Changes in human Langerhans cells following intradermal injection of influenza virus-like particle vaccines

A human ex vivo skin model breaking boundaries

Ex vivo human skin models are valuable tools in skin research due to their physiological relevance. Traditionally, standard cultivation is performed in a cell culture incubator with a defined temperature of 37 °C and a specific atmosphere enriched with CO2 to ensure media stability. Maintaining the model under these specific conditions limits its flexibility in assessing exposures to which the skin is exposed to in daily life, for example changes in atmospheric compositions. In this study we demonstrated that the foreskin-derived skin model can be successfully cultured at room temperature outside a CO2 incubator using a CO2-independent, serum-free media. Over a cultivation period of three days, the integrity of the tissue and the preservation of immune cells is well maintained, indicating the model's stability and resilience under the given conditions. Exposing our Medical University of Graz - human Organotypic Skin Explant Culture (MUG-hOSEC) model to cytotoxic and inflammatory stimuli results in responses analyzable within the supernatant. Besides the common analysis of released proteins upon treatment, such as cytokines and enzymes, we have included extracellular vesicle to obtain a more comprehensive picture of cell communication.

Immune responses, therapeutic anti-tumor effects, and tolerability upon therapeutic HPV16/18 E6/E7 DNA vaccination via needle-free biojector

IMPORTANCE

Respectively, HPV16 and HPV18 cause 50% and 20% of cervical cancer cases globally. Viral proteins E6 and E7 are obligate drivers of oncogenic transformation. We recently developed a candidate therapeutic DNA vaccine, pBI-11, that targets HPV16 and HPV18 E6 and E7. Single-site intramuscular delivery of pBI-11 via a needle elicited therapeutic anti-tumor effects in mice and is now being tested in high-risk human papillomavirus+ head and neck cancer patients (NCT05799144). Needle-free biojectors such as the Tropis device show promise due to ease of administration, high patient acceptability, and the possibility of improved delivery. For example, vaccination of patients with the ZyCoV-D DNA vaccine using the Tropis device is effective against COVID19, well tolerated, and licensed. Here we show that split-dose, multi-site administration and intradermal delivery via the Tropis biojector increase the delivery of pBI-11 DNA vaccine, enhance HPV antigen-specific CD8+ T-cell responses, and improve anti-tumor therapeutic effects, suggesting its translational potential to treat HPV16/18 infection and disease.

The immunological effects of intradermal particle-based vaccine delivery using a novel microinjection needle studied in a human skin explant model

For intradermal (ID) immunisation, novel needle-based delivery systems have been proposed as a better alternative to the Mantoux method. However, the penetration depth of needles in the human skin and its effect on immune cells residing in the different layers of the skin has not been analyzed. A novel and user-friendly silicon microinjection needle (Bella-mu^TM) has been developed, which allows for a perpendicular injection due to its short needle length (1.4-1.8 mm) and ultrashort bevel. We aimed to characterize the performance of this microinjection needle in the context of the delivery of a particle-based outer membrane vesicle (OMV) vaccine using an ex vivo human skin explant model. We compared the needles of 1.4 and 1.8 mm with the conventional Mantoux method to investigate the depth of vaccine injection and the capacity of the skin antigen-presenting cell (APC) to phagocytose the OMVs. The 1.4 mm needle deposited the antigen closer to the epidermis than the 1.8 mm needle or the Mantoux method. Consequently, activation of epidermal Langerhans cells was significantly higher as determined by dendrite shortening. We found that five different subsets of dermal APCs are able to phagocytose the OMV vaccine, irrespective of the device or injection method. ID delivery using the 1.4 mm needle of a OMV-based vaccine allowed epidermal and dermal APC targeting, with superior activation of Langerhans cells. This study indicates that the use of a microinjection needle improves the delivery of vaccines in the human skin.

