Nasal vaccines

Mucosal delivery of a prefusogenic-F, glycoprotein, and matrix proteins-based virus-like particle respiratory syncytial virus vaccine induces protective immunity as evidenced by challenge studies in mice

RSV infection remains a serious threat to the children all over the world, especially, in the low-middle income countries. Vaccine delivery via the mucosa holds great potential for inducing local immune responses in the respiratory tract. Previously, we reported the development of highly immunogenic RSV virus-like-particles (RSV-VLPs) based on the conformationally stable prefusogenic-F protein (preFg), glycoprotein and matrix protein. Here, to explore whether mucosal delivery of RSV-VLPs is an effective strategy to induce RSV-specific mucosal and systemic immunity, RSV-VLPs were administered via the nasal, sublingual and pulmonary routes to BALB/c mice. The results demonstrate that immunization with the VLPs via the mucosal routes induced minimal mucosal response and yet facilitated modest levels of serum IgG antibodies, enhanced T cell responses and the expression of the lung-homing marker CXCR3 on splenocytes. Immunization with VLPs via all three mucosal routes provided protection against RSV challenge with no signs of RSV induced pathology.

Evaluation of Efficacy of Surface Coated versus Encapsulated Influenza Antigens in Mannose-Chitosan Nanoparticle-Based Intranasal Vaccine in Swine

This study focuses on the development and characterization of an intranasal vaccine platform using adjuvanted nanoparticulate delivery of swine influenza A virus (SwIAV). The vaccine employed whole inactivated H1N2 SwIAV as an antigen and STING-agonist ADU-S100 as an adjuvant, with both surface adsorbed or encapsulated in mannose-chitosan nanoparticles (mChit-NPs). Optimization of mChit-NPs included evaluating size, zeta potential, and cytotoxicity, with a 1:9 mass ratio of antigen to NP demonstrating high loading efficacy and non-cytotoxic properties suitable for intranasal vaccination. In a heterologous H1N1 pig challenge trial, the mChit-NP intranasal vaccine induced cross-reactive sIgA antibodies in the respiratory tract, surpassing those of a commercial SwIAV vaccine. The encapsulated mChit-NP vaccine induced high virus-specific neutralizing antibody and robust cellular immune responses, while the adsorbed vaccine elicited specific high IgG and hemagglutinin inhibition antibodies. Importantly, both the mChit-NP vaccines reduced challenge heterologous viral replication in the nasal cavity higher than commercial swine influenza vaccine. In summary, a novel intranasal mChit-NP vaccine platform activated both the arms of the immune system and is a significant advancement in swine influenza vaccine design, demonstrating its potential effectiveness for pig immunization.

Characterizing regional drug delivery within the nasal airways

INTRODUCTION

The nose has been receiving increased attention as a route for drug delivery. As the site of deposition constitutes the first point of contact of the body with the drug, characterization of the regional deposition of intranasally delivered droplets or particles is paramount to formulation and device design of new products.

AREAS COVERED

This review article summarizes the recent literature on intranasal regional drug deposition evaluated in vivo, in vitro and in silico, with the aim of correlating parameters measured in vitro with formulation and device performance. We also highlight the relevance of regional deposition to two emerging applications: nose-to-brain drug delivery and intranasal vaccines.

EXPERT OPINION

As in vivo studies of deposition can be costly and time-consuming, researchers have often turned to predictive in vitro and in silico models. Variability in deposition is high due in part to individual differences in nasal geometry, and a complete predictive model of deposition based on spray characteristics remains elusive. Carefully selected or idealized geometries capturing population average deposition can be useful surrogates to in vivo measurements. Continued development of in vitro and in silico models may pave the way for development of less variable and more effective intranasal drug products.

Nasal delivery as a strategy for the prevention and treatment of COVID-19

INTRODUCTION

The upper respiratory tract is a major route of infection for COVID-19 and other respiratory diseases. Thus, it appears logical to exploit the nose as administration site to prevent, fight, or minimize infectious spread and treat the disease. Numerous nasal products addressing these aspects have been considered and developed for COVID-19.

AREAS COVERED

This review gives a comprehensive overview of the different approaches involving nasal delivery, i.e., nasal vaccination, barrier products, and antiviral pharmacological treatments that have led to products on the market or under clinical evaluation, highlighting the peculiarities of the nose as application and absorption site and pointing at key aspects of nasal drug delivery.

EXPERT OPINION

From the analysis of nasal delivery strategies to prevent or fight COVID-19, it emerges that, especially for nasal immunization, formulations appear the same as originally designed for parenteral administration, leading to suboptimal results. On the other hand, mechanical barrier and antiviral products, designed to halt or treat the infection at early stage, have been proven effective but were rarely brought to the clinics. If supported by robust and targeted product development strategies, intranasal immunization and drug delivery can represent valid and sometimes superior alternatives to more conventional parenteral and oral medications.

Feasibility of intranasal delivery of thin-film freeze-dried, mucoadhesive vaccine powders

Intranasal vaccination by directly applying a vaccine dry powder is appealing. However, a method that can be used to transform a vaccine from a liquid to a dry powder and a device that can be used to administer the powder to the desired region(s) of the nasal cavity are critical for successful intranasal vaccination. In the present study, using a model vaccine that contains liposomal monophosphoryl lipid A and QS-21 adjuvant (AdjLMQ) and ovalbumin (OVA) as a model antigen, it was shown that thin-film freeze-drying can be applied to convert the liquid vaccine containing sucrose at a sucrose to lipid ratio of 15:1 (w/w) into dry powders, in the presence or absence of carboxymethyl cellulose sodium salt (CMC) as a mucoadhesive agent. Ultimately, the thin-film freeze-dried AdjLMQ/OVA vaccine powder containing 1.9% (w/w) of CMC (i.e., TFF AdjLMQ/OVA/CMC_1.9% powder) was selected for additional evaluation because the TFF AdjLMQ/OVA/CMC_1.9% powder was mucoadhesive and maintained the integrity of the antigen and the physical properties of the vaccine. Compared to the TFF AdjLMQ/OVA powder that did not contain CMC, the TFF AdjLMQ/OVA/CMC_1.9% powder had a lower moisture content and a higher glass transition temperature. In addition, the TFF AdjLMQ/OVA/CMC_1.9% thin films were relatively thicker than the TFF AdjLMQ/OVA thin films without CMC. When sprayed with Aptar Pharma's Unidose Powder Nasal Spray System (UDSP), the TFF AdjLMQ/OVA powder and the TFF AdjLMQ/OVA/CMC_1.9% powder generated similar particle size distribution curves, spray patterns, and plume geometries. Importantly, after the TFF AdjLMQ/OVA/CMC_1.9% powder was sprayed with the UDSP nasal device, the integrity of the OVA antigen and the AdjLMQ liposomes did not change. Finally, a Taguchi L4 orthogonal array was applied to identify the optimal parameters for using the UDSP device to deliver the TFF AdjLMQ/OVA/CMC_1.9% vaccine powder to the middle and lower turbinate and the nasopharynx regions in both adult and child nasal replica casts. Results from this study showed that it is feasible to apply the TFF technology to transform a nasal vaccine candidate from liquid to a dry powder and then use the UDSP nasal device to deliver the TFF vaccine powder to the desired regions in the nasal cavity for intranasal vaccination.

