Novel approaches to vaccine delivery

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.

Enhancement of immune responses using ovalbumin-conjugated Eucommia ulmoides leaf polysaccharides encapsulated in a cubic liquid-crystalline phase delivery system

BACKGROUND

To improve the adjuvant activity of polysaccharides from Eucommia ulmoides leaves (PsEUL) in inducing an effective immune response against ovalbumin (OVA), PsEUL were conjugated to OVA using the N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) method. The synthesized PsEUL-OVA was encapsulated using phytantriol and F127 to produce PsEUL-OVA cubosomes (Cubs), a novel delivery system. The physicochemical properties and immune modulation effects of this novel delivery system were explored.

RESULTS

In vitro, PsEUL-OVA/Cubs carrying large amounts of OVA were rapidly phagocytized by macrophages and upregulated macrophage proliferation, thereby stimulating cytokine production (interleukin (IL)-6 and IL-4). In vivo, PsEUL-OVA/Cubs increased the titer of OVA-specific antibodies (immunoglobulin (Ig)G, IgG2b, IgG2a and IgG1) and cytokine levels (IL-2, IL-6, IL-4 and interferon-γ). In addition, the cubosomes promoted the differentiation of CD8⁺ and CD4⁺ T cells in the spleen and the maturation of dendritic cells (DCs). These results indicated that PsEUL-OVA/Cubs stimulated both cellular and humoral immune responses by enhancing the phagocytic activity of DCs and macrophages and increasing the antigen presentation efficiency.

CONCLUSION

Collectively, the findings demonstrate that PsEUL-antigen/Cubs can be a useful delivery vehicle with immune response-promoting effects. Therefore, this study lays the foundation for the development of novel adjuvant-antigen delivery systems with potential applications in vaccine design. © 2022 Society of Chemical Industry.

RBD decorated PLA nanoparticle admixture with aluminum hydroxide elicit robust and long lasting immune response against SARS-CoV-2

Nanoparticles-based multivalent antigen display has the capability of mimicking natural virus infection characteristics, making it useful for eliciting potent long-lasting immune response. Several vaccines are developed against global pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However these subunit vaccines use mammalian expression system, hence mass production with rapid pace is a bigger challenge. In contrast E. coli based subunit vaccine production circumvents these limitations.The objective of the present investigation was to develop nanoparticle vaccine with multivalent display of receptor binding domain (RBD) of SARS-CoV-2 expressed in E. coli. Results showed that RBD entrapped PLA (Poly lactic acid) nanoparticle in combination with aluminum hydroxide elicited 9-fold higher immune responses as compared to RBD adsorbed aluminum hydroxide, a common adjuvant used for human immunization. It was interesting to note that RBD entrapped PLA nanoparticle with aluminum hydroxide not only generated robust and long-lasting antibody response but also provided Th1 and Th2 balanced immune response. Moreover, challenge with 1 µg of RBD alone was able to generate secondary antibody response, suggesting that immunization with RBD-PLA nanoparticleshas the ability to elicit memory antibody against RBD. Plaque assay revealed that the antibody generated using the polymeric formulation was able to neutralize SARS-CoV-2.The RBD entrapped PLA nanoparticles blended with aluminum hydroxide thus has potential to develop asa subunit vaccine against COVID-19.

A Dual-Delivery Platform for Vaccination using Antigen-loaded Nanoparticles in Dissolving Microneedles

Effective vaccines delivered via painless methods would revolutionize the way people approach vaccinations. This study focused on the development of fast-dissolving microneedles (MNs) to deliver antigen-loaded sustained release polymeric nanoparticles (NPs), achieving a dual-delivery platform for vaccination through the skin. The platform utilizes dissolving MNs (dMNs), which penetrate to the epidermal layer of the skin and rapidly dissolve, releasing the antigen-loaded NPs. In this study, seven dissolving microneedle formulations were tested based on screening of various biocompatible and biodegradable polymers and sugars. The lead dMN formulation was selected based on optimal mechanical strength and dissolution of the needles and was loaded with poly(lactic-co-glycolic) acid (PLGA) NPs encapsulating a model influenza matrix 2 (M2) protein antigen. Antigen-loading efficiency in the needles was determined by centrifugation of the lead formulation containing various concentrations of antigen nanoparticles. Next, the reproducibility and translatability of ex vivo mechanical strength and dissolvability of the lead M2 PLGA NP-loaded dMN formulation was assessed by formulating and testing two different microneedle arrays on murine and porcine skin. Finally, the lead microneedle array was loaded with fluorescent dye NPs and evaluated for pore formation and closure in vivo in a murine model. This proof-of-concept study yielded an easy-to-formulate, well-characterized, translatable antigen NP-loaded dMN platform for transdermal vaccine administration.

Stability of lyophilized and spray dried vaccine formulations

Liquid formulations of vaccines are subject to instabilities that result from degradation processes that proceed via a variety of physical and chemical pathways. In dried formulations, such as those prepared by lyophilization or spray drying, many of these degradation pathways may be avoided or inhibited. Thus, the stability of vaccine formulations can be enhanced significantly in the absence of bulk water. Potential advantages of dry vaccine formulations include extended shelf lives and less stringent cold-chain storage requirements, both of which offer possibilities of reduced vaccine wastage and facilitated distribution to resource-poor areas. Lyophilization and spray drying represent the most common methods of stabilizing vaccines through drying. This article reviews several lyophilized and spray dried vaccines that address a diverse set of pathogens, as well as some of the assays used to quantify their stability. Recent dry vaccine trends include needle-free delivery of dry powder via non-parenteral routes of administration and the incorporation of advanced vaccine adjuvants into formulations, which further contribute to the goal of increasing vaccine distribution to resource-poor areas. Challenges associated with development of these newer technologies are also discussed.

