Targeting the skin for microneedle delivery of influenza vaccine

Novel strategy for Poxviridae prevention: Thermostable combined subunit vaccine patch with intense immune response

Poxviruses gained international attention due to the sharp rise in monkeypox cases in recent years, highlighting the urgent need for the development of a secure and reliable vaccine. This study involved the development of an innovative combined subunit vaccine (CSV) targeting poxviruses, with lumpy skin disease virus (LSDV) serving as the model virus. To this end, the potential sites for poxvirus vaccines were fully evaluated to develop and purify four recombinant proteins. These proteins were then successfully delivered to the dermis in a mouse model by utilizing dissolvable microneedle patches (DMPs). This approach simplified the vaccination procedure and significantly mitigated the associated risk. CSV-loaded DMPs contained four recombinant proteins and a novel adjuvant, CpG, which allowed DMPs to elicit the same intensity of humoral and cellular immunity as subcutaneous injection. Following immunization with SC and DMP, the mice exhibited notable levels of neutralizing antibodies, albeit at a low concentration. It is noteworthy that the CSV loaded into DMPs remained stable for at least 4 months at room temperature, effectively addressing the storage and transportation challenges. Based on the study findings, CSV-loaded DMPs are expected to be utilized worldwide as an innovative technique for poxvirus inoculation, especially in underdeveloped regions. This novel strategy is crucial for the development of future poxvirus vaccines.

Fabrication of microneedle patches with lyophilized influenza vaccine suspended in organic solvent

Skin vaccination by microneedle (MN) patch simplifies the immunization process to increase access to vaccines for global health. Lyophilization has been widely used to stabilize vaccines and other biologics during storage, but is generally not compatible with the MN patch manufacturing processes. In this study, our goal was to develop a method to incorporate lyophilized inactivated H1N1 influenza vaccine into MN patches during manufacturing by suspending freeze-dried vaccine in anhydrous organic solvent during the casting process. Using a casting formulation containing chloroform and polyvinylpyrrolidone, lyophilized influenza vaccine maintained activity during manufacturing and subsequent storage for 3 months at 40 °C. Influenza vaccination using these MN patches generated strong immune responses in a murine model. This manufacturing process may enable vaccines and other biologics to be stabilized by lyophilization and administered via a MN patch.

Self-healing encapsulation and controlled release of vaccine antigens from PLGA microparticles delivered by microneedle patches

There is an urgent need to reduce reliance on hypodermic injections for many vaccines to increase vaccination safety and coverage. Alternative approaches include controlled release formulations, which reduce dosing frequencies, and utilizing alternative delivery devices such as microneedle patches (MNPs). This work explores development of controlled release microparticles made of poly (lactic-co-glycolic acid) (PLGA) that stably encapsulate various antigens though aqueous active self-healing encapsulation (ASE). These microparticles are incorporated into rapid-dissolving MNPs for intradermal vaccination. PLGA microparticles containing Alhydrogel are loaded with antigens separate from microparticle fabrication using ASE. This avoids antigen expsoure to many stressors. The microparticles demonstrate bi-phasic release, with initial burst of soluble antigen, followed by delayed release of Alhydrogel-complexed antigen over approximately 2 months in vitro. For delivery, the microparticles are incorporated into MNPs designed with pedestals to extend functional microneedle length. These microneedles readily penetrate skin and rapidly dissolve to deposit microparticles intradermally. Microparticles remain in the tissue for extended residence, with MNP-induced micropores resealing readily. In animal models, these patches generate robust immune responses that are comparable to conventional administration techniques. This lays the framework for a versatile vaccine delivery system that could be self-applied with important logistical advantages over hypodermic injections.

