Transcutaneous immunization induces mucosal CTLs and protective immunity by migration of primed skin dendritic cells

Immune cell trafficking: a novel perspective on the gut-skin axis

Immune cell trafficking, an essential mechanism for maintaining immunological homeostasis and mounting effective responses to infections, operates under a stringent regulatory framework. Recent advances have shed light on the perturbation of cell migration patterns, highlighting how such disturbances can propagate inflammatory diseases from their origin to distal organs. This review collates and discusses current evidence that demonstrates atypical communication between the gut and skin, which are conventionally viewed as distinct immunological spheres, in the milieu of inflammation. We focus on the aberrant, reciprocal translocation of immune cells along the gut-skin axis as a pivotal factor linking intestinal and dermatological inflammatory conditions. Recognizing that the translation of these findings into clinical practices is nascent, we suggest that therapeutic strategies aimed at modulating the axis may offer substantial benefits in mitigating the widespread impact of inflammatory diseases.

Non-Invasive Vaccines: Challenges in Formulation and Vaccine Adjuvants

Given the limitations of conventional invasive vaccines, such as the requirement for a cold chain system and trained personnel, needle-based injuries, and limited immunogenicity, non-invasive vaccines have gained significant attention. Although numerous approaches for formulating and administrating non-invasive vaccines have emerged, each of them faces its own challenges associated with vaccine bioavailability, toxicity, and other issues. To overcome such limitations, researchers have created novel supplementary materials and delivery systems. The goal of this review article is to provide vaccine formulation researchers with the most up-to-date information on vaccine formulation and the immunological mechanisms available, to identify the technical challenges associated with the commercialization of non-invasive vaccines, and to guide future research and development efforts.

Ionic Liquid-Based Transcutaneous Peptide Antitumor Vaccine: Therapeutic Effect in a Mouse Tumor Model

Traditional vaccinations need to be injected with needles, and since some people have a strong aversion to needles, a needle-free alternative delivery system is important. In this study, we employed ionic liquids (ILs) for transcutaneous delivery of cancer antigen-derived peptides to obtain anticancer therapeutic effects in a needle-free manner. ILs successfully increased the in vitro skin permeability of a peptide from Wilms tumor 1 (WT1), one of the more promising cancer antigens, plus or minus an adjuvant, resiquimod (R848), a toll-like receptor 7 agonist. In vivo studies demonstrated that concomitant transcutaneous delivery of WT1 peptide and R848 by ILs induced WT1-specific cytotoxic T lymphocyte (CTL) in mice, resulting in tumor growth inhibition in Lewis lung carcinoma-bearing mice. Interestingly, administrating R848 in ILs before WT1 peptides in ILs increased tumor growth inhibition effects compared to co-administration of both. We found that the prior application of R848 increased the infiltration of leukocytes in the skin and that subsequent delivery of WT1 peptides was more likely to induce WT1-specific CTL. Furthermore, sequential immunization with IL-based formulations was applicable to different types of peptides and cancer models without induction of skin irritation. IL-based transcutaneous delivery of cancer antigen-derived peptides and adjuvants, either alone or together, could be a novel approach to needle-free cancer therapeutic vaccines.

Skin-Based Vaccination: A Systematic Mapping Review of the Types of Vaccines and Methods Used and Immunity and Protection Elicited in Pigs

The advantages of skin-based vaccination include induction of strong immunity, dose-sparing, and ease of administration. Several technologies for skin-based immunisation in humans are being developed to maximise these key advantages. This route is more conventionally used in veterinary medicine. Skin-based vaccination of pigs is of high relevance due to their anatomical, physiological, and immunological similarities to humans, as well as being a source of zoonotic diseases and their livestock value. We conducted a systematic mapping review, focusing on vaccine-induced immunity and safety after the skin immunisation of pigs. Veterinary vaccines, specifically anti-viral vaccines, predominated in the literature. The safe and potent skin administration to pigs of adjuvanted vaccines, particularly emulsions, are frequently documented. Multiple methods of skin immunisation exist; however, there is a lack of consistent terminology and accurate descriptions of the route and device. Antibody responses, compared to other immune correlates, are most frequently reported. There is a lack of research on the underlying mechanisms of action and breadth of responses. Nevertheless, encouraging results, both in safety and immunogenicity, were observed after skin vaccination that were often comparable to or superior the intramuscular route. Further research in this area will underlie the development of enhanced skin vaccine strategies for pigs, other animals and humans.

Use of Iontophoresis Technology for Transdermal Delivery of a Minimal mRNA Vaccine as a Potential Melanoma Therapeutic

mRNA vaccines have attracted considerable attention as a result of the 2019 coronavirus pandemic; however, challenges remain regarding use of mRNA vaccines, including insufficient delivery owing to the high molecular weights and high negative charges associated with mRNA. These characteristics of mRNA vaccines impair intracellular uptake and subsequent protein translation. In the current study, we prepared a minimal mRNA vaccine encoding a tumor associated antigen human gp100_25-33 peptide (KVPRNQDWL), as a potential treatment for melanoma. Minimal mRNA vaccines have recently shown promise at improving the translational process, and can be prepared via a simple production method. Moreover, we previously reported the successful use of iontophoresis (IP) technology in the delivery of hydrophilic macromolecules into skin layers, as well as intracellular delivery of small interfering RNA (siRNA). We hypothesized that combining IP technology with a newly synthesized minimal mRNA vaccine can improve both transdermal and intracellular delivery of mRNA. Following IP-induced delivery of a mRNA vaccine, an immune response is elicited resulting in activation of skin resident immune cells. As expected, combining both technologies led to potent stimulation of the immune system, which was observed via potent tumor inhibition in mice bearing melanoma. Additionally, there was an elevation in mRNA expression levels of various cytokines, mainly interferon (IFN)-γ, as well as infiltration of cytotoxic CD8⁺ T cells in the tumor tissue, which are responsible for tumor clearance. This is the first report demonstrating the application of IP for delivery of a minimal mRNA vaccine as a potential melanoma therapeutic.

Sars-Cov-2 virus and vaccination; biological and statistical framework

Introduction

The Development of the SARS-CoV-2 virus vaccine and its update on an ongoing pandemic is the first subject of the world health agenda.

