Bordetella pertussis antigens encapsulated into N-trimethyl chitosan nanoparticulate systems as a novel intranasal pertussis vaccine

Chitosan Nanoparticles for Intranasal Drug Delivery

This manuscript explores the use of nanostructured chitosan for intranasal drug delivery, targeting improved therapeutic outcomes in neurodegenerative diseases, psychiatric care, pain management, vaccination, and diabetes treatment. Chitosan nanoparticles are shown to enhance brain delivery, improve bioavailability, and minimize systemic side effects by facilitating drug transport across the blood-brain barrier. Despite substantial advancements in targeted delivery and vaccine efficacy, challenges remain in scalability, regulatory approval, and transitioning from preclinical studies to clinical applications. The future of chitosan-based nanomedicines hinges on advancing clinical trials, fostering interdisciplinary collaboration, and innovating in nanoparticle design to overcome these hurdles and realize their therapeutic potential.

The Neonatal Immune System and Respiratory Pathogens

Neonates are more susceptible to some pathogens, particularly those that cause infection in the respiratory tract. This is often attributed to an incompletely developed immune system, but recent work demonstrates effective neonatal immune responses to some infection. The emerging view is that neonates have a distinctly different immune response that is well-adapted to deal with unique immunological challenges of the transition from a relatively sterile uterus to a microbe-rich world, tending to suppress potentially dangerous inflammatory responses. Problematically, few animal models allow a mechanistic examination of the roles and effects of various immune functions in this critical transition period. This limits our understanding of neonatal immunity, and therefore our ability to rationally design and develop vaccines and therapeutics to best protect newborns. This review summarizes what is known of the neonatal immune system, focusing on protection against respiratory pathogens and describes challenges of various animal models. Highlighting recent advances in the mouse model, we identify knowledge gaps to be addressed.

In silico design and in vivo evaluation of two multi-epitope vaccines containing build-in adjuvant with chitosan nanoparticles against uropathogenic Escherichia coli

BACKGROUND

Urinary pathogenic Escherichia coli (UPEC) is one of the most important bacterial causes of urinary tract infections (UTIs). Rising antimicrobial resistance and serious clinical challenges such as persistent and recurrent UTIs make it a serious public health concern. Therefore, preventative approaches such as vaccinations are required.

METHODS

In this study, we selected three conserve and protective antigens (FdeC, Hma and UpaB) and also subunit B of cholera toxin (as build-in adjuvant) to design two multi-epitope vaccines (construct B containing B cell epitopes and construct T containing T epitopes) using different bioinformatics methods. The expression of the recombinant protein was performed using the BL21(DE3)/pET28 expression system and purified through a Ni-NTA column. Vaccine proteins were encapsulated in chitosan nanoparticles (CNP) based on ionic gelation via a microfluidic system. Mice were immunized intranasally with different vaccine formulations. Antibody responses and also cytokine expression (IFN-γ and IL-4) were measured by ELISA and real-time PCR respectively. The effectiveness of immune responses was assessed by bladder challenge.

RESULTS

Based on the in silico study, construct B and construct T have high confidence value and stable structure in vivo. High yield expression of both constructs was confirmed by SDS-PAGE and western blot assay. Immunization of mice with construct B induced strong Th2 (IgG1 and IL4) responses and construct T shift immune responses to Th1 (IFNγ and IgG2a). Vaccine protein-encapsulated CNP elicited higher levels of antibodies and cell-mediated responses than the vaccine proteins alone.

CONCLUSIONS

The results of this study suggest that intranasal administration of the construct B has the potential to enhance humoral immunity and construct T has the potential to stimulate cellular immunity. In addition, the combination of CTB as a build-in adjuvant and CNP can be proposed as a potent adjuvant for the development of a novel vaccine against UTI.

Emerging nanoparticle designs against bacterial infections

The rise of antibiotic resistance has caused the prevention and treatment of bacterial infections to be less effective. Therefore, researchers turn to nanomedicine for novel and effective antibacterial therapeutics. The effort resulted in the first-generation antibacterial nanoparticles featuring the ability to improve drug tolerability, circulation half-life, and efficacy. Toward developing the next-generation antibacterial nanoparticles, researchers have integrated design elements that emphasize physical, broad-spectrum, biomimetic, and antivirulence mechanisms. This review highlights four emerging antibacterial nanoparticle designs: inorganic antibacterial nanoparticles, responsive antibacterial nanocarriers, virulence nanoscavengers, and antivirulence nanovaccines. Examples in each design category are selected and reviewed, and their structure-function relationships are discussed. These emerging designs open the door to nontraditional antibacterial nanomedicines that rely on mechano-bactericidal, function-driven, nature-inspired, or virulence-targeting mechanisms to overcome antibiotic resistance for more effective antibacterial therapy. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease.