Stable incorporation of GM-CSF into dissolvable microneedle patch improves skin vaccination against influenza

The widely used influenza subunit vaccine would benefit from increased protection rates in vulnerable populations. Skin immunization by microneedle (MN) patch can increase vaccine immunogenicity, as well as increase vaccination coverage due to simplified administration. To further increase immunogenicity, we used granulocyte-macrophage colony stimulating factor (GM-CSF), an immunomodulatory cytokine already approved for skin cancer therapy and cancer support treatment. GM-CSF has been shown to be upregulated in skin following MN insertion. The GM-CSF-adjuvanted vaccine induced robust and long-lived antibody responses cross-reactive to homosubtypic and heterosubtypic influenza viruses. Addition of GM-CSF resulted in increased memory B cell persistence relative to groups given influenza vaccine alone and led to rapid lung viral clearance following lethal infection with homologous virus in the mouse model. Here we demonstrate that successful incorporation of the thermolabile cytokine GM-CSF into MN resulted in improved vaccine-induced protective immunity holding promise as a novel approach to improved influenza vaccination. To our knowledge, this is the first successful incorporation of a cytokine adjuvant into dissolvable MNs, thus advancing and diversifying the rapidly developing field of MN vaccination technology.

Skin immunization by microneedle patch overcomes statin-induced suppression of immune responses to influenza vaccine

Recent studies indicated that in elderly individuals, statin therapy is associated with a reduced response to influenza vaccination. The present study was designed to determine effects on the immune response to influenza vaccination induced by statin administration in a mouse model, and investigate potential approaches to improve the outcome of vaccination on the background of statin therapy. We fed middle aged BALB/c mice a high fat “western” diet (WD) alone or supplemented with atorvastatin (AT) for 14 weeks, and control mice were fed with the regular rodent diet. Mice were immunized with a single dose of subunit A/Brisbane/59/07 (H1N1) vaccine, either systemically or with dissolving microneedle patches (MNPs). We observed that a greater age-dependent decline in the hemagglutinin inhibition titers occurred in systemically-immunized mice than in MNP- immunized mice. AT dampened the antibody response in the animals vaccinated by either route of vaccine delivery. However, the MNP-vaccinated AT-treated animals had ~20 times higher total antibody levels to the influenza vaccine than the systemically vaccinated group one month postvaccination. We propose that microneedle vaccination against influenza provides an approach to ameliorate the immunosuppressive effect of statin therapy observed with systemic immunization.

Self-Assembly DNA Polyplex Vaccine inside Dissolving Microneedles for High-Potency Intradermal Vaccination

The strong immunogenicity induction is the powerful weapon to prevent the virus infections. This study demonstrated that one-step synthesis of DNA polyplex vaccine in microneedle (MN) patches can induce high immunogenicity through intradermal vaccination and increase the vaccine stability for storage outside the cold chain. More negative charged DNA vaccine was entrapped into the needle region of MNs followed by DNA polyplex formation with branched polyethylenimine (bPEI) pre-coated in the cavities of polydimethylsiloxane (PDMS) molds that can deliver more DNA vaccine to immune-cell rich epidermis with high transfection efficiency. Our data in this study support the safety and immunogenicity of the MN-based vaccine; the MN patch delivery system induced an immune response 3.5-fold as strong as seen with conventional intramuscular administration; the DNA polyplex formulation provided excellent vaccine stability at high temperature (could be stored at 45ºC for at least 4 months); the DNA vaccine is expected to be manufactured at low cost and not generate sharps waste. We think this study is significant to public health because there is a pressing need for an effective vaccination in developing countries.

Tolerability, usability and acceptability of dissolving microneedle patch administration in human subjects

To support translation of microneedle patches from pre-clinical development into clinical trials, this study examined the effect of microneedle patch application on local skin reactions, reliability of use and acceptability to patients. Placebo patches containing dissolving microneedles were administered to fifteen human participants. Microneedle patches were well tolerated in the skin with no pain or swelling and only mild erythema localized to the site of patch administration that resolved fully within seven days. Microneedle patches could be administered by hand without the need of an applicator and delivery efficiencies were similar for investigator-administration and self-administration. Microneedle patch administration was not considered painful and the large majority of subjects were somewhat or fully confident that they self-administered patches correctly. Microneedle patches were overwhelmingly preferred over conventional needle and syringe injection. Altogether, these results demonstrate that dissolving microneedle patches were well tolerated, easily usable and strongly accepted by human subjects, which will facilitate further clinical translation of this technology.