Interoperability of RTN1A in dendrite dynamics and immune functions in human Langerhans cells

Skin is an active immune organ where professional antigen-presenting cells such as epidermal Langerhans cells (LCs) link innate and adaptive immune responses. While Reticulon 1A (RTN1A) was recently identified in LCs and dendritic cells in cutaneous and lymphoid tissues of humans and mice, its function is still unclear. Here, we studied the involvement of this protein in cytoskeletal remodeling and immune responses toward pathogens by stimulation of Toll-like receptors (TLRs) in resident LCs (rLCs) and emigrated LCs (eLCs) in human epidermis ex vivo and in a transgenic THP-1 RTN1A+ cell line. Hampering RTN1A functionality through an inhibitory antibody induced significant dendrite retraction of rLCs and inhibited their emigration. Similarly, expression of RTN1A in THP-1 cells significantly altered their morphology, enhanced aggregation potential, and inhibited the Ca2+ flux. Differentiated THP-1 RTN1A+ macrophages exhibited long cell protrusions and a larger cell body size in comparison to wild-type cells. Further, stimulation of epidermal sheets with bacterial lipoproteins (TLR1/2 and TLR2 agonists) and single-stranded RNA (TLR7 agonist) resulted in the formation of substantial clusters of rLCs and a significant decrease of RTN1A expression in eLCs. Together, our data indicate involvement of RTN1A in dendrite dynamics and structural plasticity of primary LCs. Moreover, we discovered a relation between activation of TLRs, clustering of LCs, and downregulation of RTN1A within the epidermis, thus indicating an important role of RTN1A in LC residency and maintaining tissue homeostasis.

Production of Multi-Subtype Influenza Virus-Like Particles by Molecular Fusion with BAFF or APRIL for Vaccine Development

Virus-like particle (VLP) technology is an alternative platform for developing vaccines to combat seasonal and pandemic influenza. Influenza VLPs are non-infectious nanoparticles that can elicit effective vaccine immunogenicity in hosts. B-cell-activating factor (BAFF, or BLyS) and a proliferation-inducing ligand (APRIL) are members of the tumor necrosis factor (TNF) superfamily of cytokines. Both BAFF and APRIL are homotrimers that interact with homotrimeric receptors. Here, we report a method of the production of influenza VLPs by molecular incorporation with BAFF or APRIL homotrimers to interact with their receptors. We engineered the VLPs by direct fusion of BAFF or APRIL to the transmembrane anchored domain of the hemagglutinin (HA) gene. We also describe procedures for the production of BAFF-VLPs containing H5H7 and H1H5H7 for multi-subtype vaccine development.

The Antiseptic Octenidine Inhibits Langerhans Cell Activation and Modulates Cytokine Expression upon Superficial Wounding with Tape Stripping

Ideal agents for the topical treatment of skin wounds should have antimicrobial efficacy without negative influence on wound healing. Octenidine (OCT) has become a widely used antiseptic in professional wound care, but its influence on several components of the wound healing process remains unclear. In the present study, we have used a superficial wound model using tape stripping on human full-thickness skin ex vivo to investigate the influence of OCT on epidermal Langerhans cells (LCs) and cytokine secretion pattern of skin cells during wound healing in a model without disruption of the normal skin structure. Histological and immunofluorescence studies showed that OCT neither altered human skin architecture nor the viability of skin cells upon 48 hours of culture in unwounded or wounded skin. The epidermis of explants and LCs remained morphologically intact throughout the whole culture period upon OCT treatment. OCT inhibited the upregulation of the maturation marker CD83 on LCs and prevented their emigration in wounded skin. Furthermore, OCT reduced both pro- and anti-inflammatory mediators (IL-8, IL-33, and IL-10), while angiogenesis and growth factor mediators (VEGF and TGF-β1) remained unchanged in skin explant cultures. Our data provide novel insights into the host response to OCT in the biologically relevant environment of viable human (wounded) skin.