Areas covered

First, we will scrutinize the biological features of the measles virus (MV), variola virus (smallpox virus), influenza virus, and their vaccines to compare them with the SARS-CoV-2 virus and vaccine. Next, we will discuss the statistical details of measuring the effectiveness of an improved vaccine.

Expert opinion

Amidst the pandemic, we ought to acknowledge our prior experiences with respiratory viruses and vaccines. In the planning stage of observational Phase-III vaccine effectiveness studies, the sample size, sampling method, statistical model, and selection of variables are crucial in obtaining high-quality and valid results.

The pig as a medical model for acquired respiratory diseases and dysfunctions: An immunological perspective

By definition no model is perfect, and this also holds for biology and health sciences. In medicine, murine models are, and will be indispensable for long, thanks to their reasonable cost and huge choice of transgenic strains and molecular tools. On the other side, non-human primates remain the best animal models although their use is limited because of financial and obvious ethical reasons. In the field of respiratory diseases, specific clinical models such as sheep and cotton rat for bronchiolitis, or ferret and Syrian hamster for influenza and Covid-19, have been successfully developed, however, in these species, the toolbox for biological analysis remains scarce. In this view the porcine medical model is appearing as the third, intermediate, choice, between murine and primate. Herein we would like to present the pros and cons of pig as a model for acquired respiratory conditions, through an immunological point of view. Indeed, important progresses have been made in pig immunology during the last decade that allowed the precise description of immune molecules and cell phenotypes and functions. These progresses might allow the use of pig as clinical model of human respiratory diseases but also as a species of interest to perform basic research explorations.

Induction of SARS-CoV-2 Protein S-Specific CD8+ T Cells in the Lungs of gp96-Ig-S Vaccinated Mice

Given the aggressive spread of COVID-19-related deaths, there is an urgent public health need to support the development of vaccine candidates to rapidly improve the available control measures against SARS-CoV-2. To meet this need, we are leveraging our existing vaccine platform to target SARS-CoV-2. Here, we generated cellular heat shock chaperone protein, glycoprotein 96 (gp96), to deliver SARS-CoV-2 protein S (spike) to the immune system and to induce cell-mediated immune responses. We showed that our vaccine platform effectively stimulates a robust cellular immune response against protein S. Moreover, we confirmed that gp96-Ig, secreted from allogeneic cells expressing full-length protein S, generates powerful, protein S polyepitope-specific CD4+ and CD8+ T cell responses in both lung interstitium and airways. These findings were further strengthened by the observation that protein-S -specific CD8+ T cells were induced in human leukocyte antigen HLA-A2.1 transgenic mice thus providing encouraging translational data that the vaccine is likely to work in humans, in the context of SARS-CoV-2 antigen presentation.

Transcutaneous Vaccination with Conjugate Typhoid Vaccine Vi-DT Induces Systemic, Mucosal, and Memory Anti-Polysaccharide Responses

Transcutaneous vaccination can induce both mucosal and systemic immune responses. However, there are few data on anti-polysaccharide responses following transcutaneous vaccination of polysaccharides, despite the role that anti-polysaccharide responses play in protecting against intestinal mucosal and respiratory pathogens. Whether transcutaneous vaccination with a conjugate polysaccharide vaccine would be able to induce memory responses is also unknown. To address this, we transcutaneously vaccinated mice with virulence antigen (Vi) polysaccharide of Salmonella enterica serovar Typhi (the cause of typhoid fever), either in unconjugated or conjugated form (the latter as a Vi-DT conjugate). We also assessed the ability of the immunoadjuvant cholera toxin to impact responses following vaccination. We found that presenting Vi in a conjugate versus nonconjugate form transcutaneously resulted in comparable serum IgG responses but higher serum and lamina propria lymphocyte IgA anti-Vi responses, as well as increased IgG memory responses. The addition of immunoadjuvant did not further increase these responses; however, it boosted fecal IgA and serum IgG anti-Vi responses. Our results suggest that transcutaneous vaccination of a conjugate vaccine can induce systemic as well as enhanced mucosal and memory B-cell anti-polysaccharide responses.

Evaluation of the Immunogenicity and Protective Efficacy of an Enterotoxigenic Escherichia coli CFA/I Adhesin-Heat-Labile Toxin Chimera

Recent efforts to develop an enterotoxigenic Escherichia coli (ETEC) vaccine have focused on the antigenically conserved tip adhesins of colonization factors. We showed previously that intranasal immunization with dsc₁₉CfaE, a soluble variant of the in cis donor strand-complemented tip adhesin of a colonization factor of the class 5 family (CFA/I) fimbria, is highly immunogenic and protects against oral challenge with CFA/I-positive (CFA/I⁺) ETEC strain H10407 in the Aotus nancymaae nonhuman primate. We also reported a cholera toxin (CT)-like chimera (called dsc₁₉CfaE-CTA2/CTB) in which the CTA1 domain of CT was replaced by dsc₁₉CfaE that was strongly immunogenic when administered intranasally or orogastrically in mice. Here, we evaluate the immunogenicity and protective efficacy (PE) of a refined and more stable chimera comprised of a pentameric B subunit of ETEC heat-labile toxin (LTB) in lieu of the CTB pentamer and a donor strand truncation (dsc₁₄) of CfaE. The refined chimera, dsc₁₄CfaE-sCTA2/LTB, was highly immunogenic in mice when administered intranasally or intradermally, eliciting serum and fecal antibody responses against CfaE and LTB, as well as strong hemagglutination inhibition titers, a surrogate for neutralization of intestinal adhesion mediated by CfaE. Moreover, the chimera was safe and highly immunogenic when administered intradermally to guinea pigs. In A. nancymaae, intradermal (i.d.) immunization with chimera plus single-mutant heat-labile toxin [LT(R192G)] elicited strong serum anti-CfaE and anti-LTB antibody responses and conferred significant reduction of diarrhea compared to phosphate-buffered saline (PBS) controls (PE = 84.1%; P < 0.02). These data support the further evaluation of dsc₁₄CfaE-sCTA2/LTB as an ETEC vaccine in humans.

