Adjuvant Delivery System Research Articles

Mn and Zn-Doped Multivariate Metal-Organic Framework as a Metalloimmunological Adjuvant to Promote Protection Against Tuberculosis Infection.

A first-in-class vaccine adjuvant delivery system, Mn-ZIF, is developed by incorporating manganese (Mn) into the zinc-containing zeolitic-imidazolate framework-8 (ZIF-8). The mixed metal approach, which allowed for tunable Mn doping, is made possible by including a mild reducing agent in the reaction mixture. This approach allows up to 50% Mn, with the remaining 50% Zn within the ZIF. This multivariate approach exhibits significantly decreased cytotoxicity compared to ZIF-8. The porous structure of Mn-ZIF enables the co-delivery of the STING agonist cyclic di-adenosine monophosphate (CDA) through post-synthetic loading, forming CDA@Mn-ZIF. The composite demonstrated enhanced cellular uptake and synergistic activation of the cGAS-STING pathway, producing proinflammatory cytokines and activating antigen-presenting cells (APCs). In a preclinical Mycobacterium tuberculosis (Mtb) model, CDA@Mn-ZIF formulates with the CysVac2 fusion protein elicited a potent antigen-specific T-cell response and significantly reduced the mycobacterial burden in the lungs of infected mice. These findings highlight the potential of CDA@Mn-ZIF as a promising adjuvant for subunit vaccines, offering a novel approach to enhancing vaccine efficacy and protection against infectious diseases such as tuberculosis.

The aluminum nanoparticle-encircled SQ-in-water emulsions (ANSWE) as a vaccine adjuvant-delivery system (VADS) for developing robust mucosal subunit vaccines

The aluminum nanoparticle-encircled squalene (SQ)-in-water emulsions (ANSWE) were engineered as a VADS (vaccine adjuvant-delivery system) using a simple procedure for carrying antigens (Ag) to develop subunit vaccines. In vitro, due to possessing the synergistic adjuvanticity of both AN and SQ, ANSWE were efficiently taken up by APC (antigen-presenting cells) and triggered them to mature and make extra ROS (reactive oxygen species) and multiple cytokines, such as IL-12, IL-1β and IFN-β, which favor balanced Th1/Th2 immunoresponses. Within APC, ANSWE managed lysosome escape and consequently enhanced proteasome activities to facilitate Ag cross-presentation. Mice given twice ovalbumin-ANSWE via intrapulmonary vaccination (IPV) produced high levels of anti-Ag antibodies as well as cytotoxic T lymphocytes, which efficiently erased cells bearing cognate Ag. Thus, ANSWE as a potent VADS may be feasible for developing mucosal subunit vaccines that can elicit comprehensive immunity against infectious diseases, including especially the respiratory infections, and even aggressive cancers.

Cistanche deserticola polysaccharide-functionalized dendritic fibrous nano-silica as oral delivery system for H9N2 vaccine to promote systemic and mucosal immune response

Most infectious diseases are caused by pathogens that invade the body tissues through mucosal tract. Therefore, it is essential to develop effective vaccines administered through the mucosa as a first-line of defense against major infectious diseases. Oral delivery of vaccines is currently of great interest due to its potential to elicit both mucosal and systemic immune responses, high compliance rate and non-invasive nature. However, their development is limited by the challenging gastrointestinal (GI) environment, the low permeability of the mucus barrier, and the lack of effective and safe mucosal adjuvants. Currently, nanoparticle-based strategies show significant potential for improving oral vaccine delivery systems. Herein, the dendritic fibrous nano-silica (DFNS) grafted with Cistanche deserticola polysaccharide (CDP) nanoparticles (CDP-DFNS) were developed for oral delivery of H9N2 antigen. CDP-DFNS induced the activation of macrophages, thereby enhancing antigen uptake in vitro. Additionally, CDP-DFNS/H9N2 significantly activated the dendritic cells (DCs) in Peyer's patches (PPs), and T/B cells in mesenteric lymph nodes (MLNs). Moreover, CDP-DFNS/H9N2 enhanced the HI titers and levels of H9N2-specific antibody IgG, secretory IgA (SIgA) and H9N2-specific IgA in intestinal and respiratory mucosa, as well as Th-associated cytokines. Our results indicate that CDP-DFNS could be a promising oral vaccine adjuvant delivery system.

