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

Recent advances in immunotherapy targeting CETP proteins for atherosclerosis prevention

Cholesteryl ester transfer protein (CETP) plays a key role in lipoprotein metabolism, and its activity has been linked to the risk of atherosclerosis (AS). CETP inhibitors, such as obicetrapib, represent a novel approach in immunotherapy to reduce the risk of atherosclerotic cardiovascular disease (ASCVD) by targeting lipid metabolism. In addition, CETP vaccines are being explored as a novel strategy for the prevention and treatment of ASCVD by inducing the body to produce antibodies against CETP, which is expected to reduce CETP activity, thereby increasing high-density lipoproteins (HDL) levels. This paper provides a comprehensive overview of the structure of CETP, the mechanisms of lipid transfer and the progress of immunotherapy in the last decade, which provides possible ideas for future development of novel drugs and optimization of immunization strategies.

Current insights into polymeric micelles for nasal drug delivery

INTRODUCTION

The nasal administration route has gained peak interest in recent literature and as a noninvasive alternative for efficient drug delivery and increasing bioavailability of active substances. Technological challenges arise from the drug's physicochemical properties and the nasal mucosal barrier for which innovative particle engineering techniques must be implemented, such as using polymeric nanocarriers.

AREAS COVERED

This review deals with the importance of the nasal administration route and its connection to polymeric micelles as innovative nanocarriers. The period between 2015-2025 up to date was chosen to search for original research articles where polymeric micelles were applied nasally. The first part demonstrates the utilization of polymeric micelles, followed by a summary of how drug release and permeability can be achieved in the nasal cavity and through the nasal epithelium. The second part reviews the studies conducted on this matter.

EXPERT OPINION

The nasal route could be superior to perform as a suitable alternative to conventional routes. Multiple studies have already demonstrated that the main advantages lie in the nose-to-brain drug delivery pathway, which can be conquered via adequately formulated polymeric micelles. As an innovative solution, vaccine delivery is also of great potential by combining the advantages of the delivery route and the polymeric nanocarriers.

Nanotechnology-driven advances in intranasal vaccine delivery systems against infectious diseases

Outbreaks of emerging and re-emerging infectious diseases have consistently threatened human health. Since vaccinations are a powerful tool for preventing infectious illnesses, developing new vaccines is essential. Compared to traditional injectable vaccines, mucosal vaccines have the potential to offer more effective immune protection at mucosal sites. Mucosal immunization strategies include sublingual, oral, intranasal, genital, and rectal routes, in which intranasal immunization being the most efficient and applicable method for mucosal vaccine delivery. Nevertheless, low antigen availability and weak immunogenicity making it challenging to elicit a potent immune response when administered intranasally, necessitating the incorporation of immune delivery systems. However, there is a notable absence of reviews that summarize the intranasal vaccine delivery system against infectious disease. Therefore, this review summarizes the recent advances in intranasal delivery systems, classified by physical and chemical properties, and proposes potential improvement strategies for clinical translation. This review elucidates the potential and current status of intranasal delivery systems, while also serving as a reference point for the future development of intranasal vaccines.

Intranasal vaccination with multi-neuraminidase and M2e virus-like particle vaccine results in greater mucosal immunity and protection against influenza than intramuscular injection

Intramuscular injection of seasonal influenza vaccines provides strain-specific neutralizing antibodies, but not against variants, and no effective mucosal immunity. Here, we report that multi-subtype neuraminidase (NA) and M2 ectodomain repeat (5xM2e) virus-like particle vaccine (NA-M2e) conferred higher efficacy of broad cross-protection after two doses of intranasal delivery than intramuscular injection. The intranasally vaccinated mice displayed high levels of IgA antibodies, IFN-γ+ CD4 and CD8 T cells, germinal center B cells, plasma cells, and early innate immune cells locally in the lungs. In contrast, intramuscular vaccination systemically induced innate and adaptive immune responses in the spleen. Our findings demonstrate that the intranasal delivery of NA-M2e vaccine induces enhanced mucosal immunity and comparable serum IgG antibodies, offering improved efficacy of cross-protection against diverse influenza virus strains compared to the intramuscular injection in a mouse model.

Intranasally administered whole virion inactivated vaccine against clade 2.3.4.4b H5N1 influenza virus with optimized antigen and increased cross-protection

The global spread, frequent antigenic changes, and pandemic potential of clade 2.3.4.4b highly pathogenic avian influenza H5N1 underscore the urgent need for robust cross-protective vaccines. Here, we developed a clade 2.3.4.4b H5N1 whole inactivated virus (WIV) vaccine strain with improved structural stability, productivity, and safety. By analyzing the evolutionary trends of clade 2.3.4.4b H5N1 viruses, we identified a key mutation (R90K) that increases heat stability while preserving antigenicity. Additionally, the PB2 gene of PR8 was replaced with a prototypical avian PB2 gene to increase replication efficiency in embryonated chicken eggs and reduce replication efficiency in mammalian cells, thereby improving productivity and biosafety. We found that our optimized clade 2.3.4.4b H5N1 vaccine strain (22W_KY), inactivated with binary ethylenimine (BEI), had superior antigen internalization into respiratory epithelial cells compared to those inactivated with formaldehyde or beta-propiolactone. Following intranasal administration to mice, the BEI-inactivated 22W_KY also elicited significantly stronger systemic IgG, mucosal IgA, and T-cell responses, especially in the lungs. Protective efficacy studies revealed that the BEI-inactivated 22W_KY vaccine provided complete protection against heterologous viral challenges and significant protection against heterosubtypic viral challenges, with no weight loss and complete suppression of the viral load in the respiratory tract in 2 of 3 mice. These results indicate that the BEI-inactivated 22W_KY vaccine could serve as a promising candidate for a safe, stable, cost-efficient, and broadly protective intranasal influenza vaccine against zoonotic and pandemic threats.