Ebola Vaccination Using a DNA Vaccine Coated on PLGA-PLL/γPGA Nanoparticles Administered Using a Microneedle Patch

Ebola DNA vaccine is incorporated into PLGA-PLL/γPGA nanoparticles and administered to skin using a microneedle (MN) patch. The nanoparticle delivery system increases vaccine thermostability and immunogenicity compared to free vaccine. Vaccination by MN patch produces stronger immune responses than intramuscular administration.

Fluzone® intra-dermal (Intanza®/Istivac® Intra-dermal): An updated overview

Influenza is a highly contagious respiratory acute viral disease which imposes a very heavy burden both in terms of epidemiology and costs, in the developed countries as well as in the developing ones. It represents a serious public health concern and vaccination constitutes an important tool to reduce or at least mitigate its burden. Despite the existence of a broad armamentarium against influenza and despite all the efforts and recommendations of international organisms to broaden immunization, influenza vaccination coverage is still far from being optimal. This, taken together with logistic and technical difficulties that can result into vaccine shortage, makes intra-dermal (ID) vaccines, such as Fluzone® ID and Intanza®, particularly attractive. ID vaccines are comparable and, in some cases, superior to intra-muscular/sub-cutaneous vaccines in terms of immunogenicity, safety, reactogenicity, tolerability and cross-protection profiles, as well as in terms of patient preference, acceptance and vaccine selection. Further advances, such as Fluzone® ID with alternative B strains and Quadrivalent Fluzone® ID or the possibility of self-administering the vaccines, make influenza ID vaccines even more valuable.

Improved immunogenicity of individual influenza vaccine components delivered with a novel dissolving microneedle patch stable at room temperature

Prevention of seasonal influenza epidemics and pandemics relies on widespread vaccination coverage to induce protective immunity. In addition to a good antigenic match with the circulating viruses, the effectiveness of individual strains represented in the trivalent vaccines depends on their immunogenicity. In this study, we evaluated the immunogenicity of H1N1, H3N2, and B seasonal influenza virus vaccine strains delivered individually with a novel dissolving microneedle patch and the stability of this formulation during storage at 25 °C. Our data demonstrate that all strains retained their antigenic activity after incorporation in the dissolving patches as measured by single radial diffusion (SRID) assay and immune responses to vaccination in BALB/c mice. After a single immunization, all three antigens delivered with microneedle patches induced superior neutralizing antibody titers compared to intramuscular immunization. Cutaneous antigen delivery was especially beneficial for the less immunogenic B strain. Mice immunized with dissolving microneedle patches encapsulating influenza A/Brisbane/59/07 (H1N1) vaccine were fully protected against lethal challenge by homologous mouse-adapted influenza virus. All vaccine components retained activity during storage at room temperature for at least 3 months as measured in vitro by SRID assay and in vivo by mouse immunization studies. Our data demonstrate that dissolving microneedle patches are a promising advance for influenza cutaneous vaccination due to improved immune responses using less immunogenic influenza antigens and enhanced stability.

Enhanced Stability of Inactivated Influenza Vaccine Encapsulated in Dissolving Microneedle Patches

PURPOSE

This study tested the hypothesis that encapsulation of influenza vaccine in microneedle patches increases vaccine stability during storage at elevated temperature.

METHODS

Whole inactivated influenza virus vaccine (A/Puerto Rico/8/34) was formulated into dissolving microneedle patches and vaccine stability was evaluated by in vitro and in vivo assays of antigenicity and immunogenicity after storage for up to 3 months at 4, 25, 37 and 45°C.

RESULTS

While liquid vaccine completely lost potency as determined by hemagglutination (HA) activity within 1-2 weeks outside of refrigeration, vaccine in microneedle patches lost 40-50% HA activity during or shortly after fabrication, but then had no significant additional loss of activity over 3 months of storage, independent of temperature. This level of stability required reduced humidity by packaging with desiccant, but was not affected by presence of oxygen. This finding was consistent with additional stability assays, including antigenicity of the vaccine measured by ELISA, virus particle morphological structure captured by transmission electron microscopy and protective immune responses by immunization of mice in vivo.