Chinese yam polysaccharide-loaded aluminium hydroxide nanoparticles used as vaccine adjuvant to induce potent humoral and cellular immune responses

Due to their safety and efficacy, aluminium salts (Alum) are considered the most important adjuvants in human vaccines. However, Alum adjuvants are unable to elicit a cellular immune response, which is vital for the prevention of various chronic infectious diseases and cancers. Herein, we isolated and purified a water-soluble polysaccharide from Chinese yam, named CYP, which was primarily composed of →4)-α-D-Glcp-(1→, →4,6)-α-D-Glcp-(1→, and α-D-Glcp-(1→. Meanwhile, we prepared aluminium hydroxide nanoparticles (Al NPs) with a nanometer-scale size and thin stick-like shape. Being an immunostimulant, the CYP was then loaded onto the Al NPs to obtain a novel adjuvant delivery system (CYP-Al NPs) that enhances the immunostimulatory activity of CYP. Our findings showed that the CYP-Al NPs facilitated macrophages activation and promoted the antigen uptake by macrophages. The in vivo experiment showed that the CYP-Al NPs, as the adjuvant to ovalbumin, promoted the activation of dendritic cells and germinal center B cells in draining lymph nodes, induced a durable and strong antibody response, especially the Th1-type IgG2a antibody response, and improved the cytotoxic T lymphocytes response. These results demonstrated that the CYP-Al NPs could generate robust humoral and cellular responses, and has the great potential to serve as an adjuvant delivery system.

A Polysaccharide-Based Oral-Vaccine Delivery System and Adjuvant for the Influenza Virus Vaccine.

Influenza virus enters the host body through the mucosal surface of the respiratory tract. An efficient immune response at the mucosal site can interfere with virus entry and prevent infection. However, formulating oral vaccines and eliciting an effective mucosal immune response including at respiratory mucosa presents numerous challenges including the potential degradation of antigens by acidic gastric fluids and the risk of antigen dilution and dispersion over a large surface area of the gut, resulting in minimal antigen uptake by the immune cells. Additionally, oral mucosal vaccines have to overcome immune tolerance in the gut. To address the above challenges, in the current study, we evaluated inulin acetate (InAc) nanoparticles (NPs) as a vaccine adjuvant and antigen delivery system for oral influenza vaccines. InAc was developed as the first polysaccharide polymer-based TLR4 agonist; when tailored as a nanoparticulate vaccine delivery system, it enhanced antigen delivery to dendritic cells and induced a strong cellular and humoral immune response. This study compared the efficacy of InAc-NPs as a delivery system for oral vaccines with Poly (lactic-co-glycolic acid) (PLGA) NPs, utilizing influenza A nucleoprotein (Inf-A) as an antigen. InAc-NPs effectively protected the encapsulated antigen in both simulated gastric (pH 1.1) and intestinal fluids (pH 6.8). Moreover, InAc-NPs facilitated enhanced antigen delivery to macrophages, compared to PLGA-NPs. Oral vaccination studies in Balb/c mice revealed that InAc-Inf-A NPs significantly boosted the levels of Influenza virus-specific IgG and IgA in serum, as well as total and virus-specific IgA in the intestines and lungs. Furthermore, mice vaccinated with InAc-Inf-A-NPs exhibited notably higher hemagglutination inhibition (HI) titers at mucosal sites compared to those receiving the antigen alone. Overall, our study underscores the efficacy of InAc-NPs in safeguarding vaccine antigens post-oral administration, enhancing antigen delivery to antigen-presenting cells, and eliciting higher virus-neutralizing antibodies at mucosal sites following vaccination.

Enhanced Systemic and Mucosal Immune Responses to Haemophilus parasuis by Intranasal Administration of Lactic-Co-Glycolic Acid Microspheres.

Swine Glasser's disease, instigated by Haemophilus parasuis (H. parasuis), is a significant bacterial infection that causes substantial economic losses in pig farming operations. The role of mucosal immunity is pivotal in defending against H. parasuis. This study focused on the construction of PLGA microspheres that encapsulate the outer membrane protein OMP16 from H. parasuis (PLGA-OMP16) and evaluated their immunological effectiveness in a mouse model. After being intranasally immunized twice, the PLGA-OMP16 microspheres effectively induced IgAs in saliva and nasal and lung fluids. The PLGA-OMP16 microspheres also significantly increased the number of anti H. parasuis IgGs in serum. Furthermore, the PLGA-OMP16 microspheres triggered elevated levels of IL-2, IL-4, and IFN-γ. The mice vaccinated with PLGA-OMP16 showed a significant reduction in H. parasuis burden in the spleen and lungs following bacterial challenge. These results indicate that intranasal immunization using PLGA microspheres is a promising adjuvant delivery system for vaccines targeting H. parasuis.

