Pre-clinical evaluation of a novel nanoemulsion-based hepatitis B mucosal vaccine

Vaccine adjuvants for infectious disease in the clinic

Adjuvants, materials added to vaccines to enhance the resulting immune response, are important components of vaccination that are many times overlooked. While vaccines always include an antigen to tell the body what to vaccinate to, of equal importance the adjuvant provides the how, a significant factor in producing a complete response. The adjuvant space has been slow to develop with the first use of an adjuvant in a licensed vaccine occurring in the 1930s, and remaining the only adjuvant in licensed vaccines for the next 80 years. However, with vaccination at the forefront of protection against new and complex pathogens, it is important to consider all components when designing an effective vaccine. Here we summarize the adjuvant space in licensed vaccines as well as the novel adjuvant space in clinical trials with a specific focus on the materials utilized and their resulting impact on the immune response. We discuss five major categories of adjuvant materials: aluminum salts, nanoparticles, viral vectors, TLR agonists, and emulsions. For each category, we delve into the current clinical trials space, the impact of these materials on vaccination, as well as some of the ways in which they could be improved. Adjuvants present an exciting opportunity to improve vaccine responses and stability, this review will help inform about the current progress of this space.

Translational impact statement

In the aftermath of the COVID-19 pandemic, vaccines for infectious diseases have come into the spotlight. While antigens have always been an important focus of vaccine design, the adjuvant is a significant tool for enhancing the immune response to the vaccine that has been largely underdeveloped. This article provides a broad review of the history of adjuvants and, the current vaccine adjuvant space, and the progress seen in adjuvants in clinical trials. There is specific emphasis on the material landscape for adjuvants and their resulting mechanism of action. Looking ahead, while the novel vaccine adjuvant space features exciting new technologies and materials, there is still a need for more to meet the protective needs of new and complex pathogens.

W/O/W Microemulsions for Nasal Delivery of Hydrophilic Compounds: A Preliminary Study

The administration of hydrophilic therapeutics has always been a great challenge because of their low bioavailability after administration. For this purpose, W/O/W microemulsion resulted to be a potential successful strategy for the delivery of hydrophilic compounds, interesting for the nasal mucosal therapy. Herein, an optimized biphasic W/O microemulsion was designed, through a preliminary screening, and it was inverted in a triphasic W/O/W microemulsion, intended for the nasal administration. In order to enhance the mucosal retention, surface modification of the biphasic W/O microemulsion was performed adding didodecyldimethylammonium bromide, and then converting the system into a cationic triphasic W/O/W microemulsion. The developed samples were characterized in terms of droplet size, polydispersity, zeta potential, pH and osmolality. The physical long-term stability was analyzed storing samples at accelerated conditions (40 ± 2 °C and 75 ± 5 % RH) for 6 months in a constant climate chamber, following ICH guidelines Q1A (R2). In order to verify the potential retention on the nasal mucosa, the two triphasic systems were analyzed in terms of mucoadhesive properties, measuring the in vitro interaction with mucin over time. Furthermore, fluorescein sodium salt was selected as a model hydrophilic drug to be encapsulated into the inner core of the two triphasic W/O/W microemulsions, and its release was analyzed compared to the free probe solution. The cytocompatibility of the two platforms was assessed on two cell lines, human fibroblasts HFF1 and Calu-3 cell lines, chosen as pre-clinical models for nasal and bronchial/tracheal airway epithelium.

HBV Vaccines: Advances and Development

Hepatitis B virus (HBV) infection is a global public health problem that is closely related to liver cirrhosis and hepatocellular carcinoma (HCC). The prevalence of acute and chronic HBV infection, liver cirrhosis, and HCC has significantly decreased as a result of the introduction of universal HBV vaccination programs. The first hepatitis B vaccine approved was developed by purifying the hepatitis B surface antigen (HBsAg) from the plasma of asymptomatic HBsAg carriers. Subsequently, recombinant DNA technology led to the development of the recombinant hepatitis B vaccine. Although there are already several licensed vaccines available for HBV infection, continuous research is essential to develop even more effective vaccines. Prophylactic hepatitis B vaccination has been important in the prevention of hepatitis B because it has effectively produced protective immunity against hepatitis B viral infection. Prophylactic vaccines only need to provoke neutralizing antibodies directed against the HBV envelop proteins, whereas therapeutic vaccines are most likely needed to induce a comprehensive T cell response and thus, should include other HBV antigens, such as HBV core and polymerase. The existing vaccines have proven to be highly effective in preventing HBV infection, but ongoing research aims to improve their efficacy, duration of protection, and accessibility. The routine administration of the HBV vaccine is safe and well-tolerated worldwide. The purpose of this type of immunization is to trigger an immunological response in the host, which will halt HBV replication. The clinical efficacy and safety of the HBV vaccine are affected by a number of immunological and clinical factors. However, this success is now in jeopardy due to the breakthrough infections caused by HBV variants with mutations in the S gene, high viral loads, and virus-induced immunosuppression. In this review, we describe various types of available HBV vaccines, along with the recent progress in the ongoing battle to develop new vaccines against HBV.

Stressed stability and protective efficacy of lead lyophilized formulations of ID93+GLA-SE tuberculosis vaccine

With the recent exception of coronavirus disease 2019 (COVID-19), tuberculosis (TB) causes more deaths globally than any other infectious disease, and approximately 1/3 of the world's population is infected with Mycobacterium tuberculosis (Mtb). However, encouraging progress in TB vaccine development has been reported, with approximately 50% efficacy achieved in Phase 2b clinical testing of an adjuvanted subunit TB vaccine candidate. Nevertheless, current lead vaccine candidates require cold-chain transportation and storage. In addition to temperature stress, vaccines may be subject to several other stresses during storage and transport, including mechanical, photochemical, and oxidative stresses. Optimal formulations should enable vaccine configurations with enhanced stability and decreased sensitivity to physical and chemical stresses, thus reducing reliance on the cold chain and facilitating easier worldwide distribution. In this report, we describe the physicochemical stability performance of three lead thermostable formulations of the ID93 + GLA-SE TB vaccine candidate under various stress conditions. Moreover, we evaluate the impact of thermal stress on the protective efficacy of the vaccine formulations. We find that formulation composition impacts stressed stability performance, and our comprehensive evaluation enables selection of a lead single-vial lyophilized candidate containing the excipient trehalose and Tris buffer for advanced development.

Retinoic Acid Signaling Is Required for Dendritic Cell Maturation and the Induction of T Cell Immunity

Vitamin A and its biologically active metabolites, all-trans and 9-cis retinoic acid (RA), are thought to be important in generating and modulating immune function. However, RA modulates the function of many types of immune cells, and its specific role in dendritic cell (DC) activation, Ag presentation, and T cell effector function has not been fully characterized. Because RA works primarily through RA receptor (RAR)α, we examined mice with a myeloid cell-specific defect in RA signaling. These transgenic mice have a CD11c-cre-driven expression of a truncated form of RARα that specifically blocks the signaling of all forms of RARs in myeloid cells. This defect results in abnormal DC function, with impaired DC maturation and activation, and reduced Ag uptake and processing. These DC abnormalities were associated with a reduced ability to mount Ag-specific T cell responses to immunization despite having normally functioning T cells. In contrast, the loss of DC-specific RA signaling did not significantly alter levels of Ag-specific Abs postimmunization and resulted in an increase in bronchial IgA. Our findings indicate that RA signaling in DCs is crucial for immune activation, and its absence impairs the development of Ag-specific effector functions of T cell immunity.

