Nanodelivery system enhances the immunogenicity of dengue-2 nonstructural protein 1, DENV-2 NS1

Ag/Au-incorporated trimethyl chitosan-shell hybrid particles as reinforcing and antioxidant fillers for trimethyl chitosan hydrogel

N,N,N-Trimethyl chitosan (TMC) is a quaternized chitosan with versatile biological features. However, low mechanical strength limits its uses, for example, as hydrogels for tissue engineering applications. This study illustrates a viable synthesis of metal/polymer hybrid, core-shell colloidal particles and their use as reinforcing and antioxidant fillers for TMC hydrogels. The core-shell particles were initially synthesized by surfactant-free emulsion polymerization, induced by a photo-redox initiating system of riboflavin assisted by a 3° amine and 2° alcohol co-initiators. The synthesized core-shell particles were based on two polymeric shells: TMC and chitosan, and two polymeric cores: poly (hydroxypropyl methacrylate) (PHPMA) and poly(2-hydroxy ethyl methacrylate) (PHEMA). The presence of both 3° amine on TMC and 2° alcohol on HPMA monomer enhanced the photopolymerization performance. The TMC-based particles had sizes of 122-154 nm and zeta potentials of 10-35 mV, bringing the colloidal stability in the 4-10 pH range. Furthermore, due to the presence of TMC on the shell layer, the core-shell particles could be used as templates to grow the Ag/Au bimetallic nanoparticles with alloy and core-shell types through a thermal reduction. The prepared hybrid particles were incorporated in TMC hydrogels as a multifunctional filler, improving their mechanical and antioxidant properties.

Intranasal immunization with the bivalent SARS-CoV-2 vaccine effectively protects mice from nasal infection and completely inhibits disease development

With the continuous emergence of coronavirus disease 2019 (COVID-19) waves, the scientific community has developed a vaccine that offers broad-spectrum protection at virus-targeted organs for inhibiting the transmission and protection of disease development. In the present study, a bivalent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine containing receptor-binding domain (RBD) protein of spike from Wuhan-1 and omicron BA.1 loaded in nanoparticles, bivalent RBD NPs, was developed. The immunogenicity and protective efficacy of this vaccine candidate were evaluated using an in vivo model. Results showed that mice that received intranasal cGAMP-adjuvanted bivalent RBD-NPs vaccine elicited robust and durable antibody responses. The stimulated antibody broadly neutralized the ancestral strain and variants of concerns (delta and omicron BA.1) in the upper and lower respiratory tracts. Furthermore, the immunized mice developed T-cell response in their lung tissue. Importantly, intranasal immunization with this vaccine candidate efficiently protected mice from nasal infection caused by both Wuhan-1 and BA.1 viruses. Immunized mice that remained susceptible to nasal infection did not develop any symptoms. This is because activated responses in the nasal cavity significantly suppressed virus production. Another word is this nasal vaccine completely protected the mice from disease development and mortality. Therefore, the bivalent RBD vaccine platform has potential to be developed into an anti-SARS-CoV-2 universal vaccine.

The Adjuvant Activity of BCG Cell Wall Cytoskeleton on a Dengue Virus-2 Subunit Vaccine

The uneven immunogenicity of the attenuated tetravalent dengue vaccine has made it difficult to achieve balanced protection against all four serotypes of the dengue virus (DENV). To overcome this problem, non-replicative vaccines have come into focus, as their immunogenicity is adjustable. This approach is excellent for multivalent vaccines but commonly faces the issue of low immunogenicity. In this present study, we developed a non-replicating dengue vaccine composed of UV-inactivated dengue virus-2 (UV-DENV-2) and DENV-2 NS1-279 protein encapsidated within nanoparticles. This vaccine candidate was administered in the presence of BCG cell wall cytoskeleton (BCG-CWS) as an adjuvant. We revealed, here, that encapsidated immunogens with BCG-CWS exerted potent activities on both B and T cells and elicited Th-1/Th-2 responses in mice. This was evidenced by BCG-CWS significantly augmenting antibody-mediated complement-fixing activity, strongly stimulating the antigen-specific polyfunctional T cell responses, and activating mixed Th-1/Th-2 responses specific to DENV-2- and NS1-279 antigens. In conclusion, BCG-CWS potently adjuvanted the inactivated DENV-2 and DENV subunit immunogens. The mechanism of adjuvanticity remains unclear. This study revealed the potential use of BCG-CWS in vaccine development.