Human Organotypic Models for Anti-infective Research

The use of human organotypic models for biomedical research is experiencing a significant increase due to their biological relevance, the possibility to perform high-throughput analyses, and their cost efficiency. In the field of anti-infective research, comprising the search for novel antipathogenic treatments including vaccines, efforts have been made to reduce the use of animal models. That is due to two main reasons: unreliability of data obtained with animal models and the increasing willingness to reduce the use of animals in research for ethical reasons. Human three-dimensional (3-D) models may substitute and/or complement in vivo studies, to increase the translational value of preclinical data. Here, we provide an overview of recent studies utilizing human organotypic models, resembling features of the cervix, intestine, lungs, brain, and skin in the context of anti-infective research. Furthermore, we focus on the future applications of human skin models and present methodological protocols to culture human skin equivalents and human skin explants.

Electroporation as a vaccine delivery system and a natural adjuvant to intradermal administration of plasmid DNA in macaques

In vivo electroporation (EP) is used to enhance the uptake of nucleic acids and its association with DNA vaccination greatly stimulates immune responses to vaccine antigens delivered through the skin. However, the effect of EP on cutaneous cell behavior, the dynamics of immune cell recruitment and local inflammatory factors, have not been fully described. Here, we show that intradermal DNA vaccination combined with EP extends antigen expression to the epidermis and the subcutaneous skin muscle in non-human primates. In vivo fibered confocal microscopy and dynamic ex vivo imaging revealed that EP promotes the mobility of Langerhans cells (LC) and their interactions with transfected cells prior to their migration from the epidermis. At the peak of vaccine expression, we detected antigen in damaged keratinocyte areas in the epidermis and we characterized recruited immune cells in the skin, the hypodermis and the subcutaneous muscle. EP alone was sufficient to induce the production of pro-inflammatory cytokines in the skin and significantly increased local concentrations of Transforming Growth Factor (TGF)-alpha and IL-12. Our results show the kinetics of inflammatory processes in response to EP of the skin, and reveal its potential as a vaccine adjuvant.

Efficacy, Safety and Targets in Topical and Transdermal Active and Excipient Delivery

A key requirement for topical and transdermal active delivery is the effective delivery of an active to a desired target site, to achieve both safe and efficacious outcomes. This chapter seeks to explore the importance of the pharmacological, toxicological and therapeutic properties of actives and excipients, as well as the site of action as complementary components in percutaneous absorption. This is crucial for optimized topical and transdermal product design.

Multi-subtype influenza virus-like particles incorporated with flagellin and granulocyte-macrophage colony-stimulating factor for vaccine design

Virus-like particle (VLP) technology is an attractive platform for seasonal and pandemic influenza vaccine development. We previously showed that influenza VLPs can be modified using M2 fusion with molecular adjuvants such as Salmonella typhimurium flagellin (FliC) to enhance VLP immunogenicity. For this study, three types of chimeric VLPs were incorporated with FliC, granulocyte-macrophage colony-stimulating factor (GM-CSF), or both GM-CSF and FliC (GM-CSF/FliC) to enhance anti-influenza immunogenicity. Our results indicate that immunizations with the chimeric FliC VLPs and GM-CSF/FliC H5N1 VLPs elicited more potent and broadly neutralizing antibodies and neuraminidase-inhibiting antibodies in sera, and induced higher numbers of hemagglutinin-specific antibody-secreting cells and germinal center B cell subsets in splenoctyes. Immunization with the chimeric GM-CSF H5N1 VLPs induced stronger Th1 and Th2 cellular responses. The chimeric GM-CSF/FliC H5N1 VLP constructs were further obtained to include H7 or H1H7 bi- or tri-subtype. It is our hope that these findings provide useful information for developing multi-subtype influenza vaccines.