Constructing the cGAMP-Aluminum Nanoparticles as a Vaccine Adjuvant-Delivery System (VADS) for Developing the Efficient Pulmonary COVID-19 Subunit Vaccines.

The cGAMP-aluminum nanoparticles (CAN) are engineered as a vaccine adjuvant-delivery system to carry mixed RBD (receptor-binding domain) of the original severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its new variant for developing bivalent pulmonary coronavirus disease 2019 (COVID-19) vaccines (biRBD-CAN). High phosphophilicity/adsorptivity made intrapulmonary CAN instantly form the pulmonary ingredient-coated CAN (piCAN) to possess biomimetic features enhancing biocompatibility. In vitro biRBD-CAN sparked APCs (antigen-presenting cells) to mature and make extra reactive oxygen species, engendered lysosome escape effects and enhanced proteasome activities. Through activating the intracellular stimulator of interferon genes (STING) and nucleotide-binding domain and leucine-rich repeat and pyrin domain containing proteins 3 (NALP3) inflammasome pathways to exert synergy between cGAMP and AN, biRBD-CAN stimulated APCs to secret cytokines favoring mixed Th1/Th2 immunoresponses. Mice bearing twice intrapulmonary biRBD-CAN produced high levels of mucosal antibodies, the long-lasting systemic antibodies, and potent cytotoxic T lymphocytes which efficiently erased cells displaying cognate epitopes. Notably, biRBD-CAN existed in mouse lungs and different lymph nodes for at least 48h, unveiling their sustained immunostimulatory activity as the main mechanism underlying the long-lasting immunity and memory. Hamsters bearing twice intrapulmonary biRBD-CAN developed high resistance to pseudoviral challenges performed using different recombinant strains including the ones with distinct SARS-CoV-2-spike mutations. Thus, biRBD-CAN as a broad-spectrum pulmonary COVID-19 vaccine candidate may provide a tool for controlling the emerging SARS-CoV-2 variants.

Poria cocos polysaccharide-loaded Alum Pickering emulsion as vaccine adjuvant to enhance immune responses

Traditional Alum adjuvants mainly elicit a Th2 humoral immune response, but fail to generate a robust Th1 cellular immune response. However, the cellular immune response is essential for vaccination against cancer and a number of chronic infectious diseases, including human immunodeficiency virus infection and tuberculosis. In our previous study, we demonstrated that the polysaccharide from Poria cocos (PCP) has the potential to serve as an immunologic stimulant, enhancing both humoral and cellular immune responses. However, this effect was only observed at high concentrations. In this study, to enhance the immune-stimulation effect of PCP and modify the type of immune response elicited by Alum adjuvant, we successfully developed a Pickering emulsion delivery system (PCP-Al-Pickering) using PCP-loaded Alhydrogel particles as the stabilizer. After optimization, the Pickering emulsion exhibited excellent storage capacity and effectively adsorbed the PCP and antigen. As an adjuvant delivery system, the PCP-Al-Pickering emulsion facilitated the antigen uptake by macrophages, increased the recruitment of cells at injection sites, improved the activation of dendritic cells in draining lymph nodes, elicited a potent and durable antibody response, and promoted the activation of CD4+ and CD8+ T cells. Importantly, the PCP-Al-Pickering emulsion adjuvant elicited a balanced Th1 and Th2 immune response, in comparison to Alum adjuvant. The PCP-Al-Pickering emulsion may serve as a safe and promising adjuvant delivery system to enhance immune responses.

Exploration of chitosan and its modified derivatives as vaccine adjuvant: A review

Chitosan is a natural polysaccharide that has earned much credit in the pharmaceutical field due to its broad implementation in drugs, antigens, and vaccine delivery. Owing to unique characteristics of biocompatibility, biodegradability, mucoadhesiveness, and less toxicity, chitosan holds promise as a vaccine adjuvant or vaccine delivery system. Furthermore, chitosan exhibits antiviral properties making it an ideal vaccine adjuvant and carrier for the delivery of vaccine. The presence of ridiculous functional groups in the parent structure of chitosan enables the creation of modified chitosan derivatives having improved physiochemical properties which provide enhanced vaccine adjuvant properties of chitosan. This review summarizes the potential of chitosan and its modified derivatives as an antiviral agent and vaccine adjuvant along with patents related to the application of chitosan as a vaccine adjuvant and vaccine carrier.