A clinical perspective of chitosan nanoparticles for infectious disease management

Infectious diseases and their effective management are still a challenge in this modern era of medicine. Diseases, such as the SARS-CoV-2, Ebola virus, and Zika virus, still put human civilization at peril. Existing drug banks, which include antivirals, antibacterial, and small-molecule drugs, are the most advocated method for treatment, although effective but they still flounder in many instances. This calls for finding more effective alternatives for tackling the menace of infectious diseases. Nanoformulations are progressively being implemented for clinical translation and are being considered a new paradigm against infectious diseases. Natural polymers like chitosan are preferred to design nanoparticles owing to their biocompatibility, biodegradation, and long shelf-life. The chitosan nanoparticles (CNPs) being highly adaptive delivers contemporary prevention for infectious diseases. Currently, they are being used as antibacterial, drug, and vaccine delivery vehicles, and wound-dressing materials, for infectious disease treatment. Although the recruitment of CNPs in clinical trials associated with infectious diseases is minimal, this may increase shortly due to the sudden emergence of unknown pathogens like SARS-CoV-2, thus turning them into a panacea for the management of microorganisms. This review particularly focuses on the all-around application of CNPs along with their recent clinical applications in infectious disease management.

Green synthesis of quaternized chitosan nanogel using emulsion-photopolymerization as redox-responsive drug carrier

We report the green synthesis of trimethyl chitosan-functionalized poly(2-hydroxyethyl methacrylate) (PHEMA-TMC) nanogels via surfactant-free emulsion photopolymerization. TMC, a quaternized derivative of chitosan, was synthesized through methylation of chitosan, resulting in quaternary and tertiary amine groups as the main substitution products. TMC tertiary amine moiety and riboflavin (RF) acted as a redox photo-initiating system to generate free radicals for the polymerization under light irradiation. The effects of polymerization parameters such as irradiation time, concentrations of TMC and RF were investigated using MBA as crosslinker. Under the optimal condition of 1 % TMC, 4 % HEMA, 0.8 μM RF, 5 % MBA, and 4 h of polymerization time, the cationic PHEMA-TMC nanogel was synthesized with 76 % monomer conversion and an average diameter of about 106 nm. Moreover, the disulfide-crosslinked PHEMA-TMC nanogel was also synthesized using the disulfide dimethacrylate crosslinker, which exhibited a redox-induced degradation and release of encapsulated melatonin, potentially useful as a redox-responsive drug delivery carrier.

A bivalent form of nanoparticle-based dengue vaccine stimulated responses that potently eliminate both DENV-2 particles and DENV-2-infected cells

Dengue is the most prevalent mosquito-borne viral disease and continues to be a global public health concern. Although a licensed dengue vaccine is available, its efficacy and safety profile are not satisfactory. Hence, there remains a need for a safe and effective dengue vaccine. We are currently developing a bivalent dengue vaccine candidate. This vaccine candidate is composed of a C-terminus truncated non-structural protein 1 (NS1_1-279) and envelope domain III (EDIII) of DENV-2 encapsidated in the nanocarriers, N, N, N-trimethyl chitosan nanoparticles (TMC NPs). The immunogenicity of this bivalent vaccine candidate was investigated in the present study using BALB/c mice. In this work, we demonstrate that NS1 + EDIII TMC NP-immunized mice strongly elicited antigen-specific antibody responses (anti-NS1 and anti-EDIII IgG) and T-cell responses (NS1- and EDIII-specific-CD4⁺ and CD8⁺ T cells). Importantly, the antibody response induced by NS1 + EDIII TMC NPs provided antiviral activities against DENV-2, including serotype-specific neutralization and antibody-mediated complement-dependent cytotoxicity. Moreover, the significant upregulation of Th1- and Th2-associated cytokines, as well as the increased levels of antigen-specific IgG2a and IgG1, indicated a balanced Th1/Th2 response. Collectively, our findings suggest that NS1 + EDIII TMC NPs induced protective responses that can not only neutralize infectious DENV-2 but also eliminate DENV-2-infected cells.