Synthetic selenium nanoparticles as co-adjuvant improved immune responses against methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the leading causes of hospital-acquired infections worldwide, which is resistant to many antibiotics, resulting in significant mortality in societies. Vaccination is a well-known approach to preventing disease. Autolysin, a surface-associated protein in S. aureus with multiple functions, is a suitable candidate for vaccine development. As a co-adjuvant, selenium nanoparticles (SeNPs) can increase the immune system, presumably resulting in increased vaccine efficacy. The present study evaluated the immunogenicity and defense of recombinant autolysin formulated in SeNPs and Alum adjuvants against MRSA. r-Autolysin was expressed and purified by the Ni-NTA affinity chromatography. SeNPs were synthetically obtained from sodium dioxide, followed by an assessment of shape and size using SEM and DLS. Balb/c mice were injected subcutaneously with 20 mg of r-autolysin formulated in Alum and SeNps adjuvants three times with the proper control group in 2 weeks intervals. Cytokine profile and isotyping ELISA were conducted to determine the type of induced immunity. Opsonophagocytosis tests assessed the functional activity of the vaccine, and the bacterial burden from the infected tissues was determined. Results showed that mice receiving SeNps and r-Autolysin had higher levels of total IgG and isotypes (IgG1 and IgG2a) and increased cytokine levels (IFN-γ, TNF-α, IL-12, and IL-4) as compared with those only receiving autolysin and PBS as a control. More importantly, mice immunized with SeNps and r-Autolysin exhibited a decrease in mortality and bacterial burden compared to the control group. We concluded that SeNps could stimulate immune responses and can be used as an adjuvant element in vaccine formulation.

Different Formulations of Inactivated SARS-CoV-2 Vaccine Candidates in Human Compatible Adjuvants: Potency Studies in Mice Showed Different Platforms of Immune Responses

Several inactivated SARS-CoV-2 vaccines have been approved for human use, but are not highly potent. In this study, different formulations of the inactivated SARS-CoV-2 virus were developed in Alum, Montanide 51VG, and Montanide ISA720VG adjuvants, followed by assessment of immune responses. The SARS-CoV-2 virus was inactivated with formalin and formulated in the adjuvants. BALB/c mice were immunized subcutaneously with 4 μg of vaccines on days 0 and 14; (IL-4) and (IFN-g), cytotoxic T lymphocyte (CTL) activity, and specific immunoglobulin G (IgG) titer and IgG1, IgG2a, and IgG2a/IgG1 ratio, and anti-receptor-binding domain (RBD) IgG response were assessed 2 weeks after the final immunization. Immunization with SARS-CoV-2-Montanide ISA51VG showed a significant increase in the IFN-γ cytokine versus SARS-CoV-2-Alum, SARS-CoV-2-Montanide ISA720VG, and control groups (p < 0.0033). Cytokine IL-4 response in SARS-CoV-2-Alum group showed a significant increase compared with SARS-CoV-2-Montanide ISA51VG, SARS-CoV-2-Montanide ISA720VG, and control groups (p < 0.0206). In addition, SARS-CoV-2-Montanide ISA51VG vaccine induced the highest IFN-γ/IL-4 cytokine ratio versus other groups (p < 0.0004). CTL activity in SARS-CoV-2-Montanide ISA51VG and SARS-CoV-2-Montanide ISA720VG groups showed a significant increase compared with SARS-CoV-2-Alum and control groups (p < 0.0075). Specific IgG titer in SARS-CoV-2-Montanide ISA51 VG and SARS-CoV-2-Montanide ISA720VG showed a significant increase compared with SARS-CoV-2-Alum and control groups (p < 0.0143). Results from specific IgG1and IgG2a in SARS-CoV-2-Alum, SARS-CoV-2-Montanide ISA51VG, and SARS-CoV-2-Montanide ISA720VG vaccine showed a significant increase compared with phosphate buffer saline (PBS) group (p < 0.0001), but SARS-CoV-2-Montanide ISA51VG and SARS-CoV-2-Montanide ISA 720VG groups showed the highest IgG2a/IgG1 ratio and a significant increase compared with SARS-CoV-2-Alum group (p < 0.0379). Moreover, inactivated SARS-CoV-2+Alum and SARS-CoV-2-Montanide ISA 720VG groups demonstrated a significant increase in anti-RBD IgG response versus the SARS-CoV-2-Montanide ISA51VG group. It seems that the type of vaccine formulation is a critical parameter, influencing the immunologic pattern and vaccine potency and human-compatible oil-based adjuvants were more potent than Alum adjuvant in the vaccine formulation.

