Intratumoral delivery of a highly active form of XCL1 enhances antitumor CTL responses through recruitment of CXCL9-expressing conventional type-1 dendritic cells.

Conventional type 1 dendritic cells (cDC1s) play a crucial role in antitumor immunity through the induction and activation of tumor-specific CD8+ cytotoxic T cells (CTLs). The chemokine XCL1 is a major chemotactic factor for cDC1s and its receptor XCR1 is selectively expressed on cDC1s. Here, we investigated the effect of intratumoral delivery of a highly active form of murine XCL1 (mXCL1-V21C/A59C) on cDC1-mediated antitumor immunity using a hydrophilic gel patch. The hydrophilic gel patch containing mXCL1-V21C/A59C increased cDC1 accumulation in the tumor masses and promoted their migration to the regional lymph nodes, resulting in enhanced induction of tumor-specific CTLs. Tumor-infiltrating cDC1s not only expressed XCR1 but also produced CXCL9, a ligand for CXCR3 which is highly expressed on CTLs and NK cells. Consequently, CTLs and NK cells were increased in the tumor masses of mice treated with mXCL1-V21C/A59C, while immunosuppressive cells such as monocyte-derived suppressive cells and regulatory T cells were decreased. We also confirmed that anti-CXCL9 treatment decreased the tumor infiltration of CTLs. The intratumoral delivery of mXCL1-V21C/A59C significantly decreased tumor growth and prolonged survival in E.G7-OVA and B16-F10 tumor-bearing mice. Furthermore, the antitumor effect of mXCL1-V21CA59C was enhanced in combination with anti-programmed cell death protein 1 treatment. Finally, using The Cancer Genome Atlas database, we found that XCL1 expression was positively correlated with tumor-infiltrating cDC1s and a better prognosis in melanoma patients. Collectively, our findings provide a novel therapeutic approach to enhance tumor-specific CTL responses through the selective recruitment of CXCL9-expressing cDC1s into the tumor masses.

Immunogenicity of Milk Protein-Containing Hydrophilic Gel Patch for Epicutaneous Immunotherapy for Milk Allergy.

PURPOSE: Epicutaneous immunotherapy (EPIT) involving the skin's immune system is easy to use, painless and has a low risk of systemic side effects; it can be applied to food allergies that have a high morbidity rate in children. In this study, we evaluated the safety and efficacy of hydrophilic gel patch (HG) for EPIT. METHODS: Milk protein concentrate (MPC)-containing HG was applied to the skin that maintained a barrier function or formed puncture holes with microneedle, and MPC-specific antibodies were measured. The clinical study was conducted involving patients with severe milk allergy. RESULTS: No specific immune response was induced when immunizing to intact skin, and antibody production was observed by forming puncture holes. It was suggested that MPC contained in HG has immunogenicity and a very small amount of MPC was delivered to intact skin. In the clinical study, the symptom induction threshold increased in four of eight subjects, allowing them to consume milk and switch to oral immunotherapy. Although local skin reactions and temporary elevation of specific IgE antibodies were observed, no systemic side effects appeared throughout the study. CONCLUSIONS: EPIT using HG is a safe method to enable oral administration even in patients with severe milk allergies.

Transcutaneous immunization with a highly active form of XCL1 as a vaccine adjuvant using a hydrophilic gel patch elicits long-term CD8+ T cell responses.

Memory CD8+ cytotoxic T-lymphocytes (CTLs) play a key role in protective immunity against infection and cancer. However, the induction of memory CTLs with currently available vaccines remains difficult. The chemokine receptor XCR1 is predominantly expressed on CD103+ cross-presenting dendritic cells (DCs). Recently, we have demonstrated that a high activity form of murine lymphotactin/XCL1 (mXCL1-V21C/A59C), a ligand of XCR1, can induce antigen-specific memory CTLs by increasing the accumulation of CD103+ DCs in the vaccination site and the regional lymph nodes. Here, we combined a hydrophilic gel patch as a transcutaneous delivery device and mXCL1-V21C/A59C as an adjuvant to further enhance memory CTL responses. The transcutaneous delivery of ovalbumin (OVA) and mXCL1-V21C/A59C by the hydrophilic gel patch increased CD103+ DCs in the vaccination site and the regional lymph nodes for a prolonged period of time compared with the intradermal injection of OVA and mXCL1-V21C/A59C. Furthermore, the hydrophilic gel patch containing OVA and mXCL1-V21C/A59C strongly induced OVA-specific memory CTLs and efficiently inhibited the growth of OVA-expressing tumors more than the intradermal injection of OVA and mXCL1-V21C/A59C. Collectively, this type of hydrophilic gel patch and a high activity form of XCL1 may provide a useful tool for the induction of memory CTL responses.