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

The importance of vaccination has been proven particularly significant the last three years, as it is revealed to be the most efficient weapon for the prevention of several infections including SARS-COV-2. Parenteral vaccination is the most applicable method of immunization, for the prevention of systematic and respiratory infections, or central nervous system disorders, involving T and B cells to a whole-body immune response. However, the mucosal vaccines, such as nasal vaccines, can additionally activate the immune cells localized on the mucosal tissue of the upper and lower respiratory tract. This dual stimulation of the immune system, along with their needle-free administration favors the development of novel nasal vaccines to produce long-lasting immunity. In recent years, the nanoparticulate systems have been extensively involved in the formulation of nasal vaccines as polymeric, polysaccharide and lipid ones, as well as in the form of proteosomes, lipopeptides and virosomes. Advanced delivery nanosystems have been designed and evaluated as carriers or adjuvants for nasal vaccination. To this end, several nanoparticulate vaccines are undergone clinical trials as promising candidates for nasal immunization, while nasal vaccines against influenza type A and B and hepatitis B have been approved by health authorities. This comprehensive literature review aims to summarize the critical aspects of these formulations and highlight their potential for the future establishment of nasal vaccination. Both preclinical (in vitro and in vivo) and clinical studies are incorporated, summarized, and critically discussed, as well as the limitations of nasal immunization.

Intranasal nanoemulsion adjuvanted S-2P vaccine demonstrates protection in hamsters and induces systemic, cell-mediated and mucosal immunity in mice

With the rapid progress made in the development of vaccines to fight the SARS-CoV-2 pandemic, almost >90% of vaccine candidates under development and a 100% of the licensed vaccines are delivered intramuscularly (IM). While these vaccines are highly efficacious against COVID-19 disease, their efficacy against SARS-CoV-2 infection of upper respiratory tract and transmission is at best temporary. Development of safe and efficacious vaccines that are able to induce robust mucosal and systemic immune responses are needed to control new variants. In this study, we have used our nanoemulsion adjuvant (NE01) to intranasally (IN) deliver stabilized spike protein (S-2P) to induce immunogenicity in mouse and hamster models. Data presented demonstrate the induction of robust immunity in mice resulting in 100% seroconversion and protection against SARS-CoV-2 in a hamster challenge model. There was a significant induction of mucosal immune responses as demonstrated by IgA- and IgG-producing memory B cells in the lungs of animals that received intranasal immunizations compared to an alum adjuvanted intramuscular vaccine. The efficacy of the S-2P/NE01 vaccine was also demonstrated in an intranasal hamster challenge model with SARS-CoV-2 and conferred significant protection against weight loss, lung pathology, and viral clearance from both upper and lower respiratory tract. Our findings demonstrate that intranasal NE01-adjuvanted vaccine promotes protective immunity against SARS-CoV-2 infection and disease through activation of three arms of immune system: humoral, cellular, and mucosal, suggesting that an intranasal SARS-CoV-2 vaccine may play a role in addressing a unique public health problem and unmet medical need.

Protection of hamsters challenged with SARS-CoV-2 after two doses of MVC-COV1901 vaccine followed by a single intranasal booster with nanoemulsion adjuvanted S-2P vaccine

Intramuscular vaccines have greatly reduced hospitalization and death due to severe COVID-19. However, most countries are experiencing a resurgence of infection driven predominantly by the Delta and Omicron variants of SARS-CoV-2. In response, booster dosing of COVID-19 vaccines has been implemented in many countries to address waning immunity and reduced protection against the variants. However, intramuscular boosting fails to elicit mucosal immunity and therefore does not solve the problem of persistent viral carriage and transmission, even in patients protected from severe disease. In this study, two doses of stabilized prefusion SARS-CoV-2 spike (S-2P)-based intramuscular vaccine adjuvanted with Alum/CpG1018, MVC-COV1901, were used as a primary vaccination series, followed by an intranasal booster vaccination with nanoemulsion (NE01)-adjuvanted S-2P vaccine in a hamster model to demonstrate immunogenicity and protection from viral challenge. Here we report that this vaccination regimen resulted not only in the induction of robust immunity and protection against weight loss and lung pathology following challenge with SARS-CoV-2, but also led to increased viral clearance from both upper and lower respiratory tracts. Our findings showed that intramuscular MVC-COV1901 vaccine followed by a booster with intranasal NE01-adjuvanted vaccine promotes protective immunity against both viral infection and disease, suggesting that this immunization protocol may offer a solution in addressing a significant, unmet medical need for both the COVID-19 and future pandemics.

Oil-in-ionic liquid nanoemulsion-based intranasal delivery system for influenza split-virus vaccine

Effective antigen delivery and immune stimulation in nasal mucosa determine the success of mucosal immunity. Here, an oil-in-ionic liquid (o/IL) nanoemulsion formulated with choline and niacin IL ([Cho][Nic]), squalene, and Tween 80 surfactant is explored as a vaccine delivery system for intranasal mucosal immunization. Compared to the o/w emulsion counterpart without the ILs, the o/IL manoemulsion showed a reduced and more uniform size of approximately 168 nm and significantly improved stability. Studies in mice model showed that when was used as an intranasal vaccine delivery system for influenza split-virus antigens, the antigens in the o/IL nanoemulsion induced strong mucosal immune responses with secretory IgA titers 25- and 5.8-fold higher than those of naked and commercial MF59-adjuvanted antigens, respectively. The o/IL nanoemulsion system also induced stronger systemic humoral responses. The excellent mucosal adjuvant effects of the o/IL nanoemulsion mainly benefited from the prolonged retention of antigens in the nasal cavity, enhanced antigen permeation into the submucosa, and the consequently promoted proliferation of CD11b cells and CD4⁺ T cells in nasal mucosa-associated lymphoid tissue. Moreover, when used as an injection adjuvant, the o/IL nanoemulsion also induced stronger humoral immune responses than MF59. Thus, the [Cho][Nic]-based o/IL nanoemulsion vaccine delivery system can serve as a promising adjuvant platform.

Nanoemulsions: Formulation, characterization, biological fate, and potential role against COVID-19 and other viral outbreaks

Viral diseases are emerging as global threats. Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), that causes coronavirus disease (COVID-19), has severe global impacts. Safety, dosage, and potency of vaccines recently approved for emergency use against SARS-CoV-2 need further evaluation. There is still no effective treatment against COVID-19; therefore, safe, and effective vaccines or therapeutics against SARS-CoV-2 are urgently needed. Oil-in-water nanoemulsions (O/W NEs) are emerging as sophisticated, protective, and therapeutic platforms. Encapsulation capacity, which offers better drug pharmacokinetics, coupled with the tunable surfaces present NEs as promising tools for pharmaceutical applications. The challenges facing drug discovery, and the advancements of NEs in drug delivery demonstrate the potential of NEs against evolving diseases, like COVID-19. Here we summarize current COVID-19 knowledge and discuss the composition, stability, preparation, characterization, and biological fate of O/W NEs. We also provide insights into NE structural-functional properties that may contribute to therapeutic or preventative solutions against COVID-19.