Validation and clinical performance of a non-commercial ELISA for SARS-CoV-2 anti-RBD IgA antibodies

COVID-19 is caused by SARS-CoV-2, first identified in 2019. The Cuban vaccines, Abdala and Mambisa, have demonstrated efficacy in preventing SARS-CoV-2 infection. Immunoglobulin A (IgA) are the main line of defense against pathogens invading the respiratory or digestive tract and its presence in serum can be measured to assess vaccine efficacy. ELISAs are a valuable tool for assessing vaccine immunogenicity. These tests should be validated to ensure their reliability and suitability. The objective of this study was to validate a non-commercial ELISA for the quantification of total anti-RBD IgA in serum samples to support clinical studies. This assay demonstrated high clinical specificity (97.3 %). The accuracy and precision of the assay showed an overall error of less than 20 % at all levels in QCs. Re-evaluation of samples showed a mean difference of less than 30 % in 90.2 % of cases. Anti-RBD IgA titers correlated with viral neutralization titers and percentage inhibition of RBD-ACE2 binding. This assay was found to be highly accurate and reproducible for the quantification of anti-RBD IgA, met the most stringent acceptance criteria and is fit for purpose. It is currently being used to evaluate the immunogenicity of the Abdala and Mambisa vaccines.

Bridging Gaps in Antibody Responses and Animal Welfare: Assessing Blood Collection Methods and Vaginal Immunity in Mice Immunized with Intranasal Gonococcal Vaccines

Assessing antibody titers and functional responses is essential for evaluating vaccine efficacy, yet the impact of blood collection methods on these immunological assessments remains unclear. Retro-orbital (RO) blood collection is commonly used but significant complications can occur. Increasingly, investigators have adopted alternative blood collection approaches, such as saphenous vein (SV) sampling to improve laboratory animal welfare. This study compared RO and SV sampling in the development of a Neisseria gonorrhoeae (Ng) vaccine, evaluating Adhesin Complex Protein (ACP) and multiple transferable resistance (Mtr) E protein (MtrE) as antigen candidates. Epitope mapping revealed that ACP and MtrE possess multiple, highly accessible B-cell and T-cell epitope clusters, reinforcing their immunological potential. Following intranasal immunization with rACP, rACP+CpG, and rMtrE+CpG, we assessed the specificity, magnitude, kinetics, and functional quality of immune responses elicited by the immunization regimens. Out of 45 comparisons, only eight significant differences were detected in antibody titers, while the human serum bactericidal assays revealed no differences between RO and SV in antigen-immunized groups. However, antibodies elicited by rACP alone or ACP+CpG in SV samples restored 30.05% and 75.2% of human lysozyme hydrolytic activity compared to 19.3 and 59.9 % in RO, respectively suggesting that SV sampling may be more reliable for assessing functional antibody responses. Beyond its immunological advantages, SV sampling reduces stress, minimizes ocular trauma, and improves animal welfare, making it a viable alternative to RO collection. Given its widespread use in vaccine research, standardizing SV sampling could improve data reliability, ethical compliance, and translational relevance in preclinical studies.

Mucosal immunotherapy targeting APC in lung disease

Several studies have demonstrated that the pulmonary immune response is primarily facilitated by antigen-presenting cells (APCs), and that both professional and non-professional APCs contribute to overall pulmonary immunity. APCs play unique roles and mechanisms in pathogen elimination and immunomodulation. Mucosal immunity exhibits potential advantages over traditional parenteral immunity in that it stimulates immune defenses in mucosal and systemic tissues, which is important for reducing the burden of lung disease. However, obtaining a comprehensive understanding of the crosstalk between mucosal immunity and APC in the context of various lung diseases remains challenging. This mini-review aimed to elucidate the mechanisms of novel mucosal immunity, targeting APC action during lung infections, allergies, and malignant tumorigenesis. This minreview provides important insights into more effective therapeutic approaches for various lung diseases.

Investigation of powder properties and application aspects impacting nasal deposition of spray-dried powders in a nasal cast

In this study, spray-dried formulations differing in morphology (spherical and wrinkled), surface polarity (hydrophilic and hydrophobic), and size (20-30 µm and 3 µm) were evaluated in a nasal cast to assess their deposition profiles. The objective was to identify how formulation properties and application aspects influence the deposition profile. For this purpose, the formulations were administered at different application angles (45° and 60°), fill weights (20 mg and 40 mg), and airflow rates (0 L/min and 15 L/min) in conjunction with a UDS powder device. The results indicate a more posterior deposition profile for 45° compared to 60° due to increased deposition in the turbinate region; conversely, deposition profiles between fill weights were comparable. Application with simultaneous airflow should be avoided because of an increasing postnasal fraction. No influence of morphology could be observed, but for the surface polarity an influence was apparent, if the powder was applied with a simulated inspiration. In these cases, a hydrophobic formulation was better dispersible than a hydrophilic formulation, which led to an increased postnasal fraction. A particle size for pulmonary application demonstrated comparable results to nasal formulations with respect to the turbinate deposition but exhibited a high postnasal fraction for hydrophobic formulations.

Assessment of In Vitro Models of the Human Buccal Mucosa for Vaccine and Adjuvant Development

To understand requirements for immunization via the oral mucosa, an in vitro model that recapitulates the physical barrier of the mouth, allows for quantification of antigen uptake and permeability and mounts an inflammatory response to antigen and adjuvant is needed. The physical structure of 4 models of the human oral mucosa was determined by histochemical staining and transepithelial electrical resistance (TEER) measurements. A TR146 based air-liquid interface (ALI) model most closely mimicked in vivo conditions. This was confirmed by validation studies using dextran and caffeine as diffusant molecules. Apparent permeability coefficients (Papp) of adenovirus (Ad) and adeno-associated virus (AAV) in this model were 4.3 × 10-13 and 2.2 × 10-10 respectively, while 100% of the total dose of H1N1 influenza remained in the epithelial layer. Sodium glycocholate and a hyperosmotic formulation improved the amount of Ad (p = 0.02) and AAV (p = 0.003) that entered the epithelium, respectively. Significant amounts of IL-6 (45.1 pg/mL), GM-CSF (94.7 pg/mL) and IFN-γ (4.3 pg/mL) were produced in response to influenza infection. Treatment with an AS03-like adjuvant induced production of IL-6 (34.9 pg/mL), TNF-∝ (43 pg/mL), GM-CSF (121.2 pg/mL) and IFN-γ (14.1 pg/mL). This highlights the contribution of differentiated epithelial cells to the immune response to vaccines and adjuvants.