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.

Tunable degradation of acetalated dextran microparticles enables controlled vaccine adjuvant and antigen delivery to modulate adaptive immune responses

Subunit vaccines are often poorly immunogenic, and adjuvants and/or delivery vehicles, such as polymeric microparticles (MPs), can be used to enhance immune responses. MPs can also be used to understand cell activation kinetics and the significant impact antigen and adjuvant release has on adaptive immune responses. By controlling antigen and adjuvant release, we can determine if it is important to have precise temporal control over release of these elements to optimize the peak and duration of protective immunity and improve vaccine safety profiles. In order to study the effect of tunable adjuvant or antigen delivery on generation of adaptive immunity, we used acetalated dextran (Ace-DEX) MPs. Ace-DEX MPs were used because their tunable degradation can be controlled based on polymer cyclic acetal coverage (CAC). Ace-DEX MPs of varying degradation profiles were used to deliver murabutide or ovalbumin (OVA) as a model adjuvant or antigen, respectively. When murabutide was encapsulated within Ace-DEX MPs to test for controlled adjuvant delivery, fast-degrading MPs exhibited higher humoral and cellular responses in vivo at earlier time points, while slow-degrading MPs resulted in stronger responses at later time points. When OVA was encapsulated within Ace-DEX MPs to test for controlled antigen delivery, fast-degrading MPs induced greater antibody and cytokine production throughout the length of the experiment. This differential response suggests the need for distinct, flexible control over adjuvant or antigen delivery and its impact on immune response modulation.

The immune profile induced is crucial to determine the effects of immunocastration over gonadal function, fertility, and GnRH-I expression

PROBLEM

Immunocastration or vaccination against the GnRH-I hormone is a promising alternative to reproductive control in different animal species. Given the low immunogenicity of this hormone, the use of adjuvants becomes necessary.

METHOD OF STUDY

This study evaluated the effects of three adjuvants that induce different immune response profiles over gonadal function, fertility, and expression of GnRH-I. Female mice (n = 6) were vaccinated at days 1 and 30 with a recombinant antigen for immunocastration and different adjuvants that induced preferentially Th1/Th2, Th2, and Th1 immune profiles.

RESULTS

Th1/Th2 response is the most efficient to block reproductive activity in vaccinated animals, reducing the number of luteal bodies and pre-ovulatory follicles. Th2 and Th1/Th2 responses induced an increase in GnRH-I at the hypothalamus.

CONCLUSION

The immune profile induced by different adjuvants is essential on the effects over fertility, gonadal function, and hypothalamic GnRH-I expression in immunocastrated animals.

Cationic liposomes suppress intracellular calcium ion concentration increase via inhibition of PI3 kinase pathway in mast cells

Cationic liposomes are commonly used as vectors to effectively introduce foreign genes (antisense DNA, plasmid DNA, siRNA, etc.) into target cells. Cationic liposomes are also known to affect cellular immunocompetences such as the mast cell function in allergic reactions. In particular, we previously showed that the cationic liposomes bound to the mast cell surface suppress the degranulation induced by cross-linking of high affinity IgE receptors in a time- and dose-dependent manner. This suppression is mediated by impairment of the sustained level of intracellular Ca²⁺ concentration ([Ca²⁺]_i) via inhibition of store-operated Ca²⁺ entry (SOCE). Here we study the mechanism underlying an impaired [Ca²⁺]_i increase by cationic liposomes in mast cells. We show that cationic liposomes inhibit the phosphorylation of Akt and PI3 kinases but not Syk and LAT. As a consequence, SOCE is suppressed but Ca²⁺ release from endoplasmic reticulum (ER) is not. Cationic liposomes inhibit the formation of STIM1 puncta, which is essential to SOCE by interacting with Orai1 following the Ca²⁺ concentration decrease in the ER. These data suggest that cationic liposomes suppress SOCE by inhibiting the phosphorylation of PI3 and Akt kinases in mast cells.

Self-encapsulating Poly(lactic-co-glycolic acid) (PLGA) Microspheres for Intranasal Vaccine Delivery

Herein we describe a formulation of self-encapsulating poly(lactic-co-glycolic acid) (PLGA) microspheres for vaccine delivery. Self-healing encapsulation is a novel encapsulation method developed by our group that enables the aqueous loading of large molecules into premade PLGA microspheres. Calcium phosphate (CaHPO4) adjuvant gel was incorporated into the microspheres as a protein-trapping agent for improved encapsulation of antigen. Microspheres were found to have a median size of 7.05 ± 0.31 μm, with a w/w loading of 0.60 ± 0.05% of ovalbumin (OVA) model antigen. The formulation demonstrated continuous release of OVA over a 49-day period. Released OVA maintained its antigenicity over the measured period of >21 days of release. C57BL/6 mice were immunized via the intranasal route with prime and booster doses of OVA (10 μg) loaded into microspheres or coadministered with cholera toxin B (CTB), the gold standard of mucosal adjuvants. Microspheres generated a Th2-type response in both serum and local mucosa, with IgG antibody responses approaching those generated by CTB. The results suggest that this formulation of self-encapsulating microspheres shows promise for further study as a vaccine delivery system.