Intranasal delivery of allergen in a nanoemulsion adjuvant inhibits allergen-specific reactions in mouse models of allergic airway disease

BACKGROUND

Atopic diseases are an increasing problem that involve both immediate hypersensitivity reactions mediated by IgE and unique cellular inflammation. Many forms of specific immunotherapy involve the administration of allergen to suppress allergic immune responses but are focused on IgE-mediated reactions. In contrast, the effect of allergen-specific immunotherapy on allergic inflammation is complex, not entirely consistent and not well understood. We have previously demonstrated the ability of allergen administered in a nanoemulsion (NE) mucosal adjuvant to suppress IgE-mediated allergic responses and protect from allergen challenge in murine food allergy models. This activity was associated with decreases in allergen-specific IL-10 and reductions in allergic cytokines and increases in regulatory T cells.

OBJECTIVE

Here, we extend these studies to using 2 distinct models, the ovalbumin (OVA) and cockroach (CRA) models of allergic airway disease, which are based predominantly on allergic inflammation.

METHODS

Acute or chronic allergic airway disease was induced in mice using ovalbumin and cockroach allergen models. Mice received three therapeutic immunizations with allergen in NE, and reactivity to airway challenge was determined.

RESULTS

Therapeutic immunization with cockroach or OVA allergen in NE markedly reduced pathology after airway challenge. The 2 models demonstrated protection from allergen challenge-induced pathology that was associated with suppression of Th2-polarized immune responses in the lung. In addition, the reduction in ILC2 numbers in the lungs of allergic mice along with reduction in epithelial cell alarmins, IL-25 and IL-33, suggests an overall change in the lung immune environment induced by the NE immunization protocol.

CONCLUSIONS AND CLINICAL RELEVANCE

These results demonstrate that suppression of allergic airway inflammation and bronchial hyper-reactivity can be achieved using allergen-specific immunotherapy without significant reductions in allergen-specific IgE and suggest that ILC2 cells may be critical targets for this activity.

Moderate Heat-Assisted Gene Electrotransfer for Cutaneous Delivery of a DNA Vaccine Against Hepatitis B Virus

An estimated 350 million people are living with chronic Hepatitis B virus (HBV) worldwide. Preventative HBV vaccination in infants has reduced the disease burden; however, insufficient immunization programs and access obstacles leave vulnerable populations at risk for infection in endemic regions. Gene electrotransfer (GET) using a noninvasive multielectrode array (MEA) provides an alternative platform for DNA vaccination in the skin. DNA vaccines are nonlive and nonreplicating and temperature stable unlike their counterparts. In addition, their simple engineering allows them to be manufactured quickly at a low cost. In the current work, we present the combination of GET and moderate heating for delivery of a DNA vaccine against HBV. Our laboratory has previously shown the synergy between moderate tissue preheating at 43°C and GET with the MEA as a means to reduce both the applied voltage and pulse number to achieve similar if not higher gene expression than GET alone. In this study, we expand upon this work, by optimizing the plasmid dose to achieve the highest level of expression. Using the reporter gene luciferase, we found that an intradermal injection of 100 μL at 1 mg/mL induced the highest expression levels across all tested GET conditions. We then evaluated our moderate heat-assisted GET platform for the intradermal delivery of a plasmid encoding Hepatitis B surface antigen (pHBsAg) via a prime and prime plus boost vaccination protocol. At 18 weeks, following the prime plus boost protocol, we observed that a high-voltage low-pulse GET condition with moderate heating (45 V 36 p+heat) generated antibodies against Hepatitis B surface antigen (HBsAb) at peak measuring 230-fold over injection of plasmid DNA alone with moderate heating. HBsAbs remained robust over the 30-week observation period. These data suggest that moderate heat-assisted GET has the potential to induce strong immune responses, an attractive feature for development of an alternative vaccine delivery platform.

Development of thermostable vaccine adjuvants

INTRODUCTION

The importance of vaccine thermostability has been discussed in the literature. Nevertheless, the challenge of developing thermostable vaccine adjuvants has sometimes not received appropriate emphasis. Adjuvants comprise an expansive range of particulate and molecular compositions, requiring innovative thermostable formulation and process development approaches.

AREAS COVERED

Reports on efforts to develop thermostable adjuvant-containing vaccines have increased in recent years, and substantial progress has been made in enhancing the stability of the major classes of adjuvants. This narrative review summarizes the current status of thermostable vaccine adjuvant development and looks forward to the next potential developments in the field.

EXPERT OPINION

As adjuvant-containing vaccines become more widely used, the unique challenges associated with developing thermostable adjuvant formulations merit increased attention. In particular, more focused efforts are needed to translate promising proof-of-concept technologies and formulations into clinical products.

Vaccines as therapies for food allergies

Food allergy is a growing public health epidemic with few available treatments beyond allergen avoidance and rescue medications for accidental exposures. A major focus of therapeutic development for food allergies is allergen-specific immunotherapy (AIT) in which patients are exposed to increasing amounts of allergen in controlled dosing to induce desensitization or tolerance. The work of the past few decades has culminated in the recent FDA approval of a peanut product for oral AIT for peanut allergies. Despite these advances, current AIT protocols are cumbersome, take a long time to reach clinical benefit and often have significant side effects. Therefore, there is a great need to develop new therapeutics for food allergy. One area of research aims to improve AIT through the use of adjuvants which are substances traditionally added to vaccines to stimulate or direct a specific immune response. Adjuvants that induce Th1-polarized and regulatory immune responses while suppressing Th2 immunity have shown the most promise in animal models. The addition of adjuvants to AIT may reduce the amount and frequency of allergen required to achieve clinical benefit and may induce more long-lasting immune responses. In this chapter, we highlight examples of adjuvanted AIT and vaccines in development to treat food allergies.

Mucosal Nanoemulsion Allergy Vaccine Suppresses Alarmin Expression and Induces Bystander Suppression of Reactivity to Multiple Food Allergens

We have demonstrated that intranasal immunotherapy with allergens formulated in a nanoemulsion (NE) mucosal adjuvant suppresses Th2/IgE-mediated allergic responses and protects from allergen challenge in murine food allergy models. Protection conferred by this therapy is associated with strong suppression of allergen specific Th2 cellular immunity and increased Th1 cytokines. Here we extend these studies to examine the effect of NE-allergen immunization in mice sensitized to multiple foods. Mice were sensitized to both egg and peanut and then received NE vaccine formulated with either one or both of these allergens. The animals were then subjected to oral challenges with either egg or peanut to assess reactivity. Immunization with NE formulations containing both egg and peanut markedly reduced reactivity after oral allergen challenge with either allergen. Interestingly, mice that received the vaccine containing only peanut also had reduced reactivity to challenge with egg. Protection from oral allergen challenge was achieved despite the persistence of allergen-specific IgE and was associated with strong suppression of both Th2-polarized immune responses, alarmins and type 2 innate lymphoid cells (ILC2). NE-induced bystander suppression of reactivity required IFN-γ and the presence of an allergen in the NE vaccine. These results demonstrate that anaphylactic reactions to food allergens can be suppressed using allergen-specific immunotherapy without having to eliminate allergen-specific IgE and suggests that modulation of Th2 immunity towards one allergen may induce bystander effects that suppress reactivity to other allergens through the induction of IFN-γ and suppression of alarmins in the intestine. In addition, these data suggest that a NE vaccine for a single food allergen may lead to a global suppression of allergic responses to multiple foods.