Recent advances on chitosan as an adjuvant for vaccine delivery

Chitosan (CS) is a natural polymer derived from chitin that has wide applications in drugs, vaccines, and antigen delivery. The distinctive mucoadhesive, biocompatibility, biodegradable, and less toxic properties of chitosan compared to the currently used vaccine adjuvants made it a promising candidate for use as an adjuvant/carrier in vaccine delivery. In addition, chitosan exhibits intrinsic immunomodulating properties making it a suitable adjuvant in preparing vaccines delivery systems. Nanoparticles (NPs) of chitosan and its derivatives loaded with antigen have been shown to induce cellular and humoral responses. Versatility in the physicochemical properties of chitosan can provide an excellent opportunity to engineer antigen-specific adjuvant/delivery systems. This review discusses the recent advances of chitosan and its derivatives as adjuvants in vaccine deliveryand the published literature in the last fifteen years. The impact of physicochemical properties of chitosan on vaccine formulation has been described in detail. Applications of chitosan and its derivatives, their physicochemical properties, and mechanisms in enhancing immune responses have been discussed. Finally, challenges and future aspects of chitosan use has been pointed out.

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.

Improvement of hepatitis B vaccine to induce IFN-γ cytokine response: A new formulation

Hepatitis B virus (HBV) infection is limited through vaccination against HBsAg formulated in the Alum adjuvant. However, this alum-formulated vaccine fails to be preventive in some cases, also known as non-responders. Recent studies have shown the immunomodulatory effect of α-tocopherol in various models. Here, we developed a new formulation for HBsAg using α-tocopherol, followed by assessment of immune responses. Experimental BALB/c mice were immunized with a commercial alum-based vaccine or the one formulated in α-tocopherol at different doses. Mice were immunized subcutaneously with 5 μg of HBsAg with different formulations three times with 2-week intervals. Specific total IgG, IgG1, and IgG2a isotypes of antibodies were measured by ELISA. Immunologic cytokines, such as IFN-γ, IL-4, IL-2, and TNF-α, were also evaluated through commercial ELISA kits. Our results showed that the new α-tocopherol-formulated vaccine had the ability to reinforce specific total IgG responses. Moreover, α-tocopherol in the HBsAg vaccine increased IFN-γ, IL-2, and TNF-α cytokines at higher concentrations; however, the vaccine suppressed IL-4 cytokine release. At a lower concentration of α-tocopherol, the IL-4 cytokine response increased without a positive effect on IFN-γ and TNF-α cytokine response. It seems that α-tocopherol can change the immune responses against HBsAg; however, the type of response depends on the dose of α-tocopherol used in the vaccine formulation.

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.

Mucosal Immunization Against Pertussis: Lessons From the Past and Perspectives

Background

Current vaccination strategies against pertussis are sub-optimal. Optimal protection against Bordetella pertussis, the causative agent of pertussis, likely requires mucosal immunity. Current pertussis vaccines consist of inactivated whole B. pertussis cells or purified antigens thereof, combined with diphtheria and tetanus toxoids. Although they are highly protective against severe pertussis disease, they fail to elicit mucosal immunity. Compared to natural infection, immune responses following immunization are short-lived and fail to prevent bacterial colonization of the upper respiratory tract. To overcome these shortcomings, efforts have been made for decades, and continue to be made, toward the development of mucosal vaccines against pertussis.

Objectives

In this review we systematically analyzed published literature on protection conferred by mucosal immunization against pertussis. Immune responses mounted by these vaccines are summarized.

Method

The PubMed Library database was searched for published studies on mucosal pertussis vaccines. Eligibility criteria included mucosal administration and the evaluation of at least one outcome related to efficacy, immunogenicity and safety.

Results

While over 349 publications were identified by the search, only 63 studies met the eligibility criteria. All eligible studies are included here. Initial attempts of mucosal whole-cell vaccine administration in humans provided promising results, but were not followed up. More recently, diverse vaccination strategies have been tested, including non-replicating and replicating vaccine candidates given by three different mucosal routes: orally, nasally or rectally. Several adjuvants and particulate formulations were tested to enhance the efficacy of non-replicating vaccines administered mucosally. Most novel vaccine candidates were only tested in animal models, mainly mice. Only one novel mucosal vaccine candidate was tested in baboons and in human trials.