Functionalization promotes pathogen-mimicking characteristics of polyanhydride nanoparticle adjuvants

Rational design of adjuvants and delivery systems will promote development of next-generation vaccines to control emerging and re-emerging diseases. To accomplish this, understanding the immune-enhancing properties of new adjuvants relative to those induced by natural infections can help with the development of pathogen-mimicking materials that will effectively initiate innate immune signaling cascades. In this work, the surfaces of polyanhydride nanoparticles composed of sebacic acid (SA) and 1,6-bis(p-carboxyphenoxy) hexane were decorated with an ethylene diamine spacer partially modified with either a glycolic acid linker or an α-1,2-linked di-mannopyranoside (di-mannose) to confer "pathogen-like" properties and enhance adjuvanticity. Co-incubation of linker-modified nanoparticles with dendritic cells (DCs) elicited significant increases in surface expression of MHC I, MHC II, CD86, and CD40, and enhanced secretion of IL-6, IL-12p40, and TNF-α. An 800% increase in uptake of ethylene-diamine-spaced, linker and di-mannose functionalized polyanhydride nanoparticles was also observed. Together, our data showed that linker-functionalized polyanhydride nanoparticles demonstrate similar patterns of uptake, intracellular trafficking, particle persistence, and innate activation as did DCs exposed to Yersinia pestis or Escherichia coli. These results set the stage for rational selection of adjuvant chemistries to induce pathogen-mimicking immune responses. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2762-2771, 2017.

Non-invasive administration of biodegradable nano-carrier vaccines

Polymeric nanoparticulate carriers play an important role and holding a significant potential for the development of novel immunomodulatory agents as easily they are taken up by antigen presenting cells. They allow an enhanced antigen stability, better immunogenicity and immunostimulatory effect with sustained and controlled release of the antigen to the target sites. Better information and vital understanding of mechanism of action, interaction of such vectors with the APCs and dendritic cells and antigen release kinetics in immunomodulatory effects, and improved knowledge of their in vivo fate and distribution are now needed, those collectively would speed up the rational strategies of nanoparticles as carriers for vaccines and other protein antigens. The evolution of such innovative adjuvants for protein and DNA immunizations are an exciting and growing zone in immunology, which may enhance the clinical outcomes in many infectious and non-infectious diseases. This review summarizes the recent advances in nano-vaccinology with polymeric (especially biodegradable) carriers, their methods of preparation, surface modification, their interaction with antigen presenting cells, release of antigens, its kinetics and mechanism in the delivery of vaccines via non-invasive routes.

Preparation and Characterization of Magnetic Nano-in-Microparticles for Pulmonary Delivery

The purpose of this chapter is to detail the formulation and characterization of a magnetically-targeted drug delivery vehicle, termed nano-in-microparticles (NIMs), for pulmonary drug delivery. Currently, chemotherapeutics and antibiotics are delivered systemically and result in whole body side-effects. NIMs are formulated with superparamagnetic iron oxide nanoparticles, termed SPIONs, making these particles targetable to specific lung regions using a strong external magnet. Additionally, these particles can be formulated to contain any drug or therapeutic agent, such that a therapeutic dose can be delivered to a specific tissue location using the SPIONs-magnet interaction. Finally, these particles are in the appropriate size range for pulmonary delivery, making NIMs therapeutics feasibly inhalable.To generate these particles a solution containing lactose, SPIONs, and a microsphere dye (used as a drug surrogate) is spray-dried using a laboratory-scale spray dryer. The resulting dry powder microparticles (NIMs) can be characterized for their size and morphological properties by various techniques that are presented in this chapter.The utility of NIMs as a magnetic field-dependent targeting delivery platform in an in vivo mouse model has been demonstrated, and a protocol detailing the intratracheal delivery of NIMs dry powder is included as a separate chapter in this book.

Induction of antibody response in the oral cavity of dogs following intraocular (eye drop) immunization with Porphyromonas gingivalis cell lysate incorporated in pH-sensitive fusogenic polymer-modified liposomes

Induction of mucosal immune responses against Porphyromonas gingivalis within the oral cavity of dogs was studied by immunizing with pH-sensitive fusogenic polymer (MGluPG)-modified liposome-associated cell lysate. Dogs immunized with P. gingivalis cell lysate-containing MGluPG-modified liposomes by intraocular (eye drop) route displayed significant levels of P. gingivalis cell lysate-specific serum IgG and IgA as well as mucosal IgA antibodies in saliva secretion. Serum and salivary antibodies generated by intraocularly immunized with MGluPG-modified liposome-associated P. gingivalis cell lysate revealed a significant aggregation activity against P. gingivalis, whereas serum and saliva from dogs receiving MGluPG-modified liposomes unentrapping P. gingivalis cell lysate did not show the aggregation activity against P. gingivalis. Furthermore, P. gingivalis-specific antibodies in saliva of immunized dogs inhibited the adherence of P. gingivalis to cultured HeLa cells. More importantly, salivary antibodies induced by intraocular immunization with P. gingivalis cell lysate-containing MGluPG-modified liposomes significantly inhibited the coaggregation of P. gingivalis with Actinomyces naeslundii and the cell damage activity of P. gingivalis against FaDu cells, an oral epithelial cell. These results suggest that intraocularly administered P. gingivalis cell lysate-containing MGluPG-modified liposomes should be an effective mucosal vaccine against P. gingivalis infection in dogs and may be an important tool for the prevention of periodontitis.

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.

Genital Chlamydia trachomatis: understanding the roles of innate and adaptive immunity in vaccine research

Chlamydia trachomatis is the leading cause of bacterial sexually transmitted disease worldwide, and despite significant advances in chlamydial research, a prophylactic vaccine has yet to be developed. This Gram-negative obligate intracellular bacterium, which often causes asymptomatic infection, may cause pelvic inflammatory disease (PID), ectopic pregnancies, scarring of the fallopian tubes, miscarriage, and infertility when left untreated. In the genital tract, Chlamydia trachomatis infects primarily epithelial cells and requires Th1 immunity for optimal clearance. This review first focuses on the immune cells important in a chlamydial infection. Second, we summarize the research and challenges associated with developing a chlamydial vaccine that elicits a protective Th1-mediated immune response without inducing adverse immunopathologies.

