Induction of high antitoxin titers against tetanus toxoid in rabbits by intranasal immunization with dextran microspheres

Advances in intranasal vaccine delivery: A promising non-invasive route of immunization

The importance of vaccination has been proven particularly significant the last three years, as it is revealed to be the most efficient weapon for the prevention of several infections including SARS-COV-2. Parenteral vaccination is the most applicable method of immunization, for the prevention of systematic and respiratory infections, or central nervous system disorders, involving T and B cells to a whole-body immune response. However, the mucosal vaccines, such as nasal vaccines, can additionally activate the immune cells localized on the mucosal tissue of the upper and lower respiratory tract. This dual stimulation of the immune system, along with their needle-free administration favors the development of novel nasal vaccines to produce long-lasting immunity. In recent years, the nanoparticulate systems have been extensively involved in the formulation of nasal vaccines as polymeric, polysaccharide and lipid ones, as well as in the form of proteosomes, lipopeptides and virosomes. Advanced delivery nanosystems have been designed and evaluated as carriers or adjuvants for nasal vaccination. To this end, several nanoparticulate vaccines are undergone clinical trials as promising candidates for nasal immunization, while nasal vaccines against influenza type A and B and hepatitis B have been approved by health authorities. This comprehensive literature review aims to summarize the critical aspects of these formulations and highlight their potential for the future establishment of nasal vaccination. Both preclinical (in vitro and in vivo) and clinical studies are incorporated, summarized, and critically discussed, as well as the limitations of nasal immunization.

Different Methods and Formulations of Drugs and Vaccines for Nasal Administration

Nasal drug delivery is advantageous when compared with other routes of drug delivery as it avoids the hepatic first-pass effect, blood–brain barrier penetration, and compliance issues with parenteral administration. However, nasal administration also has some limitations, such as its low bioavailability due to metabolism on the mucosal surface, and irreversible damage to the nasal mucosa due to the ingredients added into the formula. Moreover, the method of nasal administration is not applicable to all drugs. The current review presents the nasal anatomy and mucosal environment for the nasal delivery of vaccines and drugs, as well as presents various methods for enhancing nasal absorption, and different drug carriers and delivery devices to improve nasal drug delivery. It also presents future prospects on the nasal drug delivery of vaccines and drugs.

Structure, function and enzymatic synthesis of glucosaccharides assembled mainly by α1 → 6 linkages - A review

A variety of glucosaccharides composed of glucosyl residues can be classified into α- and β-type and have wide application in food and medicine areas. Among these glucosaccharides, β-type, such as cellulose and α-type, such as starch and starch derivatives, both contain 1 → 4 linkages and are well studied. Notably, in past decades also α1 → 6 glucosaccharides obtained increasing attention for unique physiochemical and biological properties. Especially in recent years, α1 → 6 glucosaccharides of different molecular weight distribution have been created and proved to be functional. However, compared to β- type and α1 → 4 glucosaccharides, only few articles provide a systematic overview of α1 → 6 glucosaccharides. This motivated, the present first comprehensive review on structure, function and synthesis of these α1 → 6 glucosaccharides, aiming both at improving understanding of traditional α1 → 6 glucosaccharides, such as isomaltose, isomaltooligosaccharides and dextrans, and to draw the attention to newly explored α1 → 6 glucosaccharides and their derivatives, such as cycloisomaltooligosaccharides, isomaltomegalosaccharides, and isomalto/malto-polysaccharides.

T helper type 1 biased immune responses by PPE17 loaded core-shell alginate-chitosan nanoparticles after subcutaneous and intranasal administration

PURPOSE

Tuberculosis, a cost and life threatening disease, was being subjected for improving vaccine strategies beyond BCG. Thus, a novel particulate delivery system using alginate-coated chitosan nanoparticles including PPE17 protein and CpG were administered through intranasal (IN) and subcutaneous (SC) routes.

METHODS

The encapsulated nanoparticles were first characterized for size, surface charge, encapsulation efficiency and in vitro release of PPE17 antigen. The nanoparticles were then administered intranasal and subcutaneously to evaluate the induction of systemic and/or mucosal immune responses in mice.

RESULTS

According to our result, the mean size of nanoparticles was measured about 427 nm, and exhibited a negative zeta potential of -37 mV. Following subcutaneous and intranasal administration, the results from cytokines assay showed that an increasing in the level of IFN-γ, and adversely a decrease in the level of IL-4 (presumptive Th1 biased immune response) was happened and also a notable elicitation in IL-17 cytokine was observed.