Conclusion

Three vaccination strategies drew our attention, as they provided protective and durable immunity in the respiratory tract, including the upper respiratory tract: acellular vaccines adjuvanted with lipopeptide LP1569 and c-di-GMP, outer membrane vesicles and the live attenuated BPZE1 vaccine. Among all experimental vaccines, BPZE1 is the only one that has advanced into clinical development.

Secretory System Components as Potential Prophylactic Targets for Bacterial Pathogens

Bacterial secretory systems are essential for virulence in human pathogens. The systems have become a target of alternative antibacterial strategies based on small molecules and antibodies. Strategies to use components of the systems to design prophylactics have been less publicized despite vaccines being the preferred solution to dealing with bacterial infections. In the current review, strategies to design vaccines against selected pathogens are presented and connected to the biology of the system. The examples are given for Y. pestis, S. enterica, B. anthracis, S. flexneri, and other human pathogens, and discussed in terms of effectiveness and long-term protection.

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.

Chitosan oligosaccharide combined with running benefited the immune status of rats

Chitosan oligosaccharide (COS) degraded by chitosan, is an easily accessible and biocompatible natural molecule, which can facilitate the immune system. Running is one of the most effective forms of exercise. Persistence in running can effectively improve the body's resistance against pathogens. However, whether the combination of COS and running could benefit immune status still remains to be elucidated. We used Sprague-Dawley (SD) rats to explore the combinatory effect of COS and running. The organs and blood of the rats were collected after four weeks and the organ body mass index, biochemical and blood routine examination, cytokines, and T cells in the spleen and blood were detected and analyzed. In the group intragastric administration of COS only, the level of blood lactate dehydrogenase was increased, while the blood creatinine, red blood cells, lymphocytes, and serum TNF were decreased. Furthermore, COS combined with running promoted the development of spleen and lung, the level of lymphocytes, T cell and CD8⁺ T cell ratio in the blood, and serum TNF level. At the same time, the level of lactate dehydrogenase, serum IL-2, and T cell ratio in spleen were decreased. Therefore, our study indicated that COS combined with running could improve the immune status of rats.

Nanoparticle-Based Vaccines for Brucellosis: Calcium Phosphate Nanoparticles-Adsorbed Antigens Induce Cross Protective Response in Mice

Introduction

Vaccine formulation with appropriate adjuvants is an attractive approach to develop protective immunity against pathogens. Calcium phosphate nanoparticles (CaPNs) are considered as ideal adjuvants and delivery systems because of their great potential for enhancing immune responses. In the current study, we have designed nanoparticle-based vaccine candidates to induce immune responses and protection against B. melitensis and B. abortus.

Materials and Methods

For this purpose, we used three Brucella antigens (FliC, 7α-HSDH, BhuA) and two multi-epitopes (poly B and poly T) absorbed by CaPNs. The efficacy of each formulation was evaluated by measuring humoral, cellular and protective responses in immunized mice.

Results

The CaPNs showed an average size of about 90 nm with spherical shape and smooth surface. The CaPNs-adsorbed proteins displayed significant increase in cellular and humoral immune responses compared to the control groups. In addition, our results showed increased ratio of specific IgG2a (associated with Th1) to specific IgG1 (associated with Th2). Also, immunized mice with different vaccine candidate formulations were protected against B. melitensis 16M and B. abortus 544, and showed same levels of protection as commercial vaccines (B. melitensis Rev.1 and B. abortus RB51) except for BhuA-CaPNs.

Discussion

Our data support the hypothesis that these antigens absorbed with CaPNs could be effective vaccine candidates against B. melitensis and B. abortus.

Designation of chitosan nano-vaccine based on MxiH antigen of Shigella flexneri with increased immunization capacity

Shigella flexneri is a gram-negative pathogen that causes shigellosis in humans and primates. MxiH antigen is known as one of the invasive factors in most Gram-negative bacteria consisting of a needle-like structure in the main backbone of the type 3 secretory system. Recombinant MxiH antigen was produced by E. coli BL21 and purified antigen was loaded into chitosan nanoparticles (CS-MxiH). After 20^thand 55^th of intranasal vaccinations, the titers of IgG, IgA, IL-4, and IFN-γ were evaluated. The results indicated the successful synthesis of CS nanoparticles followed by the effective loading of MxiH antigen. The results of animal experiments showed that the intranasal administration of CS-MxiH increased IgG and IgA compared to control groups. Increased levels of IL-4 and IFN-γ in groups immunized with CS-MxiH are probably due to the activation of plasmacytoid and myeloid cells presenting antigen in nasal epithelial mucosa and stimulating B cells.