Improvement of Transdermal Delivery of Exendin-4 Using Novel Tip-Loaded Microneedle Arrays Fabricated from Hyaluronic Acid.

The purpose of this study was to evaluate the characteristics of exendin-4 tip-loaded microneedle arrays and to compare their acute efficacy with subcutaneous injections in type 2 diabetic GK/Slc rats. Fluorescein isothiocyanate labeled dextran with an average molecular weight of 4,000 (FD4) was selected as a model drug, and FD4 tip-loaded microneedle arrays were prepared in this study. In addition, intraperitoneal glucose tolerance tests after application of exendin-4 tip-loaded microneedle arrays were also compared with those after subcutaneous injection in type 2 diabetic GK/Slc rats. The release of FD4 from the tip-loaded microneedle arrays was very rapid, particularly in the initial 30 s, and most of the FD4 was released within 5 min. In addition, glucose tolerance was improved and the insulin secretion was enhanced after application of exendin-4 tip-loaded microneedle arrays, and these effects were comparable to those after subcutaneous injection of exendin-4. Similar plasma concentration profiles were seen after application of exendin-4 tip-loaded microneedle arrays, as was the case with subcutaneous injection in type 2 diabetic GK/Slc rats. These findings indicate that exendin-4 tip-loaded microneedle arrays can be used as an alternative to achieve sufficient delivery of exendin-4 for treatment of type 2 diabetes. To our knowledge, this is the first report of transdermal exendin-4 delivery using tip-loaded microneedle arrays.

Improvement of transdermal delivery of sumatriptan succinate using a novel self-dissolving microneedle array fabricated from sodium hyaluronate in rats.

The purpose of the present study was to develop an alternative transdermal formulation containing sumatriptan succinate (SS) for the treatment of migraine. Novel self-dissolving SS-loaded microneedle arrays (MNs) were fabricated from sodium hyaluronate and their efficacy for transdermal delivery of SS was characterized. The resulting MNs maintained their skin piercing abilities for at least 30 min after being placed at a high relative humidity of 75%. Rapid release of SS from the MNs was also observed in vitro. Optical coherence tomography images demonstrated that MNs were able to successfully pierce into rat skin without any bending or cracking, and needles were completely dissolved within 1 h. MNs significantly increased transepidermal water loss; however, skin barrier function gradually recovered to control levels within 24 h, in contrast to the skin damage observed after tape stripping treatment. These findings indicated that the micropores created by MNs quickly resealed, and that the skin damage was reversible. Furthermore, a dose-dependent plasma concentration of SS was obtained after transdermal delivery using SS-loaded MNs in rats. Absorption of SS delivered by MNs was similar to that observed after subcutaneous injection and was associated with high bioavailability (ca. 90%), which was much higher than that produced by oral administration. These findings suggested that application of SS-loaded MNs to the skin provided an effective alternative approach to enhance the transdermal delivery of SS without serious skin damage, and would be likely to improve patient compliance.

Development and clinical study of a self-dissolving microneedle patch for transcutaneous immunization device.

PURPOSE: We previously reported the safety and efficacy in animal experiments of transcutaneous immunization (TCI) using a self-dissolving microneedle patch (MicroHyala; MH) made of hyaluronic acid and collagen. However, this MH was an unsuitable TCI device for the human skin, as collagen is suspected to induce inflammation. In this study, we developed an improved collagen-free MH (new-MH) and conducted clinical study to evaluate the fundamental properties and safety in human. METHODS: Microneedle dissolution, skin irritation, and antigen-specific antibody production about new-MH were measured in mice and/or rats. On the basis of the results, the clinical study was conducted in healthy volunteers to evaluate local and systemic adverse events caused by new-MH application. RESULTS: We confirmed that the microneedles of new-MH, as well as those on our old-MH that contained collagen, could easily pierce stratum corneum without severe skin irritation, and that TCI using new-MH efficiently increased antibody titer with comparable to TCI using old-MH. Application of new-MH caused no severe adverse reactions in 20 healthy volunteers enrolled in a clinical study. CONCLUSIONS: These results verified that new-MH is a safe TCI device in human, and greatly encouraged us to advance PI/PII clinical studies of antigen-loaded new-MH.

