Curdlan sulfate/O-linked quaternized chitosan nanoparticles acting as potential adjuvants promote multiple arms of immune responses

Biological evaluation of curdlan sulfate-based nanoparticles in trained immunity enhancement: In vitro and in vivo approaches

OBJECTIVES

Recently, more and more evidences suggest that β-glucans can induce trained immunity and non-specific protections against pathogens. However, most of the reports evaluated the immunological activities of β-glucans through injection route but no nasal inhalation. In this study, the effects of curdlan sulfate-based nanoparticles, CS/O-HTCC on trained immunity through intranasal administration were evaluated.

METHODS

Macrophages were treated with CS/O-HTCC and the metabolisms of the macrophages were detected. Mice were intranasal administered with CS/O-HTCC for 3 times with a 14 days interval, then the antitumor or infection prevention effects were assessed.

RESULTS

In vitro, CS/O-HTCC enhanced the macrophage metabolism significantly through upregulating glycolysis (26.1 ± 4.3 mpH/min) and oxidative phosphorylation (36.0 ± 9.0 pmol/min) compared with that of negative group (7.5 ± 2.3 mpH/min and 19.5 ± 4.9 pmol/min). In vivo, CS/O-HTCC inhibited lung metastasis of B16F10 tumor cells and improved the survival time (26.5 days) of the nmice compared with negative group (19.5 days). Moreover, CS/O-HTCC prevented the lung infections by Escherichia coli or Streptococcus pneumoniae (less bacterial residual) and reduced lung damages.

CONCLUSIONS

CS/O-HTCC can induce trained immunity through enhancing the metabolism of macrophages and enhance the non-specific protection against pathogens through intranasal immunization.

Preparation and immunological activity evaluation of an intranasal protein subunit vaccine against ancestral and mutant SARS-CoV-2 with curdlan sulfate/O-linked quaternized chitosan nanoparticles as carrier and adjuvant

Chitosan and its derivatives are ideal nasal vaccine adjuvant to deliver antigens to immune cells. Previously, we successfully used a chitosan derivative, O-(2-Hydroxyl) propyl-3-trimethyl ammonium chitosan chloride (O-HTCC), and a β-glucan derivative, curdlan sulfate (CS), to prepare a nanoparticle adjuvant CS/O-HTCC which could deliver ovalbumin to antigen presenting cells (APCs) through nasal inhalation. In this article, we used SARS-CoV-2 spike receptor binding domain (S-RBD) as the antigen and CS/O-HTCC nanoparticles as the adjuvant to develop a nasal mucosal protein subunit vaccine, CS/S-RBD/O-HTCC. The humoral immunity, cell-mediated immunity and mucosal immunity induced by vaccines were evaluated. The results showed that CS/S-RBD/O-HTCC could induce desirable immunization with single or bivalent antigen through nasal inoculation, giving one booster vaccination with mutated S-RBD (beta) could bring about a broad cross reaction with ancestral and different mutated S-RBD, and vaccination of the BALB/c mice with CS/S-RBD/O-HTCC containing S-RBD mix antigens (ancestral and omicron) could induce the production of binding and neutralizing antibodies against both of the two antigens. Our results indicate that CS/O-HTCC is a promising nasal mucosal adjuvant to prepare protein subunit vaccine for both primary and booster immunization, and the adjuvant is suitable for loading more than one antigen for preparing multivalent vaccines.