CONCLUSION

In conclusion, our study demonstrated that alginate-coated chitosan nanoparticles showed to be an effective way to improve BCG efficiency as booster strategy for subcutaneous vaccine, and also can induce strong immune responses as prime strategy through intranasal vaccination.

Intranasal delivery of nanoparticle-based vaccines

Most pathogens gain access to the human body and initiate systemic infections through mucosal sites. A large number of currently marketed licensed vaccines are parenterally administered; they generate strong systemic immunity but not mucosal immunity. Nasal vaccination is an appealing strategy for the induction of mucosal-specific immunity; however, its development is mostly challenged by several factors, such as inefficient antigen uptake, its rapid mucociliary clearance, size-restricted permeation across epithelial barriers and absence of safe human mucosal adjuvants. Therefore, a safer mucosal-adjuvanting strategy or efficient mucosal delivery platform is much warranted. This review summarizes challenges and the rationale for nasal vaccine development with a special focus on the use of nanoparticles based on polymers and lipids for mucosal vaccine delivery.

Immunoadjuvant potential of cross-linked dextran microspheres mixed with chitosan nanospheres encapsulated with tetanus toxoid

CONTEXT

Nasal mucosa is a desirable route for mucosal vaccine delivery. Mucosal co-administration of chitosan nanoparticles with absorption enhancers such as cross-linked dextran microspheres (CDM, Sephadex^®) is a promising antigen delivery system.

OBJECTIVE

In the current study, the chitosan nanospheres loaded with tetanus toxoid (CHT:TT NPs) was prepared and characterized. The immune responses against tetanus toxoid after nasal administration of CHT:TT NPs alone or mixed with CDM were also determined.

MATERIALS AND METHODS

Chitosan nanospheres were prepared by ionic gelation method. Particle size, releasing profile and antigen stability were evaluated by dynamic light scattering, diffusion chamber and SDS-PAGE methods, respectively. Rabbits were nasally immunized with different formulations loaded with 40 Lf TT. After three times immunizations with 2 weeks intervals, sera IgG titres and nasal lavage sIgA titres were determined.

RESULTS

Mean size of CHT NPs and CHT:TT NPs were 205 ± 42 nm and 432 ± 85 nm, respectively. The release profile showed that 42.4 ± 10.5% of TT was released after 30 min and reached to a steady state after 1.5 h. Stability of encapsulated TT in nanospheres was confirmed by SDS-PAGE. The antibody titres showed that CHT:TT NPs-induced antibody titres were higher than TT solution. CHT NPs mixed with CDM induced the systemic IgG and nasal lavage sIgA titres higher than intranasal administration of TT solution (p < 0.001).

DISCUSSION AND CONCLUSION

As the results indicated, these CHT:TT NPs when co-administered with CDM were able to induce more immune responses and have the potential to be used in mucosal immunization.

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.

Alginate nanoparticles as a promising adjuvant and vaccine delivery system

During last decades, diphtheria has remained as a serious disease that still outbreaks and can occur worldwide. Recently, new vaccine delivery systems have been developed by using the biodegradable and biocompatible polymers such as alginate. Alginate nanoparticles as a carrier with adjuvant and prolong release properties that enhance the immunogenicity of vaccines. In this study diphtheria toxoid loaded nanoparticles were prepared by ionic gelation technique and characterized with respect to size, zeta potential, morphology, encapsulation efficiency, release profile, and immunogenicity. Appropriate parameters (calcium chloride and sodium alginate concentration, homogenization rate and homogenization time) redounded to the formation of suitable nanoparticles with a mean diameter of 70±0.5 nm. The loading studies of the nanoparticles resulted in high loading capacities (>90%) and subsequent release studies showed prolong profile. The stability and antigenicity of toxoid were evaluated by sodium dodecyl sulfate polyacrylamide gel electrophoresis and ouchterlony test and proved that the encapsulation process did not affect the antigenic integrity and activity. Guinea pigs immunized with the diphtheria toxoid-loaded alginate nanoparticles showed highest humoral immune response than conventional vaccine. It is concluded that, with regard to the desirable properties of nanoparticles and high immunogenicity, alginate nanoparticles could be considered as a new promising vaccine delivery and adjuvant system.

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.

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.

