and zeta potential were 0.322–0.354 and −36.4 ± 0.6, respectively, and the encapsulation efficiency reached its maximum of 77.9 ± 1.56. Catalase distributed between the solid lipid and inner aqueous phase and gradually released from Poloxmer coated SLNs up to 20% within 20 h. Catalase-loaded SLN remained at 30% of H₂O₂-degrading activity after being incubated with Proteinase K for 24 h, while free catalase lost activity within 1 h.

Progress towards a needle-free hepatitis B vaccine

Hepatitis B virus (HBV) infection is a worldwide public health problem. Vaccination is the most efficient way to prevent hepatitis B. Despite the success of the currently available vaccine, there is a clear need for the development of new generation of HBV vaccines. Needle-free immunization is an attractive approach for mass immunization campaigns, since avoiding the use of needles reduces the risk of needle-borne diseases and prevents needle-stick injuries and pain, thus augmenting patient compliance and eliminating the need for trained medical personnel. Moreover, this kind of immunization was shown to induce good systemic as well as mucosal immunological responses, which is important for the creation of both a prophylactic and therapeutic vaccine. In order to produce a better, safer, more efficient and more suitable vaccine, adjuvants have been used. In this article, several adjuvants tested over the years for their potential to help create a needle-free vaccine against HBV are reviewed.

Evaluation of ISCOM vaccines for mucosal immunization against hepatitis B

Immune stimulating complexes (ISCOMs) incorporating recombinant hepatitis B surface antigen (HBsAg) was prepared for induction of humoral, cellular and mucosal immunity by intranasal administration. Prepared ISCOMs were characterized for its size, shape, incorporation efficiency, zeta potential, and antigen integrity. Designed ISCOMs possessed negative zeta potential (-21.7 mV) and an average size of 44.1 nm with antigen incorporation efficiency approximately 39 %. Serum anti-HBsAg IgG titer after three high nasal doses of ISCOMs was comparable with titer recorded after alum-HBsAg administered subcutaneously. Similarly, modest but higher cellular response (cytokines level in spleen homogenates) and significantly higher secretory sIgA response in mucosal secretions was observed (P < 0.001) in case of HBsAg ISCOM vaccines. Whereas, alum-HBsAg vaccine did not elicit considerable cellular or mucosal response. Thus, ISCOMs produced humoral, mucosal, and cellular immune responses upon nasal administration although high and multidose administrations were required to elicit potent immune responses. These data demonstrate potential of ISCOMs in their use as a carrier adjuvant for nasal subunit vaccines against hepatitis B.

Immunoglobulin immobilized liposomal constructs for transmucosal vaccination through nasal route

The aim of the present investigation was to evaluate the prospective of surface-engineered vesicular carriers for mucosal immunization via the nasal route. IgG antibody was immobilized on the surface of hepatitis B surface antigen (HBsAg) antigen-loaded liposomes. The developed formulations were characterized on the basis of physicochemical parameters, such as morphology, particle size, polydispersity index, entrapment efficiency, and zeta potential. Liposomal formulations were then evaluated for in-process antigen stability and storage stability. In vivo studies were conducted to visualize targeting potential, localization pattern, and immunogenicity. In addition, immune response was compared with alum-HBsAg vaccine injected intramuscularly. The serum anti-HBsAg titer, obtained from the postnasal administration of IgG-coupled liposomes, was significantly higher than plain liposomes. Moreover, IgG-coupled liposomes generated both humoral (i.e., systemic and mucosal) and cellular immune responses upon nasal administration, while the alum-adsorbed antigen displayed neither cellular (cytokine level) nor mucosal (IgA) response. The formulation also displayed enhanced transmucosal transport, improved in vitro stability, and effective immunoadjuvant property. To conclude, IgG antibody-coupled liposomes may serve as novel carriers to augment the secretory immune response of antigen encapsulated in the liposomes, apparently by escalating liposome uptake via M cells, thereby rationalizing their use as a carrier adjuvant for nasal subunit vaccines.