Identification of skin immune cells in non-human primates

The skin is a valuable target for vaccine delivery because it contains many immune cell populations, notably antigen presenting cells. Skin immune cells have been extensively described in mice and humans but not in non-human primates, which are pertinent models for immunological research in vaccination. The aim of this work was to describe immune cell populations in the epidermis, dermis and skin draining lymph nodes in cynomolgus macaques by a single 12-parameter flow cytometry protocol. Given that skin cells share several markers, we defined a gating strategy to identify accurately immune cells and to limit contamination of one immune cell population by another. The epidermis contained CD1a(+)CD1c(-) Langerhans cells (LCs), CD3(+) T cells and putative NK cells. The dermis contained CD1a(+)CD1c(-) cells, which were similar to LCs, CD1a(+)CD1c(+) dermal dendritic cells (DDCs), CD163(high)CD11b(+) resident macrophages, CD3(+) T cells and putative NK cells. The skin also contained CD66(+) polymorphonuclear cells in some animals. Thus, immune cell populations in the macaque are similar to those in humans despite some differences in phenotype. In skin draining lymph nodes, we identified migratory LCs, CD1a(+)CD1c(+) DDCs and macrophages. The simultaneous identification of these different immune cells with one panel of markers avoids the use of large amounts of precious sample and may improve the understanding of immune mechanisms in the skin after treatment or vaccination.

Immunogenicity of intramuscular MF59-adjuvanted and intradermal administered influenza enhanced vaccines in subjects aged over 60: A literature review

Because of the age-related immune system decline, 2 potentiated influenza vaccines were specifically licensed for the elderly: Fluad(®), an MF59-adjuvanted vaccine administered intramuscularly (IM-MF59), and Intanza 15 mcg(®), a non adjuvanted vaccine administered intradermally (ID). The objective of this paper was to conduct a systematic review of studies that evaluated antibody responses in the elderly following immunization with IM-MF59 or ID vaccines. The two potentiated vaccines induced immune responses satisfying, in most instances, the European Medicine Agency immunogenicity criteria, both against vaccine antigens and heterovariant drifted strains. Considering pooled data reported in the articles analyzed and papers directly comparing the 2 vaccines, the antibody responses elicited by IM-MF59 and ID were found to be generally comparable. The use of IM-MF59 and ID vaccines can be proposed as an appropriate strategy for elderly seasonal influenza vaccination although further studies are required for a more complete characterization of the 2 vaccines.

Macrophage- and neutrophil-derived TNF-α instructs skin langerhans cells to prime antiviral immune responses

Dendritic cells are major APCs that can efficiently prime immune responses. However, the roles of skin-resident Langerhans cells (LCs) in eliciting immune responses have not been fully understood. In this study, we demonstrate for the first time, to our knowledge, that LCs in cynomolgus macaque skin are capable of inducing antiviral-specific immune responses in vivo. Targeting HIV-Gag or influenza hemagglutinin Ags to skin LCs using recombinant fusion proteins of anti-Langerin Ab and Ags resulted in the induction of the viral Ag-specific responses. We further demonstrated that such Ag-specific immune responses elicited by skin LCs were greatly enhanced by TLR ligands, polyriboinosinic polyribocytidylic acid, and R848. These enhancements were not due to the direct actions of TLR ligands on LCs, but mainly dependent on TNF-α secreted from macrophages and neutrophils recruited to local tissues. Skin LC activation and migration out of the epidermis are associated with macrophage and neutrophil infiltration into the tissues. More importantly, blocking TNF-α abrogated the activation and migration of skin LCs. This study highlights that the cross-talk between innate immune cells in local tissues is an important component for the establishment of adaptive immunity. Understanding the importance of local immune networks will help us to design new and effective vaccines against microbial pathogens.

Immunogenicity of intradermal trivalent influenza vaccine with topical imiquimod: a double blind randomized controlled trial

BACKGROUND

Imiquimod, a synthetic Toll-like receptor 7 agonist enhanced immunogenicity of influenza vaccine in a mouse model. We hypothesized that topical imiquimod before intradermal influenza vaccination (TIV) would produce similar effect in human.