Targeted nasal delivery of LNP-mRNAs aerosolised by Rayleigh breakup technology

The nasal delivery of mRNA vaccines attracts great interests in both academia and industry. While the lipid nanoparticle (LNP)-mRNA complexes are vulnerable and need a subtle process for aerosolisation. In this study, a new nasal atomizer, based on the working rationale of Rayleigh breakup, was employed to aerosolise LNP-mRNAs. The data revealed no statistical differences in physiochemical properties before and after aerosolisation, strongly suggesting LNP-mRNAs be well preserved upon aerosolisation by Rayleigh breakup technology. Additionally, these Rayleigh breakup droplets showed a physical size of ∼25 µm in mean with a narrow size distribution (Span: 1.24) and demonstrated a large portion (70-80 % w/w) greater than 10 µm in aerodynamic diameter, strongly suggesting a predominate deposition in the upper airway and designating a great appropriateness for nasal drug delivery. Furthermore, the recently developed Alberta Idealized Nasal Inlet (AINI) was utilized to evaluate the regional nasal deposition of LNP-mRNA aerosols. It was demonstrated that, at the administration angle of 45°, the major deposition of mRNAs (>50 % w/w) was in the target region of turbinates. The inhalation airflow at 7.5 L/min can maximize the targeted delivery of mRNA (∼64 % w/w) and minimize the undesirable depositions in other segments. This study provides a new approach to aerosolise LNP-mRNAs with undisturbed stabilities for targeted nasal vaccine delivery.

Advancements in Nanoemulsion-Based Drug Delivery Across Different Administration Routes

Nanoemulsions (NEs) have emerged as effective drug delivery systems over the past few decades due to their multifaceted nature, offering advantages such as enhanced bioavailability, protection of encapsulated compounds, and low toxicity. In the present review, we focus on advancements in drug delivery over the last five years across (trans)dermal, oral, ocular, nasal, and intra-articular administration routes using NEs. Rational selection of components, surface functionalization, incorporation of permeation enhancers, and functionalization with targeting moieties are explored for each route discussed. Additionally, apart from NEs, we explore NE-based drug delivery systems (e.g., NE-based gels) while highlighting emerging approaches such as vaccination and theranostic applications. The growing interest in NEs for drug delivery purposes is reflected in clinical trials, which are also discussed. By summarizing the latest advances, exploring new strategies, and identifying critical challenges, this review focuses on developments for efficient NE-based therapeutic approaches.

Development of a predictive model for pediatric intranasal drug delivery with nasal sprays: Leveraging intersubject variability in anatomical dimensions, administration-related parameters, and airway patency

In this study, we examined the correlation between anatomical dimensions, spray administration parameters, pressure drop across 40 pediatric nasal cavities, and in vitro posterior drug delivery (PDD) using Nasacort ALLERGY 24HR and FLONASE SENSIMIST nasal suspensions sprays, with different nozzle and actuation designs. The importance of each parameter and their interaction in the outcome (PDD) was evaluated. To do so, initially we measured anatomical and administration-related parameters, and the pressure drop of each cavity. Afterwards, a stepwise regression method was used to find a combination of parameters that can effectively predict the outcome. Two strong correlations, r2 = 0.802 and 0.895, were found between a combination of three explored parameters and the PDD of Nasacort and Flonase Sensimist, respectively. While, based on the p-values, the insertion depth was found to be the most influential parameter for determining the PDD with Nasacort, and the administration coronal angle was found to be the most important one for Flonase Sensimist, anatomical parameters, or an interaction between anatomical and administration parameters were among the five most important parameters for both sprays. Furthermore, variable importance assessment, based on the variance of the response, demonstrated the tip-to-INV distance as the most important parameter for Nasacort and coronal angle for Flonase Sensimist, while cross sectional area at the end of the anterior piece was the only parameter that found to be in the three most important parameters for both sprays. Having this in mind, as well as the wide range of PDD within the pediatric population, it can be concluded that the performance of targeted intranasal drug delivery, even when using a set of patient-specific administration parameters, is strongly influenced by the anatomical features of the subject. Additionally, comparing the key factors in predicting PDD in pediatric and adult population for Flonase Sensimist demonstrate no similarity between the influential parameters on PDD in the two age groups, which further emphasizes the importance of airway anatomy.

Multilayer Adjuvanted Influenza Protein Nanoparticles Improve Intranasal Delivery and Antigen-Specific Immunity

Intranasal vaccination is a desired route for protection against influenza viruses by mucosal and systemic immunity. However, the nasal mucosa impedes the intranasal delivery of vaccines. Here, we formulated layer-by-layer (LBL) influenza vaccine nanoparticles for effective intranasal delivery by coating them with alternating mucoadhesive cationic chitosan and muco-inert anionic CpG adjuvants. The nanoparticle cores were formed by desolvating influenza M2e antigen and coating it with hemagglutinin (HA) antigen via biotin-streptavidin conjugation. LBL modification promoted nasal delivery and interaction with the resident immune cells. Intranasal administration with LBL nanoparticles significantly improved cellular and humoral immune responses against HA and M2e including high IgA titers, a hallmark of potent mucosal immunity and persistence of immune responses. Distinct trends for antigen-specific immune responses were observed for different routes of vaccination. The enhanced immune responses conferred mice protection against the influenza challenge and prominently reduced viral titers, demonstrating the effectiveness of intranasal LBL vaccine nanoparticles.