A multiple-target mRNA-LNP vaccine induces protective immunity against experimental multi-serotype DENV in mice

Dengue virus (DENV) is a mosquito-borne virus with a rapid spread to humans, causing mild to potentially fatal illness in hundreds of millions of people each year. Due to the large number of serotypes of the virus, there remains an unmet need to develop protective vaccines for a broad spectrum of the virus. Here, we constructed a modified mRNA vaccine containing envelope domain III (E-DIII) and non-structural protein 1 (NS1) coated with lipid nanoparticles. This multi-target vaccine induced a robust antiviral immune response and increased neutralizing antibody titers that blocked all four types of DENV infection in vitro without significant antibody-dependent enhancement (ADE). In addition, there was more bias for Th1 than Th2 in the exact E-DIII and NS1-specific T cell responses after a single injection. Importantly, intramuscular immunization limited DENV transmission in vivo and eliminated vascular leakage. Our findings highlight that chimeric allogeneic structural and non-structural proteins can be effective targets for DENV vaccine and that they can prevent the further development of congenital DENV syndrome.

Mice immunized with trimethyl chitosan nanoparticles containing DENV-2 envelope domain III elicit neutralizing antibodies with undetectable antibody-dependent enhancement activity

Dengue is a disease that poses a significant global public health concern. Although a tetravalent live-attenuated dengue vaccine has been licensed, its efficacy is still debated due to evidence of vaccine breakthrough infection. To avoid this issue, dengue vaccines should stimulate a high degree of serotype-specific response. Thus, envelope domain III (EDIII), which contains serotype-specific neutralizing epitopes, is an attractive target for dengue vaccine development. In this study, we investigated how EDIII encapsidated in N, N, N-trimethyl chitosan chloride nanoparticles (TMC NPs) stimulates a serotype-specific response and whether this response exerts a potential in vitro breakthrough infection. The immune response to DENV-2 elicited by EDIII TMC NP-immunized mice was monitored. We demonstrated that immunization with EDIII TMC NPs resulted in a high level of anti-EDIII antibody production. These antibodies included IgG, IgG1, and IgG2a subtypes. Importantly, antibodies from the immunized mice exerted efficient neutralizing activity with undetectable antibody dependent enhancement (ADE) activity. We also found that EDIII TMC NPs activated functional EDIII-specific CD4⁺ and CD8⁺ T cell responses. In conclusion, EDIII TMC NPs stimulated humoral immunity with a strong neutralizing antibody response, as well as a cellular immune response against DENV-2.

The STING Ligand and Delivery System Synergistically Enhance the Immunogenicity of an Intranasal Spike SARS-CoV-2 Vaccine Candidate

The respiratory organ serves as a primary target site for SARS-CoV-2. Thus, the vaccine-stimulating immune response of the respiratory tract is significant in controlling SARS-CoV-2 transmission and disease development. In this study, mucoadhesive nanoparticles were used to deliver SARS-CoV-2 spike proteins (S-NPs) into the nasal tracts of mice. The responses in the respiratory organ and the systemic responses were monitored. The administration of S-NPs along with cGAMP conferred a robust stimulation of antibody responses in the respiratory tract, as demonstrated by an increase of IgA and IgG antibodies toward the spike proteins in bronchoalveolar lavages (BALs) and the lungs. Interestingly, the elicited antibodies were able to neutralize both the wild-type and Delta variant strains of SARS-CoV-2. Significantly, the intranasal immunization also stimulated systemic responses. This is evidenced by the increased production of circulating IgG and IgA, which were able to neutralize and bind specifically to the SARS-CoV-2 virion and spike protein. Additionally, this intranasal administration potently activated a splenic T cell response and the production of Th-1 cytokines, suggesting that this vaccine may well activate a cellular response in the respiratory tract. The results demonstrate that STING agonist strongly acts as an adjuvant to the immunogenicity of S-NPs. This platform may be an ideal vaccine against SARS-CoV-2.