Immunology-Guided Biomaterial Design for Mucosal Cancer Vaccines

Cancer of mucosal tissues is a major cause of worldwide mortality for which only palliative treatments are available for patients with late-stage disease. Engineered cancer vaccines offer a promising approach for inducing antitumor immunity. The route of vaccination plays a major role in dictating the migratory pattern of lymphocytes, and thus vaccine efficacy in mucosal tissues. Parenteral immunization, specifically subcutaneous and intramuscular, is the most common vaccination route. However, this induces marginal mucosal protection in the absence of tissue-specific imprinting signals. To circumvent this, the mucosal route can be utilized, however degradative mucosal barriers must be overcome. Hence, vaccine administration route and selection of materials able to surmount transport barriers are important considerations in mucosal cancer vaccine design. Here, an overview of mucosal immunity in the context of cancer and mucosal cancer clinical trials is provided. Key considerations are described regarding the design of biomaterial-based vaccines that will afford antitumor immune protection at mucosal surfaces, despite limited knowledge surrounding mucosal vaccination, particularly aided by biomaterials and mechanistic immune-material interactions. Finally, an outlook is given of how future biomaterial-based mucosal cancer vaccines will be shaped by new discoveries in mucosal vaccinology, tumor immunology, immuno-therapeutic screens, and material-immune system interplay.

Understanding the basis of transcutaneous vaccine delivery

Under many circumstances, prophylactic immunizations are considered as the only possible strategy to control infectious diseases. Considerable efforts are typically invested in immunogen selection but, erroneously, the route of administration is not usually a major concern despite the fact that it can strongly influence efficacy. The skin is now considered a key component of the lymphatic system with tremendous potential as a target for vaccination. The purpose of this review is to present the immunological basis of the skin-associated lymphoid tissue, so as to provide understanding of the skin vaccination strategies. Several strategies are currently being developed for the transcutaneous delivery of antigens. The classical, mechanical or chemical disruptions versus the newest approaches based on microneedles for antigen delivery through the skin are discussed herein.

Evaluation of the reactogenicity, adjuvanticity and antigenicity of LT(R192G) and LT(R192G/L211A) by intradermal immunization in mice

The development of an effective subunit vaccine is frequently complicated by the difficulty of eliciting protective immune responses, often requiring the co-administration of an adjuvant. Heat-labile toxin (LT), an enterotoxin expressed by enterotoxigenic E. coli (ETEC) with an AB5 structure similar to cholera toxin, is a strong adjuvant. While the mucosa represents the natural route of exposure to LT and related toxins, the clinical utility of LT and similar adjuvants given by mucosal routes has been limited by toxicity, as well as the association between intranasal delivery of LT and Bell's palsy. Single and double amino acid mutants of LT, LT(R192G)/mLT and LT(R192G/L211A)/dmLT respectively, have been proposed as alternatives to reduce the toxicity associated with the holotoxin. In the present study, we compared mLT and dmLT given via a non-mucosal route (i.e. intradermally) to investigate their adjuvanticity when co-administrated with an enterotoxigenic E. coli vaccine candidate, CfaEB. Antigenicity (i.e. ability to elicit response against LT) and reactogenicity at the injection site were also evaluated. BALB/c mice were immunized by the intradermal route with CfaEB plus increasing doses of either mLT or dmLT (0.01 to 2.5 μg). Both adjuvants induced dose-dependent skin reactogenicity, with dmLT being less reactogenic than mLT. Both adjuvants significantly boosted the anti-CfaE IgG and functional hemagglutination inhibiting (HAI) antibody responses, compared to the antigen alone. In addition to inducing anti-LT responses, even at the lowest dose tested (0.01 μg), the adjuvants also prompted in vitro cytokine responses (IFN-γ, IL-4, IL-5, IL-10 and IL-17) that followed different patterns, depending on the protein used for stimulation (CfaE or LTB) and/or the dose used for immunization. The two LT mutants evaluated here, mLT and dmLT, are potent adjuvants for intradermal immunization and should be further investigated for the intradermal delivery of subunit ETEC vaccines.

Dissolving Microneedles for Intradermal Vaccination against Shigellosis

Intradermal (ID) immunization is of increasing interest due to the easy accessibility and excellent immunogenic properties of the skin. Among ID immunization methods, dissolving microneedles (MNs) have appeared as an alternative to traditional hypodermic immunization, offering many advantages, such as being an easily administered method, with no need for health personnel, painless, and avoiding the use of needles and sharp wastage. In this study, an affordable and easy-to-produce MNs method was developed based on aqueous blends of 30% w/w poly (methyl vinyl ether-co-maleic anhydride). As an antigen model, a subunit vaccine candidate based on outer membrane vesicles from Shigella flexneri was used. Both unloaded and antigen-loaded MNs were synthetized and characterized. The MNs were successfully validated in an in vitro Parafilm M^® skin model and in a pig skin ex vivo model. Biodistribution studies were performed in BALB/c mice using ^99mTcO₄⁻ radiolabeled samples. Results indicated that the vesicle vaccine was successfully released from the MNs and targeted gastrointestinal tract after 6 h post-administration. In vivo immunization and protection studies were performed in BALB/c mice. Mice were intradermally immunized through ear skin with one single dose of 200 μg antigenic complex, eliciting the production of specific systemic IgG and mucosal IgA. Moreover, MNs were able to protect mice from an experimental infection with 1×10⁶ CFU/mouse of S. flexneri four weeks after immunization. This work demonstrates for the first time the potential of outer membrane vesicle-loaded dissolving MNs for ID vaccination against enteropathogens like Shigella.

Innate gene signature distinguishes humoral versus cytotoxic responses to influenza vaccination

BACKGROUND

Systems vaccinology allows cutting-edge analysis of innate biomarkers of vaccine efficacy. We have been exploring novel strategies to shape the adaptive immune response, by targeting innate immune cells through novel immunization routes.

METHODS

This randomized phase I/II clinical study (n=60 healthy subjects aged 18-45 years old) used transcriptomic analysis to discover early biomarkers of immune response quality after transcutaneous (t.c.), intradermal (i.d.), and intramuscular (i.m.) administration of a trivalent influenza vaccine (TIV season 2012-2013) (1:1:1 ratio). Safety and immunogenicity (hemagglutinin inhibition (HI), microneutralization (MN) antibodies and CD4, CD8 effector T cells) were measured at baseline Day (D)0 and at D21. Blood transcriptome was analyzed at D0 and D1.