Transcutaneous Administration of Imiquimod Promotes T and B Cell Differentiation into Effector Cells or Plasma Cells.

We are interested in promoting the development of transcutaneous immunization using microneedle technology and attempting to apply an adjuvant with transcutaneous immunization to improve the efficacy and reduce the amount of antigen and number of administrations needed. In this study, we collected basic information to help elucidate the mechanism responsible for the transcutaneous adjuvant activity of imiquimod (IMQ), which is a ligand of toll-like receptor (TLR) 7. In mouse groups administered ovalbumin (OVA), the OVA-specific IgG antibody titer of the IMQ-adjuvanted group was higher than that of the group administered OVA alone. No immune response bias due to transcutaneous IMQ administration was observed in terms of IgG1 (T helper cell [Th]2-type IgG subclass) and IgG2c (Th1-type IgG subclass) antibody titers. After the initial immunization, the IMQ-adjuvanted group showed increased migration of Langerhans cells to draining lymph nodes (dLNs) and active proliferation of OVA-specific CD4+ T cells. Transcutaneously administered IMQ did not affect the direction of CD4+ T cell differentiation, while promoted B cell activation and germinal center (GC) B cell differentiation. Immune staining revealed greater GC formation in the dLNs with the IMQ-adjuvanted group than in the OVA-alone group. In the secondary immune response, effector T cells increased in the dLNs and spleen, and effector memory T cells also increased in the spleen in the IMQ-adjuvanted group. In addition, our results suggested that the administration of IMQ enhanced B cell differentiation into plasma cells and GC B cells in the dLNs and spleen. In this study, we partially clarified the mechanism underlying the adjuvant activity of transcutaneously administered IMQ, which is required for the practical application of transcutaneous immunization with IMQ.

Characterization of transcutaneous protein delivery by a hydrogel patch in animal, human, and tissue-engineered skin models.

The development of a simple, easy-to-use, and noninvasive vaccination system is in high demand. For transcutaneous immunization (TCI), we previously reported that a hydrogel patch was an effective TCI device that accelerates antigen penetration through the stratum corneum in mouse and rat models. The present study was performed to characterize the transcutaneous protein delivery induced by the hydrogel patch in mouse, guinea pig, LWD pig, human, or tissue-engineered skin models, and to assess the activity of proteins delivered into the skin. The hydrogel patch promoted protein penetration through the stratum corneum in all skin models, indicating that our original hydrogel patch might have practical application for use in humans. In addition, proteins delivered into the skin by the hydrogel patch retained their activity, suggesting that the hydrogel patch is applicable for the delivery of therapies for other diseases as well. On the basis of these results, translational research in human is now in progress.

Compositional optimization and safety assessment of a hydrogel patch as a transcutaneous immunization device.

The development of a simple, easy-to-use, and non-invasive vaccination system is in high demand. For transcutaneous immunization (TCI), we previously developed a hydrogel patch formulation that accelerates the penetration of an antigen (Ag) through the stratum corneum (SC) and effectively elicits Ag-specific immune responses. The present studies were performed to optimize the composition and assess the safety of the patch formulation. A hydrogel patch with a water content ratio of 5% more effectively induced an immune response compared to patches with a different composition, suggesting that the moisture content of the hydrogel patch formulation has optimal ratio for SC hydration to promote Ag penetration through the SC. TCI using a hydrogel patch induced few local and systemic adverse reactions. Based on these results, we are now advancing translational research to evaluate the safety and efficacy of our novel TCI system in humans.

Characteristics of immune induction by transcutaneous vaccination using dissolving microneedle patches in mice.

Transcutaneous immunization (TCI) is an appealing vaccination method. Compared with conventional injectable immunization, TCI is easier and less painful. We previously developed a dissolving microneedle (MN) patch and demonstrated that TCI using MN patches demonstrates high vaccination efficacy without adverse events in humans. In this study, we investigated the immune induction mechanism of TCI using our MN patch, focusing on inflammatory responses in the skin and on the dynamics, activation, and differentiation of various immunocompetent cells in draining lymph nodes (dLNs). We demonstrate that inflammatory cytokines such as IL-6 and TNF-α increased in the skin at an early stage after MN patch application, inducing the infiltration of macrophages and neutrophils and promoting the activation and migration of skin-resident antigen-presenting cells (Langerhans and Langerin- dermal dendritic cells) to dLNs. Moreover, the activated antigen-presenting cells reaching the dLNs enhanced the differentiation of T (Teff, Tem, and Tcm) and B (plasma and memory) cells. This may contribute to the efficient antigen-specific antibody production induced by TCI using MN patches. We believe that our findings reveal a part of the immune induction mechanism by TCI and provide useful information for the development and improvement of TCI formulations based on the immune induction mechanism.