Peritoneal Administration of a Subunit Vaccine Encapsulated in a Nanodelivery System Not Only Augments Systemic Responses against SARS-CoV-2 but Also Stimulates Responses in the Respiratory Tract

The COVID-19 pandemic has currently created an unprecedented threat to human society and global health. A rapid mass vaccination to create herd immunity against SARS-CoV-2 is a crucial measure to ease the spread of this disease. Here, we investigated the immunogenicity of a SARS-CoV-2 subunit vaccine candidate, a SARS-CoV-2 spike glycoprotein encapsulated in N,N,N-trimethyl chitosan particles or S-TMC NPs. Upon intraperitoneal immunization, S-TMC NP-immunized mice elicited a stronger systemic antibody response, with neutralizing capacity against SARS-CoV-2, than mice receiving the soluble form of S-glycoprotein. S-TMC NPs were able to stimulate the circulating IgG and IgA as found in SARS-CoV-2-infected patients. In addition, spike-specific T cell responses were drastically activated in S-TMC NP-immunized mice. Surprisingly, administration of S-TMC NPs via the intraperitoneal route also stimulated SARS-CoV-2-specific immune responses in the respiratory tract, which were demonstrated by the presence of high levels of SARS-CoV-2-specific IgG and IgA in the lung homogenates and bronchoalveolar lavages of the immunized mice. We found that peritoneal immunization with spike nanospheres stimulates both systemic and respiratory mucosal immunity.

Viral Toxin NS1 Implication in Dengue Pathogenesis Making It a Pivotal Target in Development of Efficient Vaccine

The mosquito-borne viral disease dengue is a global public health problem causing a wide spectrum of clinical manifestations ranging from mild dengue fever to severe dengue with plasma leakage and bleeding which are often fatal. To date, there are no specific medications to treat dengue and prevent the risk of hemorrhage. Dengue is caused by one of four genetically related but antigenically distinct serotypes DENV-1–DENV-4. The growing burden of the four DENV serotypes has intensified both basic and applied research to better understand dengue physiopathology. Research has shown that the secreted soluble hexameric form of DENV nonstructural protein-1 (sNS1) plays a significant role in the pathogenesis of severe dengue. Here, we provide an overview of the current knowledge about the role of sNS1 in the immunopathogenesis of dengue disease. We discuss the potential use of sNS1 in future vaccine development and its potential to improve dengue vaccine efficiency, particularly against severe dengue illness.

Mucosal Vaccine Delivery Using Mucoadhesive Polymer Particulate Systems

Vaccination has been recently attracted as one of the most successful medical treatments of the prevalence of many infectious diseases. Mucosal vaccination has been interested in many researchers because mucosal immune responses play part in the first line of defense against pathogens. However, mucosal vaccination should find out an efficient antigen delivery system because the antigen should be protected from degradation and clearance, it should be targeted to mucosal sites, and it should stimulate mucosal and systemic immunity. Accordingly, mucoadhesive polymeric particles among the polymeric particles have gained much attention because they can protect the antigen from degradation, prolong the residence time of the antigen at the target site, and control the release of the loaded vaccine, and results in induction of mucosal and systemic immune responses. In this review, we discuss advances in the development of several kinds of mucoadhesive polymeric particles for mucosal vaccine delivery.