RESULTS

TIV-specific CD8+GranzymeB+(GRZ) T cells appeared in more individuals immunized by the t.c. and i.d. routes, while immunization by the i.d. and i.m. routes prompted high levels of HI antibody titers and MN against A/H1N1 and A/H3N2 influenza viral strains. The early innate gene signature anticipated immunological outcome by discriminating two clusters of individuals with either distinct humoral or CD8 cytotoxic responses. Several pathways explained this dichotomy confirmed by nine genes and serum level of CXCL10 were correlated with either TIV-specific cytotoxic CD8+GRZ+ T-cell or antibody responses. A logistic regression analysis demonstrated that these nine genes and serum levels of CXCL10 (D1/D0) best foreseen TIV-specific CD8+GRZ+ T-cell and antibody responses at D21.

CONCLUSION

This study provides new insight into the impact of immunization routes and innate signature in the quality of adaptive immune responses.

A surface charge dependent enhanced Th1 antigen-specific immune response in lymph nodes by transfersome-based nanovaccine-loaded dissolving microneedle-assisted transdermal immunization

The efficient delivery of vaccines to draining lymph nodes and the induction of robust local immune responses are crucial for immunotherapy.

Noninvasive vaccination against infectious diseases

The development of a successful vaccine, which should elicit a combination of humoral and cellular responses to control or prevent infections, is the first step in protecting against infectious diseases. A vaccine may protect against bacterial, fungal, parasitic, or viral infections in animal models, but to be effective in humans there are some issues that should be considered, such as the adjuvant, the route of vaccination, and the antigen-carrier system. While almost all licensed vaccines are injected such that inoculation is by far the most commonly used method, injection has several potential disadvantages, including pain, cross contamination, needlestick injury, under- or overdosing, and increased cost. It is also problematic for patients from rural areas of developing countries, who must travel to a hospital for vaccine administration. Noninvasive immunizations, including oral, intranasal, and transcutaneous administration of vaccines, can reduce or eliminate pain, reduce the cost of vaccinations, and increase their safety. Several preclinical and clinical studies as well as experience with licensed vaccines have demonstrated that noninvasive vaccine immunization activates cellular and humoral immunity, which protect against pathogen infections. Here we review the development of noninvasive immunization with vaccines based on live attenuated virus, recombinant adenovirus, inactivated virus, viral subunits, virus-like particles, DNA, RNA, and antigen expression in rice in preclinical and clinical studies. We predict that noninvasive vaccine administration will be more widely applied in the clinic in the near future.

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

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

Multigenic DNA vaccine induces protective cross-reactive T cell responses against heterologous influenza virus in nonhuman primates

Recent avian and swine-origin influenza virus outbreaks illustrate the ongoing threat of influenza pandemics. We investigated immunogenicity and protective efficacy of a multi-antigen (MA) universal influenza DNA vaccine consisting of HA, M2, and NP antigens in cynomolgus macaques. Following challenge with a heterologous pandemic H1N1 strain, vaccinated animals exhibited significantly lower viral loads and more rapid viral clearance when compared to unvaccinated controls. The MA DNA vaccine induced robust serum and mucosal antibody responses but these high antibody titers were not broadly neutralizing. In contrast, the vaccine induced broadly-reactive NP specific T cell responses that cross-reacted with the challenge virus and inversely correlated with lower viral loads and inflammation. These results demonstrate that a MA DNA vaccine that induces strong cross-reactive T cell responses can, independent of neutralizing antibody, mediate significant cross-protection in a nonhuman primate model and further supports development as an effective approach to induce broad protection against circulating and emerging influenza strains.

Mucosal vaccine delivery: Current state and a pediatric perspective

Most childhood infections occur via the mucosal surfaces, however, parenterally delivered vaccines are unable to induce protective immunity at these surfaces. In contrast, delivery of vaccines via the mucosal routes can allow antigens to interact with the mucosa-associated lymphoid tissue (MALT) to induce both mucosal and systemic immunity. The induced mucosal immunity can neutralize the pathogen on the mucosal surface before it can cause infection. In addition to reinforcing the defense at mucosal surfaces, mucosal vaccination is also expected to be needle-free, which can eliminate pain and the fear of vaccination. Thus, mucosal vaccination is highly appealing, especially for the pediatric population. However, vaccine delivery across mucosal surfaces is challenging because of the different barriers that naturally exist at the various mucosal surfaces to keep the pathogens out. There have been significant developments in delivery systems for mucosal vaccination. In this review we provide an introduction to the MALT, highlight barriers to vaccine delivery at different mucosal surfaces, discuss different approaches that have been investigated for vaccine delivery across mucosal surfaces, and conclude with an assessment of perspectives for mucosal vaccination in the context of the pediatric population.

Novel Delivery Routes for Allergy Immunotherapy: Intralymphatic, Epicutaneous, and Intradermal

Current allergy immunotherapy protocols suffer from two main problems: long treatment duration and systemic allergic side effects of the allergen administrations. The immunologic effects of allergen administration could be enhanced and the number of allergen administrations and treatment duration reduced by choosing a tissue for administration that contains a high density of antigen-presenting cells. Local side effects could be reduced by choosing a route characterized by a low density of mast cells, and systemic side effects could be reduced by administration to nonvascularized tissues, so that inadvertent systemic distribution of the allergen and consequent systemic allergic side effects are minimized.