Prospects for mucosal vaccine: shutting the door on SARS-CoV-2

The sudden emergence of a highly transmissible and pathogenic coronavirus SARS-CoV-2 in December 2019 from China and its rapid global spread has posed an international health emergency. The rapid development of an effective vaccine is imperative to control the spread of SARS-CoV-2. A number of concurrent efforts to find an effective therapeutic agent or vaccine for COVID-19 (coronavirus disease 2019) are being undertaken globally. Oral and nasal mucosal surfaces serve as the primary portal of entry for pathogens like coronaviruses in the human body. As evidenced by studies on similar coronaviruses (SARS-CoV and MERS-CoV), mucosal vaccination can provide a safe and effective means for the induction of long-lasting systemic and mucosal immunity to confer protection against SARS-CoV-2. This article summarizes the approaches to an effective mucosal vaccine formulation which can be a rewarding approach to combat the unprecedented threat posed by this emerging global pandemic.

Modulation of immune responses with nanoparticles and reduction of their immunotoxicity

Particles with a size range of 1-100 nm used in various fields of life sciences are called nanoparticles (NPs). Currently, nanotechnology has a wide range of applications in biomedical research, industries and in almost all types of modern technology. The growing applications of nanotechnology in medicine urge scientists to analyze the impact of NPs on human body tissues and the immune system. Easy surface modifications of the NPs enable the modulation of the immune system either by evading the immune system to prevent allergic reactions or by enhancing the immunogenic response. In this review, we discussed the various possible theories and practical implications reported to date for the applications of nanotechnology in immunostimulation and immunosuppression for favorable immune response, such as vaccine delivery and cancer treatments. In the last part of this paper, we also discussed the biocompatibility and unfavorable immunotoxicity of NPs and methods for lowering their toxicity.

Combined Intranasal Nanoemulsion and RIG-I Activating RNA Adjuvants Enhance Mucosal, Humoral, and Cellular Immunity to Influenza Virus

Current influenza virus vaccines are focused on humoral immunity and are limited by the short duration of protection, narrow cross-strain efficacy, and suboptimal immunogenicity. Here, we combined two chemically and biologically distinct adjuvants, an oil-in-water nanoemulsion (NE) and RNA-based agonists of RIG-I, to determine whether the diverse mechanisms of these adjuvants could lead to improved immunogenicity and breadth of protection against the influenza virus. NE activates TLRs, stimulates immunogenic apoptosis, and enhances cellular antigen uptake, leading to a balanced T_H1/T_H2/T_H17 response when administered intranasally. RIG-I agonists included RNAs derived from Sendai and influenza viral defective interfering RNAs (IVT DI, 3php, respectively) and RIG-I/TLR3 agonist, poly(I:C) (pIC), which induce IFN-Is and T_H1-polarized responses. NE/RNA combined adjuvants potentially allow for costimulation of multiple innate immune receptor pathways, more closely mimicking patterns of activation occurring during natural viral infection. Mice intranasally immunized with inactivated A/Puerto Rico/8/1934 (H1N1) (PR/8) adjuvanted with NE/IVT DI or NE/3php (but not NE/pIC) showed synergistic enhancement of systemic PR/8-specific IgG with significantly greater avidity and virus neutralization activity than the individual adjuvants. Notably, NE/IVT DI induced protective neutralizing titers after a single immunization. Hemagglutinin stem-specific antibodies were also improved, allowing recognition of heterologous and heterosubtypic hemagglutinins. All NE/RNAs elicited substantial PR/8-specific sIgA. Finally, a unique cellular response with enhanced T_H1/T_H17 immunity was induced with the NE/RNAs. These results demonstrate that the enhanced immunogenicity of the adjuvant combinations was synergistic and not simply additive, highlighting the potential value of a combined adjuvant approach for improving the efficacy of vaccination against the influenza virus.

Intranasal nanoemulsion vaccine confers long-lasting immunomodulation and sustained unresponsiveness in a murine model of milk allergy

BACKGROUND

Immunotherapy for food allergy requires prolonged treatment protocols and, in most cases, does not lead to durable modulation of the allergic immune response. We have demonstrated an intranasal (IN) nanoemulsion adjuvant that redirects allergen-specific Th2 responses toward Th1 and Th17 immunity, and protects from allergen challenge after only 2-4 monthly administrations. Here, we investigate the ability of this technology to provide long-term modulation of allergy in a murine model of cow's milk allergy.

METHODS

Six weeks after sensitization to bovine casein, mice received four, monthly IN immunizations with nanoemulsion formulated with casein. Protection from casein challenge was assessed at 4 and 16 weeks after the final vaccine administration.

RESULTS

The NE vaccine significantly blunted the physiological responses to allergen challenge, and this effect persisted for at least 16 weeks. The protection from challenge was associated with the suppression of casein-specific Th2 immunity and induced Th1 and Th17 cytokines as well as induction of IL-10. Of interest, while immunized animals showed significantly decreased Th2 cytokine responses, cow's milk-specific IgE remained elevated in the serum at levels associated with reactivity in control sensitized animals. Protection was associated with suppressed mast cell activation and markedly reduced mast cell infiltration into the small intestine.

CONCLUSION

The sustained unresponsiveness of at least 16 weeks after vaccination suggests that the nanoemulsion vaccine alters the allergic phenotype in a persistent manner different from traditional desensitization, and this leads to long-term suppressive effects on allergic disease without eliminating serum IgE.

Nanoparticles for mucosal vaccine delivery

Mucosal surfaces represent important routes of entry into the human body for the majority of pathogens, and they constitute unique sites for targeted vaccine delivery. Nanoparticle-based drug delivery systems are emerging technologies for delivering and improving the efficacy of mucosal vaccines. Recent studies have provided new insights into formulation and delivery aspects of importance for the design of safe and efficacious mucosal subunit vaccines based on nanoparticles. These include novel nanomaterials, their physicochemical properties and formulation approaches, nanoparticle interaction with immune cells in the mucosa, and mucosal immunization and delivery strategies. Here, we present recent progress in the application of nanoparticle-based approaches for mucosal vaccine delivery and discuss future research challenges and opportunities in the field.

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.