CCR4 Involvement in the Expansion of T Helper Type 17 Cells in a Mouse Model of Psoriasis.

Psoriasis is a chronic skin disease associated with T helper (Th)17-mediated inflammation. Because CCR4 is a major chemokine receptor expressed on Th17 cells, we investigated the role of CCR4 in a modified imiquimod-induced psoriasis model that showed enhanced skin infiltration of Th17 cells. CCR4-deficient mice had less severe skin disease than wild-type mice. Th17 cells were decreased in the skin lesions and regional lymph nodes of CCR4-deficient mice. In the regional lymph nodes of wild-type mice, CD44+ memory Th17 cells expressing CCR4 were found to be clustered with dendritic cells expressing CCL22, a ligand for CCR4. Such dendritic cell‒Th17 cell clusters were significantly decreased in CCR4-deficient mice. Similar results were obtained using the IL-23‒induced psoriasis model. In vitro, compound 22, a CCR4 antagonist, significantly reduced the expansion of Th17 cells in the coculture of CD11c+ dendritic cells and CD4+ T cells separately prepared from the regional lymph nodes of wild-type mice with psoriasis. In vivo, compound 22 ameliorated the psoriasis-like skin disease in wild-type mice with significant decreases of Th17 cells in the regional lymph nodes and skin lesions. Collectively, CCR4 is likely to play a role in the pathogenesis of psoriasis through the expansion of Th17 cells.

Characteristic of K3 (CpG-ODN) as a Transcutaneous Vaccine Formulation Adjuvant.

Transcutaneous immunization (TCI) is easy to use, minimally invasive, and has excellent efficacy in vaccines against infections. We focused on toll-like receptor (TLR) ligands as applicable adjuvants for transcutaneous formulations and characterized immune responses. TCI was performed using poke-and-patch methods, in which puncture holes are formed with a polyglycolic acid microneedle on the back skin of mice. Various TLR ligands were applied to the puncture holes and covered with an ovalbumin-loaded hydrophilic gel patch. During the screening process, K3 (CpG-oligonucleotide) successfully produced more antigen-specific antibodies than other TLR ligands and induced T helper (Th) 1-type polarization. Transcutaneously administered K3 was detected in draining lymph nodes and was found to promote B cell activation and differentiation, suggesting a direct transcutaneous adjuvant activity on B cells. Furthermore, a human safety test of K3-loaded self-dissolving microneedles (sdMN) was performed. Although a local skin reaction was observed at the sdMN application site, there was no systemic side reaction. In summary, we report a K3-induced Th1-type immune response that is a promising adjuvant for transcutaneous vaccine formulations using MN and show that K3-loaded sdMN can be safely applied to human skin.

Trypsin as a novel potential absorption enhancer for improving the transdermal delivery of macromolecules.

OBJECTIVES: The aim was to assess the effect of trypsin on the transdermal delivery of macromolecules by applying its specific biochemical properties to the stratum corneum of the skin. METHODS: Fluorescein isothiocyanate (FITC)-labelled dextrans (FDs), with molecular weights of 4 to 250 kDa, and FITC-insulin were used as model macromolecules and a model polypeptide, and the in-vitro transdermal permeation experiments, with or without trypsin (0.1-2.5%), were carried out using rat skin and cultured human epidermis. The mechanism for the enhancement of trypsin was also studied using fluorescence and conventional light microscopy. KEY FINDINGS: Trypsin significantly increased the transdermal permeability of all FDs through the rat skin (2.0- to 10.0-fold). It also markedly enhanced the permeation of FD4 through three-dimensional cultured human epidermis (3.1-fold), which was used to evaluate the transport pathways other than the transfollicular route. Furthermore, the permeation flux of FITC-insulin was increased by 10.0-fold with trypsin pretreatment (from 0.02 +/- 0.00 to 0.20 +/- 0.07 microg/cm(2) per h). Mechanistic studies indicated that trypsin affects both the intercellular pathway and the hair follicular route, and may alter stratum corneum protein structures, thereby affecting skin barrier properties. CONCLUSIONS: This study suggests that trypsin could be effective as a biochemical enhancer for the transdermal delivery of macromolecules including peptide and protein drugs.

A CCR4 antagonist ameliorates atopic dermatitis-like skin lesions induced by dibutyl phthalate and a hydrogel patch containing ovalbumin.