Intradermal immunisation using the TLR3-ligand Poly (I:C) as adjuvant induces mucosal antibody responses and protects against genital HSV-2 infection

Development of vaccines able to induce mucosal immunity in the genital and gastrointestinal tracts is a major challenge to counter sexually transmitted pathogens such as HIV-1 and HSV-2. Herein, we showed that intradermal (ID) immunisation with sub-unit vaccine antigens (i.e., HIV-1 gp140 and HSV-2 gD) delivered with Poly(I:C) or CpG1668 as adjuvant induces long-lasting virus-specific immunoglobulin (Ig)-G and IgA antibodies in the vagina and feces. Poly(I:C)-supplemented sub-unit viral vaccines caused minimal skin reactogenicity at variance to those containing CpG1668, promoted a delayed-type hypersensitivity (DTH) to the vaccine and protected mice from genital and neurological symptoms after a lethal vaginal HSV-2 challenge. Interestingly, Poly(I:C_12U) (Ampligen), a Poly(I:C) structural analogue that binds to TLR3 but not MDA-5, promoted robust mucosal and systemic IgG antibodies, a weak skin DTH to the vaccine but not IgA responses and failed to confer protection against HSV-2 infection. Moreover, Poly(I:C) was far superior to Poly(I:C_12U) at inducing prompt and robust upregulation of IFNß transcripts in lymph nodes draining the injection site. These data illustrate that ID vaccination with glycoproteins and Poly(I:C) as adjuvant promotes long-lasting mucosal immunity and protection from genital HSV-2 infection, with an acceptable skin reactogenicity profile. The ID route thus appears to be an unexpected inductive site for mucosal immunity and anti-viral protection suitable for sub-unit vaccines. This works further highlights that TLR3/MDA5 agonists such as Poly(I:C) may be valuable adjuvants for ID vaccination against sexually transmitted diseases.

Topical CpG Oligodeoxynucleotide Adjuvant Enhances the Adaptive Immune Response against Influenza A Infections

Current influenza vaccines generate humoral immunity, targeting highly variable epitopes and thus fail to achieve long-term protection. T cells recognize and respond to several highly conserved epitopes across influenza serotypes. A strategy of raising strong cytotoxic T cell memory responses to epitopes conserved across serotypes would provide cross serotype protection, eliminating the need for annual vaccination. We explored the adjuvant potential of epicutaneous (ec) and subcutaneous (sc) delivery of CpG oligodeoxynucleotide in conjunction with sc protein immunization to improve protection against influenza A virus (IAV) infections using a mouse model. We found enhanced long-term protection with epicutaneous CpG ODN (ecCpG) compared to subcutaneous CpG ODN (scCpG) as demonstrated by reduced viral titers in the lungs. This correlated with increased antigen-specific CD8 T cells in the airways and the lungs. The memory T cell response after immunization with ecCpG adjuvant was comparable to memory response by priming with IAV infection in the lungs. In addition, ecCpG was more efficient than scCpG in inducing the generation of IFN-γ producing CD4 T cells. The adjuvant effect of ecCpG was accompanied with its ability to modulate tissue-homing molecules on T cells that may direct them to the site of infection. Together, this work provides evidence for using ecCpG to induce strong antibody and memory T cell responses to confer protection against IAV infection.

Induction of mucosal immunity through systemic immunization: Phantom or reality?

Generation of protective immunity at mucosal surfaces can greatly assist the host defense against pathogens which either cause disease at the mucosal epithelial barriers or enter the host through these surfaces. Although mucosal routes of immunization, such as intranasal and oral, are being intensely explored and appear promising for eliciting protective mucosal immunity in mammals, their application in clinical practice has been limited due to technical and safety related challenges. Most of the currently approved human vaccines are administered via systemic (such as intramuscular and subcutaneous) routes. Whereas these routes are acknowledged as being capable to elicit antigen-specific systemic humoral and cell-mediated immune responses, they are generally perceived as incapable of generating IgA responses or protective mucosal immunity. Nevertheless, currently licensed systemic vaccines do provide effective protection against mucosal pathogens such as influenza viruses and Streptococcus pneumoniae. However, whether systemic immunization induces protective mucosal immunity remains a controversial topic. Here we reviewed the current literature and discussed the potential of systemic routes of immunization for the induction of mucosal immunity.

Recent insights into cutaneous immunization: How to vaccinate via the skin

Technologies and strategies for cutaneous vaccination have been evolving significantly during the past decades. Today, there is evidence for increased efficacy of cutaneously delivered vaccines allowing for dose reduction and providing a minimally invasive alternative to traditional vaccination. Considerable progress has been made within the field of well-established cutaneous vaccination strategies: Jet and powder injection technologies, microneedles, microporation technologies, electroporation, sonoporation, and also transdermal and transfollicular vaccine delivery. Due to recent advances, the use of cutaneous vaccination can be expanded from prophylactic vaccination for infectious diseases into therapeutic vaccination for both infectious and non-infectious chronic conditions. This review will provide an insight into immunological processes occurring in the skin and introduce the key innovations of cutaneous vaccination technologies.

Immunoprevention of chemical carcinogenesis through early recognition of oncogene mutations

Prevention of tumors induced by environmental carcinogens has not been achieved. Skin tumors produced by polyaromatic hydrocarbons, such as 7,12-dimethylbenz(a)anthracene (DMBA), often harbor an H-ras point mutation, suggesting that it is a poor target for early immunosurveillance. The application of pyrosequencing and allele-specific PCR techniques established that mutations in the genome and expression of the Mut H-ras gene could be detected as early as 1 d after DMBA application. Further, DMBA sensitization raised Mut H-ras epitope-specific CTLs capable of eliminating Mut H-ras(+) preneoplastic skin cells, demonstrating that immunosurveillance is normally induced but may be ineffective owing to insufficient effector pool size and/or immunosuppression. To test whether selective pre-expansion of CD8 T cells with specificity for the single Mut H-ras epitope was sufficient for tumor prevention, MHC class I epitope-focused lentivector-infected dendritic cell- and DNA-based vaccines were designed to bias toward CTL rather than regulatory T cell induction. Mut H-ras, but not wild-type H-ras, epitope-focused vaccination generated specific CTLs and inhibited DMBA-induced tumor initiation, growth, and progression in preventative and therapeutic settings. Transferred Mut H-ras-specific effectors induced rapid tumor regression, overcoming established tumor suppression in tumor-bearing mice. These studies support further evaluation of oncogenic mutations for their potential to act as early tumor-specific, immunogenic epitopes in expanding relevant immunosurveillance effectors to block tumor formation, rather than treating established tumors.

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.