PLGA particulate delivery systems for subunit vaccines: Linking particle properties to immunogenicity

Among the emerging subunit vaccines are recombinant protein- and synthetic peptide-based vaccine formulations. However, proteins and peptides have a low intrinsic immunogenicity. A common strategy to overcome this is to co-deliver (an) antigen(s) with (an) immune modulator(s) by co-encapsulating them in a particulate delivery system, such as poly(lactic-co-glycolic acid) (PLGA) particles. Particulate PLGA formulations offer many advantages for antigen delivery as they are biocompatible and biodegradable; can protect the antigens from degradation and clearance; allow for co-encapsulation of antigens and immune modulators; can be targeted to antigen presenting cells; and their particulate nature can increase uptake and cross-presentation by mimicking the size and shape of an invading pathogen. In this review we discuss the pros and cons of using PLGA particulate formulations for subunit vaccine delivery and provide an overview of formulation parameters that influence their adjuvanticity and the ensuing immune response.

Effect of vaccine administration modality on immunogenicity and efficacy

The many factors impacting the efficacy of a vaccine can be broadly divided into three categories: features of the vaccine itself, including immunogen design, vaccine type, formulation, adjuvant and dosing; individual variations among vaccine recipients and vaccine administration-related parameters. While much literature exists related to vaccines, and recently systems biology has started to dissect the impact of individual subject variation on vaccine efficacy, few studies have focused on the role of vaccine administration-related parameters on vaccine efficacy. Parenteral and mucosal vaccinations are traditional approaches for licensed vaccines; novel vaccine delivery approaches, including needless injection and adjuvant formulations, are being developed to further improve vaccine safety and efficacy. This review provides a brief summary of vaccine administration-related factors, including vaccination approach, delivery route and method of administration, to gain a better understanding of their potential impact on the safety and immunogenicity of candidate vaccines.

Phage-fused epitopes fromLeishmania infantumused as immunogenic vaccines confer partial protection againstLeishmania amazonensisinfection

Two mimotopes ofLeishmania infantumidentified by phage display were evaluated as vaccine candidates in BALB/c mice againstLeishmania amazonensisinfection. The epitope-based immunogens, namely B10 and C01, presented as phage-fused peptides; were used without association of a Th1 adjuvant, and they were administered isolated or in combination into animals. Both clones showed a specific production of interferon-gamma (IFN-γ), interleukin-12 (IL-12) and granulocyte/macrophage colony-stimulating factor (GM-CSF) afterin vitrospleen cells stimulation, and they were able to induce a partial protection against infection. Significant reductions of parasite load in the infected footpads, liver, spleen, bone marrow and paws’ draining lymph nodes were observed in the immunized mice, in comparison with the control groups (saline, saponin, wild-type and non-relevant clones). Protection was associated with an IL-12-dependent production of IFN-γ, mediated mainly by CD8+T cells, against parasite proteins. Protected mice also presented low levels of IL-4 and IL-10, as well as increased levels of parasite-specific IgG2a antibodies. The association of both clones resulted in an improved protection in relation to their individual use. More importantly, the absence of adjuvant did not diminish the cross-protective efficacy againstLeishmaniaspp. infection. This study describes for the first time two epitope-based immunogens selected by phage display technology againstL. infantuminfected dogs sera, which induced a partial protection in BALB/c mice infected withL. amazonensis.

Innate endogenous adjuvants prime to desirable immune responses via mucosal routes

Vaccination is an effective strategy to prevent infectious or immune related diseases, which has made remarkable contribution in human history. Recently increasing attentions have been paid to mucosal vaccination due to its multiple advantages over conventional ways. Subunit or peptide antigens are more reasonable immunogens for mucosal vaccination than live or attenuated pathogens, however adjuvants are required to augment the immune responses. Many mucosal adjuvants have been developed to prime desirable immune responses to different etiologies. Compared with pathogen derived adjuvants, innate endogenous molecules incorporated into mucosal vaccines demonstrate prominent adjuvanticity and safety. Nowadays, cytokines are broadly used as mucosal adjuvants for participation of signal transduction of immune responses, activation of innate immunity and polarization of adaptive immunity. Desired immune responses are promptly and efficaciously primed on basis of specific interactions between cytokines and corresponding receptors. In addition, some other innate molecules are also identified as potent mucosal adjuvants. This review focuses on innate endogenous mucosal adjuvants, hoping to shed light on the development of mucosal vaccines.

Chitosan-HPMC-blended microspheres as a vaccine carrier for the delivery of tetanus toxoid

The purpose of this research was to develop a suitable and alternate adjuvant for the tetanus toxoid (TT) vaccine that induces long term immunity after a single-dose immunization. In our study, the preformulation studies were carried out by using different ratios (7/3, 8/2, and 9/1) of chitosan-hydroxypropyl methylcellulose (HPMC)-blended empty microspheres. Moreover, TT was stabilized with heparin (at heparin concentrations of 1%, 2%, 3%, and 4% w/v) and encapsulated in ideal chitosan - HPMC (CHBMS) microspheres, by the water-in-oil-in-water (W/O/W) multiple emulsion method. The vaccine entrapment and the in vitro release efficiency of the CHBMS was evaluated for a period of 90 days. The release of antigens from the microspheres was determined by ELISA. Antigen integrity was investigated by SDS-PAGE. From the optimization studies, it was found that a chitosan/HPMC ratio of 8/2 produced a good yield, with microspheres that were spherical, regular and uniformly-sized. In the CHBMS, a heparin concentration of 3% w/v resulted in well-sustained antigen delivery for a period of 90 days. It was found that the characteristics of initial release could be observed in 2 days, followed by a constant release, and an almost 100% complete release in 90 days. From the in vitro release characteristics, the ideal batch of CHBMS (3% w/v heparin) was evaluated for in vivo studies by the antibody induction method. The antibody levels were measured for different combinations for the period of 9 months, and finally, with a second booster dose after 1 year. In conclusion, it was observed that CHBMS (combination-1) resulted in the antibody level of 4.5 IU/mL of guinea pig serum, and the level was 3.5 IU/mL for the Central Research Institute's alum-adsorbed tetanus toxoid (CRITT) (combination 2), after 1 year, with a second booster dose. This novel approach of using CHBMS may have potential advantages for single-step immunization with vaccines.

