Evaluation of albumin microspheres as oral delivery system for Mycobacterium tuberculosis vaccines

Demystifying particle-based oral vaccines

Introduction: The oral route of vaccination is pain- and needle-free and can induce systemic and mucosal immunity. However, gastrointestinal barriers and antigen degradation impose significant hurdles in the development of oral vaccines. Live attenuated viruses and bacteria can overcome these barriers but at the risk of introducing safety concerns. As an alternative, particles have been investigated for antigen protection and delivery, yet there are no FDA-approved oral vaccines based on particle-based delivery systems. Our objective was to discover underlying determinants that can explain the current inadequacies and identify paradigms that can be implemented in future for successful development of oral vaccines relying on particle-based delivery systems.Areas covered: We reviewed literature related to the use of particles for oral vaccination and placed special emphasis on formulation characteristics and administration schedules to gain an insight into how these parameters impact production of antigen-specific antibodies in systemic and mucosal compartments.Expert opinion: Despite the long history of vaccines, particle-based oral vaccination is a relative new field with the first study published in 1989. Substantial variability exists between different studies with respect to dosing schedules, number of doses, and the amount of vaccine per dose. Most studies have not used adjuvants in the formulations. Better standardization in vaccination parameters is required to improve comparison between experiments, and adjuvants should be used to enhance the systemic and mucosal immune responses and to reduce the number of doses, which will make oral vaccines more attractive.

Recent developments in nanocarrier-aided mucosal vaccination

To date, most of the licensed vaccines for mucosal delivery are based on live-attenuated viruses which carry the risk of regaining their pathogenicity. Therefore, the development of efficient nonviral vectors allowing the induction of potent humoral and cell-mediated immunity is regarded as an imperative scientific challenge as well as a commercial breakthrough for the pharma industries. For a successful translation to the clinic, such nanocarriers should protect the antigens from mucosal enzymes, facilitate antigen uptake by microfold cells and allow the copresentation of robust, safe for human use, mucosal adjuvants to antigen-presenting cells. Finally, the developed formulations should exhibit accuracy regarding the administered dose, a major drawback of mucosal vaccines in comparison with parenteral ones.

Novel protein-loaded chondroitin sulfate-N-[(2-hydroxy-3-trimethylammonium)propyl]chitosan nanoparticles with reverse zeta potential: preparation, characterization, and ex vivo assessment

A facile polyelectrolyte complexation method for the preparation of both positively and negatively surface charged nanoparticles composed of chondroitin sulfate (ChS) and N-[(2-hydroxy-3-trimethylammonium)propyl]chitosan (HTCC) is reported. Production of ChS-HTCC nanoparticles with reverse zeta potential was easily controlled by varying the ChS/HTCC mass ratio. The encapsulation efficiency increased with the increase in initial FITC-BSA concentration in positively charged NPs and reached 75%. However, a maximum of 20% encapsulation efficiency was achieved in the case of negatively charged NPs. In vitro release studies of positively charged ChS-HTCC NPs showed a small burst effect followed by a continued and controlled release. Both charges of ChS-HTCC NPs showed no cytotoxicity in HUVECs. The confocal images showed that ChS-HTCC NPs of both charges can be incorporated and retained by the A549 cells. Flow cytometric analysis data demonstrated that ChS-HTCC NPs of both charges were detected in more than 80% of the A549 cells.

Development of a microparticulate prostate cancer vaccine and evaluating the effect of route of administration on its efficacy via the skin

The skin has been identified as a promising target to deliver vaccines. In this study, prostate cancer antigens were delivered in a spray-dried microparticulate carrier to a murine model via the transdermal route and the subcutaneous route. There was a significant increase in the humoral responses as determined by the total serum IgG titres (p < 0.05) and the cellular responses as determined by the T- and B-cells sub-population in spleen samples and delay in tumour growth till 8 weeks post-tumour challenge of both vaccinated groups when compared to the controls. The vaccine microparticles administered via the transdermal route induced a Th2-mediated immune response versus a mixed Th1- and Th2-mediated immune response via the subcutaneous route. Thus, the particulate vaccine delivery system proves to be a promising alternative for generation of a robust immune response against prostate cancer via the skin in a murine model.

Induction of death receptor CD95 and co-stimulatory molecules CD80 and CD86 by meningococcal capsular polysaccharide-loaded vaccine nanoparticles