Bridging Gaps in Antibody Responses and Animal Welfare: Assessing Blood Collection Methods and Vaginal Immunity in Mice Immunized with Intranasal Gonococcal Vaccines

Assessing antibody titers and functional responses is essential for evaluating vaccine efficacy, yet the impact of blood collection methods on these immunological assessments remains unclear. Retro-orbital (RO) blood collection is commonly used but significant complications can occur. Increasingly, investigators have adopted alternative blood collection approaches, such as saphenous vein (SV) sampling to improve laboratory animal welfare. This study compared RO and SV sampling in the development of a Neisseria gonorrhoeae (Ng) vaccine, evaluating Adhesin Complex Protein (ACP) and multiple transferable resistance (Mtr) E protein (MtrE) as antigen candidates. Epitope mapping revealed that ACP and MtrE possess multiple, highly accessible B-cell and T-cell epitope clusters, reinforcing their immunological potential. Following intranasal immunization with rACP, rACP+CpG, and rMtrE+CpG, we assessed the specificity, magnitude, kinetics, and functional quality of immune responses elicited by the immunization regimens. Out of 45 comparisons, only eight significant differences were detected in antibody titers, while the human serum bactericidal assays revealed no differences between RO and SV in antigen-immunized groups. However, antibodies elicited by rACP alone or ACP+CpG in SV samples restored 30.05% and 75.2% of human lysozyme hydrolytic activity compared to 19.3 and 59.9 % in RO, respectively suggesting that SV sampling may be more reliable for assessing functional antibody responses. Beyond its immunological advantages, SV sampling reduces stress, minimizes ocular trauma, and improves animal welfare, making it a viable alternative to RO collection. Given its widespread use in vaccine research, standardizing SV sampling could improve data reliability, ethical compliance, and translational relevance in preclinical studies.

Product and trial design considerations on the path towards a vaccine to combat opioid overdose

Opioid overdose deaths are an evolving public health emergency in the United States. Recent advancements in drug conjugate vaccine design and adjuvantation technologies have re-ignited interest in the potential clinical utility of opioid vaccination. Here we present the concept of fentanyl vaccination as a complementary strategy for opioid overdose prevention with a focus on vaccine safety, efficacy, and considerations for vaccine development and testing in early phase human clinical trials.

Discovery and development of INNA-051, a TLR2/6 agonist for the prevention of complications resulting from viral respiratory infections

Viral respiratory infection is associated with significant morbidity and mortality. The diversity of viruses implicated, coupled with their propensity for mutation, ignited an interest in host-directed antiviral therapies effective across a wide range of viral variants. Toll-like receptors (TLRs) are potential targets for the development of broad-spectrum antivirals given their central role in host immune defenses. Synthetic agonists of TLRs have been shown to boost protective innate immune responses against respiratory viruses. However, clinical success was hindered by short duration of benefit and/or induction of systemic adverse effects. INNA-051, a TLR2/6 agonist, is in development as an intranasal innate immune enhancer for prophylactic treatment in individuals at risk of complications resulting from respiratory viral infections. In vivo animal studies demonstrated the efficacy as prophylaxis against multiple viruses including SARS-CoV-2, influenza, and rhinovirus. Early clinical trials demonstrated an acceptable safety and tolerability profile. Intranasal delivery to the primary site of infection in humans induced a local innate host defense response characterized by innate immune cell infiltration into the nasal epithelium and activation and antiviral response genes. Taken together, the preclinical and clinical data on INNA-051 support further investigation of its use in community infection settings.

Mixed lipopeptide-based mucosal vaccine candidate induces cross-variant immunity and protects against SARS-CoV-2 infection in hamsters

The global dissemination of SARS-CoV-2 led to a worldwide pandemic in March 2020. Even after the official downgrading of the COVID-19 pandemic, infection with SARS-CoV-2 variants continues. The rapid development and deployment of SARS-CoV-2 vaccines helped to mitigate the pandemic to a great extent. However, the current vaccines are suboptimal; they elicit incomplete and short-lived protection and are ineffective against evolving virus variants. Updating the spike antigen according to the prevailing variant and repeated boosters is not the long-term solution. We have designed a lipopeptide-based, mucosal, pan-coronavirus vaccine candidate, derived from highly conserved and/or functional regions of the SARS-CoV-2 spike, nucleocapsid, and membrane proteins. Our studies demonstrate that the designed lipopeptides (LPMix) induced both cellular and humoral (mucosal and systemic) immune responses upon intranasal immunization in mice. Furthermore, the antibodies bound to the wild-type and mutated S proteins of SARS-CoV-2 variants of concern, including Alpha, Beta, Delta and Omicron, and also led to efficient neutralization in a surrogate viral neutralization assay. Our sequence alignment and 3-dimensional molecular modeling studies demonstrated that spike-derived epitopes, P1 and P2, are sequentially and/or structurally conserved among the SARS-CoV-2 variants. The addition of a novel mucosal adjuvant, heat-killed Caulobacter crescentus, to the lipopeptide vaccine significantly bolstered mucosal antibody responses. Finally, the lipopeptide-based intranasal vaccine demonstrated significant improvement in lung pathologies in a hamster model of SARS-CoV-2 infection. These studies are fundamentally important and open new avenues in the investigation of an innovative, broadly protective intranasal vaccine platform for SARS-CoV-2 and its variants.

Intranasal Immunization with Nasal Immuno-Inducible Sequence-Fused Antigens Elicits Antigen-Specific Antibody Production

Intranasal immunization is one of the most effective methods for eliciting lung mucosal immunity. Multiple intranasal immunization with bacterial polypeptide, termed as a modified PnxIIIA (MP3) protein, is known to elicit production of a specific antibody in mice. In this study, a nasal immuno-inducible sequence (NAIS) was designed to remove the antigenicity of the MP3 protein that can induce mucosal immunity by intranasal immunization, and was examined to induce antigen-specific antibodies against the fused bacterial thioredoxin (Trx) as a model antigen. A NAIS was modified and generated to remove a large number of predicted MHC (Major Histocompatibility Complex)-I and MHC-II binding sites in parent protein PnxIIIA and MP3 in order to reduce the number of antigen epitope sites. For comparative analysis, full-length NAIS291, NAIS230, and NAIS61 fused with Trx and 6× His tag and Trx-fused 6× His tag were used as antigen variants for the intranasal immunization of BALB/c mice every two weeks for three immunizations. Anti-Trx antibody titers in serum and bronchoalveolar lavage fluid (BALF) IgA obtained from NAIS291-fused Trx-immunized mice were significantly higher than those from Trx-immunized mice. The antibody titers against NAIS alone were significantly lower than those against Trx alone in the serum IgG, serum IgA, and BALF IgA. These results indicate that the NAIS contributes to antibody elicitation of the fused antigen as an immunostimulant in intranasal vaccination vaccines. The results indicate that the NAIS and target inactivated antigen fusions can be applied to intranasal vaccine systems.