METHODS

We performed a prospective 1-year follow-up, double-blind, randomized, controlled trial with adults with comorbidities. Participants were randomized to 1 of the following 3 vaccinations: topical 5% 250 mg imiquimod ointment followed by intradermal TIV, topical aqueous-cream followed by intradermal TIV, or topical aqueous-cream followed by intramuscular TIV. Patients and investigators were blinded to the type of topical treatment applied. Hemagglutination inhibition (HI) and microneutralization antibody titers were measured. The primary outcome was the day 7 seroconversion rate.

RESULTS

Ninety-one recruited participants completed the study. The median age was 73 years. On day 7, 27/30 (90%) patients who received imiquimod and intradermal TIV achieved seroconversion against the H1N1 strain by HI, compared with 4/30 (13.3%) who received aqueous-cream and intramuscular TIV (P < .001), and 12/31 (38.7%) who received aqueous-cream and intradermal TIV (P < .001). The seroconversion, seroprotection, and geometric mean titer-fold increase were met in all 3 strains in the imiquimod and intradermal TIV group 2 weeks earlier, and the better seroconversion rate was sustained from day 7 to year 1 (P ≤ .001). The better immunogenicity was associated with fewer hospitalizations for influenza or pneumonia (P < .05). All adverse reactions were self-limited.

CONCLUSIONS

Pretreatment with topical imiquimod significantly expedited, augmented, and prolonged the immunogenicity of influenza vaccination. This strategy for influenza immunization should be considered for the elderly population.

Immunogenicity and safety of intradermal trivalent influenza vaccination in nursing home older adults: a randomized controlled trial

OBJECTIVE

To compare the immunogenicity and safety between full-dose (15 μg) intramuscular (i.m.) and full-dose (15 μg) intradermal (i.d.) immunization of the trivalent influenza vaccine in nursing home older adults.

DESIGN

A single-center, randomized, controlled, open-label, parallel group trial from October 2013 to April 2014.

SETTING

Nine nursing homes in Hong Kong.

PARTICIPANTS

Hundred nursing home older adults (mean age: 82.9 ± 7.4 years).

INTERVENTION

Fifty received i.d. (Intanza) and 50 received i.m. (Vaxigrip) vaccination.

MEASUREMENTS

Baseline measurements included demographics, comorbidity, frailty and nutritional status. Day 21 and day 180 immunogenicity (seroconversion rate, seroprotection rate, geometric mean titer [GMT] fold increase in antibody titer) using hemagglutination-inhibition and adverse events were measured. Noninferiority and superiority of i.d. compared with i.m. vaccination in immunogenicity were analyzed. The study was registered on ClinicalTrials.gov; identifier: NCT 01967368.

RESULTS

At day 21, noninferiority in immunogenicity of the i.d. vaccination was demonstrated. The seroconversion rate of the H1N1 strain was significantly higher in the i.d. group. At day 180, immunogenicity of both groups fell but the GMT of all strains in i.d. group was higher and the difference was significant for H3N2 strain. The seroconversion rate and GMT fold increase of H3N2 strain was significantly higher in the i.d. group. Local adverse events was significantly more in i.d. group, but they were mild and resolved in 72 hours.

CONCLUSIONS

I.d. vaccination is noninferior, and even superior in some parts of immunogenicity assessment, to i.m. vaccination without compromising safety in nursing home older adults. I.d. vaccination is a good alternative to i.m. vaccination in this population.

Dynamic visualization of dendritic cell-antigen interactions in the skin following transcutaneous immunization

Delivery of vaccines into the skin provides many advantages over traditional parenteral vaccination and is a promising approach due to the abundance of antigen presenting cells (APC) residing in the skin including Langerhans cells (LC) and dermal dendritic cells (DDC). However, the main obstacle for transcutaneous immunization (TCI) is the effective delivery of the vaccine through the stratum corneum (SC) barrier to the APC in the deeper skin layers. This study therefore utilized microneedles (MN) and a lipid-based colloidal delivery system (cubosomes) as a synergistic approach for the delivery of vaccines to APC in the skin. The process of vaccine uptake and recruitment by specific types of skin APC was investigated in real-time over 4 hours in B6.Cg-Tg (Itgax-EYFP) 1 Mnz/J mice by two-photon microscopy. Incorporation of the vaccine into a particulate delivery system and the use of MN preferentially increased vaccine antigen uptake by a highly motile subpopulation of skin APC known as CD207⁺ DC. No uptake of antigen or any response to immunisation by LC could be detected.