Intranasal nanoemulsion-adjuvanted HSV-2 subunit vaccine is effective as a prophylactic and therapeutic vaccine using the guinea pig model of genital herpes

Genital herpes is a sexually transmitted disease representing a major global health concern. Currently, there is no approved vaccine and existing antiviral therapies exhibit limited efficacy. Herein, we describe an intranasal (IN) vaccine comprised of HSV-2 surface glycoproteins gD2 and gB2 formulated in a nanoemulsion adjuvant (NE01-gD2/gB2). Using the HSV-2 genital herpes guinea pig model, we demonstrate that IN NE01-gD2/gB2 induces higher levels of neutralizing antibody compared to a monovalent IN NE01-gD2 vaccine, but less than an intramuscular (IM) Alum/MPL-gD2 vaccine. Following intravaginal (IVag) challenge with HSV-2, the group immunized with IN NE01-gD2/gB2 exhibited significantly reduced acute and recurrent disease scores compared to placebo recipients. Significantly, latent virus was only detected in the dorsal root ganglia of 1 of 12 IN NE01-gD2/gB2-vaccinated animals compared to 11 of 12 placebo recipient. In the therapeutic model, IN NE01-gD2/gB2 immunized guinea pigs exhibited a significant reduction in the recurrent lesions scores (64%, p < 0.01), number of animal days with disease (64%, p < 0.01), number of animals with viral shedding (50%, p < 0.04) and reduction in virus positive vaginal swabs (56%, p < 0.04), These data suggests that the treatment may be effective in treating chronic disease and minimizing virus transmission. These results warrant advancing the development of IN NE01-gD2/gB2 as both a prophylactic and therapeutic vaccine against HSV-2.

A nanoemulsion-adjuvanted intranasal H5N1 influenza vaccine protects ferrets against homologous and heterologous H5N1 lethal challenge

BACKGROUND

Flu vaccines administered intramuscularly (IM) have shown seasonally fluctuating efficacy, 20-60%, throughout the last 15 years. We formulated a recombinant H5 (rH5) in our Nanovax® (NE01) (rH5/NE01) adjuvant for intranasal vaccination in ferrets. We evaluated the regimen, one vs two immunization, and cross clade protection a ferret challenge model.

METHODS

Plant derived recombinant H5 (rH5) antigen was formulated with NE01 and administered intranasally to ferrets. Immunogenicity (IgG), hemagglutination inhibition (HI), and protection against lethal challenge, were measured following one or two immunizations. Protection against homologous (strain A/Indo) and heterologous (strain A/Vn) was evaluated in ferrets following two immunizations.

RESULTS

IN immunization with rH5/NE01 induced significant IgG levels after one and two immunizations. One vaccination did not induce any HI while low HI was measured after two immunizations. Homologous challenge with H5N1 A/ Indonesia showed 100% survival, with minimal weight loss in animals vaccinated twice compared to the unvaccinated controls. Analysis of nasal wash from these challenged ferrets vaccinated twice showed decreased viral shedding compared to unvaccinated controls. Interestingly, animals that received one vaccination showed 88% survival with moderate weight loss. Cross clade protection was evaluated using an increased antigen dose (45 µg rH5). Vaccinated animals demonstrated increased IgG and HAI antibody responses. Both homologous (A/Indo) and heterologous challenge (A/Vietnam) following two immunizations showed 100% survival with no loss of body weight. However viral clearance was more rapid against the homologous (day 3) compared to the heterologous (day 5) post challenge.

CONCLUSION

Intranasal administration of NE01 adjuvant-formulated rH5 vaccine elicited systemic and probably mucosal immunity that conferred protection against lethal challenge with homologous or heterologous viral strains. It also enhanced viral clearance with decreased shedding. These outcomes strongly suggest that intranasal immunization using NE01 against flu infections warrants clinical testing.

Molecular Evaluation of Oral Immunogenicity of Hepatitis B Antigen Delivered by Hydrogel Microparticles

The development of oral vaccine formulation is crucial to facilitate an effective mass immunization program for various vaccine-preventable diseases. In this work, the efficacy of hepatitis B antigen delivered by bacterial nanocellulose/poly(acrylic acid) composite hydrogel microparticles (MPs) as oral vaccine carriers was assessed to induce both local and systemic immunity. Optimal pH-responsive swelling, mucoadhesiveness, protein drug loading, and drug permeability were characterized by MPs formulated with minimal irradiation doses and acrylic acid concentration. The composite hydrogel materials of bacterial nanocellulose and poly(acrylic acid) showed significantly greater antigen release in simulated intestinal fluid while ensuring the integrity of antigen. In in vivo study, mice orally vaccinated with antigen-loaded hydrogel MPs showed enhanced vaccine immunogenicity with significantly higher secretion of mucosal immunoglobulin A, compared to intramuscular vaccinated control. The splenocytes from the same group demonstrated lymphoproliferation and significant increased secretion of interleukin-2 cytokines upon stimulation with hepatitis B antigen. Expression of CD69 in CD4⁺ T lymphocytes and CD19⁺ B lymphocytes in splenocytes from mice orally vaccinated with antigen-loaded hydrogel MPs was comparable to that of the intramuscular vaccinated control, indicating early activation of lymphocytes elicited by our oral vaccine formulation in just two doses. These results demonstrated the potential of antigen-loaded hydrogel MPs as an oral vaccination method for hepatitis B.

Nanoemulsion Adjuvant Augments Retinaldehyde Dehydrogenase Activity in Dendritic Cells via MyD88 Pathway

Mucosal surfaces are the primary point of entry for many infectious agents and mucosal immune responses serve as the primary defense to these pathogens. In order to mount an effective mucosal immune response, it is important to induce T cell homing to mucosal surfaces. Conventional vaccine adjuvants induce strong systemic immunity but often fail to produce mucosal immunity. We have developed an oil-in-water nanoemulsion (NE) adjuvant that provides mucosal immunity and efficient protection against mucosal pathogens when administered as part of an intranasal vaccine. In the present study, we demonstrate that intranasal immunization with NE indirectly activates the retinaldehyde dehydrogenase (RALDH) activity in dendritic cells through epithelial cell activity leading to SIgA as well as potent cellular responses and expression of α4β7 and CCR9 gut homing receptors on T cells. Confirming these findings, ex-vivo stimulation of splenocytes from NE nasally immunized animals showed increase in Th1/Th17 cytokines while suppressing Th2 responses. In examining mechanisms underlying this activation NE activated RALDH via MyD88 dependent pathways in DCs but did not activate the retinoic acid receptor directly. These results suggest that RALDH immune activities can be achieved by epithelial activation without direct RAR activation, which has significant implications for understanding mucosal immunity and the design of mucosal vaccines.

Topological Aspects of the Design of Nanocarriers for Therapeutic Peptides and Proteins

Supramolecular chemistry holds great potential for the design of versatile and safe carriers for therapeutic proteins and peptides. Nanocarriers can be designed to meet specific criteria for given application (exact drug, administration route, target tissue, etc.). However, alterations in the topology of formulation components can drastically change their activity. This is why the supramolecular topology of therapeutic nanoconstructions has to be considered. Herein, we discuss several topological groups used for the design of nanoformulations for peptide and protein delivery: modification of polypeptide chains by host-guest interactions; packaging of proteins and peptides into liposomes; complexation and conjugation with dendrimers. Each topological type has its own advantages and disadvantages, so careful design of nanoformulations is needed. Ideally, each case where nanomedicine is needed requires a therapeutic construction specially created for that taking into account features of the administration route, target tissue, or organ, properties of a drug, its bioavailability, etc. The wide number of studies in the field of protein delivery by supramolecular and nanocarriers for proteins and peptides evidence their increasing potential for different aspects of the innovative medicine. Although significant progress has been achieved in the field, there are several remaining challenges to be overcome in future.