Cationic Nanoemulsion-Encapsulated Retinoic Acid as an Adjuvant to Promote OVA-Specific Systemic and Mucosal Responses.

Cationic nanostructures have emerged as an adjuvant and antigen delivery system that enhances dendritic cell maturation, ROS generation, and antigen uptake and then promotes antigen-specific immune responses. In recent years, retinoic acid (RA) has received increasing attention due to its effect in activating the mucosal immune response; however, in order to use RA as a mucosal adjuvant, it is necessary to solve the problem of its dissolution, loading, and delivery. Here, we describe a cationic nanoemulsion-encapsulated retinoic acid (CNE-RA) delivery system composed of the cationic lipid 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOTAP), retinoic acid, squalene as the oil phase, polysorbate 80 as surfactant, and sorbitan trioleate 85 as co-surfactant. Its physical and chemical properties were characterized using dynamic light scattering and a spectrophotometer. Immunization of mice with the mixture of antigen (ovalbumin, OVA) and CNE-RA significantly elevated the levels of anti-OVA secretory immunoglobulin A (sIgA) in vaginal lavage fluid and the small intestinal lavage fluid of mice compared with OVA alone. This protocol describes a detailed method for the preparation, characterization, and evaluation of the adjuvant effect of CNE-RA.

Cistanche deserticola polysaccharide-functionalized dendritic fibrous nano-silica as oral vaccine adjuvant delivery enhancing both the mucosal and systemic immunity

Oral vaccines are a safe and convenient alternative to injected vaccines and have great potential to prevent major infectious diseases. However, the harsh gastrointestinal (GI) environment, mucus barriers, low immunogenicity, and lack of effective and safe mucosal adjuvants are the major challenges for oral vaccine delivery. In recent years, nanoparticle-based strategies have become attractive for improving oral vaccine delivery. Here, the dendritic fibrous nano-silica (DFNS) grafted with Cistanche deserticola polysaccharide (CDP) nanoparticles (CDP-DFNS) were prepared and investigated how to impact the immune responses. CDP-DFNS facilitated the antigen uptake in mouse bone marrow-derived dendritic cells (BMDCs), and induce the activation of DCs in vitro. Furthermore, in vivo experiments, the result showed that the uptake efficiency by Peyer's patches (PPs) of CDP-DFNS/BSA was the best. And CDP-DFNS/BSA then significantly activated the DCs in lamina propria (LP), and T/B cells in PPs and mesenteric lymph nodes (MLNs). Moreover, the memory T cell responses in later period of vaccination was stronger than other groups. In addition, CDP-DFNS/BSA enhanced BSA-specific antibody IgG, IgA production, and SIgA secretion, was effective at inducing a strong mixed Th1/Th2 response and mucosal antibody responses. These results indicated that CDP-DFNS deserves further consideration as an oral vaccine adjuvant delivery system.

Innovative translational platforms for rapid developing clinical vaccines against COVID-19 and other infectious disease.

A vaccine is a biological preparation that contains the antigen capable of stimulating the immune system to form the defense against pathogens. Vaccine development often confronts big challenges, including time/energy-consuming, low efficacy, lag to pathogen emergence and mutation, and even safety concern. However, these seem now mostly conquerable through constructing the advanced translational platforms that can make innovative vaccines, sometimes, potentiated with a distinct multifunctional VADS (vaccine adjuvant delivery system), as evidenced by the development of various vaccines against the covid-19 pandemic at warp speed. Particularly, several covid-19 vaccines, such as the viral-vectored vaccines, mRNA vaccines and DNA vaccines, regarded as the innovative ones that are rapidly made via the high technology-based translational platforms. These products have manifested powerful efficacy while showing no unacceptable safety profile in clinics, allowing them to be approved for massive vaccination at also warp speed. Now, the proprietary translational platforms integrated with the state-of-the-art biotechnologies, and even the artificial intelligence (AI), represent an efficient mode for rapid making innovative clinical vaccines against infections, thus increasingly attracting interests of vaccine research and development. Herein, the advanced translational platforms for making innovative vaccines, together with their design principles and immunostimulatory efficacies, are comprehensively elaborated.