Cutaneous immunization: an evolving paradigm in influenza vaccines

INTRODUCTION

Most vaccines are administered by intramuscular injection using a hypodermic needle and syringe. Some limitations of this procedure include reluctance to be immunized because of fear of needlesticks, and concerns associated with the safe disposal of needles after their use. Skin delivery is an alternate route of vaccination that has potential to be painless and could even lead to dose reduction of vaccines. Recently, microneedles have emerged as a novel painless approach for delivery of influenza vaccines via the skin.

AREAS COVERED

In this review, we briefly summarize the approaches and devices used for skin vaccination, and then focus on studies of skin immunization with influenza vaccines using microneedles. We discuss both the functional immune response and the nature of this immune response following vaccination with microneedles.

EXPERT OPINION

The cutaneous administration of influenza vaccines using microneedles offers several advantages: it is painless, elicits stronger immune responses in preclinical studies and could improve responses in high-risk populations. These dry formulations of vaccines provide enhanced stability, a property of high importance in enabling their rapid global distribution in response to possible outbreaks of pandemic influenza and newly emerging infectious diseases.

Skin immunization with influenza vaccines

Problems with existing influenza vaccines include the strain specificity of the immune response, resulting in the need for frequent reformulation in response to viral antigenic drift. Even in years when the same influenza strains are prevalent, the duration of immunity is limited, and results in the need for annual revaccination. The immunogenicity of the present split or subunit vaccines is also lower than that observed with whole inactivated virus, and the vaccines are not very effective in high risk groups such as the young or the elderly. Vaccine coverage is incomplete, due in part to concerns about the use of hypodermic needles for delivery. Alternative approaches for vaccination are being developed which address many of these concerns. Here we review new approaches which focus on skin immunization, including the development of needle-free delivery systems which use stable dry formulations and induce stronger and longer-lasting immune responses.

Host responses in human skin after conventional intradermal injection or microneedle administration of virus-like-particle influenza vaccine

Miniaturized microneedle devices are being developed for painlessly targeting vaccines to the immune cell populations in skin. As skin immunization studies are generally restricted to animal models however, where skin architecture and immunity is greatly different to human, surprisingly little is known about the local human response to intradermal (ID) vaccines. Here surgically excised human skin is used to explore for the first time the complex molecular and cellular host responses to a candidate influenza vaccine comprising nanoparticulate virus-like-particles (VLPs), administered via conventional hypodermic injection or reduced scale microneedles. Responses at the molecular level are determined by microarray analysis (47,296 discrete transcripts) and validated by quantitative PCR (96 genes). Cellular response is probed through monitoring migration of dendritic cells in viable skin tissue. Gene expression mapping, ontological analysis, and qPCR reveal up-regulation of a host of genes responsible for key immunomodulatory processes and host viral response, including cell recruitment, activation, migration, and T cell interaction following both ID and microneedle injection of VLPs; the response from the microneedles being more subtle. Significant morphological and migratory changes to skin dendritic cells are also apparent following microneedle VLP delivery. This is the first study displaying the global, multifaceted immunological events that occur at the site of vaccine deposition in human skin and will subsequently influence the degree and nature of innate and adaptive immune responses. An increased understanding of the detailed similarities and differences in response against antigen administered via different delivery modalities will inform the development of improved vaccines and vaccine delivery systems.