Tailoring biomaterials for vaccine delivery

Biomaterials are substances that can be injected, implanted, or applied to the surface of tissues in biomedical applications and have the ability to interact with biological systems to initiate therapeutic responses. Biomaterial-based vaccine delivery systems possess robust packaging capabilities, enabling sustained and localized drug release at the target site. Throughout the vaccine delivery process, they can contribute to protecting, stabilizing, and guiding the immunogen while also serving as adjuvants to enhance vaccine efficacy. In this article, we provide a comprehensive review of the contributions of biomaterials to the advancement of vaccine development. We begin by categorizing biomaterial types and properties, detailing their reprocessing strategies, and exploring several common delivery systems, such as polymeric nanoparticles, lipid nanoparticles, hydrogels, and microneedles. Additionally, we investigated how the physicochemical properties and delivery routes of biomaterials influence immune responses. Notably, we delve into the design considerations of biomaterials as vaccine adjuvants, showcasing their application in vaccine development for cancer, acquired immunodeficiency syndrome, influenza, corona virus disease 2019 (COVID-19), tuberculosis, malaria, and hepatitis B. Throughout this review, we highlight successful instances where biomaterials have enhanced vaccine efficacy and discuss the limitations and future directions of biomaterials in vaccine delivery and immunotherapy. This review aims to offer researchers a comprehensive understanding of the application of biomaterials in vaccine development and stimulate further progress in related fields.

Fabrication of chitosan-based emulsion as an adjuvant to enhance nasal mucosal immune responses

Nasal vaccine is a non-invasive vaccine that activates systemic and mucosal immunity in the presence of an adjuvant, thereby enhancing immune function. In this work, chitosan/oligochitosan/tween 80 (CS-COS-T80) co-stabilized emulsion was designed and further used as the nasal adjuvant. CS-COS-T80 emulsion exhibited outstanding stability under pH 6-8 with uniformly dispersed droplets and nano-scale particle size (<0.25 μm), and maintained stable at 4 °C for 150-day storage. Addition of model antigen ovalbumin (OVA) had no effect on the stability of CS-COS-T80 emulsion. In vivo nasal immunity indicated that CS-COS-T80 emulsion prolonged the retention time of OVA in the nasal cavity (from 4 to 8 h to >12 h), as compared to T80-emulsion. CS-COS-T80 emulsion produced a stronger mucosal immune response to OVA, with secretory IgA levels 5-fold and 2-fold higher than those of bare OVA and commercial adjuvant MF59, respectively. Compared to MF59, CS-COS-T80 induced a stronger humoral immune response and a mixed Th1/Th2 immune response of OVA after immunization. Furthermore, in the presence of CS-COS-T80 emulsion, the secretion of IL-4 and IFN-γ and the activation of splenocyte memory T-cell differentiation increased from 173.98 to 210.21 pg/mL and from 75.46 to 104.01 pg/mL, respectively. Therefore, CS-COS-T80 emulsion may serve as a promising adjuvant platform.

Preparation and characterization of curdlan-chitosan conjugate nanoparticles as mucosal adjuvants for intranasal influenza H1N1 subunit vaccine

Intranasal vaccination offers crucial protection against influenza virus pandemics. However, antigens, especially subunit antigens, often fail to induce effective immune responses without the help of immune adjuvants. Our research has demonstrated that a polyelectrolyte complex, composed of curdlan sulfate/O-(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride (CS/O-HTCC), effectively triggers both mucosal and systemic immune responses when administrated intranasal. In this study, stable nanoparticles formed by curdlan-O-HTCC conjugate (CO NP) were prepared and characterized. Furthermore, the efficacy of CO NP was evaluated as a mucosal adjuvant in an intranasal influenza H1N1 subunit vaccine. The results revealed that CO NP exhibits uniform and spherical morphology, with a size of 190.53 ± 4.22 nm, and notably, it remains stable in PBS at 4 °C for up to 6 weeks. Biological evaluation demonstrated that CO NP stimulates the activation of antigen-presenting cells (APCs), including macrophages and dendritic cells (DCs), both in vitro and in vivo. Furthermore, intranasal administration of CO NP effectively elicits cellular and humoral immune responses, notably enhancing mucosal immunity. Thus, CO NP emerges as a promising mucosal adjuvant for influenza subunit vaccines.