Modified thermoresponsive Poloxamer 407 and chitosan sol-gels as potential sustained-release vaccine delivery systems

Thermoresponsive, particle-loaded, Poloxamer 407 (P407)-Pluronic-R® (25R4) or chitosan-methyl cellulose (MC) formulations were developed as single-dose, sustained release vaccines. The sol-gels, loaded either with a particulate vaccine (cubosomes) or soluble antigen (ovalbumin) and adjuvants (Quil A and monophosphoryl lipid A), were free-flowing liquids at room temperature and formed stable gels at physiological temperatures. Rheological results showed that both systems meet the criteria of being thermoresponsive gels. The P407-25R4 sol-gels did not significantly sustain the release of antigen in vivo while the chitosan-MC sol-gels sustained the release of antigen up to at least 14 days after administration. The chitosan-MC sol-gels stimulated both cellular and humoral responses. The inclusion of cubosomes in the sol-gels did not provide a definitive beneficial effect. Further analysis of the formulations with small-angle X-ray scattering (SAXS) revealed that while cubosomes were stable in chitosan-MC gels they were not stable in P407-25R4 formulations. The reason for the mixed response to cubosome-loaded vehicles requires more investigation, however it appears that the cubosomes did not facilitate synchronous vaccine release and may in fact retard release, reducing efficacy in some cases. From these results, chitosan-MC sol-gels show potential as sustained release vaccine delivery systems, as compared to the P407-25R4 system that had a limited ability to sustain antigen release.

Adjuvanted inactivated influenza A(H3N2) vaccines induce stronger immunogenicity in mice and confer higher protection in ferrets than unadjuvanted inactivated vaccines

Influenza viruses are major respiratory pathogens and the development of improved vaccines to prevent these infections is of high priority. Here, we evaluated split inactivated A(H3N2) vaccines (A/Uruguay/716/2007) combined or not with adjuvants (AS03, AS25 and Protollin) and administered by three different routes, intramuscular (i.m.), intranasal (i.n.) or intradermal (i.d.), both in BALB/c mice and in ferrets. Ferrets were challenged with the homologous strain A/Uruguay/716/2007 (H3N2) or the heterologous strain A/Perth/16/2009 (H3N2) 4 weeks after the second immunization with A/Uruguay/716/2007 vaccines. Temperature, weight loss and clinical signs were monitored on a daily basis and nasal washes were performed to evaluate viral titers in the upper respiratory tract. All adjuvanted vaccines induced stronger humoral immune responses than unadjuvanted ones in both mice and ferrets. In mice, the AS03- and AS25-adjuvanted i.m. vaccines generated a mixed Th1-Th2 response at 6 and 19 weeks after the last immunization as shown by the production of IgG1 and IgG2a antibodies as well as the production of IL-2, IL-4 and IFN-γ by CD4+ and CD8+ T cells. HAI and MN titers were also higher in those groups when compared to the i.n. Protollin-adjuvanted and unadjuvanted groups. The Protollin-adjuvanted i.n. vaccine induced a more Th1 oriented response with a significant production of IgA in bronchoalveolar lavages. In ferrets, the AS03- and AS25-adjuvanted i.m. vaccines also induced higher HAI and MN titers compared to the other groups. These vaccines also significantly decreased viral titers after challenge with both the homologous A/Uruguay/716/2007 (H3N2) and the heterologous A/Perth/16/2009 (H3N2) strains. In conclusion, adjuvanted influenza vaccines elicited stronger humoral response in mice and conferred greater protection in naive ferrets than unadjuvanted ones. Interestingly, the AS25 adjuvant system containing monophosphoryl-lipid-A appears particularly promising for developing more potent inactivated influenza vaccines.

Immunologic treatments for precancerous lesions and uterine cervical cancer

Development of HPV-associated cancers not only depends on efficient negative regulation of cell cycle control that supports the accumulation of genetic damage, but also relies on immune evasion that enable the virus to go undetected for long periods of time. In this way, HPV-related tumors usually present MHC class I down-regulation, impaired antigen-processing ability, avoidance of T-cell mediated killing, increased immunosuppression due to Treg infiltration and secrete immunosuppressive cytokines. Thus, these are the main obstacles that immunotherapy has to face in the treatment of HPV-related pathologies where a number of different strategies have been developed to overcome them including new adjuvants. Although antigen-specific immunotherapy induced by therapeutic HPV vaccines was proved extremely efficacious in pre-clinical models, its progression through clinical trials suffered poor responses in the initial trials. Later attempts seem to have been more promising, particularly against the well-defined precursors of cervical, anal or vulvar cancer, where the local immunosuppressive milieu is less active. This review focuses on the advances made in these fields, highlighting several new technologies (such as mRNA vaccine, plant-derived vaccine). The most promising immunotherapies used in clinical trials are also summarized, along with integrated strategies, particularly promising in controlling tumor metastasis and in eliminating cancer cells altogether.

After the early promising clinical results, the development of therapeutic HPV vaccines need to be implemented and applied to the users in order to eradicate HPV-associated malignancies, eradicating existing perception (after the effectiveness of commercial preventive vaccines) that we have already solved the problem.