Introducing adjuvant-loaded particulate hepatitis B core antigen as an alternative therapeutic hepatitis B vaccine component

Particulate hepatitis B core antigen (HBcoreAg) is a potent immunogen used as a vaccine carrier platform. HBcoreAg produced in E.coli encapsidates random bacterial RNA (bRNA). Using the heterologous protein-prime, viral-vector-boost therapeutic hepatitis B vaccine TherVacB, we compared the properties of different HBcoreAg forms. We explored how the content of HBcoreAg modulates antigen stability, immunogenicity, and antiviral efficacy. bRNA was removed from HBcoreAg by capsid disassembly, followed by reassembly in the absence or presence of specific nucleic acid-based adjuvants poly I:C or CpG. The morphology and structure of empty, bRNA-containing and adjuvant-loaded HBcoreAg were monitored by electron microscopy and nuclear magnetic resonance spectroscopy. Empty, bRNA-containing or adjuvant-loaded HBcoreAg were applied together with HBsAg and with or without nucleic acid-based external adjuvants within the TherVacB regimen in both wild-type and HBV-carrier mice. While HBcoreAg retained its structure upon bRNA removal, its stability and immunogenicity decreased significantly. Loading HBcoreAg with nucleic acid-based adjuvants re-established stability of the capsid-like antigen. Immunization with poly I:C- or CpG-loaded HBcoreAg induced high antibody titers against co-administered HBsAg. When applied within the TherVacB regimen, they activated vigorous HBcoreAg- and HBsAg-specific T-cell responses in wild-type and HBV-carrier mice, requiring a significantly lower dose of adjuvant compared to externally added adjuvant. Finally, immunization with adjuvant-loaded HBcoreAg mixed with HBsAg led to long-term control of persistent HBV replication in the HBV-carrier mice. Adjuvant-loaded HBcoreAg retained capsid integrity and stability, was as immunogenic invivo as externally adjuvanted HBcoreAg, requiring lower adjuvant levels, and supported immunity against co-administered, non-adjuvanted HBsAg. Thus, adjuvant-loaded HBcoreAg represents a promising novel platform for vaccine development. Hepatitis B core antigen (HBcoreAg) recapitulates the capsid of the HBV that hosts the viral genome. Produced recombinantly, it is not infectious but emerges as a potent immunogen in vaccine development. In this preclinical study, we show that loading HBcoreAg with defined nucleic-acid-based adjuvants on the one hand stabilizes the HBcoreAg with standardized capsid content and, on the other hand, efficiently promotes the immunity of HBcoreAg and a co-administered antigen, allowing for reduced adjuvant doses. Therefore, adjuvant-loaded HBcoreAg not only serves as an encouraging option for therapeutic hepatitis B vaccines, but could also act as an efficient adjuvant delivery system for other types of vaccine.

A CAF01-adjuvanted whole asexual blood-stage liposomal malaria vaccine induces a CD4+ T-cell-dependent strain-transcending protective immunity in rodent models.

Malaria is a devastating disease that has claimed many lives, especially children <5 years of age in Sub-Saharan Africa, as documented in World Malaria Reports by WHO. Even though vector control and chemoprevention tools have helped with elimination efforts in some, if not all, endemic areas, these efforts have been hampered by serious issues (including drug and insecticide resistance and disruption to social cohesion caused by the COVID-19 pandemic). Development of an effective malaria vaccine is the alternative preventative tool in the fight against malaria. Vaccines save millions of lives each year and have helped in elimination and/or eradication of global diseases. Development of a highly efficacious malaria vaccine that will ensure long-lasting protective immunity will be a "game-changing" prevention strategy to finally eradicate the disease. Such a vaccine will need to counteract the significant obstacles that have been hampering subunit vaccine development to date, including antigenic polymorphism, sub-optimal immunogenicity, and waning vaccine efficacy.