Apoptosis of antigen-specific CTLs contributes to low immune response in gut-associated lymphoid tissue post vaccination

The gut-associated lymphoid tissue (GALT) represents a major reservoir of HIV in infected individuals. Vaccines can induce strong systemic immune responses but these have less impact on CD4 T cells activity and numbers in GALT. In this study, we vaccinated mice with an adenovirus vector that expressed the envelope gene from HIV and observed immune responses in the peripheral blood, spleen, liver, mesenteric lymph nodes, and Peyer's patches. We found that (1) the number of HIV-specific CD8 T cells was dramatically lower in GALT than in other tissues; (2) the programmed cell death protein-1 (PD-1) was expressed at high levels in HIV-specific CD8 T cells including memory T cells in GALT; and (3) high levels of HIV-specific CD8 T cell apoptosis were occurring in GALT. These results suggest that contributing to GALT becoming an HIV reservoir during infection is a combination of exhaustion and/or dysfunction of HIV-specific CTLs at that site. These results emphasize the importance of developing of an effective mucosal vaccine against HIV.

Non-invasive, epicutaneous immunisation with toxoid in deformable vesicles protects mice against tetanus, chiefly owing to a Th2 response

A non-invasive, intra/transcutaneous immunisation of mice with a suitable combination of tetanus toxoid, ultradeformable vesicle (Transfersome®) carrier, and monophosphoryl lipid A adjuvant targets immuno-competent cells in a body and can protect 100% of the tested mice against an otherwise lethal (50×LD50) parenteral tetanus toxin challenge. The late immune response to the epicutaneously applied tetanus toxoid in such vesicles consists chiefly of circulating IgG1 and IgG2b antibody isotypes, indicative of a specific Th2 cellular response bias. Immunisations by subcutaneous injections moreover protect 100% of mice against a similar, otherwise lethal, dose of tetanus toxin. However, the immune response to transcutaneous and invasive immunisation differs. The latter elicits mainly IgG1 and IgG2b as well as IgG2a antibody isotypes, indicative of a mixed Th1/Th2 response. The cytokine response of the intra/transcutaneously and subcutaneously immunised mice reflects the difference in the organ-specific manner. IFN-γ concentration is appreciably increased in the draining lymph nodes and IL-10 in spleen. Since tetanus is a neutral antigen, both the Th1-specific IFN-γ and the Th-2 specific-IL-10 are observable.

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.

Epicutaneous Immunotherapy for Aeroallergen and Food Allergy

IgE-mediated allergies today affect up to 30 % of the population in industrialized countries. Allergen immunotherapy is the only disease-modifying treatment option with a long-term effect. However, very few patients (<5 %) choose immunotherapy, due to the long treatment duration (between 3-5 years) and possible local and systemic allergic side effects of the allergen administrations. The latter occur when an allergen accidentally reaches the blood circulation. Therefore, the ideal application route for allergen immunotherapy should be characterized by two hallmarks: firstly, by a high number of potent antigen-presenting cells, which enhance efficacy and thus shorten treatment duration. Secondly, the allergen administration site is ideally non-vascularized, so that inadvertent systemic distribution of the allergen and consequent systemic allergic side effects are minimized. The epidermis contains high numbers of potent antigen-presenting Langerhans cells and, as an epithelium, is non-vascularized. Therefore, the epidermis represents an interesting administration route. Historical evidence for the clinical efficacy of epicutaneous allergy immunotherapy (EPIT) has now been strengthened by a number of recent double-blinded placebo-controlled clinical trials performed by independent groups. We review the immunological rationale, history and clinical experience with epicutaneous allergy immunotherapy.

Transcutaneous antigen delivery system

Transcutaneous immunization refers to the topical application of antigens onto the epidermis. Transcutaneous immunization targeting the Langerhans cells of the skin has received much attention due to its safe, needle-free, and noninvasive antigen delivery. The skin has important immunological functions with unique roles for antigen-presenting cells such as epidermal Langerhans cells and dermal dendritic cells. In recent years, novel vaccine delivery strategies have continually been developed; however, transcutaneous immunization has not yet been fully exploited due to the penetration barrier represented by the stratum corneum, which inhibits the transport of antigens and adjuvants. Herein we review recent achievements in transcutaneous immunization, focusing on the various strategies for the enhancement of antigen delivery and vaccination efficacy. [BMB Reports 2013; 46(1): 17-24]

The integration of T cell migration, differentiation and function

T cells function locally. Accordingly, T cells' recognition of antigen, their subsequent activation and differentiation, and their role in the processes of infection control, tumour eradication, autoimmunity, allergy and alloreactivity are intrinsically coupled with migration. Recent discoveries revise our understanding of the regulation and patterns of T cell trafficking and reveal limitations in current paradigms. Here, we review classic and emerging concepts, highlight the challenge of integrating new observations with existing T cell classification schemes and summarize the heuristic framework provided by viewing T cell differentiation and function first through the prism of migration.

Dendritic cells and vaccine design for sexually-transmitted diseases

Dendritic cells (DCs) are major antigen presenting cells (APCs) that can initiate and control host immune responses toward either immunity or tolerance. These features of DCs, as immune orchestrators, are well characterized by their tissue localizations as well as by their subset-dependent functional specialties and plasticity. Thus, the level of protective immunity to invading microbial pathogens can be dependent on the subsets of DCs taking up microbial antigens and their functional plasticity in response to microbial products, host cellular components and the cytokine milieu in the microenvironment. Vaccines are the most efficient and cost-effective preventive medicine against infectious diseases. However, major challenges still remain for the diseases caused by sexually-transmitted pathogens, including HIV, HPV, HSV and Chlamydia. We surmise that the establishment of protective immunity in the female genital mucosa, the major entry and transfer site of these pathogens, will bring significant benefit for the protection against sexually-transmitted diseases. Recent progresses made in DC biology suggest that vaccines designed to target proper DC subsets may permit us to establish protective immunity in the female genital mucosa against sexually-transmitted pathogens.