Nanoparticles for nasal vaccination

The great interest in mucosal vaccine delivery arises from the fact that mucosal surfaces represent the major site of entry for many pathogens. Among other mucosal sites, nasal delivery is especially attractive for immunization, as the nasal epithelium is characterized by relatively high permeability, low enzymatic activity and by the presence of an important number of immunocompetent cells. In addition to these advantageous characteristics, the nasal route could offer simplified and more cost-effective protocols for vaccination with improved patient compliance. The use of nanocarriers provides a suitable way for the nasal delivery of antigenic molecules. Besides improved protection and facilitated transport of the antigen, nanoparticulate delivery systems could also provide more effective antigen recognition by immune cells. These represent key factors in the optimal processing and presentation of the antigen, and therefore in the subsequent development of a suitable immune response. In this sense, the design of optimized vaccine nanocarriers offers a promising way for nasal mucosal vaccination.

Well-defined and potent liposomal hepatitis B vaccines adjuvanted with lipophilic MDP derivatives

The characterization of immunological cascades of the innate immune system activated by invariant molecular structures termed as pathogen-associated molecular patterns recognized by pattern recognition receptors of macrophages and dendritic cells, have allowed the elucidation of the mechanisms underlying the immunomodulatory properties of adjuvants. Thus, adjuvant-active lipophilic analogues of N-acetyl muramyl dipeptide (MDP) were incorporated in liposomal hepatitis B surface antigen (HBsAg) formulations. The immunoreactivity of the formulations was evaluated by measuring anti-HBs, immunoglobulin G (IgG), and isotype antibody titer and compared with alum-adsorbed HBsAg formulation. The formulations were also evaluated for cell-mediated immune response by HBsAg-specific proliferation of splenocytes and simultaneous estimation of cytokines (interleukin-4 [IL-4], interferon-gamma [IFN-gamma]). Results indicate that the serum IgG and anti-HBs titer obtained after intramuscular administration of liposomal muramyl tripeptide-phosphatidylethanolamine (MTP-PE) and liposomal N-acetylmuramyl-l-alanyl-d-isoglutamine-glycerol dipalmitate (MDP-GDP) antigenic formulations were significantly higher. The incorporation of MTP-PE on the liposomal HBsAg increased the stimulation index (SI) four to five times as compared to plain HBsAg solution, and it also induced significantly higher Th1 cellular immune response with a predominant IFN-gamma level. So it is the novel effective and potentially safe approach in which liposomes act as delivery vehicles for hepatitis B viral antigen to antigen-presenting cells and is ornamented with a biological response modifier that could activate these target cells to enhance the antigen presentation to T lymphocytes.

FROM THE CLINICAL EDITOR

In this study, adjuvant-active lipophilic analogues on N-acetyl muramyl dipeptide (MDP) were incorporated in liposomal hepatitis B surface antigen (HBsAg) formulations. The immunoreactivity of the formulations was evaluated and found effective, leading to a potentially enhanced immune response against the delivered antigen.

Pre-clinical evaluation of a novel nanoemulsion-based hepatitis B mucosal vaccine

BACKGROUND

Hepatitis B virus infection remains an important global health concern despite the availability of safe and effective prophylactic vaccines. Limitations to these vaccines include requirement for refrigeration and three immunizations thereby restricting use in the developing world. A new nasal hepatitis B vaccine composed of recombinant hepatitis B surface antigen (HBsAg) in a novel nanoemulsion (NE) adjuvant (HBsAg-NE) could be effective with fewer administrations.

METHODOLOGY AND PRINCIPAL FINDINGS

Physical characterization indicated that HBsAg-NE consists of uniform lipid droplets (349+/-17 nm) associated with HBsAg through electrostatic and hydrophobic interactions. Immunogenicity of HBsAg-NE vaccine was evaluated in mice, rats and guinea pigs. Animals immunized intranasally developed robust and sustained systemic IgG, mucosal IgA and strong antigen-specific cellular immune responses. Serum IgG reached > or = 10(6) titers and was comparable to intramuscular vaccination with alum-adjuvanted vaccine (HBsAg-Alu). Normalization showed that HBsAg-NE vaccination correlates with a protective immunity equivalent or greater than 1000 IU/ml. Th1 polarized immune response was indicated by IFN-gamma and TNF-alpha cytokine production and elevated levels of IgG(2) subclass of HBsAg-specific antibodies. The vaccine retains full immunogenicity for a year at 4 degrees C, 6 months at 25 degrees C and 6 weeks at 40 degrees C. Comprehensive pre-clinical toxicology evaluation demonstrated that HBsAg-NE vaccine is safe and well tolerated in multiple animal models.