Intranasal delivery of nanoparticle-based vaccines

Most pathogens gain access to the human body and initiate systemic infections through mucosal sites. A large number of currently marketed licensed vaccines are parenterally administered; they generate strong systemic immunity but not mucosal immunity. Nasal vaccination is an appealing strategy for the induction of mucosal-specific immunity; however, its development is mostly challenged by several factors, such as inefficient antigen uptake, its rapid mucociliary clearance, size-restricted permeation across epithelial barriers and absence of safe human mucosal adjuvants. Therefore, a safer mucosal-adjuvanting strategy or efficient mucosal delivery platform is much warranted. This review summarizes challenges and the rationale for nasal vaccine development with a special focus on the use of nanoparticles based on polymers and lipids for mucosal vaccine delivery.

Nanoemulsion adjuvant-driven redirection of TH2 immunity inhibits allergic reactions in murine models of peanut allergy

BACKGROUND

Immunotherapy for food allergies involves progressive increased exposures to food that result in desensitization to food allergens in some subjects but not tolerance to the food. Therefore new approaches to suppress allergic immunity to food are necessary. Previously, we demonstrated that intranasal immunization with a nanoemulsion (NE) adjuvant induces robust mucosal antibody and T_H17-polarized immunity, as well as systemic T_H1-biased cellular immunity with suppression of pre-existing T_H2-biased immunity.

OBJECTIVE

We hypothesized that immunization with food in conjunction with the nanoemulsion adjuvant could lead to modulation of allergic reactions in food allergy by altering pre-existing allergic immunity and enhancing mucosal immunity.

METHODS

Mice were sensitized to peanut with aluminum hydroxide or cholera toxin. The animals were then administered 3 monthly intranasal immunizations with peanut in the nanoemulsion adjuvant or saline. Mice were then challenged with peanut to examine allergen reactivity.

RESULTS

The NE intranasal immunizations resulted in marked decreases in T_H2 cytokine, IgG₁, and IgE levels, whereas T_H1 and mucosal T_H17 immune responses were increased. After allergen challenge, these mice showed significant reductions in allergic hypersensitivity. Additionally, the NE immunizations significantly increased antigen-specific IL-10 production and regulatory T-cell counts, and the protection induced by NE was dependent in part on IL-10. Control animals immunized with intranasal peanut in saline had no modulation of their allergic response.

CONCLUSIONS

NE adjuvant-mediated induction of mucosal T_H17 and systemic T_H1-biased immunity can suppress T_H2-mediated allergy through multiple mechanisms and protect against anaphylaxis. These results suggest the potential therapeutic utility of this approach in the setting of food allergy.

Lipid-Based Particles: Versatile Delivery Systems for Mucosal Vaccination against Infection

Vaccination is the process of administering immunogenic formulations in order to induce or harness antigen (Ag)-specific antibody and T cell responses in order to protect against infections. Important successes have been obtained in protecting individuals against many deleterious pathological situations after parenteral vaccination. However, one of the major limitations of the current vaccination strategies is the administration route that may not be optimal for the induction of immunity at the site of pathogen entry, i.e., mucosal surfaces. It is now well documented that immune responses along the genital, respiratory, or gastrointestinal tracts have to be elicited locally to ensure efficient trafficking of effector and memory B and T cells to mucosal tissues. Moreover, needle-free mucosal delivery of vaccines is advantageous in terms of safety, compliance, and ease of administration. However, the quest for mucosal vaccines is challenging due to (1) the fact that Ag sampling has to be performed across the epithelium through a relatively limited number of portals of entry; (2) the deleterious acidic and proteolytic environment of the mucosae that affect the stability, integrity, and retention time of the applied Ags; and (3) the tolerogenic environment of mucosae, which requires the addition of adjuvants to elicit efficient effector immune responses. Until now, only few mucosally applicable vaccine formulations have been developed and successfully tested. In animal models and clinical trials, the use of lipidic structures such as liposomes, virosomes, immune stimulating complexes, gas-filled microbubbles and emulsions has proven efficient for the mucosal delivery of associated Ags and the induction of local and systemic immune reponses. Such particles are suitable for mucosal delivery because they protect the associated payload from degradation and deliver concentrated amounts of Ags via specialized sampling cells (microfold cells) within the mucosal epithelium to underlying antigen-presenting cells. The review aims at summarizing recent development in the field of mucosal vaccination using lipid-based particles. The modularity ensured by tailoring the lipidic design and content of particles, and their known safety as already established in humans, make the continuing appraisal of these vaccine candidates a promising development in the field of targeted mucosal vaccination.

Advances Towards Painless Vaccination and Newer Modes of Vaccine Delivery

Vaccines have been successful in reducing the mortality and morbidity, but most of them are delivered by intramuscular or intravenous route. They are associated with pain to the baby and bring lot of anxiety for the parents. There has been a marked increase in the number of injections required in first two years of life for completing the vaccination schedule. Hence, there is a need to have a painless vaccine delivery system. Numerous new routes of vaccination like, oral, nasal and transdermal routes are being tried. Oral polio and intranasal influenza have already been a success. Other newer approaches like edible vaccines, nasal sprays, dry powder preparations, jet injectors, microneedles and nanopatches are promising in delivering painless vaccines. Many of them are under clinical trials. These vaccine delivery systems will not only be painless but also cost effective, safe and easy to administer in mass population. They may be devoid of the need of cold chain. Painless delivery system will ensure better compliance to vaccination schedule.

Nasal Vaccine Delivery

The mucosal surfaces represent the major site of entry of many pathogens, and major challenges in vaccine development include safety and stability in a suitable dosage form. Micro- and nanocarrier-based delivery systems as nasal vaccines induce humoral, cellular, and mucosal immunity. The nasal route of vaccination could also offer immunity at several distant mucosal sites (oral, rectal, vaginal, and pulmonary), which is considered a simplified and cost-effective mode of vaccination with enhanced patient compliance. Most of the nasal vaccine delivery systems in the form of microparticulates, nanoparticulates, and liposomes are currently under development and prove to offer immunity in animal models. The importance and potential of the nasal route of administration for vaccines is unexplored, and this chapter outlines the opportunities, challenges, and potential delivery solutions to facilitate the development of improved nasal vaccines for infectious diseases.