A Dendrimer Peptide (KK2DP7) Delivery System with Dual Functions of Lymph Node Targeting and Immune Adjuvants as a General Strategy for Cancer Immunotherapy

The clinical efficacy of personalized cancer vaccines still needs to be improved due to their insufficient immune effect. The development of innovative adjuvants and lymph node-targeted delivery systems is the key to improving the clinical efficacy of personalized vaccines. However, there is still a lack of an adjuvant delivery system that is simple in preparation and capable of mass production and integrates adjuvant and lymph node targeted delivery functions. Here, this work reports that a simple dendrimer polypeptide (KK2DP7) nanoparticle enhances the immune efficacy of an OVA/neoantigen-based vaccine. Due to its multiple functions as a delivery vehicle, immune adjuvant, and facilitator of dendritic cell migration, KK2DP7 efficiently increases the efficiency of antigen uptake and cross-presentation by antigen-presenting cells (APCs) and delivers antigens to lymph nodes via APCs. Strikingly, the antitumor effect of KK2DP7/OVA is superior to that of commonly used adjuvants such as poly(I:C), CpG, and aluminum adjuvant combined with OVA. Furthermore, KK2DP7/OVA combined with anti-PD-1 antibody is able to prevent tumor recurrence in a postoperative recurrent tumor model. Thus, KK2DP7-based cancer vaccines alone or in combination with immune checkpoint blockade therapies to treat tumors or postoperative tumor recurrence are a powerful strategy to enhance antitumor immunity.

Lycium barbarum polysaccharides-loaded Particulate Alum via Pickering emulsion as an adjuvant to enhance immune responses

Pickering emulsion has great potential as a vaccine adjuvant due to its unique advantages such as its high antigen loading efficiency, great stability, etc. Among several adjuvants on the market, aluminum adjuvant (Alum) is the most widely used at present. However, problems such as the inability to effectively induce cellular immunity and the poor effect on subunit vaccines limit the application of Alum. As an immunopotentiator, Lycium barbarum polysaccharides (LBP) have been proven to have the ability to regulate humoral and cellular immunity. To overcome the insufficiency of Alum, we explored a new adjuvant delivery system. The Lycium barbarum polysaccharides-loaded Particulate Alum via Pickering emulsion (LBPPE) was prepared by loading Alum on the squalene/water interphase following LBP was adsorbed on the Alum surface (Fig. 10). Similar to squalene, LBPPE possesses a good biosafety profile. LBPPE was spherical with uneven surface, which increased the possibility of efficient antigen adsorption on the surface and crack of LBPPE. And the result shown that the LBPPE had high antigen loading rate at approximately 90 %. In vivo experiments, LBPPE showed an excellent ability to recruit antigen-presenting cells (APCs) at the injection sites, activate dendritic cells in the lymph nodes. Then, in the evaluation of humoral immunity, LBPPE was able to effectively induce the production of IgG, IgG1, and IgG2a. Moreover, LBPPE significantly enhanced the expression and activation of T lymphocytes, and induced a strong immune memory T cells response. All the results above suggested that LBPPE is likely to provide promising insights toward a safe and efficient adjuvant platform for vaccines.

Enhanced Immune Responses to Mucosa by Functionalized Chitosan-Based Composite Nanoparticles as a Vaccine Adjuvant for Intranasal Delivery.

Nasal administration for vaccine delivery is a novel non-invasive vaccine administration approach that can induce local or systemic immune responses and overcome the disadvantages caused by traditional injectable administration. However, mucosal vaccine and adjuvant delivery systems with sustained-release ability and enhanced immune effects at mucosal sites have still been highly demanded. In this work, N-2-hydroxypropyl trimethyl ammonium chloride chitosan/N,O-carboxymethyl chitosan nanoparticles (N-2-HACC/CMCS NPs) with excellent mucosal absorption, high drug loading capacity, and enhanced immune responses were prepared by the ionic cross-linking method. To evaluate the potential capacity of the N-2-HACC/CMCS NPs as a vaccine adjuvant and the molecular mechanism for the induction of enhanced mucosal and systemic immune responses, bovine serum albumin (BSA) was employed as a general model antigen and loaded into the N-2-HACC/CMCS NPs to prepare a BSA-loaded N-2-HACC/CMCS adjuvant vaccine (N-2-HACC/CMCS/BSA NPs). It was well demonstrated that the N-2-HACC/CMCS/BSA NPs with great biostability and mucosal absorption could effectively promote the proliferation of lymphocytes and the secretion of related pro-inflammatory factors, resulting in the stimulation of specific mucosal and systemic immune responses. This study revealed that the chitosan-based nano-delivery system can act as the mucosal vaccine adjuvant and possesses great promise in viral infectious diseases and immunization therapy.