Generation of antigen-specific immunity following systemic immunization with DNA vaccine encoding CCL25 chemokine immunoadjuvant

A significant hurdle in vaccine development for many infectious pathogens is the ability to generate appropriate immune responses at the portal of entry, namely mucosal sites. The development of vaccine approaches resulting in secretory IgA and mucosal cellular immune responses against target pathogens is of great interest and in general, requires live viral infection at mucosal sites. Using HIV-1 and influenza A antigens as models, we report here that a novel systemically administered DNA vaccination strategy utilizing co-delivery of the specific chemokine molecular adjuvant CCL25 (TECK) can produce antigen-specific immune responses at distal sites including the lung and mesenteric lymph nodes in mice. The targeted vaccines induced infiltration of cognate chemokine receptor, CCR9+/CD11c+ immune cells to the site of immunization. Furthermore, data shows enhanced IFN-λ secretion by antigen-specific CD3+/CD8+ and CD3+/CD4+ T cells, as well as elevated HIV-1-specific IgG and IgA responses in secondary lymphoid organs, peripheral blood, and importantly, at mucosal sites. These studies have significance for the development of vaccines and therapeutic strategies requiring mucosal immune responses and represent the first report of the use of plasmid co-delivery of CCL25 as part of the DNA vaccine strategy to boost systemic and mucosal immune responses following intramuscular injection.

Kinetic analysis and evaluation of the mechanisms involved in the resolution of experimental nontypeable Haemophilus influenzae-induced otitis media after transcutaneous immunization

Transcutaneous immunization (TCI) is a simple and needle-free method with which to induce protective immune responses. Using a chinchilla model of nontypeable Haemophilus influenzae (NTHI)-induced otitis media (OM), we examined the efficacy afforded by TCI with a novel chimeric immunogen called 'chimV4' which targets two critical adhesins expressed by NTHI, outer membrane protein P5 and the majority subunit of NTHI Type IV pilus, PilA. Experimental OM was first established in cohorts of animals, and then TCI performed via a therapeutic immunization regime by rubbing vaccine formulations on hydrated pinnae. The kinetics of resolution of established experimental disease was evaluated by clinically-relevant assessments of OM, bacterial culture of planktonic and adherent NTHI within the middle ear and gross examination of the relative amount of NTHI mucosal biofilms within the middle ear space. Within seven days after primary TCI, a significant reduction in the signs of OM, significantly fewer NTHI adherent to the middle ear mucosa and significant resolution of mucosal biofilms was detected in animals that received chimV4+ the adjuvant LT(R192G-L211A), compared to animals administered LT(R192G-L211A) alone or saline by TCI (p<0.05) with eradication of NTHI within an additional seven days. The mechanism for rapid disease resolution involved efflux of activated dermal dendritic cells from the pinnae after TCI, secretion of factors chemotactic for CD4(+) T-cells, induction of polyfunctional IFNγ- and IL-17-producing CD4(+) T-cells and secretion of host defense peptide within the middle ear. These data support TCI as a therapeutic intervention against experimental NTHI-induced OM and begin to elucidate the host response to immunization by this noninvasive regimen.

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.

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

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

Adjuvants for human vaccines

Rational selection of individual adjuvants can often be made on the basis of innate molecular interactions of the foreign molecules with pattern recognition receptors such as Toll-like receptors. For example, monophosphoryl lipid A, a family of endotoxic TLR4 agonist molecules from bacteria, has recently been formulated with liposomes, oil emulsions, or aluminum salts for several vaccines. Combinations of antigens and adjuvants with particulate lipid or oil components may reveal unique properties of immune potency or efficacy, but these can sometimes be exhibited differently in rodents when compared to nonhuman primates or humans. New adjuvants, formulations, microinjection devices, and skin delivery techniques for transcutaneous immunization demonstrate that adjuvant systems can include combinations of strategies and delivery mechanisms for uniquely formulated antigens and adjuvants.

Shikonin enhances efficacy of a gene-based cancer vaccine via induction of RANTES

Background

Shikonin, a phytochemical purified from Lithospermum erythrorhizon, has been shown to confer diverse pharmacological activities, including accelerating granuloma formation, wound healing, anti-inflammation and others, and is explored for immune-modifier activities for vaccination in this study. Transdermal gene-based vaccine is an attractive approach for delivery of DNA transgenes encoding specific tumor antigens to host skin tissues. Skin dendritic cells (DCs), a potent antigen-presenting cell type, is known to play a critical role in transmitting and orchestrating tumor antigen-specific immunities against cancers. The present study hence employs these various components for experimentation.

Method

The mRNA and protein expression of RANTES were detected by RT-PCR and ELISA, respectively. The regional expression of RANTES and tissue damage in test skin were evaluated via immunohistochemistry assay. Fluorescein isothiocyanate sensitization assay was performed to trace the trafficking of DCs from the skin vaccination site to draining lymph nodes. Adjuvantic effect of shikonin on gene gun-delivered human gp100 (hgp100) DNA cancer vaccine was studied in a human gp100-transfected B16 (B16/hgp100) tumor model.

Results

Among various phytochemicals tested, shikonin induced the highest level of expression of RANTES in normal skin tissues. In comparison, mouse RANTES cDNA gene transfection induced a higher level of mRANTES expression for a longer period, but caused more extensive skin damage. Topical application of shikonin onto the immunization site before gene gun-mediated vaccination augmented the population of skin DCs migrating into the draining lymph nodes. A hgp100 cDNA gene vaccination regimen with shikonin pretreatment as an adjuvant in a B16/hgp100 tumor model increased cytotoxic T lymphocyte activities in splenocytes and lymph node cells on target tumor cells.

Conclusion

Together, our findings suggest that shikonin can effectively enhance anti-tumor potency of a gene-based cancer vaccine via the induction of RANTES expression at the skin immunization site.

Transcutaneous immunization using a dissolving microneedle array protects against tetanus, diphtheria, malaria, and influenza

Transcutaneous immunization (TCI) is an attractive alternative vaccination route compared to the commonly used injection systems. We previously developed a dissolving microneedle array for use as a TCI device, and reported that TCI with the dissolving microneedle array induced an immune response against model antigens. In the present study, we investigated the vaccination efficacy against tetanus and diphtheria, malaria, and influenza using this vaccination system. Our TCI system induced substantial increases in toxoid-specific IgG levels and toxin-neutralizing antibody titer and induced the production of anti-SE36 IgG, which could bind to malaria parasite. On influenza HA vaccination, robust antibody production was elicited in mice that provided complete protection against a subsequent influenza virus challenge. These findings demonstrate that TCI using a dissolving microneedle array can elicit large immune responses against infectious diseases. Based on these results, we are now preparing translational research for human clinical trials.