In Vitro Comparison of Local Nasal Vaccine Delivery and Correlation with Device Spray Performance

PURPOSE

This study is the first vaccine candidate in vitro investigation with a focus on finding a correlation between the spray characteristics and the delivery efficiency of the local deposition in the nasal airways of infants under 24 months using various intranasal devices.

METHODS

In vitro tests were developed to measure the spray characteristics of four intranasal delivery devices and how they regionally deliver a candidate vaccine formulation matrix in five nasal airway replicas (3 to 24 months). The correlation between the spray performance, geometric parameters, and delivery efficiency were assessed.

RESULTS

All four devices performed consistently in terms of spray characteristics and were capable of delivering a high percentage of the candidate vaccine to the target areas, with a minimum delivery efficiency of 80%. Moreover, the delivery efficiency was affected by either the spray droplet size distribution or the distance between the nozzle tip and the internal nasal valve. Correlations between the spray performance and the in vitro local dose deposition were established.

CONCLUSION

The infant nasal model tests can be complementary to device spray performance evaluation. In the absence of in vivo correlations, they can also facilitate the process of new product development by estimating delivery a priori.

Facile synthesis of multi-faceted, biomimetic and cross-protective nanoparticle-based vaccines for drug-resistant Shigella: a flexible platform technology

BACKGROUND

No commercial vaccines are available against drug-resistant Shigella due to serotype-specific/narrow-range of protection. Nanoparticle-based biomimetic vaccines involving stable, conserved, immunogenic proteins fabricated using facile chemistries can help formulate a translatable cross-protective Shigella vaccine. Such systems can also negate cold-chain transportation/storage thus overcoming challenges prevalent in various settings.

METHODS

We explored facile development of biomimetic poly (lactide-co-glycolide)/PLGA 50:50 based nanovaccines (NVs), encapsulating conserved stabilized antigen(s)/immunostimulant of S. dysenteriae 1 origin surface-modified using simple chemistries. All encapsulants (IpaC/IpaB/LPS) and nanoparticles (NPs)-bare and modified (NV), were thoroughly characterized. Effect of IpaC on cellular uptake of NPs was assessed in-vitro. Immunogenicity of the NVs was assessed in-vivo in BALB/c mice by intranasal immunization. Cross-protective efficacy was assessed by intraperitoneally challenging the immunized groups with a high dose of heterologous S. flexneri 2a and observing for visible diarrhea, weight loss and survival. Passive-protective ability of the simplest NV was assessed in the 5-day old progeny of vaccinated mice.

RESULTS

All the antigens and immunostimulant to be encapsulated were successfully purified and found to be stable both before and after encapsulation into NPs. The ~ 300 nm sized NPs with a zeta potential of ~ - 25 mV released ~ 60% antigen by 14th day suggesting an appropriate delivery kinetics. The NPs could be successfully surface-modified with IpaC and/or CpG DNA. In vitro experiments revealed that the presence of IpaC can significantly increase cellular uptake of NPs. All NVs were found to be cytocompatible and highly immunogenic. Antibodies in sera of NV-immunized mice could recognize heterologous Shigella. Immunized sera also showed high antibody and cytokine response. The immunized groups were protected from diarrhea and weight loss with ~ 70-80% survival upon heterologous Shigella challenge. The simplest NV showed ~ 88% survival in neonates.

CONCLUSIONS

Facile formulation of biomimetic NVs can result in significant cross-protection. Further, passive protection in neonates suggest that parental immunization could protect infants, the most vulnerable group in context of Shigella infection. Non-invasive route of vaccination can also lead to greater patient compliance making it amenable for mass-immunization. Overall, our work contributes towards a yet to be reported platform technology for facile development of cross-protective Shigella vaccines.

Spray dried powders for nasal delivery: Process and formulation considerations

Powders for nasal delivery have been recognized as advantageous dosage forms over liquids due to increased stability and residence time on nasal mucosa, with improved bioavailability. They can be manufactured by spray-drying, allowing the optimization of the particle properties that are critical to guarantee nasal deposition, as size and shape. It is also a scalable and flexible method already explored extensively in the pharmaceutical industry. However, it is important to understand how process parameters, particle physical properties and formulation considerations affect the product performance. Hence, this review aims to provide an overview of nasal powder formulation and processing through spray drying, with an emphasis on the variables that impact on performance. To this purpose, we describe the physical, biological and pharmacological phenomena prior to drug absorption as well as the most relevant powder properties. Formulation considerations including qualitative and quantitative composition are then reviewed, as well as manufacturing considerations including spray drying relevant parameters.

Recent Patents on Nasal Vaccines Containing Nanoadjuvants

Vaccines are one of the greatest medical achievements of modern medicine. The nasal mucosa represents an effective route of vaccination for both mucosal immunity and peripheral, being at the same time an inductive and effector site of immunity. In this paper, the innovative and patented compositions and manufacturing procedures of nanomaterials have been studied using the peerreviewed research literature. Nanomaterials have several properties that make them unique as adjuvant for vaccines. Nanoadjuvants through the influence of antigen availability over time affect the immune response. Namely, the amount of antigen reaching the immune system or its release over prolonged periods of time can be effectively increased by nanoadjuvants. Mucosal vaccines are an interesting alternative for immunization of diseases in which pathogens access the body through these epithelia. Nanometric adjuvants are not only a viable approach to improve the efficacy of nasal vaccines but in most of the cases they represent the core of the intellectual property related to the innovative vaccine.

Nasal vaccine as a booster shot: a viable solution to restrict pandemic?

The coronavirus disease 2019 (COVID-19) pandemic revolutionized the vaccine market and initiated the momentum for alternative routes of administration for vaccines. The intranasal route of immunization is one such possibility that appears to be the most promising since it has some significant advantages, particularly in the prevention of respiratory infection. To analyze and summarize the role of nasal vaccines over conventional vaccines during COVID-19 and the need for the nasal vaccine as a booster shot. In this narrative review, the required data was retrieved using keywords “COVID-19,” “Intranasal,” “Immunity,” “Nasal spray,” and “Mucosal” in databases including PubMed, Scopus, Embase, Science Direct, and Web of Sciences. The results of the study showed that the nasal vaccines were both effective and protective according to the current researches approaching during the COVID-19 period and the preclinical and clinical phase trials prove the intranasal vaccination elicits more robust and cross-protective immunity than conventional vaccines. In this narrative review article, mechanisms across the nasal mucosa will be briefly presented and the current status of nasal vaccines during the COVID-19 pandemic is summarized, and advantages over traditional vaccines are provided. Furthermore, after exploring the primary benefits and kinetics of nasal vaccine, the potential for consideration of nasal vaccine as a booster dose is also discussed.