Double-layered protein nanoparticles conjugated with truncated flagellin induce improved mucosal and systemic immune responses in mice

Influenza viral infection poses a severe risk to global public health. Considering the suboptimal protection provided by current influenza vaccines against circulating influenza A viruses, it is imperative to develop novel vaccine formulations to combat respiratory infections. Here, we report the development of an intranasally-administered, self-adjuvanted double-layered protein nanoparticle consisting of influenza nucleoprotein (NP) cores coated with hemagglutinin (HA) and a truncated form of bacterial flagellin (tFliC). Intranasal vaccination of these nanoparticles notably amplified both antigen-specific humoral and cellular immune responses in the systematic compartments. Elevated antigen-specific IgA and IgG levels in mucosal washes, along with increased lung-resident memory B cell populations, were observed in the respiratory system of the immunized mice. Furthermore, intranasal vaccination of tFliC-adjuvanted nanoparticles enhanced survival rates against homologous and heterologous H3N2 viral challenges. Intriguingly, mucosal slow delivery of the prime dose (by splitting the dose into 5 applications over 8 days) significantly enhanced germinal center reactions and effector T-cell populations in lung draining lymph nodes, therefore promoting the protective efficacy against heterologous influenza viral challenges compared to single-prime immunization. These findings highlight the potential of intranasal immunization with tFliC-adjuvanted protein nanoparticles to bolster mucosal and systemic immune responses, with a slow-delivery strategy offering a promising approach for combating influenza epidemics.

Mannose and Lactobionic Acid in Nasal Vaccination: Enhancing Antigen Delivery via C-Type Lectin Receptors

BACKGROUND/OBJECTIVES

Nasal vaccines are a promising strategy for enhancing mucosal immune responses and preventing diseases at mucosal sites by stimulating the secretion of secretory IgA, which is crucial for early pathogen neutralization. However, designing effective nasal vaccines is challenging due to the complex immunological mechanisms in the nasal mucosa, which must balance protection and tolerance against constant exposure to inhaled pathogens. The nasal route also presents unique formulation and delivery hurdles, such as the mucous layer hindering antigen penetration and immune cell access.

METHODS

This review focuses on cutting-edge approaches to enhance nasal vaccine delivery, particularly those targeting C-type lectin receptors (CLRs) like the mannose receptor and macrophage galactose-type lectin (MGL) receptor. It elucidates the roles of these receptors in antigen recognition and uptake by antigen-presenting cells (APCs), providing insights into optimizing vaccine delivery.

RESULTS

While a comprehensive examination of targeted glycoconjugate vaccine development is outside the scope of this study, we provide key examples of glycan-based ligands, such as lactobionic acid and mannose, which can selectively target CLRs in the nasal mucosa.

CONCLUSIONS

With the rise of new viral infections, this review aims to facilitate the design of innovative vaccines and equip researchers, clinicians, and vaccine developers with the knowledge to enhance immune defenses against respiratory pathogens, ultimately protecting public health.

DNA and RNA vaccines against tuberculosis: a scoping review of human and animal studies

Introduction

To comprehensively identify and provide an overview of in vivo or clinical studies of nucleic acids (NA)-based vaccines against TB we included human or animal studies of NA vaccines for the prevention or treatment of TB and excluded in vitro or in silico research, studies of microorganisms other than M. tuberculosis, reviews, letters, and low-yield reports.

Methods

We searched PubMed, Scopus, Embase, selected Web of Science and ProQuest databases, Google Scholar, eLIBRARY.RU, PROSPERO, OSF Registries, Cochrane CENTRAL, EU Clinical Trials Register, clinicaltrials.gov, and others through WHO International Clinical Trials Registry Platform Search Portal, AVMA and CABI databases, bioRxiv, medRxiv, and others through OSF Preprint Archive Search. We searched the same sources and Google for vaccine names (GX-70) and scanned reviews for references. Data on antigenic composition, delivery systems, adjuvants, and vaccine efficacy were charted and summarized descriptively.

Results

A total of 18,157 records were identified, of which 968 were assessed for eligibility. No clinical studies were identified. 365 reports of 345 animal studies were included in the review. 342 (99.1%) studies involved DNA vaccines, and the remaining three focused on mRNA vaccines. 285 (82.6%) studies used single-antigen vaccines, while 48 (13.9%) used multiple antigens or combinations with adjuvants. Only 12 (3.5%) studies involved multiepitope vaccines. The most frequently used antigens were immunodominant secretory antigens (Ag85A, Ag85B, ESAT6), heat shock proteins, and cell wall proteins. Most studies delivered naked plasmid DNA intramuscularly without additional adjuvants. Only 4 of 17 studies comparing NA vaccines to BCG after M. tuberculosis challenge demonstrated superior protection in terms of bacterial load reduction. Some vaccine variants showed better efficacy compared to BCG.

Systematic review registration

https://osf.io/, identifier F7P9G.