Neisseria meningitidis is a leading cause of bacterial meningitis and sepsis, and its capsular polysaccharides (CPS) are a major virulence factor in meningococcal infections and form the basis for serogroup designation and protective vaccines. We formulated a novel nanovaccine containing meningococcal CPS as an antigen encapsulated in albumin-based nanoparticles (NPs) that does not require chemical conjugation to a protein carrier. These nanoparticles are taken up by antigen-presenting cells and act as antigen depot by slowly releasing the antigen. In this study, we determined the ability of CPS-loaded vaccine nanoparticles to induce co-stimulatory molecules, namely CD80, CD86, and CD95 that impact effective antigen presentation. Co-stimulatory molecule gene induction and surface expression on macrophages and dendritic cells pulsed with meningococcal CPS-loaded nanoparticles were investigated using gene array and flow cytometry methods. Meningococcal CPS-loaded NP significantly induced the surface protein expression of CD80 and CD86, markers of dendritic cell maturation, in human THP-1 macrophages and in murine dendritic cells DC2.4 in a dose-dependent manner. The massive upregulation was also observed at the gene expression. However, high dose of CPS-loaded NP, but not empty NP, induced the expression of death receptor CD95 (Fas) leading to reduced TNF-α release and reduction in cell viability. The data suggest that high expression of CD95 may lead to death of antigen-presenting cells and consequently suboptimal immune responses to vaccine. The CPS-loaded NP induces the expression of co-stimulatory molecules and acts as antigen depot and can spare antigen dose, highly desirable criteria for vaccine formulations.

Micro and nanoparticle-based delivery systems for vaccine immunotherapy: an immunological and materials perspective

The development and widespread application of vaccines has been one of the most significant achievements of modern medicine. Vaccines have not only been instrumental in controlling and even eliminating life-threatening diseases like polio, measles, diphtheria, etc., but have also been immensely powerful in enhancing the worldwide outlook of public health over the past century. Despite these successes, there are still many complex disorders (e.g., cancer, HIV, and other emerging infectious diseases) for which effective preventative or therapeutic vaccines have been difficult to develop. This failure can be attributed primarily to our inability to precisely control and modulate the highly complex immune memory response, specifically the cellular response. Dominated by B and T cell maturation and function, the cellular response is primarily initiated by potent immunostimulators and antigens. Efficient and targeted delivery of these immunomodulatory and immunostimulatory molecules to appropriate cells is key to successful development of next generation vaccine formulations. Over the past decade, particulate carriers have emerged as an attractive means for enhancing the delivery efficacy and potency of vaccines and associated immunomodulatory molecules. Specifically, polymer-based micro and nanoparticles are being extensively studied for a wide variety of applications. In this review, we discuss the immunological fundamentals for developing effective vaccines and how materials and material properties can be exploited to improve these therapies. Particular emphasis is given to polymer-based particles and how the route of administration of particulate systems affects the phenotype and robustness of an immune response. Comparison of various strategies and recent advancements in the field are discussed along with insights into current limitations and future directions.

Formulation and evaluation of oral microparticulate ovarian cancer vaccines

Ovarian cancer is the fifth most leading cause of cancer related deaths in women in the US. Customized immunotherapeutic strategies may serve as an alternative method to control the recurrence or progression of ovarian cancer and to avoid severe adverse effects of chemotherapy. In this study, a microparticulate vaccine using whole cell lysate of a murine ovarian cancer cell line, ID8 was prepared with the use of a spray dryer. These particles were designed for oral delivery using enteric polymers such as methacrylic copolymer, Eudragit(®) FS30D and hydroxyl propyl methyl cellulose acetate succinate. These particles were targeted for uptake via microfold cell (M-cell) in Peyer's patches of small intestine using M-cell targeting ligand, Aleuria aurantia lectin. The interleukins (ILs) such as IL-2 and IL-12 were added to the vaccine formulation to further enhance the immune response. The particles obtained were of 1.58±0.62 μm size with a charge of 12.48±2.32 mV. The vaccine efficacy was evaluated by administering the particles via oral route to C57BL/6 female mice. At the end of vaccination, mice were challenged with live tumor cells. Vaccinated mice showed significant (around six-fold) retardation of tumor volume in comparison to non-vaccinated animals for 3 weeks after the tumor challenge (p<0.001). The serum IgG antibody levels were found to be elevated in case of vaccinated animals in comparison to non-vaccinated group (p<0.05). Analysis of IgG1 titers (indicative of Th2 response) and IgG2a titers (indicative of Th1 response) showed a mixed Th1 and Th2 immune response in case vaccine alone and Th2 response in case of vaccine with interleukins group. Moreover, CD8+ T-cell, CD4+ T-cell and B-cell populations in different lymphatic organs were elevated in case of vaccinated mice. Thus, whole cell lysate vaccine microparticles formulated by spray drying could trigger humoral as well as cellular immune response when administered orally. Such vaccine could potentially be an effective treatment for patients with residual tumor or high tumor-relapse probability.

Immunogenicity and protection of oral influenza vaccines formulated into microparticles

Influenza is a deadly disease affecting humans and animals. It is recommended that every individual should be vaccinated annually against influenza. Considering the frequency of administration of this vaccine, we have explored the oral route of vaccination with a microparticulate formulation. Microparticles containing inactivated influenza A/PR/34/8 H1N1 virus with Eudragit S and trehalose as a matrix were prepared using the Buchi spray dryer. Particle size distribution of microparticles was measured and the bioactivity of vaccine in a microparticle form was analyzed using a hemagglutination activity test. Furthermore, the efficacy of microparticle vaccines was evaluated in vivo in Balb/c mice. Analysis of serum samples showed that microparticles resulted in enhanced antigen-specific immunoglobulin G (IgG), IgG1, and IgG2a antibodies. Upon challenge with homologous and heterologous influenza viruses, microparticle vaccines showed significantly increased levels of protection. Use of microparticles to deliver vaccines could be a promising tool for the development of an oral influenza vaccine.