Virus-like particles as a highly efficient vaccine platform: diversity of targets and production systems and advances in clinical development

Virus-like particles (VLPs) are a class of subunit vaccines that differentiate themselves from soluble recombinant antigens by stronger protective immunogenicity associated with the VLP structure. Like parental viruses, VLPs can be either non-enveloped or enveloped, and they can form following expression of one or several viral structural proteins in a recombinant heterologous system. Depending on the complexity of the VLP, it can be produced in either a prokaryotic or eukaryotic expression system using target-encoding recombinant vectors, or in some cases can be assembled in cell-free conditions. To date, a wide variety of VLP-based candidate vaccines targeting various viral, bacterial, parasitic and fungal pathogens, as well as non-infectious diseases, have been produced in different expression systems. Some VLPs have entered clinical development and a few have been licensed and commercialized. This article reviews VLP-based vaccines produced in different systems, their immunogenicity in animal models and their status in clinical development.

Microneedle and mucosal delivery of influenza vaccines

In recent years with the threat of pandemic influenza and other public health needs, alternative vaccination methods other than intramuscular immunization have received great attention. The skin and mucosal surfaces are attractive sites probably because of both noninvasive access to the vaccine delivery and unique immunological responses. Intradermal vaccines using a microinjection system (BD Soluvia(TM)) and intranasal vaccines (FluMist®) are licensed. As a new vaccination method, solid microneedles have been developed using a simple device that may be suitable for self-administration. Because coated microneedle influenza vaccines are administered in the solid state, developing formulations maintaining the stability of influenza vaccines is an important issue to be considered. Marketable microneedle devices and clinical trials remain to be developed. Other alternative mucosal routes such as oral and intranasal delivery systems are also attractive for inducing cross-protective mucosal immunity, but effective non-live mucosal vaccines remain to be developed.

Measles vaccination using a microneedle patch

Measles vaccination programs would benefit from delivery methods that decrease cost, simplify logistics, and increase safety. Conventional subcutaneous injection is limited by the need for skilled healthcare professionals to reconstitute and administer injections, and by the need for safe needle handling and disposal to reduce the risk of disease transmission through needle re-use and needlestick injury. Microneedles are micron-scale, solid needles coated with a dry formulation of vaccine that dissolves in the skin within minutes after patch application. By avoiding the use of hypodermic needles, vaccination using a microneedle patch could be carried out by minimally trained personnel with reduced risk of blood-borne disease transmission. The goal of this study was to evaluate measles vaccination using a microneedle patch to address some of the limitations of subcutaneous injection. Viability of vaccine virus dried onto a microneedle patch was stabilized by incorporation of the sugar, trehalose, and loss of viral titer was less than 1 log10(TCID50) after storage for at least 30 days at room temperature. Microneedle patches were then used to immunize cotton rats with the Edmonston-Zagreb measles vaccine strain. Vaccination using microneedles at doses equaling the standard human dose or one-fifth the human dose generated neutralizing antibody levels equivalent to those of a subcutaneous immunization at the same dose. These results show that measles vaccine can be stabilized on microneedles and that vaccine efficiently reconstitutes in vivo to generate a neutralizing antibody response equivalent to that generated by subcutaneous injection.

Dose sparing intradermal trivalent influenza (2010/2011) vaccination overcomes reduced immunogenicity of the 2009 H1N1 strain

BACKGROUND

We hypothesized that low dose intradermal vaccination of the trivalent influenza vaccine (TIV) delivered by the MicronJet600™ (NanoPass Technologies, Israel) would be non-inferior to the full dose intramuscular and mid dose Intanza(®) vaccination in the elderly and the chronically ill adults.

METHODS

We performed a prospective randomized trial on elderly and chronically ill adults. Subjects were randomly assigned into 4 groups. Groups ID3 and ID9 received reduced dose ID TIV (3 μg and 9 μg of hemagglutinin (HA) per strain respectively) delivered by MicronJet600™ (NanoPass Technologies, Israel). Group INT9 received reduced dose ID TIV (9 μg) delivered by Becton Dickinson's Soluvia™ device (Intanza(®)9, Sanofi-Pasteur, France). Control group IM15 received a full dose IM TIV (15 μg). We measured antibody titers by hemagglutination inhibition (HAI) and microneutralization (MN) assays at baseline and day 21.