Chitosan-Based Nanomaterial as Immune Adjuvant and Delivery Carrier for Vaccines.

With the support of modern biotechnology, vaccine technology continues to iterate. The safety and efficacy of vaccines are some of the most important areas of development in the field. As a natural substance, chitosan is widely used in numerous fields-such as immune stimulation, drug delivery, wound healing, and antibacterial procedures-due to its good biocompatibility, low toxicity, biodegradability, and adhesion. Chitosan-based nanoparticles (NPs) have attracted extensive attention with respect to vaccine adjuvants and delivery systems due to their excellent properties, which can effectively enhance immune responses. Here, we list the classifications and mechanisms of action of vaccine adjuvants. At the same time, the preparation methods of chitosan, its NPs, and their mechanism of action in the delivery system are introduced. The extensive applications of chitosan and its NPs in protein vaccines and nucleic acid vaccines are also introduced. This paper reviewed the latest research progress of chitosan-based NPs in vaccine adjuvant and drug delivery systems.

Physical, Chemical, and Biological Properties of Chitosan-Coated Alginate Microparticles Loaded with Porcine Interleukin-1β: A Potential Protein Adjuvant Delivery System.

We previously developed chicken interleukin-1β (IL-1β) mutants as single-dose adjuvants that induce protective immunity when co-administered with an avian vaccine. However, livestock such as pigs may require a vaccine adjuvant delivery system that provides long-lasting protection to reduce the need for successive booster doses. Therefore, we developed chitosan-coated alginate microparticles as a carrier for bovine serum albumin (BSA) or porcine IL-1β (pIL-1β) and assessed their physical, chemical, and biological properties. Electrospraying of the BSA-loaded alginate microparticles (BSA/ALG MPs) resulted in an encapsulation efficiency of 50%, and those MPs were then coated with chitosan (BSA/ALG/CHI MPs). Optical and scanning electron microscopy, zeta potential analysis, and Fourier transform infrared spectroscopy were used to characterize these MPs. The BSA encapsulation parameters were applied to ALG/CHI MPs loaded with pIL-1β, which were not cytotoxic to porcine fibroblasts but had enhanced bio-activity over unencapsulated pIL-1β. The chitosan layer of the BSA/ALG/CHI MPs prevented burst release and facilitated sustained release of pIL-1β for at least 28 days. In conclusion, BSA/ALG/CHI MPs prepared as a carrier for pIL-1β may be used as an adjuvant for the formulation of pig vaccines.

Mucosal immunity of mannose-modified chitosan microspheres loaded with the nontyepable Haemophilus influenzae outer membrane protein P6 in BALB/c mice.

Nontypeable Haemophilus influenzae (NTHi) is a common opportunistic pathogen that colonizes the nasopharynx. NTHi infections result in enormous global morbidity in two clinical settings: otitis media in children and acute exacerbation of chronic obstructive pulmonary disease (COPD) in adults. Thus, there is an urgent need to design and develop effective vaccines to prevent morbidity and reduce antibiotic use. The NTHi outer membrane protein P6, a potential vaccine candidate, is highly conserved and effectively induces protective immunity. Here, to enhance mucosal immune responses, P6-loaded mannose-modified chitosan (MC) microspheres (P6-MCMs) were developed for mucosal delivery. MC (18.75%) was synthesized by the reductive amination reaction method using sodium cyanoborohydride (NaBH3CN), and P6-MCMs with an average size of 590.4±16.2 nm were successfully prepared via the tripolyphosphate (TPP) ionotropic gelation process. After intranasal immunization with P6-MCMs, evaluation of humoral immune responses indicated that P6-MCMs enhance both systemic and mucosal immune responses. Evaluation of cellular immune responses indicated that P6-MCMs enhance cellular immunity and trigger a mixed Th1/Th2-type immune response. Importantly, P6-MCMs also trigger a Th17-type immune response. They are effective in promoting lymphocyte proliferation and differentiation without toxicity in vitro. The results also demonstrate that P6-MCMs can effectively induce MHC class I- and II-restricted cross-presentation, promoting CD4+-mediated Th immune responses and CD8+-mediated cytotoxic T lymphocyte (CTL) immune responses. Evaluation of protective immunity indicated that immunization with P6-MCMs can reduce inflammation in the nasal mucosa and the lung and prevent NTHi infection. In conclusion, MCMs are a promising adjuvant-delivery system for vaccines against NTHi.