Influenza B Virus Vaccine Innovation through Computational Design

As respiratory pathogens, influenza B viruses (IBVs) cause a significant socioeconomic burden each year. Vaccine and antiviral development for influenza viruses has historically viewed IBVs as a secondary concern to influenza A viruses (IAVs) due to their lack of animal reservoirs compared to IAVs. However, prior to the global spread of SARS-CoV-2, the seasonal epidemics caused by IBVs were becoming less predictable and inducing more severe disease, especially in high-risk populations. Globally, researchers have begun to recognize the need for improved prevention strategies for IBVs as a primary concern. This review discusses what is known about IBV evolutionary patterns and the effect of the spread of SARS-CoV-2 on these patterns. We also analyze recent advancements in the development of novel vaccines tested against IBVs, highlighting the promise of computational vaccine design strategies when used to target both IBVs and IAVs and explain why these novel strategies can be employed to improve the effectiveness of IBV vaccines.

Understanding Mucosal Physiology and Rationale of Formulation Design for Improved Mucosal Immunity

The oral and nasal cavities serve as critical gateways for infectious pathogens, with microorganisms primarily gaining entry through these routes. Our first line of defense against these invaders is the mucosal membrane, a protective barrier that shields the body's internal systems from infection while also contributing to vital functions like air and nutrient intake. One of the key features of this mucosal barrier is its ability to protect the physiological system from pathogens. Additionally, mucosal tolerance plays a crucial role in maintaining homeostasis by regulating the pH and water balance within the body. Recognizing the importance of the mucosal barrier, researchers have developed various mucosal formulations to enhance the immune response. Mucosal vaccines, for example, deliver antigens directly to mucosal tissues, triggering local immune stimulation and ultimately inducing systemic immunity. Studies have shown that lipid-based formulations such as liposomes and virosomes can effectively elicit both local and systemic immune responses. Furthermore, mucoadhesive polymeric particles, with their prolonged delivery to target sites, have demonstrated an enhanced immune response. This Review delves into the critical role of material selection and delivery approaches in optimizing mucosal immunity.

Intranasal Administration of Recombinant Newcastle Disease Virus Expressing SARS-CoV-2 Spike Protein Protects hACE2 TG Mice against Lethal SARS-CoV-2 Infection

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), emerged as a global outbreak in 2019, profoundly affecting both human health and the global economy. Various vaccine modalities were developed and commercialized to overcome this challenge, including inactivated vaccines, mRNA vaccines, adenovirus vector-based vaccines, and subunit vaccines. While intramuscular vaccines induce high IgG levels, they often fail to stimulate significant mucosal immunity in the respiratory system. We employed the Newcastle disease virus (NDV) vector expressing the spike protein of the SARS-CoV-2 Beta variant (rK148/beta-S), and evaluated the efficacy of intranasal vaccination with rK148/beta-S in K18-hACE2 transgenic mice. Intranasal vaccination with a low dose (106.0 EID50) resulted in an 86% survival rate after challenge with the SARS-CoV-2 Beta variant. Administration at a high dose (107.0 EID50) led to a reduction in lung viral load and 100% survival against the SARS-CoV-2 Beta and Delta variants. A high level of the SARS-CoV-2 spike-specific IgA was also induced in vaccinated mice lungs following the SARS-CoV-2 challenge. Our findings suggest that rK148/beta-S holds promise as an intranasal vaccine candidate that effectively induces mucosal immunity against SARS-CoV-2.

An intranasal attenuated Coxsackievirus B3 vaccine induces strong systemic and mucosal immunity against CVB3 lethal challenge

Coxsackievirus B3 (CVB3) triggers viral myocarditis, with no effective vaccine yet. This fecal-oral transmitted pathogen has prompted interest in mucosal immunization strategies to impede CVB3 spread. We developed a new attenuated vaccine strain, named CVB3(mu). The potential of CVB3(mu) to stimulate mucosal immune protection remains to be elucidated. This study evaluates the attenuation characteristics of CVB3(mu) via a rapid evolution cellular model and RNA sequencing. Its temperature sensitivity and safety were evaluated through in vitro and in vivo experiments. The mucosal immunity protection of CVB3(mu) was assessed via intranasal immunization in Balb/c mice. The results indicate that CVB3(mu) exhibits temperature sensitivity and forms smaller plaques. It sustains fewer genetic mutations and still possesses certain attenuated traits up to the 25th passage, in comparison to CVB3(WT). Intranasal immunization elicited a significant serum neutralizing antibodies, and a substantial sIgA response in nasal washes. In vivo trials revealed CVB3(mu) protection in adult mice and passive protection in suckling mice against lethal CVB3(WT) challenges. In conclusion, CVB3(mu), a live attenuated intranasal vaccine, provides protection involving humoral and mucosal immunity, making it a promising candidate to control CVB3 spread and infection.

Nanoparticle-Mediated Mucosal Vaccination: Harnessing Nucleic Acids for Immune Enhancement

Recent advancements in in vitro transcribed mRNA (IVT-mRNA) vaccine manufacturing have attracted considerable interest as advanced methods for combating viral infections. The respiratory mucosa is a primary target for pathogen attack, but traditional intramuscular vaccines are not effective in generating protective ion mucosal surfaces. Mucosal immunization can induce both systemic and mucosal immunity by effectively eliminating microorganisms before their growth and development. However, there are several biological and physical obstacles to the administration of genetic payloads, such as IVT-mRNA and DNA, to the pulmonary and nasal mucosa. Nucleic acid vaccine nanocarriers should effectively protect and load genetic payloads to overcome barriers i.e., biological and physical, at the mucosal sites. This may aid in the transfection of specific antigens, epithelial cells, and incorporation of adjuvants. In this review, we address strategies for delivering genetic payloads, such as nucleic acid vaccines, that have been studied in the past and their potential applications.

Nanocarriers of antigen proteins for vaccine delivery

Nanoformulations in vaccinology provide antigen stability and enhanced immunogenicity, in addition to providing targeted delivery and controlled release. In the last years, much research has been focused on vaccine development using virus-like particles, liposomes, emulsions, polymeric, lipid, and inorganic nanoparticles. Importantly, nanoparticle interactions with innate and adaptive immune systems must be clearly understood to guide the rational development of nanovaccines. This review provides a recap and updates on different aspects advocating nanoparticles as promising antigen carriers and immune cell activators for vaccination. Moreover, it offers a discussion of how the physicochemical properties of nanoparticles are modified to target specific cells and improve vaccine efficacy.