Sublingual immunization with a subunit influenza vaccine elicits comparable systemic immune response as intramuscular immunization, but also induces local IgA and TH17 responses

Influenza is a vaccine-preventable disease that remains a major health problem world-wide. Needle and syringe are still the primary delivery devices, and injection of liquid vaccine into the muscle is still the primary route of immunization. Vaccines could be more convenient and effective if they were delivered by the mucosal route. Elicitation of systemic and mucosal innate and adaptive immune responses, such as pathogen neutralizing antibodies (including mucosal IgA at the site of pathogen entry) and CD4(+) T-helper cells (especially the Th17 subset), have a critical role in vaccine-mediated protection. In the current study, a sublingual subunit influenza vaccine formulated with or without mucosal adjuvant was evaluated for systemic and mucosal immunogenicity and compared to intranasal and intramuscular vaccination. Sublingual administration of adjuvanted influenza vaccine elicited comparable antibody titers to those elicited by intramuscular immunization with conventional influenza vaccine. Furthermore, influenza-specific Th17 cells or neutralizing mucosal IgA were detected exclusively after mucosal immunization.

Improving vaccines by incorporating immunological coadjuvants

While vaccination continues to be the most successful interventionist health policy to date, infectious disease remains a significant cause of death worldwide. A primary reason that vaccination is not able to generate effective immunity is a lack of appropriate adjuvants capable of initiating the desired immune response. Adjuvant combinations can potentially overcome this problem; however, the possible permutations to consider, which include the route and kinetics of vaccination, as well as combinations of adjuvants, are practically limitless. This review aims to summarize the current understanding of adjuvants and related immunological processes and how this knowledge can and has been applied to the strategic selection of adjuvant combinations as components of vaccines against human infectious disease.

Therapeutic and prophylactic applications of bacteriophage components in modern medicine

As the interactions of phage with mammalian innate and adaptive immune systems are better delineated and with our ability to recognize and eliminate toxins and other potentially harmful phage gene products, the potential of phage therapies is now being realized. Early efforts to use phage therapeutically were hampered by inadequate phage purification and limited knowledge of phage-bacterial and phage-human relations. However, although use of phage as an antibacterial therapy in countries that require controlled clinical studies has been hampered by the high costs of patient trials, their use as vaccines and the use of phage components such as lysolytic enzymes or lysozymes has progressed to the point of commercial applications. Recent studies concerning the intimate associations between mammalian hosts and bacterial and phage microbiomes should hasten this progress.

Inhibitory effects of a cationic liposome on allergic reaction mediated by mast cell activation

Several studies have shown that cationic liposomes exert immunomodulatory effects with low immunogenicity and toxicity, and offer advantages such as easy preparation and targeting. Cationic liposomes not only transport DNA to immune cells but also enhance the function of antigen presenting cells such as dendritic cells and macrophages. Here, we investigated the effect of a particular cationic liposome on mast cell function during allergic reaction. We found that the cationic liposomes bound to the mast cell surface suppressed degranulation induced by cross-linking of high affinity immunoglobulin E receptors in a time- and dose-dependent manner. The suppression of degranulation was mediated by impairment of the sustained level of intracellular Ca(2+) concentration ([Ca(2+)]i) derived from the inhibition of store-operated Ca(2+) entry. The decrease in sustained elevation of [Ca(2+)]i led to the suppression of phosphorylation of soluble N-ethylmaleimide-sensitive factor attachment protein receptor proteins such as SNAP-23, syntaxin-4, which are necessary for membrane fusion between secretory granules and the plasma membrane during degranulation. Furthermore, the cationic liposomes suppressed vascular permeability elevation induced by mast cell activation in mice. These results showed that cationic liposomes possess the novel property of inhibiting mast cell activation, suggesting the possibility of developing cationic liposomes as anti-allergic effectors.

Immunisation with ID83 fusion protein induces antigen-specific cell mediated and humoral immune responses in cattle

In this study we have investigated the potential of mycobacterial proteins as candidate subunit vaccines for bovine tuberculosis. In addition, we have explored the use of TLR-ligands as potential adjuvants in cattle. In vitro screening assays with whole blood from Mycobacterium bovis-infected and BCG-vaccinated cattle demonstrated that fusion protein constructs were most commonly recognised, and the ID83 fusion protein was selected for further immunisation studies. Furthermore, glucopyranosyl lipid A (GLA) and resiquimod (R848), agonists for TLR4 and TLR7/8 respectively, stimulated cytokine production (IL-12, TNF-α, MIP-1β and IL-10) in bovine dendritic cell cultures, and these were formulated as novel oil-in-water emulsions (GLA-SE and R848-SE) for immunisation studies. Immunisation with ID83 in a water-in-oil emulsion adjuvant (ISA70) induced both cell mediated and humoral immune responses, as characterised by antigen-specific IFN-γ production, cell proliferation, IgG1 and IgG2 antibody production. In comparison, ID83 immunisation with the novel adjuvants induced weaker (ID83/R848-SE) or no (ID83/GLA-SE) antigen-specific IFN-γ production and cell proliferation. However, both did induce ID83-specific antibody production, which was restricted to IgG1 antibody isotype. Overall, these results provide encouraging preliminary data for the further development of ID83 in vaccine strategies for bovine TB.

Oral delivery of human biopharmaceuticals, autoantigens and vaccine antigens bioencapsulated in plant cells

Among 12billion injections administered annually, unsafe delivery leads to >20million infections and >100million reactions. In an emerging new concept, freeze-dried plant cells (lettuce) expressing vaccine antigens/biopharmaceuticals are protected in the stomach from acids/enzymes but are released to the immune or blood circulatory system when plant cell walls are digested by microbes that colonize the gut. Vaccine antigens bioencapsulated in plant cells upon oral delivery after priming, conferred both mucosal and systemic immunity and protection against bacterial, viral or protozoan pathogens or toxin challenge. Oral delivery of autoantigens was effective against complications of type 1 diabetes and hemophilia, by developing tolerance. Oral delivery of proinsulin or exendin-4 expressed in plant cells regulated blood glucose levels similar to injections. Therefore, this new platform offers a low cost alternative to deliver different therapeutic proteins to combat infectious or inherited diseases by eliminating inactivated pathogens, expensive purification, cold storage/transportation and sterile injections.