Modified Nanoemulsions with Iron Oxide for Magnetic Resonance Imaging

A nanoemulsion (NE) is a surfactant-based, oil-in-water, nanoscale, high-energy emulsion with a mean droplet diameter of 400–600 nm. When mixed with antigen and applied nasally, a NE acts as a mucosal adjuvant and induces mucosal immune responses. One possible mechanism for the adjuvant effect of this material is that it augments antigen uptake and distribution to lymphoid tissues, where the immune response is generated. Biocompatible iron oxide nanoparticles have been used as a unique imaging approach to study the dynamics of cells or molecular migration. To study the uptake of NEs and track them in vivo, iron oxide nanoparticles were synthesized and dispersed in soybean oil to make iron oxide-modified NEs. Our results show that iron oxide nanoparticles can be stabilized in the oil phase of the nanoemulsion at a concentration of 30 µg/μL and the iron oxide-modified NEs have a mean diameter of 521 nm. In vitro experiments demonstrated that iron oxide-modified NEs can affect uptake by TC-1 cells (a murine epithelial cell line) and reduce the intensity of magnetic resonance (MR) images by shortening the T2 time. Most importantly, in vivo studies demonstrated that iron oxide-modified NE could be detected in mouse nasal septum by both transmission electron microscopy and MR imaging. Altogether these experiments demonstrate that iron oxide-modified NE is a unique tool that can be used to study uptake and distribution of NEs after nasal application.

Intranasal nanoemulsion-based inactivated respiratory syncytial virus vaccines protect against viral challenge in cotton rats

Respiratory Syncytial Virus is a leading cause of bronchiolitis and pneumonia in infants, the elderly and individuals with compromised immune systems. Despite decades of research, there is currently no available vaccine for RSV. Our group has previously demonstrated that intranasal immunization of mice with RSV inactivated by and adjuvanted with W805EC nanoemulsion elicits robust humoral and cellular immune responses, resulting in protection against RSV infection. This protection was achieved without the induction of airway hyper-reactivity or a Th2-skewed immune response. The cotton rat Sigmodon hispidus has been used for years as an excellent small animal model of RSV disease. Thus, we extended these rodent studies to the more permissive cotton rat model. Intranasal immunization of the nanoemulsion-adjuvanted RSV vaccines induced high antibody titers and a robust Th1-skewed cellular response. Importantly, vaccination provided sterilizing cross-protective immunity against a heterologous RSV challenge and did not induce marked or severe histological effects or eosinophilia in the lung after viral challenge. Overall, these data demonstrate that nanoemulsion-formulated whole RSV vaccines are both safe and effective for immunization in multiple animal models.

Immunomodulation of TH2 biased immunity with mucosal administration of nanoemulsion adjuvant

TH2-biased immune responses are associated with inadequate protection against some pathogens and with cancer, colitis, asthma and allergy. Since most currently used vaccine adjuvants induce a TH2-biased response, this has led to interest in developing adjuvants capable of activating TH1 immunity and modulating existing TH2 responses. Immunotherapies to shift immune responses from TH2 to TH1 have generally required prolonged immunization protocols and have not induced effective TH1 responses. We have demonstrated that nanoscale emulsions (NE), a novel mucosal adjuvant, induce robust IgA and IgG antibody responses and TH1/TH17 cellular immunity resulting in protection against a variety of respiratory and mucosal infections. Because intranasal (i.n.) delivery of NE adjuvant consistently induces TH1/TH17 biased responses, we hypothesized that NE could be used as a therapeutic vaccine to redirect existing TH2 polarized immunity towards a more balanced TH1/TH2 profile. To test this, a TH2 immune response was established by intramuscular immunization of mice with alum-adjuvanted hepatitis B surface antigen (HBs), followed by a single subsequent i.n. immunization with NE-HBs. These animals exhibited increased TH1 associated immune responses and IL-17, and decreased TH2 cytokines (IL-4 and IL-5) and IgG1. NE immunization induced regulatory T cells and IL-10, and IL-10 was required for the suppression of TH2 immunity. These data demonstrate that NE-based vaccines can modulate existing TH2 immune responses to promote TH1/TH17 immunity and suggest the potential therapeutic use of NE vaccines for diseases associated with TH2 immunity.

Nanoparticulate mediated transcutaneous immunization: Myth or reality

Transcutaneous immunization (TCI) is a promising route of vaccine delivery through skin due to many well documented advantages. The main obstacle in TCI is the skin's top dead layer i.e. stratum corneum which is difficult to penetrate. Efficiently delivery of antigen to the immune competent cells of epidermis or dermis in TCI might elicit an effective immune response. In this review, skin immunology with a particular focus on potential of immunological active receptors in influencing adaptive immune responses is highlighted. The challenges with TCI and methods to improve it using different adjuvants, chemical and physical approaches, delivery systems, and combination of above methods to further improve immune response following skin application of antigen are elaborately discussed. Nanoparticulate vaccine delivery systems with reference to their applications in TCI are classified according to their chronological development. Conclusively, clinical translations of above methods are also briefly reviewed.

FROM THE CLINICAL EDITOR

Transcutaneous immunization has been investigated by many as a promising route of vaccination. In this comprehensive review article, the authors described and discussed the existing knowledge and difficulties in this approach. Furthermore, ways of improving transcutaneous delivery were also reviewed.

Effect of Chronic Uremia on the Cell Surface Expression of B7 Family Costimulatory Molecules in an HLA-A2 Transgenic Mouse Model of Chronic Kidney Disease

Uremia due to chronic kidney disease (CKD) in humans is associated with immune dysfunction, increased susceptibility to infections, immune-activation-associated inflammation, and poor responses to vaccines. The pathophysiologic basis of these immune defects is hypothesized to be associated with a wide range of immunologic abnormalities, including an inability to sufficiently express the B7 family (B7-1, CD80; B7-2, CD86) of T-cell costimulatory molecules. However, testing the hypothesis that a state of chronic uremia contributes to attenuated expression of CD80 or CD86 has been difficult because few animal models faithfully recapitulate the immune defects observed in human CKD patients. We used a humanized mouse in a model of surgically induced renal failure and secondary chronic uremia to evaluate the effect of uremia on the expression of these markers. In a manner that resembles the changes observed in CKD patients, surgically induced CKD in mice resulted in decreased costimulatory CD86 expression compared with that in sham-operated controls. Immunodeficiency was functionally demonstrated in this mouse model by documenting an attenuated immune response to a cholera-toxin-based hepatitis B vaccine. This model will be useful for investigating the mechanisms involved in chronic uremia-associated immunodeficiency, poor response to vaccination, and problems associated with immunization of CKD patients.

Conjugating influenza a (H1N1) antigen to n-trimethylaminoethylmethacrylate chitosan nanoparticles improves the immunogenicity of the antigen after nasal administration

As one of the most serious infectious respiratory diseases, influenza A (H1N1) is a great threat to human health, and it has created an urgent demand for effective vaccines. Nasal immunization can induce both systemic and mucosal immune responses against viruses, and it can serve as an ideal route for vaccination. However, the low immunogenicity of antigens on nasal mucosa is a high barrier for the development of nasal vaccines. In this study, we covalently conjugated an influenza A (H1N1) antigen to the surface of N-trimethylaminoethylmethacrylate chitosan (TMC) nanoparticles (H1N1-TMC/NP) through thioester bonds to increase the immunogenicity of the antigen after nasal administration. SDS-PAGE revealed that most of the antigen was conjugated on TMC nanoparticles, and an in vitro biological activity assay confirmed the stability of the antigen after conjugation. After three nasal immunizations, the H1N1-TMC/NP induced significantly higher levels of serum IgG and mucosal sIgA compared with free antigen. A hemagglutination inhibition assay showed that H1N1-TMC/NP induced much more protective antibodies than antigen-encapsulated nanoparticles or alum-precipitated antigen (I.M.). In the mechanistic study, H1N1-TMC/NP was shown to stimulate macrophages to produce IL-1β and IL-6 and to stimulate spleen lymphocytes to produce IL-2 and IFN-γ. These results indicated that H1N1-TMC/NP may be an effective vaccine against influenza A (H1N1) viruses for use in nasal immunization.