Nano-Assembled Polyphosphazene Delivery System Enables Effective Intranasal Immunization with Nipah Virus Subunit Vaccine

The ultimate vaccine against infections caused by Nipah virus should be capable of providing protection at the respiratory tract─the most probable port of entry for this pathogen. Intranasally delivered vaccines, which target nasal-associated lymphoid tissue and induce both systemic and mucosal immunity, are attractive candidates for enabling effective vaccination against this lethal disease. Herein, the water-soluble polyphosphazene delivery vehicle assembles into nanoscale supramolecular constructs with the soluble extracellular portion of the Hendra virus attachment glycoprotein─a promising subunit vaccine antigen against both Nipah and Hendra viruses. These supramolecular constructs signal through Toll-like receptor 7/8 and promote binding interactions with mucin─an important feature of effective mucosal adjuvants. High mass contrast of phosphorus-nitrogen backbone of the polymer enables a successful visualization of nanoconstructs in their vitrified state by cryogenic electron microscopy. Here, we characterize the self-assembly of polyphosphazene macromolecule with biologically relevant ligands by asymmetric flow field flow fractionation, dynamic light scattering, fluorescence spectrophotometry, and turbidimetric titration methods. Furthermore, a polyphosphazene-enabled intranasal Nipah vaccine candidate demonstrates the ability to induce immune responses in hamsters and shows superiority in inducing total IgG and neutralizing antibodies when benchmarked against the respective clinical stage alum adjuvanted vaccine. The results highlight the potential of polyphosphazene-enabled nanoassemblies in the development of intranasal vaccines.

Advances in nano-based drug delivery systems for the management of cytokine influx-mediated inflammation in lung diseases

Asthma, lung cancer, cystic fibrosis, tuberculosis, acute respiratory distress syndrome, chronic obstructive pulmonary disease, and COVID-19 are few examples of inflammatory lung conditions that cause cytokine release syndrome. It can initiate a widespread inflammatory response and may activate several inflammatory pathways that cause multiple organ failures leading to increased number of deaths and increased prevalence rates around the world. Nanotechnology-based therapeutic modalities such as nanoparticles, liposomes, nanosuspension, monoclonal antibodies, and vaccines can be used in the effective treatment of inflammatory lung diseases at both cellular and molecular levels. This would also help significantly in the reduction of patient mortality. Therefore, nanotechnology could be a potent platform for repurposing current medications in the treatment of inflammatory lung diseases. The aim and approach of this article are to highlight the clinical manifestations of cytokine storm in inflammatory lung diseases along with the advances and potential applications of nanotechnology-based therapeutics in the management of cytokine storm. Further in-depth studies are required to understand the molecular pathophysiology, and how nanotechnology-based therapeutics can help to effectively combat this problem.

Effects of Nozzle Retraction Elimination on Spray Distribution in Middle-Posterior Turbinate Regions: A Comparative Study

The standard multi-dose nasal spray pump features an integrated actuator and nozzle, which inevitably causes a retraction of the nozzle tip during application. The retraction stroke is around 5.5 mm and drastically reduces the nozzle's insertion depth, which further affects the initial nasal spray deposition and subsequent translocation, potentially increasing drug wastes and dosimetry variability. To address this issue, we designed a new spray pump that separated the nozzle from the actuator and connected them with a flexible tube, thereby eliminating nozzle retraction during application. The objective of this study is to test the new device's performance in comparison to the conventional nasal pump in terms of spray generation, plume development, and dosimetry distribution. For both devices, the spray droplet size distribution was measured using a laser diffraction particle analyzer. Plume development was recorded with a high-definition camera. Nasal dosimetry was characterized in two transparent nasal cavity casts (normal and decongested) under two breathing conditions (breath-holding and constant inhalation). The nasal formulation was a 0.25% w/v methyl cellulose aqueous solution with a fluorescent dye. For each test case, the temporospatial spray translocation in the nasal cavity was recorded, and the final delivered doses were quantified in five nasal regions. The results indicate minor differences in droplet size distribution between the two devices. The nasal plume from the new device presents a narrower plume angle. The head orientation, the depth at which the nozzle is inserted into the nostril, and the administration angle play crucial roles in determining the initial deposition of nasal sprays as well as the subsequent translocation of the liquid film/droplets. Quantitative measurements of deposition distributions in the nasal models were augmented with visualization recordings to evaluate the delivery enhancements introduced by the new device. With an extension tube, the modified device produced a lower spray output and delivered lower doses in the front, middle, and back turbinate than the conventional nasal pump. However, sprays from the new device were observed to penetrate deeper into the nasal passages, predominantly through the middle-upper meatus. This resulted in consistently enhanced dosing in the middle-upper turbinate regions while at the cost of higher drug loss to the pharynx.

Vaccine Strategies to Elicit Mucosal Immunity

Vaccines are essential tools to prevent infection and control transmission of infectious diseases that threaten public health. Most infectious agents enter their hosts across mucosal surfaces, which make up key first lines of host defense against pathogens. Mucosal immune responses play critical roles in host immune defense to provide durable and better recall responses. Substantial attention has been focused on developing effective mucosal vaccines to elicit robust localized and systemic immune responses by administration via mucosal routes. Mucosal vaccines that elicit effective immune responses yield protection superior to parenterally delivered vaccines. Beyond their valuable immunogenicity, mucosal vaccines can be less expensive and easier to administer without a need for injection materials and more highly trained personnel. However, developing effective mucosal vaccines faces many challenges, and much effort has been directed at their development. In this article, we review the history of mucosal vaccine development and present an overview of mucosal compartment biology and the roles that mucosal immunity plays in defending against infection, knowledge that has helped inform mucosal vaccine development. We explore new progress in mucosal vaccine design and optimization and novel approaches created to improve the efficacy and safety of mucosal vaccines.