Gold-Nanostar-Chitosan-Mediated Delivery of SARS-CoV-2 DNA Vaccine for Respiratory Mucosal Immunization: Development and Proof-of-Principle

The COVID-19 pandemic is caused by the coronavirus SARS-CoV-2 (SC2). A variety of anti-SC2 vaccines have been approved for human applications, including those using messenger RNA (mRNA), adenoviruses expressing SC2 spike (S) protein, and inactivated virus. The protective periods of immunization afforded by these intramuscularly administered vaccines are currently unknown. An alternative self-administrable vaccine capable of mounting long-lasting immunity via sterilizing neutralizing antibodies would be hugely advantageous in tackling emerging mutant SC2 variants. This could also diminish the possibility of vaccinated individuals acting as passive carriers of COVID-19. Here, we investigate the potential of an intranasal (IN)-delivered DNA vaccine encoding the S protein of SC2 in BALB/c and C57BL/6J immunocompetent mouse models. The immune response to IN delivery of this SC2-spike DNA vaccine transported on a modified gold-chitosan nanocarrier shows a strong and consistent surge in antibodies (IgG, IgA, and IgM) and effective neutralization of pseudoviruses expressing S proteins of different SC2 variants (Wuhan, beta, and D614G). Immunophenotyping and histological analyses reveal chronological events involved in the recognition of SC2 S antigen by resident dendritic cells and alveolar macrophages, which prime the draining lymph nodes and spleen for peak SC2-specific cellular and humoral immune responses. The attainable high levels of anti-SC2 IgA in lung mucosa and tissue-resident memory T cells can efficiently inhibit SC2 and its variants at the site of entry and also provide long-lasting immunity.

Intranasal vaccine: Factors to consider in research and development

Most existing vaccines for human use are administered by needle-based injection. Administering vaccines needle-free intranasally has numerous advantages over by needle-based injection, but there are only a few intranasal vaccines that are currently approved for human use, and all of them are live attenuated influenza virus vaccines. Clearly, there are immunological as well as non-immunological challenges that prevent vaccine developers from choosing the intranasal route of administration. We reviewed current approved intranasal vaccines and pipelines and described the target of intranasal vaccines, i.e. nose and lymphoid tissues in the nasal cavity. We then analyzed factors unique to intranasal vaccines that need to be considered when researching and developing new intranasal vaccines. We concluded that while the choice of vaccine formulations, mucoadhesives, mucosal and epithelial permeation enhancers, and ligands that target M-cells are important, safe and effective intranasal mucosal vaccine adjuvants are needed to successfully develop an intranasal vaccine that is not based on live-attenuated viruses or bacteria. Moreover, more effective intranasal vaccine application devices that can efficiently target a vaccine to lymphoid tissues in the nasal cavity as well as preclinical animal models that can better predict intranasal vaccine performance in clinical trials are needed to increase the success rate of intranasal vaccines in clinical trials.

Self-assembled chitosan nanoparticles for intranasal delivery of recombinant protein interleukin-17 receptor C (IL-17RC): preparation and evaluation in asthma mice

Asthma is mentioned as a chronic airway inflammatory disease, whose pathogenesis is complicated. The promotion of inflammation in asthma by IL-17A and IL-17F has been confirmed. In addition to covalent homodimers, both cytokines are also able to form heterodimers, further inducing downstream pathways via binding to the IL-17RA and IL-17RC receptor complex. In recent years, IL-17RA and its signal transduction pathway have been extensively researched. IL-17RC, however, remains relatively unexplored. In the present study, we self-assembled chitosan (CS) nanoparticles for intranasal delivery of recombinant protein IL-17RC (rIL-17RC) and preliminarily investigated its effect on a murine model of allergic asthma induced by ovalbumin (OVA). rIL-17RC was produced by the prokaryotic expression system and encapsulated into the CS nanoparticles via ionic cross-linking technique. The results showed that CS-RC nanoparticles via intranasal intervention significantly caused inhibition of mucus secretion and airway inflammatory cell infiltration, and reduced IL-4, IL-17, IL-17F levels in BALF. Hence, delivering receptor proteins such as IL-17RC, through CS nanoparticles as a carrier, could be an attractive therapeutic intervention for asthma.

Nasal vaccination against SARS-CoV-2: Synergistic or alternative to intramuscular vaccines?

It is striking that all marketed SARS-CoV-2 vaccines are developed for intramuscular administration designed to produce humoral and cell mediated immune responses, preventing viremia and the COVID-19 syndrome. They have a high degree of efficacy in humans (70–95%) depending on the type of vaccine. However, little protection is provided against viral replication and shedding in the upper airways due to the lack of a local sIgA immune response, indicating a risk of transmission of virus from vaccinated individuals.

A range of novel nasal COVID-19 vaccines are in development and preclinical results in non-human primates have shown a promising prevention of replication and shedding of virus due to the induction of mucosal immune response (sIgA) in upper and lower respiratory tracts as well as robust systemic and humoral immune responses. Whether these results will translate to humans remains to be clarified. An IM prime followed by an IN booster vaccination would likely result in a better well-rounded immune response, including prevention (or strong reduction) in viral replication in the upper and lower respiratory tracts.

The influence of intranasal peste des petits ruminants (PPR) vaccine administration alone or with phytogenic mucoadhesive delivery system on PPR outbreak outcomes in goats

This study reports the influence of peste des petits ruminants (PPR) vaccination on the clinico-pathological outcomes of PPR in the face of an outbreak. Twenty-two West African dwarf goats procured for a different study started showing early signs of PPR during acclimatization. In response, PPR vaccine was administered either intranasally with phytogenic mucoadhesive gum (Group A; n = 6) or without gum (Group B; n = 6); subcutaneously (Group C; n = 6) or not vaccinated (Group D; n = 4) and studied for 21 days. The clinical scores, hematology, serology and pathology scores were evaluated. Clinical signs of PPR were present in all groups, presenting a percentage mortality of 33%; 33%; 64% and 100% for Groups A, B, C, and D, respectively. Polycythemia and mild leukopenia were observed in all groups, and all animals were seropositive by day 7 post-vaccination. The lung consolidation scores were low in Groups A and B, compared to Group C. Histopathological lesions consistent with PPR was observed in the lymphoid organs, gastrointestinal tract, and lungs with the presence of PPR antigen as detected by immunohistochemistry. The findings suggest that intranasal vaccination with or without mucoadhesive gum may influence the outcome of PPR infection more than the subcutaneous route in the face of an outbreak.

Development and in vivo evaluation of intranasal formulations of parathyroid hormone (1-34)

For efficient intranasal transport of parathyroid hormone (1-34) [PTH(1-34)], there is a great medical need to investigate permeation enhancers for intranasal formulations. In this study, the development of PTH(1-34) intranasal formulations was conducted. Based on conformation and chemical stability studies, the most preferable aqueous environment was determined to be 0.008 M acetate buffer solution (ABS). Subsequently, citric acid and Kolliphor^® HS·15 were compared as permeation enhancers. The mechanisms of action of citric acid and Kolliphor^® HS·15 were investigated using an in vitro model of nasal mucosa, and Kolliphor^® HS·15 led to higher permeability of fluorescein isothiocyanate-labeled PTH(1-34) (FITC-PTH) by enhancing both the transcellular and paracellular routes. Moreover, citric acid showed severe mucosal toxicity resulting in cilia shedding, while Kolliphor^® HS·15 did not cause obvious mucosa damage. Finally, Kolliphor^® HS·15 was studied as a permeation enhancer using a liquid chromatography tandem mass spectrometry (LC-MS/MS) method. The results showed that 5% and 10% Kolliphor^® HS·15 increased the bioavailability of PTH(1-34) to 14.76% and 30.87%, respectively. In conclusion, an effective and biosafe PTH(1-34) intranasal formulation was developed by using 10% Kolliphor^® HS·15 as a permeation enhancer. Intranasal formulations with higher concentrations of Kolliphor^® HS·15 for higher bioavailability of PTH(1-34) could be further researched.