Efficiency of pH-sensitive fusogenic polymer-modified liposomes as a vaccine carrier

The usefulness of pH-sensitive fusogenic polymer-(succinylated poly(glycidol)-(SucPG-) modified liposomes as a vaccine carrier in the induction of immune responses was evaluated. Mice were intraperitoneally immunized with ovalbumin- (OVA-) containing SucPG-modified liposomes. After immunization, significant OVA-specific antibodies were detected in the serum. When sera were analyzed for isotype distribution, OVA-specific IgG1 antibody responses were noted in mice immunized with OVA-containing polymer-unmodified liposomes, whereas immunization with OVA-containing SucPG-modified liposomes resulted in the induction of OVA-specific IgG1, IgG2a, and IgG3 Ab responses. In spleen lymphocytes from mice immunized with OVA-containing SucPG-modified liposomes, both IFN-γ-(Th1-type-) and IL-4-(Th2 type-) specific mRNA were detected. Moreover, substantial production of IFN-γ and IL-4 was demonstrated in spleen cells from OVA-containing SucPG-modified liposomes in vitro. These results suggest that the pH-sensitive fusogenic polymer-(SucPG-) modified liposomes would serve effectively as an antigen delivery vehicle for inducing Th1 and Th2 immune responses.

The effect of antigen encapsulation in chitosan particles on uptake, activation and presentation by antigen presenting cells

Particle-based vaccine delivery systems are under exploration to enhance antigen-specific immunity against safe but poorly immunogenic polypeptide antigens. Chitosan is a promising biomaterial for antigen encapsulation and delivery due to its ability to form nano- and microparticles in mild aqueous conditions thus preserving the antigenicity of loaded polypeptides. In this study, the influence of chitosan encapsulation on antigen uptake, activation and presentation by antigen presenting cells (APCs) is explored. Fluorescein isothiocyanate-labeled bovine serum albumin (FITC-BSA) and ovalbumin (OVA) were used as model protein antigens and encapsulated in chitosan particles via precipitation-coacervation at loading efficiencies >89%. Formulation conditions were manipulated to create antigen-encapsulated chitosan particles (AgCPs) with discrete nominal sizes (300 nm, 1 μm, and 3 μm). Uptake of AgCPs by dendritic cells and macrophages was found to be dependent on particle size, antigen concentration and exposure time. Flow cytometry analysis revealed that uptake of AgCPs enhanced upregulation of surface activation markers on APCs and increased the release of pro-inflammatory cytokines. Lastly, antigen-specific T cells exhibited higher proliferative responses when stimulated with APCs activated with AgCPs versus soluble antigen. These data suggest that encapsulation of antigens in chitosan particles enhances uptake, activation and presentation by APCs.

A new strategy based on SmRho protein loaded chitosan nanoparticles as a candidate oral vaccine against schistosomiasis

Background

Schistosomiasis is one of the most important neglected tropical diseases and an effective control is unlikely in the absence of improved sanitation and vaccination. A new approach of oral vaccination with alginate coated chitosan nanoparticles appears interesting because their great stability and the ease of target accessibility, besides of chitosan and alginate immunostimulatory properties. Here we propose a candidate vaccine based on the combination of chitosan-based nanoparticles containing the antigen SmRho and coated with sodium alginate.

Methods and Findings

Our results showed an efficient performance of protein loading of nanoparticles before and after coating with alginate. Characterization of the resulting nanoparticles reported a size around 430 nm and a negative zeta potential. In vitro release studies of protein showed great stability of coated nanoparticles in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF). Further in vivo studies was performed with different formulations of chitosan nanoparticles and it showed that oral immunization was not able to induce high levels of antibodies, otherwise intramuscular immunization induced high levels of both subtypes IgG1 and IgG2a SmRho specific antibodies. Mice immunized with nanoparticles associated to CpG showed significant modulation of granuloma reaction. Mice from all groups immunized orally with nanoparticles presented significant levels of protection against infection challenge with S. mansoni worms, suggesting an important role of chitosan in inducing a protective immune response. Finally, mice immunized with nanoparticles associated with the antigen SmRho plus CpG had 38% of the granuloma area reduced and also presented 48% of protection against of S. mansoni infection.

Conclusions

Taken together, this results support this new strategy as an efficient delivery system and a potential vaccine against schistosomiasis.

Schistosomiasis is one of the most important neglected tropical diseases and an effective control is unlikely in the absence of improved sanitation and vaccine. The selection of a suitable delivery system and an adjuvant to aid in the stimulation of the appropriate immune response is a critical step in the path to the development and employment of successful anti-schistosome vaccines. Here we propose a candidate vaccine based on chitosan nanoparticles associated with the antigen SmRho and coated with alginate, as an alternative strategy to induce protection against S. mansoni infection. This vaccination strategy offers many technical advantages, including the possibility of administration by oral route, which makes the vaccine safer than injectable vaccines and facilitates its use mainly in underdeveloped areas. Chitosan nanoparticles were prepared and characterized; the results showed that the formulation has features suitable to be delivery orally. Immunization studies suggest that the combination of chitosan nanoparticles associated to the antigen SmRho and CpG is an efficient vaccine candidate against schistosomiasis, which was able to modulate the granuloma area, that represents the major pathological response in schistosomiasis and also to induce protection against infection of S. mansoni.