CONCLUSIONS

These data show that inactivated influenza vaccine encapsulated in dissolving microneedle patches has enhanced stability during extended storage at elevated temperatures.

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.

Effective cutaneous vaccination using an inactivated chikungunya virus vaccine delivered by Foroderm

Foroderm is a new cutaneous delivery technology that uses high-aspect ratio, cylindrical silica microparticles, that are massaged into the skin using a 3D-printed microtextured applicator, in order to deliver payloads across the epidermis. Herein we show that this technology is effective for delivery of a non-adjuvanted, inactivated, whole-virus chikungunya virus vaccine in mice, with minimal post-vaccination skin reactions. A single topical Foroderm-based vaccination induced T cell, Th1 cytokine and antibody responses, which provided complete protection against viraemia and disease after challenge with chikungunya virus. Foroderm vaccination was shown to deliver fluorescent, virus-sized beads across the epidermis, with beads subsequently detected in draining lymph nodes. Foroderm vaccination also stimulated the egress of MHC II(+) antigen presenting cells from the skin. Foroderm thus has potential as a simple, cheap, effective, generic, needle-free technology for topical delivery of vaccines.

Modulation of influenza vaccine immune responses using an epidermal growth factor receptor kinase inhibitor

Systemic use of epidermal growth factor receptor inhibitors (EGFRIs) has been shown to alter MHC expression and that of several chemokines, and to enhance immune cell recruitment into human skin. We hypothesized that EGFRIs may have value as cutaneous immune response modifiers, and determined the effects of topical application of an irreversible EGFRI on a well-established murine model of influenza vaccination. We found that a single topical application of an EGFRI led to increased levels of antibodies that inhibit influenza mediated hemagglutination and viral cytopathic effects. The topically applied EGFRI significantly enhanced the generation of vaccine-specific IL-4 and IFN-γ producing cells within skin-draining lymph nodes as early as one week following vaccination. The EGFRI/vaccine group showed a twelve-fold reduction in detectable pulmonary viral load four days after infection as compared to the vaccine alone control group. The reduction in the lung viral titers correlated with the survival rate, which demonstrated 100% protection in the EGFRI/vaccine immunized group but only 65% protection in the mice immunized with vaccine alone. These findings are significant because they demonstrate that inhibition of defined signaling pathways within the skin using small molecule kinase inhibitors provides a novel approach to enhance immune responses to vaccines.

Inactivated polio vaccination using a microneedle patch is immunogenic in the rhesus macaque

The phased replacement of oral polio vaccine (OPV) with inactivated polio vaccine (IPV) is expected to significantly complicate mass vaccination campaigns, which are an important component of the global polio eradication endgame strategy. To simplify mass vaccination with IPV, we developed microneedle patches that are easy to administer, have a small package size, generate no sharps waste and are inexpensive to manufacture. When administered to rhesus macaques, neutralizing antibody titers were equivalent among monkeys vaccinated using microneedle patches and conventional intramuscular injection for IPV types 1 and 2. Serologic response to IPV type 3 vaccination was weaker after microneedle patch vaccination compared to intramuscular injection; however, we suspect the administered type 3 dose was lower due to a flawed pre-production IPV type 3 analytical method. IPV vaccination using microneedle patches was well tolerated by the monkeys. We conclude that IPV vaccination using a microneedle patch is immunogenic in rhesus macaques and may offer a simpler method of IPV vaccination of people to facilitate polio eradication.