Single shot tetanus vaccine manufactured by a supercritical fluid encapsulation technology

Single shot vaccines of tetanus toxoid (TT) were manufactured using the NanoMix process - a low temperature solvent free encapsulation technology using supercritical fluids. The formulations were injected into mice, and compared to multiple injections of a commercially available alum adsorbed TT vaccine. After 5 months the antibody titres were found to be similar for both the alum adsorbed and microparticle formulations, demonstrating for the first time the potential of formulating antigens in PLA microparticles using the supercritical fluid (NanoMix) technique to produce single shot vaccines. The results are likely to be due to the maintenance of toxoid bioactivity and some degree of sustained release of the encapsulated antigens, resulting in repeated stimulation of antigen presenting cells eliminating the need for multiple immunisations. This demonstrates the potential of this supercritical fluid processing technique to reduce the need for booster doses in a vaccine regimen.

Preparation and in vivo study of dry powder microspheres for nasal immunization

The immunoadjuvant potential of alginate microspheres as delivery system, and cross-linked dextran microspheres (CDM) as absorption enhancer and excipient for powder of alginate microspheres, were evaluated. Alginate microspheres were prepared by emulsification method. Microspheres encapsulated with tetanus toxoid (TT) or Quillaja saponin (QS) were nasally administered to rabbits, three times in 2 weeks interval and serum IgG and nasal lavage sIgA titers were determined by ELISA. The mean diameter of microspheres was about 1.5 mum. Release of TT and QS was 13.1 +/- 1.4% and 31.8 +/- 4.3% after 4 h. The serum IgG titer induced with (TT)(ALG) microspheres was higher than TT solution (P<0.001). Addition of QS or CDM adjuvant, in separate, to (TT)(ALG) microspheres could not significantly increase the immune responses (P>0.05), but the highest systemic IgG titers induced with (TT+QS)(ALG)+CDM (P<0.01). The sIgA titer induced with (TT)(ALG) microspheres was higher than TT solution (P<0.05). The highest mucosal sIgA titers were seen in animals immunized with (TT)(ALG)+CDM (P<0.05). Co-encapsulation of QS and TT in microspheres did not increase the sIgA titers. When CDM was added to alginate microspheres encapsulated with TT or TT+QS, the highest mucosal and systemic responses were observed.

Dextran microspheres could enhance immune responses against PLGA nanospheres encapsulated with tetanus toxoid and Quillaja saponins after nasal immunization in rabbit

Potent immunoadjuvants are needed to elicit responses following mucosal delivery. PLGA (poly[D,L-lactic-co-glycolic acid]) nanospheres, Quillaja saponin (QS) and cross-linked dextran microspheres (CDM) as drug delivery and absorption enhancer adjuvants were evaluated. PLGA nanospheres were prepared by solvent evaporation method. Particulate characteristics of nanospheres were studied by optical and scanning electron microscopes and dynamic light scattering technique. The mean diameter of nanospheres encapsulated with TT and TT + QS determined as 425 and 390 nm. Loadings of TT and QS were 30 ± 1.9% and 23 ± 2.8%. Nanospheres encapsulated with TT or QS were intranasally administered to rabbits, three times in two-week intervals and the serum IgG and nasal lavage IgA titers were determined by ELISA. The serum IgG titer induced with (TT)(PLGA) nanospheres was higher than TT solution (P < 0.001). IgG titers induced with (TT + QS)(PLGA) was higher than (TT)(PLGA) (P < 0.0001). When (TT)(PLGA) and (TT + QS)(PLGA) nanospheres were mixed with CDM, higher IgG titers were induced (P < 0.001). The highest mucosal sIgA titers were seen in animals immunized with (TT + QS)(PLGA) + CDM. Co-encapsulation of QS and TT in PLGA nanospheres increased sIgA titers. In conclusion, the highest immune responses were observed by concomitant use of three adjuvants.

Adjuvants in tuberculosis vaccine development

Tuberculosis remains a major public health problem around the world. Because the Mycobacterium bovis Bacilli-Calmette-Guerin (BCG) vaccine fails to protect adults from pulmonary tuberculosis, there is an urgent need for improved vaccine formulations. Unlike BCG, recombinant vaccines purified from bacterial expression vectors, as well as naked DNA, require an additional adjuvant. Recent improvements in our understanding of disease immunopathology, together with advances in biochemical and molecular techniques, have permitted the successful development of promising tuberculosis vaccine delivery and adjuvant combinations for human use. Here, we summarize the current state of adjuvant development and its impact on tuberculosis vaccine progress.