Vaccine adjuvants: mechanisms and platforms

Adjuvants are indispensable components of vaccines. Despite being widely used in vaccines, their action mechanisms are not yet clear. With a greater understanding of the mechanisms by which the innate immune response controls the antigen-specific response, the adjuvants' action mechanisms are beginning to be elucidated. Adjuvants can be categorized as immunostimulants and delivery systems. Immunostimulants are danger signal molecules that lead to the maturation and activation of antigen-presenting cells (APCs) by targeting Toll-like receptors (TLRs) and other pattern recognition receptors (PRRs) to promote the production of antigen signals and co-stimulatory signals, which in turn enhance the adaptive immune responses. On the other hand, delivery systems are carrier materials that facilitate antigen presentation by prolonging the bioavailability of the loaded antigens, as well as targeting antigens to lymph nodes or APCs. The adjuvants' action mechanisms are systematically summarized at the beginning of this review. This is followed by an introduction of the mechanisms, properties, and progress of classical vaccine adjuvants. Furthermore, since some of the adjuvants under investigation exhibit greater immune activation potency than classical adjuvants, which could compensate for the deficiencies of classical adjuvants, a summary of the adjuvant platforms under investigation is subsequently presented. Notably, we highlight the different action mechanisms and immunological properties of these adjuvant platforms, which will provide a wide range of options for the rational design of different vaccines. On this basis, this review points out the development prospects of vaccine adjuvants and the problems that should be paid attention to in the future.

Applications and perspectives of quaternized cellulose, chitin and chitosan: A review

Recently, increasing attention has been paid to natural polysaccharides for their low cost, biocompatibility and biodegradability. Quaternization is a modification method to improve the solubility and antibacterial ability of natural polysaccharides. Water-soluble derivatives of cellulose, chitin and chitosan offer the prospect of diverse applications in a wide range of fields, such as antibacterial products, drug delivery, wound healing, sewage treatment and ion exchange membranes. By combining the inherent properties of cellulose, chitin and chitosan with the inherent properties of the quaternary ammonium groups, new products with multiple functions and properties can be obtained. In this review, we summarized the research progress in the applications of quaternized cellulose, chitin and chitosan in recent five years. Moreover, ubiquitous challenges and personal perspectives on the further development of this promising field are also discussed.

Fabrication, characterization of carboxymethyl konjac glucomannan/ovalbumin-naringin nanoparticles with improving in vitro bioaccessibility

Naringin is potential functional and therapeutic ingredient, has low bioavailability because of poor aqueous solubility. In this study, an ovalbumin (OVA)-carboxymethyl konjac glucomannan (CKGM) nano-delivery system was developed to enhance the bioavailability of naringin. The effects of proportion (OVA: CKGM), pH and naringin concentration were studied on the formation, encapsulation efficiency (EE) and bioaccessibility of OVA/CKGM-Naringin nanoparticles (OVA/CKGM-Naringin NPs). Its morphology and size were viewed by Scanning Electron Microscope (SEM) and Transmission Electron Microscopy (TEM). The cross-linkage between OVA and CKGM was verified by Fourier Transform Infrared Spectroscopy (FTIR) and Fluorescence Intensity analysis. The size of OVA/CKGM-Naringin NPs were 463.83 ± 18.50 nm (Polydispersity Index-PDI, 0.42 ± 0.05). It indicated that 2:1 of OVA: CKGM, pH 3 and 7 mg/mL of naringin concentration were optimized processing parameters of OVA/CKGM-Naringin NPs with EE (97.90 ± 2.97 %) and remarkably improved bioaccessibility (85.01 ± 2.52 %). The OVA/CKGM-Naringin NPs was energy efficiently prepared and verified as an ideal carrier of naringin.

Development and Characterization of Antimicrobial Textiles from Chitosan-Based Compounds: Possible Biomaterials Against SARS-CoV-2 Viruses