Evaluation of Intranasal Vaccine Delivery Using Anatomical Replicas of Infant Nasal Airways

PURPOSE

Nasal delivery is a favorable route for vaccination against most respiratory infections, as antigen deposited in the nasal turbinate and Waldeyer's ring areas induce mucosal and systemic immune responses. However, little is known about the nasal distribution of the vaccines, specifically for infants.

METHODS

Anatomical nasal replicas of five subjects, 3-24 months, were developed to assess local intranasal vaccine delivery using MAD Nasal™ device, and understand impact of breathing conditions and administration parameters. High performance liquid chromatography was used to quantify the deposition pattern and determine the delivery efficiency.

RESULTS

The delivery efficiency on average for all models was found to be 86.57±14.23%. There were no significant differences in the total delivery efficiency between the models in all cases. However, the regional deposition pattern was altered based on the model and subsequent administration. Furthermore, removing the foam tip from the MAD Nasal™ device, to study the impact of insertion length, did not significantly increase the efficiency within the two models tested, 5- and 16-month.

CONCLUSION

Incorporating nasal replicas in testing provided a benchmark to determine the efficiency of a common intranasal vaccine delivery combination product. This proposed platform would allow comparing other potential nasal vaccine delivery devices.

Vaccine Based on Outer Membrane Vesicles Using Hydrogels as Vaccine Delivery System

A simple procedure for obtaining outer membrane vesicles from Salmonella enterica and the use of hydrogels as vaccine delivery system is described. A heat treatment in saline solution of whole bacteria rendered the release of outer membrane vesicles containing relevant antigenic components. The immunogenicity of these antigens when administered by the intranasal route may be improved after embedment into hydrogels to increase residence half-time and thus activate the mucosal immune system.

Type IIb Heat Labile Enterotoxin B Subunit as a Mucosal Adjuvant to Enhance Protective Immunity against H5N1 Avian Influenza Viruses

Human infections with highly pathogenic avian influenza H5N1 viruses persist as a major global health concern. Vaccination remains the primary protective strategy against H5N1 and other novel avian influenza virus infections. We investigated the use of E. coli type IIb heat labile enterotoxin B subunit (LTIIb-B5) as a mucosal adjuvant for intranasal immunizations with recombinant HA proteins against H5N1 avian influenza viruses. Use of LTIIb-B5 adjuvant elicited more potent IgG, IgA, and neutralizing antibody titers in both sera and bronchoalveolar lavage fluids, thus increasing protection against lethal virus challenges. LTIIb-B5 mucosal adjuvanticity was found to trigger stronger Th17 cellular response in spleen lymphocytes and cervical lymph nodes. Studies of anti-IL-17A monoclonal antibody depletion and IL-17A knockout mice also suggest the contribution from Th17 cellular response to anti-H5N1 protective immunity. Our results indicate a link between improved protection against H5N1 live virus challenges and increased Th17 response due to the use of LTIIb-B5 mucosal adjuvant with HA subunit proteins.

A spraying applicator device is not required for efficacy of a live intranasal respiratory vaccine in young calves, which improves user convenience

Almost all bovine intranasal respiratory vaccines require a spraying device, but there are no published reports which prove the necessity of this. The objective of this investigation was to compare the efficacy of the Bovilis® INtranasal RSP™ Live vaccine when applied with or without an (intra)nasal spraying device. This vaccine contains live, attenuated strains of bovine respiratory syncytial virus (BRSV) and bovine parainfluenza virus type 3 (BPI3V) and is licensed to protect young cattle against respiratory infections with wild-type field isolates of these viruses. Two efficacy studies, for BRSV and BPI3V respectively, were performed in which the vaccine was administered using a spraying device or directly from the tip of a syringe as a liquid stream. Both BRSV-vaccinated groups showed a reduction of nasal shedding, BRSV titres in lung washings and clinical symptoms. The BPI3V vaccinated groups showed a significant reduction of nasal shedding and a non-significant reduction of clinical symptoms. Overall, in both studies, the groups in which vaccine was administered without the spraying device performed better than the groups with the spraying device, although this difference was not statistically significant. In conclusion, a spraying device to administer Bovilis® INtranasal RSP™ Live was not required and both application methods induced a protective immune response. This makes application more convenient and flexible for future users and animals.

Chitosan nanoparticles as antigen vehicles to induce effective tumor specific T cell responses

Cancer vaccinations sensitize the immune system to recognize tumor-specific antigens de novo or boosting preexisting immune responses. Dendritic cells (DCs) are regarded as the most potent antigen presenting cells (APCs) for induction of (cancer) antigen-specific CD8+ T cell responses. Chitosan nanoparticles (CNPs) used as delivery vehicle have been shown to improve anti-tumor responses. This study aimed at exploring the potential of CNPs as antigen delivery system by assessing activation and expansion of antigen-specific CD8+ T cells by DCs and subsequent T cell-mediated lysis of pancreatic ductal adenocarcinoma (PDAC) cells. As model antigen the ovalbumin-derived peptide SIINFEKL was chosen. Using imaging cytometry, intracellular uptake of FITC-labelled CNPs of three different sizes and qualities (90/10, 90/20 and 90/50) was demonstrated in DCs and in pro- and anti-inflammatory macrophages to different extents. While larger particles (90/50) impaired survival of all APCs, small CNPs (90/10) were not toxic for DCs. Internalization of SIINFEKL-loaded but not empty 90/10-CNPs promoted a pro-inflammatory phenotype of DCs indicated by elevated expression of pro-inflammatory cytokines. Treatment of murine DC2.4 cells with SIINFEKL-loaded 90/10-CNPs led to a marked MHC-related presentation of SIINFEKL and enabled DC2.4 cells to potently activate SIINFEKL-specific CD8+ OT-1 T cells finally leading to effective lysis of the PDAC cell line Panc-OVA. Overall, our study supports the suitability of CNPs as antigen vehicle to induce potent anti-tumor immune responses by activation and expansion of tumor antigen-specific CD8+ T cells.

Intranasal Peste des petits ruminants virus vaccination of goats using Irvingia gabonensis gum as delivery system: hematological and humoral immune responses

Peste des petits ruminants (PPR) in Africa continues to defy conventional vaccinational approaches aimed at its control. There is need for route modification and immunopotentiation of the current vaccination methods, using easily affordable materials. This study evaluates the immunomodulatory potential of Irvingia gabonensis (IG) seed gum extract for intranasal PPR vaccination in goats using attenuated Nigeria 75/1 PPR vaccine. Twenty West African dwarf goats were divided into four groups (n=5). Group 1 was vaccinated intranasally using IG gum as vehicle; Group 2 was vaccinated intranasally without the gum; Group 3 via subcutaneous injection while Group 4 was not vaccinated. Hematology and Serum IgG levels were assessed weekly for 28 days post vaccination (dpv). H-PPR bELISA detected antibodies against PPR by 7th dpv, peaking by 21st dpv with mean percentage inhibitions of 78.2%; 69.6%; 87.0% and 0% in Groups 1, 2, 3 and 4, respectively. Also, significantly lower neutrophil to lymphocyte ratio (P<0.05) were observed by 14th dpv to 28th dpv in the vaccinated groups. The findings of this study show that the use of I. gabonensis seed gum extract for mucoadhesive intranasal PPR vaccine delivery has an immunomodulatory effect on the systemic immune response following PPR intranasal vaccine administration.