Formulation of meningococcal capsular polysaccharide vaccine-loaded microparticles with robust innate immune recognition

Neisseria meningitidis is a leading cause of bacterial meningitis and sepsis associated with a high mortality rate. Capsular polysaccharides (CPSs) are a major virulence factor and form the basis for serogroup designation and protective vaccines. The current polysaccharide meningococcal vaccines are available but are very expensive and require chemical conjugation. Here, we report a novel meningococcal vaccine formulation consisting of meningococcal CPS polymers encapsulated in albumin-based biodegradable microparticles that slowly release antigen and induce robust innate immune responses. Vaccines that elicit innate immunity are reported to have enhanced and protective adaptive immune responses. In this study, the meningococcal CPS-loaded microparticles, but not the empty microparticles, induced the release of IL-8, TNF-α and IL-1β, enhanced phagocytic capacity and induced robust autophagy in macrophages. The novel meningococcal vaccine microparticles are robustly taken up by macrophages and elicit strong innate immune responses that enhance antigen presentation which is a prerequisite for inducing adaptive immunity.

Novel protein-loaded chondroitin sulfate-chitosan nanoparticles: preparation and characterization

In this study, the potential of chondroitin sulfate (ChS)-chitosan (CS) nanoparticles (NPs) for the delivery of proteins was investigated. ChS-CS NPs were prepared by ionic cross-linking of CS solution with ChS. The aggregation line, particle size and zeta potential were investigated as a function of the pH, weight ratio and concentration. The water content and formation yield of the NPs were measured by gravimetry. Results indicated that ChS-CS NPs showed a higher degree of ionic cross-linking and formation yield than sodium tripolyphosphate-CS NPs. Fluorescein isothiocyanate conjugate bovine serum albumin (FITC-BSA), a model protein drug, was incorporated into the ChS-CS NPs. The encapsulation efficiency was obviously increased with the increase in initial FITC-BSA concentration and was as high as 90%. In vitro release studies of ChS-CS NPs showed a small burst effect following a continued and controlled release. Cytotoxicity tests with Caco-2 cells showed no toxic effects of ChS-CS NPs. The ex vivo cellular uptake studies using Caco-2 and HEK-293 cells indicated that NPs were found to be endocytosed into the cells. In conclusion, ChS-CS NPs are a potential new delivery system for the transport of hydrophilic compounds such as proteins.

Amoxicillin-bearing microparticles: potential in the treatment of Listeria monocytogenes infection in Swiss albino mice

The present study was aimed at evaluating the effectiveness of amoxicillin-bearing HSA (human serum albumin) and PLGA [poly(lactic-co-glycolic acid)] microparticles in combating Listeria monocytogenes infection in Swiss albino mice. Amoxicillin-bearing HSA microspheres were prepared by chemical cross-linking of a drug/albumin mixture with glutaraldehyde, and PLGA microspheres were prepared by the W/O/W (water-in-oil-in-water) emulsion technique. The microspheres were characterized for their size, ζ potential and entrapment efficiency using SEM (scanning electron microscopy) and a Zetasizer. Release kinetics was performed in a phosphate buffer (pH 7.4) at 37°C simulating physiological conditions. Bacterial burden in various vital organs and survival data established enhanced efficacy of PLGA and HSA microspheres as compared with free drug. Among the two delivery systems, PLGA microspheres, when compared with HSA microspheres, imparted better efficacy in terms of reduction in bacterial load as well as increase in survival. The results of the present study clearly demonstrate that microparticles successfully target the infected macrophages and the approach could be well exploited for targeting the intracellular pathogens as well.

Application of nanotechnologies for improved immune response against infectious diseases in the developing world

There is an urgent need for new strategies to combat infectious diseases in developing countries. Many pathogens have evolved to elude immunity and this has limited the utility of current therapies. Additionally, the emergence of co-infections and drug resistant pathogens has increased the need for advanced therapeutic and diagnostic strategies. These challenges can be addressed with therapies that boost the quality and magnitude of an immune response in a predictable, designable fashion that can be applied for wide-spread use. Here, we discuss how biomaterials and specifically nanoscale delivery vehicles can be used to modify and improve the immune system response against infectious diseases. Immunotherapy of infectious disease is the enhancement or modulation of the immune system response to more effectively prevent or clear pathogen infection. Nanoscale vehicles are particularly adept at facilitating immunotherapeutic approaches because they can be engineered to have different physical properties, encapsulated agents, and surface ligands. Additionally, nanoscaled point-of-care diagnostics offer new alternatives for portable and sensitive health monitoring that can guide the use of nanoscale immunotherapies. By exploiting the unique tunability of nanoscale biomaterials to activate, shape, and detect immune system effector function, it may be possible in the near future to generate practical strategies for the prevention and treatment of infectious diseases in the developing world.