Novel antiviral cotton fabrics impregnated with different formulations based on Chitosan (CH), citric acid (CA), and Copper (Cu) were developed. CA was selected as a CH crosslinker agent and Cu salts as enhancers of the polymer antimicrobial activity. The characterization of the polymeric-inorganic formulations was assessed by using atomic absorption spectroscopy, X-ray diffraction, Fourier transform infrared and UV–Vis spectroscopy, as well as thermogravimetric analysis. The achieved data revealed that CuO nanoparticles were formed by means of chitosan and citric acid in the reaction media. The antiviral activity of CH-based formulations against bovine alphaherpesvirus and bovine betacoronavirus was analyzed. Cotton fabrics were impregnated with the selected formulations and the antiviral properties of such textiles were examined before and after 5 to 10 washing cycles. Herpes simplex virus type 1 was selected to analyze the antiviral activities of the functionalized cotton fabrics. The resulting impregnated textiles exhibited integrated properties of good adhesion without substantially modifying their appearance and antiviral efficacy (~ 100%), which enabling to serve as a scalable biocidal layer in protective equipment’s by providing contact killing against pathogens. Thus, the results revealed a viable contribution to the design of functional-active materials based on a natural polymer such as chitosan. This proposal may be considered as a potential tool to inhibit the propagation and dissemination of enveloped viruses, including SARS-CoV-2.

Applications of nanoengineered therapeutics and vaccines: special emphasis on COVID-19

Nanomedicine provides innovative strategies that had significantly improved drug and gene delivery and allowed control over the engineering of therapeutics, diagnostics, vaccines, and other medical devices, for a diversity of medical applications. This review focuses on the current attempts to develop potent nanoengineered vaccines and therapeutics against coronaviruses, and the recent fabrication strategies and design principles to control acute infections from the escalating SARS-CoV-2 pandemic. Nanomedical approaches provide versatile platforms that can be utilized to enhance the overall potency, safety, and stability of vaccines, thus augmenting the desired immune response. Their modulable conformational features of size, shape, surface charge, antigen display, and composition allow for precise tuning and optimization of the nanoconstructs for the management of a variety of diseases and pathological conditions. The ability to control the release of their encapsulated cargoes and the possibility of surface decoration with various moieties support the construction of multifunctional nanomaterials that ultimately boost and prolong the immune response elicited and/or therapeutic effects, selectively at the diseased tissues and target sites.

Chitosan modified squalene nanostructured lipid carriers as a promising adjuvant for freeze-dried ovalbumin vaccine

As immune adjuvants assisting vaccines, nanoparticle delivery systems have been widely exploited. Squalene, the major ingredient of approved adjuvant MF59, has great potential in activating immune responses. In the current study, model antigen ovalbumin (OVA) was encapsulated into squalene-based nanostructured lipid carriers (NLCs), and the chitosan, a cationic polysaccharide, was used for modifying nanoparticles to develop a functionalized and cationic nanoparticle delivery system (OVA-csNLCs). Firstly, the optimal formulation of csNLCs was successfully screened out, and had hydrodynamic diameter of 235.80 ± 5.99 nm and zeta potential of 34.90 ± 6.95 mV. Then, the generated OVA-csNLCs had no significant difference in hydrodynamic diameter and exhibited lower zeta potential of 19.03 ± 0.31 mV and high encapsulation efficiency of 83.4%. Sucrose (10%, w/w) was selected as optimal lyoprotectant, exhibiting good stability of OVA-csNLCs in the form of freeze-dried powder. More importantly, the OVA-csNLCs effectively promoted OVA antigen uptake by macrophage, significantly enhanced the level of OVA-specific IgG, and induced a Th2-based immune response in vivo. Furthermore, mice immunization experiment demonstrated that OVA-csNLCs had well biocompatibility and facilitated spleen lymphocytes proliferation. Above findings indicate that chitosan modified squalene nanostructured lipid carriers show promise as antigen delivery system and an open adjuvant platform.