Cationic Polylactic Acid-Based Nanoparticles Improve BSA-FITC Transport Across M Cells and Engulfment by Porcine Alveolar Macrophages

This work described the development of a cationic polylactic acid (PLA)-based nanoparticles (NPs) as an antigen delivery system using dimethyldioctadecylammonium bromide (DDA) to facilitate the engulfment of BSA-FITC by porcine alveolar macrophages (3D4/2 cells) and heat-labile enterotoxin subunit B (LTB) to enhance the transport of BSA-FITC across M cells. The experimental design methodology was employed to study the influence of PLA, polyvinyl alcohol (PVA), DDA, and LTB on the physical properties of the PLA-based NPs. The size of selected cationic PLA NPs comprising 5% PLA, 5% PVA, and 0.6% DDA with or without LTB absorption was range from 367 to 390 nm with a polydispersity index of 0.26, a zeta potential of + 26.00 to + 30.55 mV, and entrapment efficiency of 41.43%. Electron micrographs revealed NPs with spherical shape. The release kinetic of BSA from the NPs followed the Korsmeyer-Peppas kinetics. The cationic PLA NPs with LTB surface absorption showed 3-fold increase in BSA-FITC transported across M cells compared with the NPs without LTB absorption. The uptake studies demonstrated 2-fold increase in BSA-FITC intensity in 3D4/2 cells with cationic NPs as compared with anionic NPs. Overall, the results suggested that LTB decreased the retention time of BSA-FITC loaded in the cationic PLA NPs within the M cells, thus promoting the transport of BSA-FITC across the M cells, and cationic NPs composed of DDA help facilitate the uptake of BSA-FITC in the 3D4/2 cells. Further studies in pigs with respiratory antigens will provide information on the efficacy of cationic PLA NPs as a nasal antigen carrier system.

Prevention of influenza virus infection and transmission by intranasal administration of a porous maltodextrin nanoparticle-formulated vaccine

Influenza vaccines administered intramuscularly exhibit poor mucosal immune responses in the respiratory tract which is the prime site of the infection. Intranasal vaccination is a potential route for vaccine delivery which has been demonstrated effective in inducing protective immune responses in both systemic and mucosal compartments. For this purpose, nanoparticles have been used as antigen delivery systems to improve antigen capture by immune cells. In this paper we demonstrate efficient delivery of viral antigens to airway epithelial cells, macrophages and dendritic cells, using polysaccharide nanoparticles (NPL), leading to a strong protection against influenza virus infection. A formulation combining split Udorn virus antigens with NPL and the mucosal protein adjuvant CTA1-DD was administered intranasally and resulted in an enhanced specific humoral immune response. Furthermore, NPL carrying split Udorn, with or without CTA1-DD, inhibited virus transmission from infected to uninfected naive mice. These results demonstrate that an intranasal delivery system combining NPL, mucosal adjuvant CTA1-DD and split virus antigens confers robust protection against influenza infection and inhibits virus transmission.

Intranasal delivery system of bacterial antigen using thermosensitive hydrogels based on a Pluronic-Gantrez conjugate

Thermosensitive hydrogels have been studied as feasible needle-avoidance alternative to vaccine delivery. In this work, we report the development of a new thermal-sensitive hydrogel for intranasal vaccine delivery. This delivery system was formulated with a combination of the polymer Gantrez® AN119 and the surfactant Pluronic® F127 (PF127), with a high biocompatibility, biodegradability and immunoadjuvant properties. Shigella flexneri outer membrane vesicles were used as the antigen model. A stable and easy-to-produce thermosensitive hydrogel which allowed the incorporation of the OMV-antigenic complex was successfully synthetized. A rapid gel formation was achieved at body temperature, which prolonged the OMV-antigens residence time in the nasal cavity of BALB/c mice when compared to intranasal delivery of free-OMVs. In addition, the bacterial antigens showed a fast release profile from the hydrogel in vitro, with a peak at 30 min of incubation at 37 °C. Hydrogels appeared to be non-cytotoxic in the human epithelial HeLa cell line and nose epithelium as well, as indicated by the absence of histopathological features. Immunohistochemical studies revealed that after intranasal administration the OMVs reached the nasal associated lymphoid tissue. These results support the use of here described thermosensitive hydrogels as a potential platform for intranasal vaccination.

Nasal formulations for drug administration and characterization of nasal preparations in drug delivery

This special report gives an insight in the rationale of utilizing the nasal cavity for drug administration and the formulation as well as characterization of nasal preparations. As the nose is an easy-to-access, noninvasive and versatile location for absorption, this route of delivery will play an increasingly important role in future drug product development both for new and repurposed drugs. The nose can be utilized for local and systemic delivery including drug delivery to the central nervous system and the immune system. Typical formulation strategies and future developments are reviewed, which nowadays mostly comprise liquid formulations. Although they are straight forward to develop, a number of aspects from choice of solvent, osmolarity, pH, viscosity and more need to be considered, which determine formulation characteristics, not at least nasal deposition. Nasal powders offer higher stability and, along with more sophisticated nasal devices, may play a major role in the future.

Intranasal Nanoparticulate Systems as Alternative Route of Drug Delivery

There is always a need for alternative and efficient methods of drug delivery. The nasal cavity can be considered as a non-invasive and efficient route of administration. It has been used for local, systemic, brain targeting, and vaccination delivery. Although many intranasal products are currently available on the market, the majority is used for local delivery with fewer products available for the other targets. As nanotechnology utilization in drug delivery has rapidly spread out, the nasal delivery has become attractive as a promising approach. Nanoparticulate systems facilitate drug transportation across the mucosal barrier, protect the drug from nasal enzyme degradation, enhance the delivery of vaccines to the lymphoid tissue of the nasal cavity with an adjuvant activity, and offer a way for peptide delivery into the brain and the systemic circulation, in addition to their potential for brain tumor treatment. This review article aims at discussing the potential benefit of the intranasal nanoparticulate systems, including nanosuspensions, lipid and surfactant, and polymer-based nanoparticles as regards productive intranasal delivery. The aim of this review is to focus on the topicalities of nanotechnology applications for intranasal delivery of local, systemic, brain, and vaccination purposes during the last decade, referring to the factors affecting delivery, regulatory aspects, and patient expectations. This review further identifies the benefits of applying the Quality by Design approaches (QbD) in product development. According to the reported studies on nanotechnology-based intranasal delivery, potential attention has been focused on brain targeting and vaccine delivery with promising outcomes. Despite the significant research effort in this field, nanoparticle-based products for intranasal delivery are not available. Thus, further efforts are required to promote the introduction of intranasal nanoparticulate products that can meet the requirements of regulatory affairs with high patient acceptance.

Evaluation of the mucoadhesive strengths of Abelmoschus esculentus and Irvingia gabonensis gums for possible application in veterinary vaccine delivery: the effect of extraction methods

This study evaluates the effects of different gum extraction methods on the mucoadhesive strengths of Abelmoschus esculentus (AE) and Irvingia gabonensis (IG) gums and the release of vaccine antigen in vaccine-gum formulations. AE and IG gums were extracted employing previously documented methods with acetone or sodium chloride (NaCl) and either oven-dried or freeze-dried. Gum extracts were analyzed for mucoadhesive strengths using a modified rotational cylinder method on animal mucosa. The time taken to detach from the mucosa was taken as the Peak Adhesion Time (PAT). The gum extracts were charged with Peste des petits ruminant vaccine and the antigen release was evaluated using agar gel immunodiffusion technique. The means of the PATS were analyzed using Mann-whitney t-test at p < .05. The NaCl extracted and freeze-dried IG gum showed sustained mean PATs of 1766 ± 73 s; 2116 ± 101 s; 7044 ± 117 s, while the oven-dried IG gum and both AE gums showed short-lived average PATs. Vaccine-gum formulations of IG at ratios 2:1, 1:1 & 1:2 had strong positive reactions while only that of AE at 2:1 showed a strong positive reaction. This study shows that NaCl extracted and freeze-dried IG gum has immunomodulatory potential for mucoadhesive vaccine delivery in ruminants.