CCR4 is a chemokine receptor highly expressed by Th2 cells, and regarded as a potential therapeutic target for atopic dermatitis (AD). CCL17 and CCL22 are the CCR4 ligands, and thymic stromal lymphopoietin (TSLP) is shown to promote the expression of CCL17 and CCL22 by dendritic cells. Here, by using dibutyl phthalate (DBP), a TSLP inducer, and a hydrogel patch as a transcutaneous delivery device for ovalbumin, we developed a novel murine AD model and investigated the effect of Compound 22, a CCR4 antagonist. We first found that the mRNA expression of TSLP together with CCL17 and CCL22 was increased in the skins treated with DBP. Furthermore, the topical application of ovalbumin and DBP efficiently and rapidly induced AD-like skin lesions in BALB/c mice, which were characterized by ear swelling accompanied by infiltration of eosinophils, mast cells, and CCR4-expressing Th2 cells in the skin lesions, and elevated total IgE levels in the sera. Using this AD model, we demonstrated that cutaneous administration of Compound 22 inhibited Th2 cell infiltration and ameliorated the AD-like skin lesions. These results suggest that our AD model could be useful for studying new therapeutic strategies. Collectively, CCR4 antagonists may be a promising approach for treating AD.

Self-Dissolving Microneedle Arrays for Transdermal Absorption Enhancement of Human Parathyroid Hormone (1-34).

Human parathyroid hormone (1-34) (PTH) has been widely used as the subcutaneous injection formulation for the treatment of osteoporosis. In the present study, we developed an efficient transdermal delivery system of PTH by using dissolving microneedle arrays (MNs) composed of hyaluronic acid (HA) for the treatment of osteoporosis. PTH-loaded MNs, with needle length 800 µm, were fabricated via a micro-molding method. The stability of PTH in MNs was found to be 6-fold higher than that of PTH solution when stored at room temperature (15⁻20 °C) for one month. Micron-scale pores were clearly visible in rat skin following application of PTH-loaded MNs. PTH-loaded MNs were completely dissolved by 60 min following application to rat skin. The bioavailability (BA) of PTH relative to subcutaneous injection was 100 ± 4% following application of PTH-loaded MNs in rats. In addition, PTH-loaded MNs were found to effectively suppress decreases in bone density in a rat model of osteoporosis. Furthermore, no skin irritation was observed at the site of application in rats. These findings indicate that our dissolving MNs have a potential use in formulations for the transdermal delivery of PTH and for the treatment of osteoporosis.

CCR4 Is Critically Involved in Skin Allergic Inflammation of BALB/c Mice.

Atopic dermatitis is a chronic inflammatory skin disease involving T-helper (Th) 2 cells, eosinophils, and mast cells. Although CCR4 is a major chemokine receptor expressed on Th2 cells and regarded as a potential therapeutic target for allergic diseases, its role in atopic dermatitis remains unclear. Here, by using a hydrogel patch as a transcutaneous delivery device for ovalbumin (an antigen) and Staphylococcus aureus δ-toxin (a mast cell activator), we efficiently induced acute atopic dermatitis-like skin lesions in BALB/c mice, a strain prone to Th2 responses, which were characterized by increased numbers of eosinophils, mast cells, and CCR4-expressing Th2 cells in the skin lesions; elevated levels of total and ovalbumin-specific IgE in the sera; and increased expression of IL-4, IL-17A, IL-22, CCL17, CCL22, and CCR4 in the skin lesions. Of note, the same model was less efficient in C57BL/6 mice, a strain prone to Th1 responses. Using this atopic dermatitis model in BALB/c mice, we demonstrated that CCR4-deficiency or a CCR4 antagonist ameliorated the allergic responses. Collectively, these results demonstrate that CCR4 plays a pivotal role in skin allergic inflammation of BALB/c mice by recruiting CCR4-expressing Th2 cells and Th17 cells.

Efficient Transdermal Delivery of Alendronate, a Nitrogen-Containing Bisphosphonate, Using Tip-Loaded Self-Dissolving Microneedle Arrays for the Treatment of Osteoporosis.