Design of novel orotransmucosal vaccine-delivery platforms using artificial intelligence

The linings of the oral cavity are excellent needle-free vaccination sites, able to induce immune responses at distal sites and confer systemic protection. However, owing to the mucosal tissues' intrinsic characteristics, the design of effective antigen-delivery systems is not an easy task. In the present work, we propose to develop and characterize thermosensitive and mucoadhesive hydrogels for orotransmucosal vaccination taking advantage of artificial intelligence tools (AIT). Hydrogels of variable composition were obtained combining Pluronic® F127 (PF127), Hybrane® S1200 (HS1200) and Gantrez® AN119 (AN119) or S97 (S97). Systems were characterized in terms of physicochemical properties, adhesion capacity to mucosal tissues and antigen-like microspheres release. Additionally, polymers biocompatibility and their immune-stimulation capacity was assessed in human macrophages. Interestingly, cells treated with HS1200 exhibited a significant proliferation enhancement compared to control. The use of AIT allowed to determine the effect of each polymer on formulations properties. The proportions of PF127 and Gantrez® are mainly the factors controlling gelation temperature, mucoadhesion, adhesion work and gel strength. Meanwhile, cohesion and short-term microsphere release are dependent on the PF127 concentration. However, long-term microsphere release varies depending on the Gantrez® variety and the PF127 concentration used. Hydrogels prepared with S97 showed slower microsphere release. The use of AIT allowed to establish the conditions able to produce ternary hydrogels with immune-stimulatory properties together with adequate mucoadhesion capacity and antigen-like microspheres release.

Chitosan: Structural modification, biological activity and application

Many by-products that are harmful to the environment and human health are generated during food processing. However, these wastes are often potential resources with high-added value. For example, crustacean waste contains large amounts of chitin. Chitin is one of the most abundant polysaccharides in natural macromolecules, and is a typical component of crustaceans, mollusks, insect exoskeleton and fungal cell walls. Chitosan is prepared by deacetylation of chitin and a copolymer of D-glucosamine and N-acetyl-D-glucosamine through β-(1 → 4)-glycosidic bonds. Chitosan has better solubility, biocompatibility and degradability compared with chitin. This review introduces the preparation, physicochemical properties, chemical and physical modification methods of chitosan, which could help us understand its biological activities and applications. According to the latest reports, the antibacterial activity, antioxidant, immune and antitumor activities of chitosan and its derivatives are summarized. Simultaneously, the various applications of chitosan and its derivatives are reviewed, including food, chemical, textile, medical and health, and functional materials. Finally, some insights into its future potential are provided, including novel modification methods, directional modification according to structure-activity relationship, activity and application development direction, etc.

Enhancement of the permeability and activities of epigallocatechin gallate by quaternary ammonium chitosan/fucoidan nanoparticles

Epigallocatechin gallate (EGCG) has many biological functions; however, the use of EGCG in biomedical and food industries was limited due to its poor oral absorption and high susceptibility to degradation. In this study, a mucoadhesive quaternary chitosan was synthesized and combined with fucoidan (FD) (or depolymerized lower molecular weight fucoidan, LMWF) to prepare EGCG-loaded nanoparticles, which extended EGCG release over 300 min and enhanced the transepithelial permeation of EGCG using Caco-2 cells as a model for intestinal absorption. The nanoparticls protected EGCG against degradation in phosphate buffer (pH 6.8) and the remaining EGCG was 1.7-folds higher than the control (EGCG alone). The additive effects of EGCG combined with FD or LMWF in the nanoparticles increased the DPPH radical scavenging activity and the enzyme inhibitory activity against α-amylase (2.82-4.92 fold increase) and α-glucosidase (1.35-1.67 fold increase), while quaternary chitosan helped to enhance the antibacterial effect of EGCG.

Engineering nanoparticulate vaccines for enhancing antigen cross-presentation

Efficient cross-presentation is pivotal for vaccination against cancer and infection by intracellular virus and bacteria. Recently, various types of nanoparticle vaccines have been developed and investigated for efficiently and specifically improving cross-presentation and CD8⁺ T cell priming. In this review, we will summarize the known intracellular pathways involved in cross-presentation, and focus on several nanoparticle strategies that have been reported for enhancing cross-presentation, including designing multifunctional nano-vaccines for increasing endosomal escape, designing nano-vaccines that can target lymph nodes to improve antigen uptake by lymph node resident CD8α⁺ dendritic cells, and co-delivering immune modulators for upregulating cross-presentation related intracellular components. We will also briefly discuss the future prospects of cross-presentation based nano-vaccine strategy for curing diseases.