Intranasal Administration of RBD Nanoparticles Confers Induction of Mucosal and Systemic Immunity against SARS-CoV-2

Mucosal immunity plays a significant role in host defense against viruses in the respiratory tract. Because the upper respiratory airway is a primary site of SARS-CoV-2 entry, immunization at the mucosa via the intranasal route could potentially lead to induction of local sterilizing immunity that protects against SARS-CoV-2 infection. In this study, we evaluated the immunogenicity of a receptor-binding domain (RBD) of SARS-CoV-2 spike glycoprotein loaded into N,N,N-trimethyl chitosan nanoparticles (RBD-TMC NPs). We showed that intranasal delivery of RBD-TMC NPs into mice induced robust local mucosal immunity, as evidenced by the presence of IgG and IgA responses in BALs and the lungs of immunized mice. Furthermore, mice intranasally administered with this platform of immunogens developed robust systemic antibody responses including serum IgG, IgG1, IgG2a, IgA and neutralizing antibodies. In addition, these immunized mice had significantly higher levels of activated splenic CD4⁺ and CD8⁺ cells compared with those that were administered with soluble RBD immunogen. Collectively, these findings shed light on an alternative route of vaccination that mimics the natural route of SARS-CoV-2 infection. This route of administration stimulated not only local mucosal responses but also the systemic compartment of the immune system.

Whole inactivated dengue virus-loaded trimethyl chitosan nanoparticle-based vaccine: immunogenic properties in ex vivo and in vivo models

Dengue virus (DENV) is a mosquito-borne virus that poses an incomparable public health problem, particularly in tropical and subtropical areas. Vaccination remains the most rational measure for controlling DENV infection. In this study, an ultraviolet irradiation (UV)-inactivated DENV-2 carried by N,N,N-trimethyl chitosan nanoparticles (UV-inactivated DENV2 TMC NPs) was investigated as a potential non-replicating dengue vaccine candidate. Using a human ex vivo model, the human monocyte-derived dendritic cells (MoDCs), we showed that TMC served as both a vaccine vehicle and a potent adjuvant. TMC NPs not only efficiently enhanced UV-inactivated DENV2 internalization into MoDCs but also greatly increased the breadth of UV-inactivated DENV2 immunogenicity to drive the maturation of MoDCs. Moreover, UV-inactivated DENV2 TMC NPs were highly immunogenic in mice, inducing greater levels of antibodies (total IgG, IgG1, IgG2a and neutralizing antibodies) and T cells (activated CD4⁺ and CD8⁺ T cells) against DENV-2 compared to soluble DENV-2 immunogens. Notably, the neutralizing activity of sera from mice immunized with UV-inactivated DENV2 TMC NPs was significantly augmented in the presence of complement activation, leading to the strong elimination of both DENV-2 particles and infected cells. We further showed that the immunogenicity of an inactivated dengue-based vaccine was significantly improved in a concentration-dependent manner. These positive results warrant further investigations of this platform of vaccine delivery for tetravalent vaccines or monovalent vaccines in sequential immunizations.

Immunostimulatory effect of chitosan and quaternary chitosan: A review of potential vaccine adjuvants

Vaccines have always been the most effective preventive treatment. Advancements in the field of vaccine is inseparable from adjuvants. Adjuvants are substances added to vaccines to enhance immunogenicity and induce a stronger immune response. Chitosan fascinated considerable attention as vaccine adjuvant due to its unique physicochemical and biological properties. Many studies have shown that chitosan and its derivatives can effectively activate antigen-presenting cells and induce cytokine stimulation to produce an effective immune response and promote the balance of Th1/Th2 response. Among many derivatives, the quaternized chitosan performs better. This review presents the main factors affecting the adjuvant performance of chitosan and quaternized chitosan firstly. Then, we introduced not only the immune response they may cause, but also their metabolic research in detail. Furthermore, their future prospects are forecasted. Overall, chitosan and quaternized chitosan are both promising adjuvant materials, and quaternized chitosan shows greater potential.