Evaluation of CpG-ODN-adjuvanted polyanhydride-based intranasal influenza nanovaccine in pigs

Influenza results in significant economic loss in the swine industry each year. A broadly protective swine influenza vaccine would have the dual benefit of protecting pigs from influenza A viruses (IAVs) and limiting their possible zoonotic transmission to humans. In this study, we developed polyanhydride nanoparticles-based swine influenza vaccine (KAg + CpG-nanovaccine) co-encapsulating inacticated/killed soluble antigen (KAg) and Toll-like receptor (TLR)-9 agonist (CpG-ODN). The immunogenicity and protective efficacy of KAg + CpG-nanovaccine was compared with KAg vaccine containing five-times greater quantity of antigens following heterologous virus challenge. Prime-boost intranasally delivered KAg + CpG-nanovaccine induced significantly higher levels of cross-reactive antigen-specific IgA antibody responses in the nasal cavity, greater lymphoproliferative response in peripheral blood mononuclear cells (PBMCs), and higher IFN-γ secretion during antigen-induced recall responses of PBMCs and tracheobronchial lymph nodes cells compared to those immunized with KAg alone. Importantly, KAg + CpG-nanovaccine provided better protective efficacy through a significant reduction in influenza-induced fever, 16-fold reduction of nasal virus shedding and 80-fold reduction in lung virus titers compared to those immunized with soluble KAg. Our results indicated that CpG-ODN-adjuvanted polyanhydride nanovaccine can induce higher mucosal antibody and cellular immune responses in pigs; and provide better protection as compared with intranasally delivered soluble KAg.

Mucosal Vaccination via the Respiratory Tract

Vaccine delivery via mucosal surfaces is an interesting alternative to parenteral vaccine administration, as it avoids the use of a needle and syringe. Mucosal vaccine administration also targets the mucosal immune system, which is the largest lymphoid tissue in the human body. The mucosal immune response involves systemic, antigen-specific humoral and cellular immune response in addition to a local response which is characterised by a predominantly cytotoxic T cell response in combination with secreted IgA. This antibody facilitates pathogen recognition and deletion prior to entrance into the body. Hence, administration via the respiratory mucosa can be favoured for all pathogens which use the respiratory tract as entry to the body, such as influenza and for all diseases directly affecting the respiratory tract such as pneumonia. Additionally, the different mucosal tissues of the human body are interconnected via the so-called “common mucosal immune system”, which allows induction of an antigen-specific immune response in distant mucosal sites. Finally, mucosal administration is also interesting in the area of therapeutic vaccination, in which a predominant cellular immune response is required, as this can efficiently be induced by this route of delivery. The review gives an introduction to respiratory vaccination, formulation approaches and application strategies.

Intranasal immunization with recombinant outer membrane protein A induces protective immune response against Stenotrophomonas maltophilia infection

Stenotrophomonas maltophilia (S. maltophilia), a multi-drug resistant opportunistic pathogen, is associated with nosocomial and community-acquired infections. Preventive and therapeutic strategies for such infections are greatly needed. In this study, sequence alignment analysis revealed that Outer membrane protein A (OmpA) was highly conserved among S. maltophilia strains but shared no significant similarity with human and mouse proteomes. In mice, intranasal immunization with S. maltophilia recombinant OmpA (rOmpA) without additional adjuvant induced sustained mucosal and systemic rOmpA-specific antibody responses. Treatment with rOmpA stimulated significantly higher levels of secretion of IFN-γ, IL-2, and IL-17A (All P<0.05) from the primary splenocytes isolated from rOmpA-immunized mice than from the primary splenocytes isolated from PBS-immunized mice. Furthermore, mice immunized with rOmpA showed significantly reduced bacterial burden in the lung and reduced levels of pro-inflammatory cytokines (TNF-α and IL-6) in bronchoalveolar lavage fluid (BALF) 24 hours after intranasal S. maltophilia infection, indicating that immunization with rOmpA may have protective effects against S. maltophilia challenge in mice. Our findings suggest that intranasal immunization with rOmpA may induce mucosal and systemic immune responses in mice, trigger Th1- and Th17-mediated cellular immune responses, and thus stimulate host immune defense against S. maltophilia infection. These results also demonstrate that intranasal vaccination may offer an alternative approach to current strategies since it induces a mucosal as well as a systemic immune response.

How to characterize a nasal product. The state of the art of in vitro and ex vivo specific methods

Nasal delivery offers many benefits over other conventional routes of delivery (e.g. oral or intravenous administration). Benefits include, among others, a fast onset of action, non-invasiveness and direct access to the central nervous system. The nasal cavity is not only limited to local application (e.g. rhinosinusitis) but can also provide direct access to other sites in the body (e.g. the central nervous system or systemic circulation). However, both the anatomy and the physiology of the nose impose their own limitations, such as a small volume for delivery or rapid mucociliary clearance. To meet nasal-specific criteria, the formulator has to complete a plethora of tests, in vitro and ex vivo, to assess the efficacy and tolerance of a new drug-delivery system. Moreover, depending on the desired therapeutic effect, the delivery of the drug should target a specific pathway that could potentially be achieved through a modified release of this drug. Therefore, this review focuses on specific techniques that should be performed when a nasal formulation is developed. The review covers both the tests recommended by regulatory agencies (e.g. the Food and Drug Administration) and other complementary experiments frequently performed in the field.

Intranasal immunization with aluminum salt-adjuvanted dry powder vaccine

Intranasal vaccination using dry powder vaccine formulation represents an attractive, non-invasive vaccination modality with better storage stability and added protection at the mucosal surfaces. Herein we report that it is feasible to induce specific mucosal and systemic antibody responses by intranasal immunization with a dry powder vaccine adjuvanted with an insoluble aluminum salt. The dry powder vaccine was prepared by thin-film freeze-drying of a model antigen, ovalbumin, adsorbed on aluminum (oxy)hydroxide as an adjuvant. Special emphasis was placed on the characterization of the dry powder vaccine formulation that can be realistically used in humans by a nasal dry powder delivery device. The vaccine powder was found to have "passable" to "good" flow properties, and the vaccine was uniformly distributed in the dry powder. An in vitro nasal deposition study using nasal casts of adult humans showed that around 90% of the powder was deposited in the nasal cavity. Intranasal immunization of rats with the dry powder vaccine elicited a specific serum antibody response as well as specific IgA responses in the nose and lung secretions of the rats. This study demonstrates the generation of systemic and mucosal immune responses by intranasal immunization using a dry powder vaccine adjuvanted with an aluminum salt.

Needle-Free Immunization with Chitosan-Based Systems

Despite successful use, needle-based immunizations have several issues such as the risk of injuries and infections from the reuse of needles and syringes and the low patient compliance due to pain and fear of needles during immunization. In contrast, needle-free immunizations have several advantages including ease of administration, high level of patient compliance and the possibility of mass vaccination. Thus, there is an increasing interest on developing effective needle-free immunizations via cutaneous and mucosal approaches. Here, we discuss several methods of needle-free immunizations and provide insights into promising use of chitosan systems for successful immunization.