The immunogenic characteristics associated with multivalent display of Vi polysaccharide antigen using biodegradable polymer particles

Polysaccharides in their great majority are thymus-independent (TI) antigens. Anti-polysaccharide antibody responses are generally weak and characterized by lack of memory, isotype restriction and delayed ontogeny. We report here the generation of protective memory antibody response by multivalent display of polysaccharide antigens on biodegradable polymeric particles. Single dose immunization using polylactide (PLA) polymer particles entrapping Vi capsular polysaccharide antigen from Salmonella typhi promoted isotype switching and induced polysaccharide-specific memory antibody response in experimental animals. PLA nanoparticles as well as microparticles entrapping Vi polysaccharides elicited high IgG titer in comparison to soluble Vi immunization. Immunizations with particles co-entrapping both Vi polysaccharide and tetanus toxoid did not improve the anti-polysaccharide antibody responses. Lower antibody response from co-entrapped formulation was mostly due to inhibition of particle phagocytosis by the macrophages. Immunization using polylactide particles entrapping only Vi polysaccharide with higher density on surface elicited highest secondary antibody response as well as promoted isotype switching. The vaccination potential of particle based immunizations was further confirmed by the generation of quick memory antibody responses while challenging the immunized animals with live S. typhi. This approach provides a multivalent display of polysaccharide antigen using polymer particles and elicits protective memory antibody response without conjugation to a carrier protein.

Transcutaneous immunization: an overview of advantages, disease targets, vaccines, and delivery technologies

Skin is an immunologically active tissue composed of specialized cells and agents that capture and process antigens to confer immune protection. Transcutaneous immunization takes advantage of the skin immune network by inducing a protective immune response against topically applied antigens. This mode of vaccination presents a novel and attractive approach for needle-free immunization that is safe, noninvasive, and overcomes many of the limitations associated with needle-based administrations. In this review we will discuss the developments in the field of transcutaneous immunization in the past decade with special emphasis on disease targets and vaccine delivery technologies. We will also briefly discuss the challenges that need to be overcome to translate early laboratory successes in transcutaneous immunization into the development of effective clinical prophylactics.

Cationic liposomes as adjuvants for influenza hemagglutinin: more than charge alone

Cationic liposomes are known as potent adjuvants for subunit vaccines. The purpose of this work was to study whether the content and the physicochemical properties of the positively charged compound affect the adjuvanticity of cationic liposomes. Cationic liposomes containing a cationic compound (DDA, DPTAP, DC-Chol, or eDPPC) and a neutral phospholipid (DPPC) were prepared by the film hydration-extrusion method and loaded with influenza hemagglutinin (HA) by adsorption. The liposomes were characterized (hydrodynamic diameter, zeta potential, membrane fluidity, HA loading) and their adjuvanticity was tested in mice. The formulations were administered twice subcutaneously and mouse sera were analyzed for HA-specific antibodies by ELISA and for HA-neutralizing antibodies by hemagglutination inhibition (HI) assay. First, the influence of cationic lipid concentration in the DC-Chol/DPPC liposomes (10 vs. 50 mol%) was investigated. The DC-Chol/DPPC (50:50) liposomes showed a higher zeta potential and HA loading, resulting in stronger immunogenicity of the HA/DC-Chol/DPPC (50:50) liposomes compared to the corresponding (10:90) liposomes. Next, we used liposomes composed of 50 mol% cationic lipids to investigate the influence of the nature of the cationic compound on the adjuvant effect. Liposomes made of the four cationic compounds showed similar hydrodynamic diameters (between 100 and 170 nm), zeta potentials (between +40 and +50 mV), HA loading (between 55% and 76%) and melting temperatures (between 40 and 55 °C), except for the DC-Chol liposomes, which did not show any phase transition. HA adjuvanted with the DC-Chol/DPPC (50:50) liposomes elicited significantly higher total IgG1 and IgG2a titers compared to the other liposomal HA formulations and non-adjuvanted HA. A similar trend was observed for the HI titers. These results show that the adjuvanticity of cationic liposomes depends on both the content and the physicochemical properties of the charged compound.

Towards tailored vaccine delivery: needs, challenges and perspectives

The ideal vaccine is a simple and stable formulation which can be conveniently administered and provides life-long immunity against a given pathogen. The development of such a vaccine, which should trigger broad and strong B-cell and T-cell responses against antigens of the pathogen in question, is highly dependent on tailored vaccine delivery approaches. This review addresses vaccine delivery in its broadest scope. We discuss the needs and challenges in the area of vaccine delivery, including restrictions posed by specific target populations, potentials of dedicated stable formulations and devices, and the use of adjuvants. Moreover, we address the current status and perspectives of vaccine delivery via several routes of administration, including non- or minimally invasive routes. Finally we suggest possible directions for future vaccine delivery research and development.

Dissolvable microneedle patches for the delivery of cell-culture-derived influenza vaccine antigens

Microneedle patches are gaining increasing attention as an alternative approach for the delivery of vaccines. In this study, a licensed seasonal influenza vaccine from 2007 to 2008 was fabricated into dissolvable microneedles using TheraJect's microneedle technology (VaxMat). The tips of the microneedles were made of antigens mixed with trehalose and sodium carboxymethyl cellulose. The patches containing 15 μg per strain of the influenza antigen were characterized extensively to confirm the stability of the antigen following fabrication into microneedles. The presence of excipients and very low concentrations of the vaccine on the microneedle patches made it challenging to characterize using the conventional single radial immunodiffusion analysis. Novel techniques such as capture enzyme-linked immunosorbent assay and enzyme digestion followed by mass spectroscopy were used to characterize the antigens on the microneedle patches. The in vivo studies in mice upon microneedle administration show immunogenicity against monovalent H1N1 at doses 0.1 and 1 μg and trivalent vaccine at a dose of 1 μg. The initial data from the mouse studies is promising and indicates the potential use of microneedle technology for the delivery of influenza vaccine.