RESULTS

Baseline characteristics for all groups were similar (group and sample sizes: ID3=63; ID9=68; INT9=65; and IM15=66). At day 21 post vaccination, the GMT ratio and the seroconversion rates difference for all three strains of the ID vaccine groups were non-inferior to the IM vaccine group. The seroconversion rate, seroprotection rate, and the GMT of the H1N1 strains by HAI and MN assays were significantly higher in the ID groups compared with the full dose IM vaccine group. The seroconversion rates of the H3N2 strain by HAI assay were also significantly higher in the ID groups when compared with the full dose IM group. Direct comparison among the three ID groups showed no significant differences. No serious adverse events related to vaccination were reported.

CONCLUSION

Dose-sparing ID TIV can overcome reduced immunogenicity of the H1N1 strain, and according to some measures, for the H3N2 strain. At risk subjects indicated for the TIV should be considered for intradermal immunization to compensate for reduced immunogenicity.

Intradermally administered TLR4 agonist GLA-SE enhances the capacity of human skin DCs to activate T cells and promotes emigration of Langerhans cells

The natural TLR4 agonist lipopolysaccharide (LPS) has notable adjuvant activity. However, it is not useful as a vaccine adjuvant due to its toxicity. Glucopyranosyl lipid A (GLA) is a synthetic derivative of the lipid A tail of LPS with limited cytotoxicity, but strong potential to induce immune responses in mice, guinea pigs, non-human primates, and humans. In this study we determined how this synthetic TLR4 agonist affects the function of different subsets of human skin dendritic cells (DCs). The effect of GLA in an aqueous formulation (GLA-AF) or in an oil-in-water emulsion (GLA-SE) was compared to that of LPS and TLR3 agonist poly(I:C) using a human skin explant model with intradermal injections for the administration of the agonists. Intradermal injection of GLA-SE or LPS, but not GLA-AF, enhanced the emigration of CD1a(high)/langerin(+) Langerhans cells (LCs), but not dermal DCs (DDCs). LCs and CD14(-) DDCs exhibited an enhanced mature phenotype following intradermal administration of either of the two GLA formulations tested, similar to DCs that emigrated from LPS-injected skin. However, only injection of GLA-SE resulted in a significant increase in the production of the wide range of cytokines that is observed with LPS. Moreover, DCs that emigrated from GLA-SE-injected skin induced stronger CD4(+) T-cell activation, as indicated by a more pronounced T-cell proliferation, than DCs from skin injected with GLA-AF or LPS. Altogether, our data show that GLA-SE has a notable potency to stimulate the function of skin DCs, indicating that GLA-SE may be a good candidate as adjuvant for vaccines administered via the intradermal route.

Intradermal immunization triggers epidermal Langerhans cell mobilization required for CD8 T-cell immune responses

The potential of the skin immune system for the generation of both powerful humoral and cellular immune responses is now well established. However, the mechanisms responsible for the efficacy of skin antigen-presenting cells (APCs) during intradermal (ID) vaccination still remain to be elucidated. We have previously demonstrated in clinical trials that preferential targeting of Langerhans cells (LCs) by transcutaneous immunization shapes the immune response toward vaccine-specific CD8 T cells. Others have shown that ID inoculation of a vaccine, which targets dermal APCs, mobilizes both the cellular and humoral arms of immunity. Here, we investigated the participation of epidermal LCs in response to ID immunization. When human or mouse skin was injected ID with a particle-based vaccine, we observed significant modifications in the morphology of epidermal LCs and their mobilization to the dermis. We further established that this LC recruitment after ID administration was essential for the induction of antigen-specific CD8 T cells, but was, however, dispensable for the generation of specific CD4 T cells and neutralizing antibodies. Thus, epidermal and dermal APCs shape the outcome of the immune responses to ID vaccination. Their combined potential provides new avenues for the development of vaccination strategies against infectious diseases.