Strategies for the development and approval of COVID-19 vaccines and therapeutics in the post-pandemic period

The spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in significant casualties and put immense strain on public health systems worldwide, leading to economic recession and social unrest. In response, various prevention and control strategies have been implemented globally, including vaccine and drug development and the promotion of preventive measures. Implementing these strategies has effectively curbed the transmission of the virus, reduced infection rates, and gradually restored normal social and economic activities. However, the mutations of SARS-CoV-2 have led to inevitable infections and reinfections, and the number of deaths continues to rise. Therefore, there is still a need to improve existing prevention and control strategies, mainly focusing on developing novel vaccines and drugs, expediting medical authorization processes, and keeping epidemic surveillance. These measures are crucial to combat the Coronavirus disease (COVID-19) pandemic and achieve sustained, long-term prevention, management, and disease control. Here, we summarized the characteristics of existing COVID-19 vaccines and drugs and suggested potential future directions for their development. Furthermore, we discussed the COVID-19-related policies implemented over the past years and presented some strategies for the future.

Mucosal and systemic immune responses after a single intranasal dose of nanoparticle and spore-based subunit vaccines in mice with pre-existing lung mycobacterial immunity

Tuberculosis (TB) is a major global health threat that claims more than one million lives annually. With a quarter of the global population harbouring latent TB, post-exposure vaccination aimed at high-risk populations that could develop active TB disease would be of great public health benefit. Mucosal vaccination is an attractive approach for a predominantly lung disease like TB because it elicits both local and systemic immunity. However, the immunological consequence of mucosal immunisation in the presence of existing lung immunity remains largely unexplored. Using a mycobacterial pre-exposure mouse model, we assessed whether pre-existing mucosal and systemic immune responses can be boosted and/or qualitatively altered by intranasal administration of spore- and nanoparticle-based subunit vaccines. Analysis of lung T cell responses revealed an increasing trend in the frequency of important CD4 and CD8 T cell subsets, and T effector memory cells with a Th1 cytokine (IFNγ and TNFα) signature among immunised mice. Additionally, significantly greater antigen specific Th1, Th17 and IL-10 responses, and antigen-induced T cell proliferation were seen from the spleens of immunised mice. Measurement of antigen-specific IgG and IgA from blood and bronchoalveolar lavage fluid also revealed enhanced systemic and local humoral immune responses among immunised animals. Lastly, peripheral blood mononuclear cells (PBMCs) obtained from the TB-endemic country of Mozambique show that individuals with LTBI showed significantly greater CD4 T cell reactivity to the vaccine candidate as compared to healthy controls. These results support further testing of Spore-FP1 and Nano-FP1 as post-exposure TB vaccines.

Transmucosal Delivery of Nasal Nanovaccines Enhancing Mucosal and Systemic Immunity

Intranasal vaccines can induce protective immune responses at the mucosa surface entrance, preventing the invasion of respiratory pathogens. However, the nasal barrier remains a major challenge in the development of intranasal vaccines. Herein, a transmucosal nanovaccine based on cationic fluorocarbon modified chitosan (FCS) is developed to induce mucosal immunity. In our system, FCS can self-assemble with the model antigen ovalbumin and TLR9 agonist CpG, effectively promoting the maturation and cross-presentation of dendritic cells. More importantly, it can enhance the production of secretory immunoglobin A (sIgA) at mucosal surfaces for those intranasally vaccinated mice, which in the meantime showed effective production of immunoglobulin G (IgG) systemically. As a proof-of-concept study, such a mucosal vaccine inhibits ovalbumin-expressing B16-OVA melanoma, especially its lung metastases. Our work presents a unique intranasal delivery system to deliver antigen across mucosal epithelia and promote mucosal and systemic immunity.

Mucosal Immunization Has Benefits over Traditional Subcutaneous Immunization with Group A Streptococcus Antigens in a Pilot Study in a Mouse Model

Group A Streptococcus (GAS) is a major human pathogen for which there is no licensed vaccine. To protect against infection, a strong systemic and mucosal immune response is likely to be necessary to prevent initial colonization and any events that might lead to invasive disease. A broad immune response will be necessary to target the varied GAS serotypes and disease presentations. To this end, we designed a representative panel of recombinant proteins to cover the stages of GAS infection and investigated whether mucosal and systemic immunity could be stimulated by these protein antigens. We immunized mice sublingually, intranasally and subcutaneously, then measured IgG and IgA antibody levels and functional activity through in vitro assays. Our results show that both sublingual and intranasal immunization in the presence of adjuvant induced both systemic IgG and mucosal IgA. Meanwhile, subcutaneous immunization generated only a serum IgG response. The antibodies mediated binding and killing of GAS cells and blocked binding of GAS to HaCaT cells, particularly following intranasal and subcutaneous immunizations. Further, antigen-specific assays revealed that immune sera inhibited cleavage of IL-8 by SpyCEP and IgG by Mac/IdeS. These results demonstrate that mucosal immunization can induce effective systemic and mucosal antibody responses. This finding warrants further investigation and optimization of humoral and cellular responses as a viable alternative to subcutaneous immunization for urgently needed GAS vaccines.

Liposome-based vaccines for minimally or noninvasive administration: an update on current advancements

INTRODUCTION

Vaccination requires innovation to provide effective protection. Traditional vaccines have several drawbacks, which can be overcome with advanced technologies and different administration routes. Over the past 10  years, a significant amount of research has focussed on the delivery of antigens into liposomes due to their dual role as antigen-carrying systems and vaccine adjuvants able to increase the immunogenicity of the carried antigen.

AREAS COVERED

This review encompasses the progress made over the last 10  years with liposome-based vaccines designed for minimally or noninvasive administration, filling the gaps in previous reviews and providing insights on composition, administration routes, results achieved, and Technology Readiness Level of the most recent formulations.

EXPERT OPINION

Liposome-based vaccines administered through minimally or noninvasive routes are expected to improve efficacy and complacency of vaccination programs. However, the translation from lab-scale production to large-scale production and collaborations with hospitals, research centers, and companies are needed to allow new products to enter the market and improve the vaccination programs in the future.