Enhanced immune responses by skin vaccination with influenza subunit vaccine in young hosts

Skin has gained substantial attention as a vaccine target organ due to its immunological properties, which include a high density of professional antigen presenting cells (APCs). Previous studies have demonstrated the effectiveness of this vaccination route not only in animal models but also in adults. Young children represent a population group that is at high risk from influenza infection. As a result, this group could benefit significantly from influenza vaccine delivery approaches through the skin and the improved immune response it can induce. In this study, we compared the immune responses in young BALB/c mice upon skin delivery of influenza vaccine with vaccination by the conventional intramuscular route. Young mice that received 5 μg of H1N1 A/Ca/07/09 influenza subunit vaccine using MN demonstrated an improved serum antibody response (IgG1 and IgG2a) when compared to the young IM group, accompanied by higher numbers of influenza-specific antibody secreting cells (ASCs) in the bone marrow. In addition, we observed increased activation of follicular helper T cells and formation of germinal centers in the regional lymph nodes in the MN immunized group, rapid clearance of the virus from their lungs as well as complete survival, compared with partial protection observed in the IM-vaccinated group. Our results support the hypothesis that influenza vaccine delivery through the skin would be beneficial for protecting the high-risk young population from influenza infection.

Animal models for cutaneous vaccine delivery

Main challenges in skin vaccination are overcoming the stratum corneum (SC) barrier and targeting the antigen presenting cells (APC) in the epidermis and the dermis. For this purpose many delivery techniques are being developed. In vivo immunogenicity and safety studies in animals are mandatory before moving to clinical trials. However, the results obtained in animals may or may not be predictive for humans. Knowledge about differences and similarities in skin architecture and immunology within a species and between species is crucial. In this review, we discuss variables, including skin morphology, skin barrier function, mechanical properties, site of application and immunology, which should be taken into account when designing animal studies for vaccination via the skin in order to support the translation to clinical trial outcomes.

Hydrogel-forming microneedles prepared from "super swelling" polymers combined with lyophilised wafers for transdermal drug delivery

We describe, for the first time, hydrogel-forming microneedle arrays prepared from "super swelling" polymeric compositions. We produced a microneedle formulation with enhanced swelling capabilities from aqueous blends containing 20% w/w Gantrez S-97, 7.5% w/w PEG 10,000 and 3% w/w Na2CO3 and utilised a drug reservoir of a lyophilised wafer-like design. These microneedle-lyophilised wafer compositions were robust and effectively penetrated skin, swelling extensively, but being removed intact. In in vitro delivery experiments across excised neonatal porcine skin, approximately 44 mg of the model high dose small molecule drug ibuprofen sodium was delivered in 24 h, equating to 37% of the loading in the lyophilised reservoir. The super swelling microneedles delivered approximately 1.24 mg of the model protein ovalbumin over 24 h, equivalent to a delivery efficiency of approximately 49%. The integrated microneedle-lyophilised wafer delivery system produced a progressive increase in plasma concentrations of ibuprofen sodium in rats over 6 h, with a maximal concentration of approximately 179 µg/ml achieved in this time. The plasma concentration had fallen to 71±6.7 µg/ml by 24 h. Ovalbumin levels peaked in rat plasma after only 1 hour at 42.36±17.01 ng/ml. Ovalbumin plasma levels then remained almost constant up to 6 h, dropping somewhat at 24 h, when 23.61±4.84 ng/ml was detected. This work represents a significant advancement on conventional microneedle systems, which are presently only suitable for bolus delivery of very potent drugs and vaccines. Once fully developed, such technology may greatly expand the range of drugs that can be delivered transdermally, to the benefit of patients and industry. Accordingly, we are currently progressing towards clinical evaluations with a range of candidate molecules.

Patient safety and beyond: what should we expect from microneedle arrays in the transdermal delivery arena?

Research based upon microneedle (MN) arrays has intensified recently. While the initial focus was on biomolecules, the field has expanded to include delivery of conventional small-molecule drugs whose water solubility currently precludes transdermal administration. Much success has been achieved, with peptides, proteins, vaccines, antibodies and even particulates delivered by MN in therapeutic/prophylactic doses. Recent innovations have focused on enhanced formulation design, scalable manufacture and extension of exploitation to minimally invasive patient monitoring, ocular delivery and enhanced administration of cosmeceuticals. Only two MN-based drug/vaccine delivery products are currently marketed, partially due to limitations with older MN designs based upon silicon and metal. Even the more promising polymeric MN have raised a number of regulatory and manufacturability queries that the field must address. MN arrays have tremendous potential to yield real benefits for patients and industry and, through diligence, innovation and collaboration, this will begin to be realised over the next 3-5 years.