Therapeutic DNA vaccine induces broad T cell responses in the gut and sustained protection from viral rebound and AIDS in SIV-infected rhesus macaques

Immunotherapies that induce durable immune control of chronic HIV infection may eliminate the need for life-long dependence on drugs. We investigated a DNA vaccine formulated with a novel genetic adjuvant that stimulates immune responses in the blood and gut for the ability to improve therapy in rhesus macaques chronically infected with SIV. Using the SIV-macaque model for AIDS, we show that epidermal co-delivery of plasmids expressing SIV Gag, RT, Nef and Env, and the mucosal adjuvant, heat-labile E. coli enterotoxin (LT), during antiretroviral therapy (ART) induced a substantial 2-4-log fold reduction in mean virus burden in both the gut and blood when compared to unvaccinated controls and provided durable protection from viral rebound and disease progression after the drug was discontinued. This effect was associated with significant increases in IFN-γ T cell responses in both the blood and gut and SIV-specific CD8+ T cells with dual TNF-α and cytolytic effector functions in the blood. Importantly, a broader specificity in the T cell response seen in the gut, but not the blood, significantly correlated with a reduction in virus production in mucosal tissues and a lower virus burden in plasma. We conclude that immunizing with vaccines that induce immune responses in mucosal gut tissue could reduce residual viral reservoirs during drug therapy and improve long-term treatment of HIV infection in humans.

Adjuvant properties of thermal component of hyperthermia enhanced transdermal immunization: effect on dendritic cells

Hyperthermia enhanced transdermal (HET) immunization is a novel needle free immunization strategy employing application of antigen along with mild local hyperthermia (42°C) to intact skin resulting in detectable antigen specific Ig in serum. In the present study, we investigated the adjuvant effect of thermal component of HET immunization in terms of maturation of dendritic cells and its implication on the quality of the immune outcome in terms of antibody production upon HET immunization with tetanus toxoid (TT). We have shown that in vitro hyperthermia exposure at 42°C for 30 minutes up regulates the surface expression of maturation markers on bone marrow derived DCs. This observation correlated in vivo with an increased and accelerated expression of maturation markers on DCs in the draining lymph node upon HET immunization in mice. This effect was found to be independent of the antigen delivered and depends only on the thermal component of HET immunization. In vitro hyperthermia also led to enhanced capacity to stimulate CD4+ T cells in allo MLR and promotes the secretion of IL-10 by BMDCs, suggesting a potential for Th2 skewing of T cell response. HET immunization also induced a systemic T cell response to TT, as suggested by proliferation of splenocytes from immunized animal upon in vitro stimulation by TT. Exposure to heat during primary immunization led to generation of mainly IgG class of antibodies upon boosting, similar to the use of conventional alum adjuvant, thus highlighting the adjuvant potential of heat during HET immunization. Lastly, we have shown that mice immunized by tetanus toxoid using HET route exhibited protection against challenge with a lethal dose of tetanus toxin. Thus, in addition to being a painless, needle free delivery system it also has an immune modulatory potential.

A combined approach of vesicle formulations and microneedle arrays for transcutaneous immunization against hepatitis B virus

In the search for an optimal approach for the transcutaneous immunization (TCI) of hepatitis B surface antigen (HBsAg), two vesicle formulations, L595 vesicles (composed of sucrose-laurate ester and octaoxyethylene-laurate ester) and sPC vesicles (composed of soybean-phosphatidylcholine and Span-80) were prepared and characterized in vitro and in vivo. HBsAg was associated to the vesicles, resulting in sPC-HBsAg vesicles (±170nm) with 79% HBsAg association and L595-HBsAg vesicles (±75nm) with only 29% HBsAg association. The vesicles induced in mice via TCI an antibody response only when the skin was pretreated with microneedles. This response was improved by the adjuvant cholera toxin. The sPC-HBsAg vesicle formulations showed to be the most immunogenic for TCI, which was related to the higher degree of HBsAg association.

Cholera toxin activates nonconventional adjuvant pathways that induce protective CD8 T-cell responses after epicutaneous vaccination

The ability to induce humoral and cellular immunity via antigen delivery through the unbroken skin (epicutaneous immunization, EPI) has immediate relevance for vaccine development. However, it is unclear which adjuvants induce protective memory CD8 T-cell responses by this route, and the molecular and cellular requirements for priming through intact skin are not defined. We report that cholera toxin (CT) is superior to other adjuvants in its ability to prime memory CD8 T cells that control bacterial and viral challenges. Epicutaneous immunization with CT does not require engagement of classic toll-like receptor (TLR) and inflammasome pathways and, surprisingly, is independent of skin langerin-expressing cells (including Langerhans cells). However, CT adjuvanticity required type-I IFN sensitivity, participation of a Batf3-dependent dendritic cell (DC) population and engagement of CT with suitable gangliosides. Chemoenzymatic generation of CT-antigen fusion proteins led to efficient priming of the CD8 T-cell responses, paving the way for development of this immunization strategy as a therapeutic option.

Anthrax vaccine antigen-adjuvant formulations completely protect New Zealand white rabbits against challenge with Bacillus anthracis Ames strain spores

In an effort to develop an improved anthrax vaccine that shows high potency, five different anthrax protective antigen (PA)-adjuvant vaccine formulations that were previously found to be efficacious in a nonhuman primate model were evaluated for their efficacy in a rabbit pulmonary challenge model using Bacillus anthracis Ames strain spores. The vaccine formulations include PA adsorbed to Alhydrogel, PA encapsulated in liposomes containing monophosphoryl lipid A, stable liposomal PA oil-in-water emulsion, PA displayed on bacteriophage T4 by the intramuscular route, and PA mixed with Escherichia coli heat-labile enterotoxin administered by the needle-free transcutaneous route. Three of the vaccine formulations administered by the intramuscular or the transcutaneous route as a three-dose regimen induced 100% protection in the rabbit model. One of the formulations, liposomal PA, also induced significantly higher lethal toxin neutralizing antibodies than PA-Alhydrogel. Even 5 months after the second immunization of a two-dose regimen, rabbits vaccinated with liposomal PA were 100% protected from lethal challenge with Ames strain spores. In summary, the needle-free skin delivery and liposomal formulation that were found to be effective in two different animal model systems appear to be promising candidates for next-generation anthrax vaccine development.