To improve the transdermal bioavailability and safety of alendronate (ALN), a nitrogen-containing bisphosphonate, we developed self-dissolving microneedle arrays (MNs), in which ALN is loaded only at the tip portion of micron-scale needles by a dip-coating method (ALN(TIP)-MN). We observed micron-scale pores in rat skin just after application of ALN(TIP)-MN, indicating that transdermal pathways for ALN were created by MN. ALN was rapidly released from the tip of MNs as observed in an in vitro release study. The tip portions of MNs completely dissolved in the rat skin within 5 min after application in vivo. After application of ALN(TIP)-MN in mice, the plasma concentration of ALN rapidly increased, and the bioavailability of ALN was approximately 96%. In addition, the decrease in growth plate was effectively suppressed by this efficient delivery of ALN in a rat model of osteoporosis. Furthermore, no skin irritation was observed after application of ALN(TIP)-MN and subcutaneous injection of ALN, while mild skin irritation was induced by whole-ALN-loaded MN (ALN-MN)-in which ALN is contained in the whole of the micron-scale needles fabricated from hyaluronic acid-and intradermal injection of ALN. These findings indicate that ALN(TIP)-MN is a promising transdermal formulation for the treatment of osteoporosis without skin irritation.

Clinical study of a retinoic acid-loaded microneedle patch for seborrheic keratosis or senile lentigo.

AIMS: Pigmented lesions such as of seborrheic keratosis and senile lentigo, which are commonly seen on skin of people>50years of age, are considered unattractive and disfiguring because of their negative psychological impact. Drug therapy using all-trans retinoic acid (ATRA) is an attractive option for self-treatment at home. We have developed an ATRA-loaded microneedle patch (ATRA-MN) and confirmed the pharmacological effects of ATRA-MN application in mice. Here, we describe a clinical study to evaluate the safety and efficacy of ATRA-MN in subjects with seborrheic keratosis or senile lentigo. MAIN METHODS: ATRA-MN was applied to the lesion site of each subject for 6h once per week for 4weeks. The skin irritation reaction was scored to assess adverse reactions and blood tests were performed to evaluate the presence of systemic adverse reactions. To assess the treatment effect using ATRA-MN, the desquamation and whitening ability of the investigational skin was observed. KEY FINDINGS: Desquamation of the stratum corneum was observed following four ATRA-MN applications at 1-week intervals, but ATRA-MN applications did not induce severe local or systemic adverse effects. SIGNIFICANCE: These results showed that ATRA-MN treatment is promising as a safe and effective therapy for seborrheic keratosis and senile lentigo.

Development of Novel Faster-Dissolving Microneedle Patches for Transcutaneous Vaccine Delivery.

Microneedle (MN) patches are promising for transcutaneous vaccination because they enable vaccine antigens to physically penetrate the stratum corneum via low-invasive skin puncturing, and to be effectively delivered to antigen-presenting cells in the skin. In second-generation MN patches, the dissolving MNs release the loaded vaccine antigen into the skin. To shorten skin application time for clinical practice, this study aims to develop novel faster-dissolving MNs. We designed two types of MNs made from a single thickening agent, carboxymethylcellulose (CMC) or hyaluronan (HN). Both CMC-MN and HN-MN completely dissolved in rat skin after a 5-min application. In pre-clinical studies, both MNs could demonstrably increase antigen-specific IgG levels after vaccination and prolong antigen deposition compared with conventional injections, and deliver antigens into resected human dermal tissue. In clinical research, we demonstrated that both MNs could reliably and safely puncture human skin without any significant skin irritation from transepidermal water loss measurements and ICDRG (International Contact Dermatitis Research Group) evaluation results.

Development of novel double-decker microneedle patches for transcutaneous vaccine delivery.

Microneedle (MN) patches have great potential as transcutaneous vaccine delivery devices because MNs can effectively deliver vaccine antigen into the skin through the micropores formed in the stratum corneum by low-invasive and painless skin puncturing. This study aims to develop novel double-decker MN patches which have not only high safety and efficacy but also broad applicability to various vaccine antigens. We developed two types of MN patches (PGA-MN and Nylon-MN) that are made from polyglycolic acid and Nylon-6. In pre-clinical studies, both MN patches could demonstrably deliver antigens into resected human dermal tissue, prolong antigen deposition and increase antigen-specific IgG levels after vaccination compared with conventional injections. We demonstrated both MN patches could be safely applied to human skin because no broken MNs or significant skin irritation were observed after applications in the clinical research. PGA-MN was suggested to be superior to Nylon-MN regarding human skin puncturability based on measurements of transepidermal water loss and needle failure force. A high content of tetravalent influenza hemagglutinin antigens loaded on PGA-MN could stably maintain HA titers at 35°C for 1year. Overall, double-decker MN patches can reliably and safely puncture human skin and are promising as effective transcutaneous vaccine delivery devices.