A protective role of murine langerin⁺ cells in immune responses to cutaneous vaccination with microneedle patches

Cutaneous vaccination with microneedle patches offers several advantages over more frequently used approaches for vaccine delivery, including improved protective immunity. However, the involvement of specific APC subsets and their contribution to the induction of immunity following cutaneous vaccine delivery is not well understood. A better understanding of the functions of individual APC subsets in the skin will allow us to target specific skin cell populations in order to further enhance vaccine efficacy. Here we use a Langerin-EGFP-DTR knock-in mouse model to determine the contribution of langerin⁺ subsets of skin APCs in the induction of adaptive immune responses following cutaneous microneedle delivery of influenza vaccine. Depletion of langerin⁺ cells prior to vaccination resulted in substantial impairment of both Th1 and Th2 responses, and decreased post-challenge survival rates, in mice vaccinated cutaneously but not in those vaccinated via the intramuscular route or in non-depleted control mice. Our results indicate that langerin⁺ cells contribute significantly to the induction of protective immune responses following cutaneous vaccination with a subunit influenza vaccine.

Colocalization of cell death with antigen deposition in skin enhances vaccine immunogenicity

Vaccines delivered to the skin by microneedles – with and without adjuvants – have increased immunogenicity with lower doses than standard vaccine delivery techniques such as intramuscular (i.m.) or intradermal (i.d.) injection. However, the mechanisms behind this skin-mediated ‘adjuvant’ effect are not clear. Here, we show that the dynamic application of a microprojection array (the Nanopatch) to skin generates localized transient stresses invoking cell death around each projection. Nanopatch application caused significantly higher levels (~65-fold) of cell death in murine ear skin than i.d. injection using a hypodermic needle. Measured skin cell death is associated with modeled stresses ~1–10 MPa. Nanopatch-immunized groups also yielded consistently higher anti-IgG endpoint titers (up to 50-fold higher) than i.d. groups after delivery of a split virion influenza vaccine. Importantly, co-localization of cell death with nearby live skin cells and delivered antigen was necessary for immunogenicity enhancement. These results suggest a correlation between cell death caused by the Nanopatch with increased immunogenicity. We propose that the localized cell death serves as a ‘physical immune enhancer’ for the adjacent viable skin cells, which also receive antigen from the projections. This natural immune enhancer effect has the potential to mitigate or replace chemical-based adjuvants in vaccines.

B cell responses to influenza infection and vaccination

Although vaccines against influenza are widely available, control of the disease remains elusive. In part, this is due to the inability of current vaccines to induce durable, broadly protective immune responses. Prevention of influenza depends primarily on effective antibody responses that block virus entry. Following infection, high-affinity IgA antibodies are generated in the respiratory tract that lead to immune exclusion, while IgG prevents systemic spread. These are effective and long-lasting but also exert immune pressure. Mutation of the antigenic determinants of influenza therefore rapidly leads to emergence of novel variants that evade previously generated protective responses. Not only do vaccines suffer from this strain-specific limitation, but also they are suboptimal in their ability to induce durable immunity. However, recent evidence has demonstrated the possibility of inducing broadly cross-reactive antibody responses. Further understanding of the ways in which high-titer, long-lived antibody responses directed against such cross-reactive epitopes can be induced would lead to the development of novel vaccines that may remove the requirement for recurrent vaccination.

Influenza vaccines: unmet needs and recent developments

Influenza is a worldwide public health concern. Since the introduction of trivalent influenza vaccine in 1978, vaccination has been the primary means of prevention and control of influenza. Current influenza vaccines have moderate efficacy, good safety, and acceptable tolerability; however, they have unsatisfactory efficacy in older adults, are dependent on egg supply for production, and are time-consuming to manufacture. This review outlines the unmet medical needs of current influenza vaccines. Recent developments in influenza vaccines are also described.