Evaluation of a temperature-restricted, mucosal tuberculosis vaccine in guinea pigs

Tuberculosis (TB) is currently the leading cause of death in humans by a single infectious agent, Mycobacterium tuberculosis. The Bacillus Calmette-Guérin (BCG) vaccine prevents pulmonary TB with variable efficacy, but can cause life-threatening systemic infection in HIV-infected infants. In this study, TBvac85, a derivative of Mycobacterium shottsii expressing M. tuberculosis Antigen 85B, was examined as a safer alternative to BCG. Intranasal vaccination of guinea pigs with TBvac85, a naturally temperature-restricted species, resulted in serum Ag85B-specific IgG antibodies. Delivery of the vaccine by this route also induced protection equivalent to intradermal BCG based on organ bacterial burdens and lung pathology six weeks after aerosol challenge with M. tuberculosis strain Erdman. These results support the potential of TBvac85 as the basis of an effective TB vaccine. Next-generation derivatives expressing multiple M. tuberculosis immunogens are in development.

Nasal priming by a murine coronavirus provides protective immunity against lethal heterologous virus pneumonia

The nasal mucosa is an important component of mucosal immunity. Immunogenic particles in inspired air are known to activate the local nasal mucosal immune system and can lead to sinonasal inflammation; however, little is known about the effect of this activation on the lung immune environment. Here, we showed that nasal inoculation of murine coronavirus (CoV) in the absence of direct lung infection primes the lung immune environment by recruiting activated monocytes (Ly6C+ inflammatory monocytes) and NK cells into the lungs. Unlike infiltration of these cells into directly infected lungs, a process that requires type I IFN signaling, nasally induced infiltration of Ly6C+ inflammatory monocytes into the lungs is IFN-I independent. These activated macrophages ingested antigen and migrated to pulmonary lymph nodes, and enhanced both innate and adaptive immunity after heterologous virus infection. Clinically, such nasal-only inoculation of MHV-1 failed to cause pneumonia but significantly reduced mortality and morbidity of lethal pneumonia caused by severe acute respiratory syndrome CoV (SARS-CoV) or influenza A virus. Together, the data indicate that the nose and upper airway remotely prime the lung immunity to protect the lungs from direct viral infections.

Cow's Milk and Immune Function in the Respiratory Tract: Potential Mechanisms

During the last decades, the world has witnessed a dramatic increase in allergy prevalence. Epidemiological evidence shows that growing up on a farm is a protective factor, which is partly explained by the consumption of raw cow’s milk. Indeed, recent studies show inverse associations between raw cow’s milk consumption in early life and asthma, hay fever, and rhinitis. A similar association of raw cow’s milk consumption with respiratory tract infections is recently found. In line with these findings, controlled studies in infants with milk components such as lactoferrin, milk fat globule membrane, and colostrum IgG have shown to reduce respiratory infections. However, for ethical reasons, it is not possible to conduct controlled studies with raw cow’s milk in infants, so formal proof is lacking to date. Because viral respiratory tract infections and aeroallergen exposure in children may be causally linked to the development of asthma, it is of interest to investigate whether cow’s milk components can modulate human immune function in the respiratory tract and via which mechanisms. Inhaled allergens and viruses trigger local immune responses in the upper airways in both nasal and oral lymphoid tissue. The components present in raw cow’s milk are able to promote a local microenvironment in which mucosal immune responses are modified and the epithelial barrier is enforced. In addition, such responses may also be triggered in the gut after exposure to allergens and viruses in the nasal cavity that become available in the GI tract after swallowing. However, these immune cells that come into contact with cow’s milk components in the gut must recirculate into the blood and home to the (upper and lower) respiratory tract to regulate immune responses locally. Expression of the tissue homing-associated markers α4β7 and CCR9 or CCR10 on lymphocytes can be influenced by vitamin A and vitamin D3, respectively. Since both vitamins are present in milk, we speculate that raw milk may influence homing of lymphocytes to the upper respiratory tract. This review focuses on potential mechanisms via which cow’s milk or its components can influence immune function in the intestine and the upper respiratory tract. Unraveling these complex mechanisms may contribute to the development of novel dietary approaches in allergy and asthma prevention.

Naegleria fowleri immunization modifies lymphocytes and APC of nasal mucosa

We investigated whether intranasal immunization with amoebic lysates plus cholera toxin modified the populations of T and B lymphocytes, macrophages and dendritic cells by flow cytometry from nose-associated lymphoid tissue (NALT), cervical lymph nodes (CN), nasal passages (NP) and spleen (SP). In all immunized groups, the percentage of CD4 was higher than CD8 cells. CD45 was increased in B cells from mice immunized. We observed IgA antibody-forming cell (IgA-AFC) response, mainly in NALT and NP. Macrophages from NP and CN expressed the highest levels of CD80 and CD86 in N. fowleri lysates with either CT or CT alone immunized mice, whereas dendritic cells expressed high levels of CD80 and CD86 in all compartment from immunized mice. These were lower than those expressed by macrophages. Only in SP from CT-immunized mice, these costimulatory molecules were increased. These results suggest that N. fowleri and CT antigens are taking by APCs, and therefore, protective immunity depends on interactions between APCs and T cells from NP and CN. Consequently, CD4 cells stimulate the differentiation from B lymphocytes to AFC IgA-positive; antibody that we previously found interacting with trophozoites in the nasal lumen avoiding the N. fowleri attachment to nasal epithelium.

The origin of prostate gland-secreted IgA and IgG

The prostate secretes immunoglobulin (Ig) A (IgA) and IgG; however, how immunoglobulins reach the secretion, where the plasma cells are located, whether immunoglobulins are antigen-specific and where activation of the adaptive response occurs are still unknown. Immune cells, including CD45RA⁺ cells, were scattered in the stroma and not organized mucosae-associated lymphoid-tissue. IgA (but not IgG) immunostaining identified stromal plasma cells and epithelial cells in non-immunized rats. Injected tetramethylrhodamine-IgA transcytosed the epithelium along with polymeric immunoglobulin receptor. Oral immunization with ovalbumin/mesopourous SBA-15 silica adjuvant resulted in more stromal CD45RA⁺/IgA⁺ cells, increased content of ovalbumin-specific IgA and IgG, and the appearance of intraepithelial CD45RA⁺/IgG⁺ cells. An increased number of dendritic cells that cooperate in other sites with transient immunocompetent lymphocytes, and the higher levels of interleukin-1β, interferon-γ and transforming growth factor-β, explain the levels of specific antibodies. Nasal immunization produced similar results except for the increase in dendritic cells. This immunomodulatory strategy seems useful to boost immunity against genitourinary infections and, perhaps, cancer.