Formulation, high throughput in vitro screening and in vivo functional characterization of nanoemulsion-based intranasal vaccine adjuvants

Vaccine adjuvants have been reported to induce both mucosal and systemic immunity when applied to mucosal surfaces and this dual response appears important for protection against certain pathogens. Despite the potential advantages, however, no mucosal adjuvants are currently approved for human use. Evaluating compounds as mucosal adjuvants is a slow and costly process due to the need for lengthy animal immunogenicity studies. We have constructed a library of 112 intranasal adjuvant candidate formulations consisting of oil-in-water nanoemulsions that contain various cationic and nonionic surfactants. To facilitate adjuvant development we first evaluated this library in a series of high-throughput, in vitro assays for activities associated with innate and adaptive immune activation in vivo. These in vitro assays screened for the ability of the adjuvant to bind to mucin, induce cytotoxicity, facilitate antigen uptake in epithelial and dendritic cells, and activate cellular pathways. We then sought to determine how these parameters related to adjuvant activity in vivo. While the in vitro assays alone were not enough to predict the in vivo adjuvant activity completely, several interesting relationships were found with immune responses in mice. Furthermore, by varying the physicochemical properties of the surfactant components (charge, surfactant polar head size and hydrophobicity) and the surfactant blend ratio of the formulations, the strength and type of the immune response generated (T_H1, T_H2, T_H17) could be modulated. These findings suggest the possibility of using high-throughput screens to aid in the design of custom adjuvants with unique immunological profiles to match specific mucosal vaccine applications.

Nanoemulsion-based mucosal adjuvant induces apoptosis in human epithelial cells

Nanoemulsions (NEs) are adjuvants that enhance antigen penetration of the nasal mucosa, increase cellular uptake of antigens by both epithelial and dendritic cells, and promote the migration of antigen-loaded dendritic cells to regional lymph nodes within 24-h of vaccine administration. The objective of this study was to elucidate cell death caused by W805EC NE and identify caspases and genes associated with death pathways. Consistent with this aim, we show that exposure of human epithelial cells (EC), both RPMI 2650 and FaDu, to NE results in the activation of caspases (1, 3/7, 6, 8, and 9) and the expression of genes involved in apoptotic as well as authophagy and necrosis pathways. Interestingly, the NE activates caspase 8 which promotes "immunogenic apoptosis". The rescue assay was employed to investigate the fate of RPMI 2650 cells treated with W805EC NE. After four-hour treatment with as little as 0.03% of NE no cells were rescued at 72h. Remarkably, immediately after four-hour treatment, the cells morphologically resembled untreated cells and most of the cells were alive. Altogether, these results suggest that NE induces death of human ECs through multiple pathways. Epithelial cell death caused by W805EC may have further implications on antigen uptake, processing, and presentation by DC's.

Nanocarriers: a versatile approach for mucosal vaccine delivery

Infectious agents generally use mucosal surfaces as entry port to the body thereby necessitating the need of development of mucosal vaccine as vaccination is important for disease avoidance and suppression. Vaccination through mucosal route is a promising strategy to elicit efficient immune response as parentally administered vaccines induce poor mucosal immunity in general. Safety, economy and stability are highly desired with vaccines and this can be achieved with use of delivery cargos. This review focuses on challenges related with mucosal vaccines and use of nanocarriers as suitable cargos to cater the antigen effectively to the desired site. The review also includes different factors which are to be considered regarding the performance of the nanocarriers and clinical status of these systems.

Mannosylated and lipid A-incorporating cationic liposomes constituting microneedle arrays as an effective oral mucosal HBV vaccine applicable in the controlled temperature chain

To develop an effective, convenient and stable mucosal vaccine against hepatitis B virus (HBV), the mannose-PEG-cholesterol/lipid A-liposomes (MLLs) loaded with HBsAg were prepared by the procedure of emulsification-lyophilization and, subsequently, filled into the microholes of microneedle array reverse molds and dried to form the proHBsAg-MLLs microneedle arrays (proHMAs). The proHMAs were stable even at 40 °C for up to 3 days and hard enough to pierce porcine skin but, upon rehydration, rapidly dissolved recovering the HBsAg-MLLs without obvious changes in size and antigen association efficiency. Notably, immunization of mice only once with the proHMAs at oral mucosa induced robust systemic and widespread mucosal immunoresponses, as evidenced by the high levels of HBsAg-specific IgG in the sera and IgA in the salivary, intestinal and vaginal secretions. In addition, a strong cellular immunity against HBV had been established through a mixed Th1/Th2 response, as confirmed by a significant increase in CD8(+) T cells as well as the enhanced levels of IgG2a and IFN-γ in the treated mice. Thus, the proHMAs can be conveniently vaccinated via oral mucosal route to set up a multiple immune defense against HBV invasion and, in addition, may be a stable HBV vaccine applicable in the controlled temperature chain for wide distribution.

Gold nanoparticles displaying tumor-associated self-antigens as a potential vaccine for cancer immunotherapy

Golden vaccine for cancers. Gold nanoparticles enable efficient antigen delivery to dendritic cells and then activate the cells to facilitate cross-presentation, inducing antigen-specific cytotoxic T-lymphocyte responses for effective cancer therapy.

Distinct pathways of humoral and cellular immunity induced with the mucosal administration of a nanoemulsion adjuvant

Nasal administration of an oil-in-water nanoemulsion (NE) adjuvant W805EC produces potent systemic and mucosal, Th-1- and Th-17-balanced cellular responses. However, its molecular mechanism of action has not been fully characterized and is of particular interest because NE does not contain specific ligands for innate immune receptors. In these studies, we demonstrate that W805EC NE adjuvant activates innate immunity, induces specific gene transcription, and modulates NF-κB activity via TLR2 and TLR4 by a mechanism that appears to be distinct from typical TLR agonists. Nasal immunization with NE-based vaccine showed that the TLR2, TLR4, and MyD88 pathways and IL-12 and IL-12Rβ1 expression are not required for an Ab response, but they are essential for the induction of balanced Th-1 polarization and Th-17 cellular immunity. NE adjuvant induces MHC class II, CD80, and CD86 costimulatory molecule expression and dendritic cell maturation. Further, upon immunization with NE, adjuvant mice deficient in the CD86 receptor had normal Ab responses but significantly reduced Th-1 cellular responses, whereas animals deficient in both CD80 and CD86 or lacking CD40 failed to produce either humoral or cellular immunity. Overall, our data show that intranasal administration of Ag with NE induces TLR2 and TLR4 activation along with a MyD88-independent Ab response and a MyD88-dependent Th-1 and Th-17 cell-mediated immune response. These findings suggest that the unique properties of NE adjuvant may offer novel opportunities for understanding previously unrecognized mechanisms of immune activation important for generating effective mucosal and systemic immune responses.