CONCLUSIONS

Our results suggest that needle-free nasal immunization with HBsAg-NE could be a safe and effective hepatitis B vaccine, or provide an alternative booster administration for the parenteral hepatitis B vaccines. This vaccine induces a Th1 associated cellular immunity and also may provide therapeutic benefit to patients with chronic hepatitis B infection who lack cellular immune responses to adequately control viral replication. Long-term stability of this vaccine formulation at elevated temperatures suggests a direct advantage in the field, since potential excursions from cold chain maintenance could be tolerated without a loss in therapeutic efficacy.

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.

Immune response by nasal delivery of hepatitis B surface antigen and codelivery of a CpG ODN in alginate coated chitosan nanoparticles

Alginate coated chitosan nanoparticles were previously developed with the aim of protecting the antigen, adsorbed on the surface of those chitosan nanoparticles, from enzymatic degradation at mucosal surfaces. In this work, this new delivery system was loaded with the recombinant hepatitis B surface antigen (HBsAg) and applied to mice by the intranasal route. Adjuvant effect of the delivery system was studied by measuring anti-HBsAg IgG in serum, anti-HBsAg sIgA in faeces extracts or nasal and vaginal secretions and interferon-gamma production in supernatants of the spleen cells. The mice were primed with 10 microg of the vaccine associated or not with nanoparticles and associated or not with 10 microg CpG oligodeoxynucleotide (ODN) followed by two sequential boosts at three week intervals. The association of HBsAg with the alginate coated chitosan nanoparticles, administered intranasally to the mice, gave rise to the humoral mucosal immune response. Humoral systemic immune response was not induced by the HBsAg loaded nanoparticles alone. The generation of Th1-biased antigen-specific systemic antibodies, however, was observed when HBsAg loaded nanoparticles were applied together with a second adjuvant, the immunopotentiator, CpG ODN. Moreover, all intranasally vaccinated groups showed higher interferon-gamma production when compared to naïve mice.

Comparison of vesicle based antigen delivery systems for delivery of hepatitis B surface antigen

There is a clinical need for a more effective vaccine against hepatitis B, and in particular vaccines that may be suitable for therapeutic administration. This study assesses the potential of cationic surfactant vesicle based formulations using two agents; the cationic amine containing [N-(N',N'-dimethylaminoethane)-carbamoyl] cholesterol (DC-Chol) or dimethyl dioctadecylammonium bromide (DDA) with hepatitis B surface antigen (HBsAg). Synthetic mycobacterial cord factor, trehalose 6,6'-dibehenate (TDB) has been used as an adjuvant and the addition of 1-monopalmitoyl glycerol (C16:0) (MP) and cholesterol (Chol) to DDA-TDB is assessed for its potential to facilitate formation of dehydration-rehydration vesicles (DRV) at room temperature, and the effect of this on immune responses. A DRV formulation is directly compared to an adsorbed formulation of the same composition and preparation protocol (MP:dioleoyl phosphoethanolamine (DOPE):Chol:DC-Chol) and the direct substitution of MP with phosphatidylcholine (PC) is also compared in DRV antigen-entrapped formulations. MP and Chol were shown to facilitate the use of DDA-TDB in DRV formulations prepared at room temperature, whilst there was marginal alteration of immunogenicity (a reduction in HBsAg-specific IL-2). The HBsAg adsorbed DRV formulation was not significantly different from the HBsAg entrapped DRV formulation. Overall, DDA formulations incorporating TDB showed markedly increased antigen specific splenocyte proliferation and elicited cytokine production concomitant with a strong T cell driven response, delineating formulations that may be useful for further evaluation of their clinical potential.