CK12a, a CCL19-like Chemokine That Orchestrates both Nasal and Systemic Antiviral Immune Responses in Rainbow Trout

Chemokines and chemokine receptors have rapidly diversified in teleost fish but their immune functions remain unclear. We report in this study that CCL19, a chemokine known to control lymphocyte migration and compartmentalization of lymphoid tissues in mammals, diversified in salmonids leading to the presence of six CCL19-like genes named CK10a, CK10b, CK12a, CK12b, CK13a, and CK13b. Salmonid CCL19-like genes all contain the DCCL-conserved motif but share low amino acid sequence identity. CK12 (but not CK10 or CK13) is constitutively expressed at high levels in all four trout MALT. Nasal vaccination with a live attenuated virus results in sustained upregulation of CK12 (but not CK10 or CK13) expression in trout nasopharynx-associated lymphoid tissue. Recombinant His-tagged trout CK12a (rCK12a) is not chemotactic in vitro but it increases the width of the nasal lamina propria when delivered intranasally. rCK12a delivered intranasally or i.p. stimulates the expression of CD8α, granulysin, and IFN-γ in mucosal and systemic compartments and increases nasal CD8α⁺ cell numbers. rCK12a is able to stimulate proliferation of head kidney leukocytes from Ag-experienced trout but not naive controls, yet it does not confer protection against viral challenge. These results show that local nasal production of CK12a contributes to antiviral immune protection both locally and systemically via stimulation of CD8 cellular immune responses and highlight a conserved role for CK12 in the orchestration of mucosal and systemic immune responses against viral pathogens in vertebrates.

Adjuvantation of Pulmonary-Administered Influenza Vaccine with GPI-0100 Primarily Stimulates Antibody Production and Memory B Cell Proliferation

Adjuvants are key components in vaccines, they help in reducing the required antigen dose but also modulate the phenotype of the induced immune response. We previously showed that GPI-0100, a saponin-derived adjuvant, enhances antigen-specific mucosal and systemic antibody responses to influenza subunit and whole inactivated influenza virus (WIV) vaccine administered via the pulmonary route. However, the impact of the GPI-0100 dose on immune stimulation and the immune mechanisms stimulated by GPI-0100 along with antigen are poorly understood. Therefore, in this study we immunized C57BL/6 mice via the pulmonary route with vaccine consisting of WIV combined with increasing amounts of GPI-0100, formulated as a dry powder. Adjuvantation of WIV enhanced influenza-specific mucosal and systemic immune responses, with intermediate doses of 5 and 7.5 μg GPI-0100 being most effective. The predominant antibody subtype induced by GPI-0100-adjuvanted vaccine was IgG1. Compared to non-adjuvanted vaccine, GPI-0100-adjuvanted WIV vaccine gave rise to higher numbers of antigen-specific IgA- but not IgG-producing B cells in the lungs along with better mucosal and systemic memory B cell responses. The GPI-0100 dose was negatively correlated with the number of influenza-specific IFNγ- and IL17-producing T cells and positively correlated with the number of IL4-producing T cells observed after immunization and challenge. Overall, our results show that adjuvantation of pulmonary-delivered WIV with GPI-0100 mostly affects B cell responses and effectively induces B cell memory.

Cross-protection conferred by immunization with an rOmpH-based intranasal fowl cholera vaccine

A previous study demonstrated that a recombinant outer membrane protein H (rOmpH)-based intranasal fowl cholera vaccine elicited efficient homologous protection against the Pasteurella multocida strain X-73 (A:1) in chickens. The present study aimed to determine the cross-protectivity against heterologous P. multocida strains. The rOmpH was purified via electroelution and formulated with two kinds of adjuvants. The vaccine formulations in a total volume of 100 µl were 100 µg rOmpH with 3 µg of Escherichia coli enterotoxin B or 10 µg of CpG ODN2007. Chickens were assigned to three experimental groups depending on bacterial strain challenge exposure as well as three control groups. The chickens were immunized intranasally three times at three-week intervals. Challenge exposures were conducted by inoculation with homologous strain X-73 or heterologous strains P-1059 (A:3) or P-1662 (A:4) at four weeks after the final immunization. The specific antibody against rOmpH was produced in vaccinated birds. Sera IgY and secretory IgA antibody titres were significantly increased (P < 0.05) post-immunization. The stimulation index values of the vaccinated groups were significantly different from stimulation index values of the non-vaccinated groups (P < 0.05). Chicken survival rates after exposure to avian P. multocida strains ranged from 70% to 100%. There was no significant difference in protection between two kinds of adjuvants in vaccine formulations. Statistical analysis indicated no significant differences in protection among avian P. multocida strains challenge exposure. We conclude that an in-house rOmpH-based intranasal fowl cholera vaccine produced efficient cross-protectivity against heterologous strains of P. multocida.

Nasal delivery of Protollin-adjuvanted H5N1 vaccine induces enhanced systemic as well as mucosal immunity in mice

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Protollin-adjuvanted H5N1 vaccine enhanced serum protective antibody responses and mucosal IgA responses.

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Protollin-adjuvanted H5N1 vaccine increased the early B cell response in the lymph nodes and spleen.

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Protollin-adjuvanted H5N1 vaccine increased the frequency of Ag-specific antibody secreting cells and T cells.

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Protollin-adjuvanted H5N1 vaccine conferred enhanced protection against viral challenge.

Sporadic, yet frequent human infections with avian H5N1 influenza A viruses continue to pose a potential pandemic threat. Poor immunogenicity of unadjuvanted H5N1 vaccines warrants developing novel adjuvants and formulations as well as alternate delivery systems to improve their immunogenicity and efficacy. Here, we show that Protollin, a nasal adjuvant composed of Neisseria meningitides outer membrane proteins non-covalently linked to Shigella flexneri 2a lipopolysaccharide, is a potent nasal adjuvant for an inactivated split virion H5N1 clade 1 A/Viet Nam1203/2004 (A/VN/1203/04) vaccine in a mouse model. Protollin-adjuvanted vaccines elicited enhanced serum protective hemagglutination inhibition titers, mucosal IgA responses, and H5N1-specific cell-mediated immunity that resulted in complete protection against a lethal challenge with a homologous virus as well as a heterologous clade 2 virus A/Indonesia/05/2005 (A/IN/05/05). Detailed analysis of adaptive immunity revealed that Protollin increased the frequency of lymphoid- as well as local tissue-resident antibody-secreting cells, local germinal center reaction of B cells, broad-spectrum of CD4 T cell response. Our findings suggest that nasal delivery of H5N1 vaccine with Protollin adjuvant can overcome the poor immunogenicity of H5N1 vaccines, induce both cellular and humoral immune responses, enhance protection against challenge with clade 1 and clade 2 H5N1 viruses and achieve significant antigen dose-sparing.

Systemic and mucosal immune responses elicited by intranasal immunization with a pneumococcal bacterium-like particle-based vaccine displaying pneumolysin mutant Plym2

Pneumolysin (Ply) is an important virulence factor in pneumococcal infection and a conserved cholesterol-binding cytotoxin expressed by all serotypes of Streptococcus pneumoniae. We previously developed a highly detoxified Ply mutant designated Plym2 by replacement of two amino acids (C428G and W433F), which lost cytotoxicity but retained the ability to induce neutralizing antibodies. In the present work, we applied bacterium-like particles (BLPs) as a carrier and immunostimulant for the development of a Plym2 intranasal vaccine, in which the Plym2 protein was displayed on the surface of BLPs. Intranasal immunization of mice with BLP-Plym2 not only induced a high level of serum IgG antibodies but also a high level of mucosal SIgA antibodies in lung lavages. Antiserum induced by the BLP-Plym2 vaccine elicited high-titer neutralization activity which could inhibit the hemolysis of wild-type Ply. In conclusion, the BLP-Plym2 vaccine was demonstrated to be a promising strategy for intranasal immunization to enhance both systemic and mucosal immune responses.