Advances in vaccine delivery: transcutaneous immunisation

Biofilm biology and vaccine strategies for otitis media due to nontypeable Haemophilus influenzae

Otitis media (OM) is one of the most common diseases of childhood, and nontypeable Haemophilus influenzae (NTHI) is the predominant causative agent of chronic and recurrent OM, as well as OM for which treatment has failed. Moreover, NTHI is now as important a causative agent of acute OM as the pneumococcus. NTHI colonizes the human nasopharynx asymptomatically. However, upon perturbation of the innate and physical defenses of the airway by upper respiratory tract viral infection, NTHI can replicate, ascend the Eustachian tube, gain access to the normally sterile middle ear space, and cause disease. Bacterial biofilms within the middle ear, including those formed by NTHI, contribute to the chronic and recurrent nature of this disease. These multicomponent structures are highly resistant to clearance by host defenses and elimination by traditional antimicrobial therapies. Herein, we review several strategies utilized by NTHI in order to persist within the human host and interventions currently under investigation to prevent and/or resolve NTHI-induced diseases of the middle ear and uppermost airway.

Elastic liposomes as novel carriers: recent advances in drug delivery

Elastic liposomes (EL) are some of the most versatile deformable vesicular carriers that comprise physiologically biocompatible lipids and surfactants for the delivery of numerous challenging molecules and have marked advantages over other colloidal systems. They have been investigated for a wide range of applications in pharmaceutical technology through topical, transdermal, nasal, and oral routes for efficient and effective drug delivery. Increased drug encapsulation efficiency, enhanced drug permeation and penetration into or across the skin, and ultradeformability have led to widespread interest in ELs to modulate drug release, permeation, and drug action more efficiently than conventional drug-release vehicles. This review provides insights into the versatile role that ELs play in the delivery of numerous drugs and biomolecules by improving drug release, permeation, and penetration across the skin as well as stability. Furthermore, it provides future directions that should ensure the widespread use of ELs across all medical fields.

Transdermal immunization of P. falciparum surface antigen (MSP-119) via elastic liposomes confers robust immunogenicity

As transdermal immunization results in poor immunogenicity, which is attributed to poor permeability of antigens through the skin, we believed ultradeformable lipid vesicles (elastic liposome) might address the challenges encountered during transdermal immunization. The elastic liposome, versatile carrier, proves better vehicle for transcutaneous delivery of protein, peptide and nucleic acid antigens. Our recently published article (1) is suggestive of improved immunogenicity of carboxyl-terminal 19 kDa fragment of merozoite surface protein-1 (PfMSP-119) of Plasmodium falciparum when administered subcutaneously via elastic liposomes ( Fig. 1 ).

Elastic liposome-mediated transdermal immunization enhanced the immunogenicity of P. falciparum surface antigen, MSP-119

Transdermal immunization results in poor immunogenicity, which can be attributed to poor permeability of antigens through the skin. Therefore, elastic liposome, ultradeformable lipid vesicles, may overcome the challenges faced during transdermal immunization. This versatile carrier proves better vehicle for transcutaneous delivery of protein, peptide and nucleic acid antigens. The present results are suggestive of improved immunogenicity of carboxyl-terminal 19 kDa fragment of merozoite surface protein-1 (PfMSP-119) of Plasmodium falciparum when administered subcutaneously through elastic liposomes. The prepared elastic liposomes were characterized with respect to vesicles shape and surface morphology, size and size distribution, entrapment efficiency, elasticity, stability and in vitro release. Humoral and cell-mediated immune (CMI) response elicited by topically applied PfMSP-119-loaded elastic liposomes, intramuscularly administered alum-adsorbed PfMSP-119 solution, and topically applied PfMSP-119-loaded conventional liposomes were compared and normalized with vehicle control. Results suggest greater transcutaneous immunization via elastic liposomes, and induced robust and perdurable IgG-specific antibody and cytophilic isotype responses. We report to have achieved sizeable CMI activating factor (IFNγ), a crucial player in conferring resistance to asexual blood stage malaria, responses with elastic liposomes when compared with other formulations. The fluorescence microscopy and histopathology results are suggestive of prominent skin permeation and biodistribution, and demonstrate efficient delivery of malaria antigen via elastic liposomes to immunocompetent Langerhans cells (LC) and lymphatics. In conclusion, elastic liposomal formulation provided greater entrapment efficiency, enhanced penetration and heightened and long-lasting immune response. Moreover, effective immunoadjuvant property of this carrier justifies its potential for improved vaccine delivery, and opens new avenues to explore further on the development of malaria vaccine.

Therapeutic Transcutaneous Immunization with a Band-Aid Vaccine Resolves Experimental Otitis Media

Transcutaneous immunization (TCI) is a noninvasive strategy to induce protective immune responses. We describe TCI with a band-aid vaccine placed on the postauricular skin to exploit the unique organization of the stratum corneum and to promote the development of immune responses to resolve active experimental otitis media due to nontypeable Haemophilus influenzae (NTHI). This therapeutic immunization strategy induced significantly earlier resolution of middle ear fluid and rapid eradication of both planktonic and mucosal biofilm-resident NTHI within 7 days after receipt of the first immunizing band-aid vaccine. Efficacy was ascribed to the homing of immunogen-bearing cutaneous dendritic cells to the nasal-associated lymphoid tissue, induction of polyfunctional CD4(+) T cells, and the presence of immunogen-specific IgM and IgG within the middle ear. TCI using band-aid vaccines could expand the use of traditional parenteral preventative vaccines to include treatment of active otitis media, in addition to other diseases of the respiratory tract due to NTHI.

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.

Transcutaneous vaccines--current and emerging strategies

INTRODUCTION

Vaccination, which is the major fundamental prophylaxis against illness and death from infectious disease, has greatly contributed to the global improvement of human health. However, the disadvantages of conventional injection systems hamper the delivery of vaccination technologies to developing countries. The imminent practice of easy-to-use vaccination methods is expected to overcome certain issues associated with injectable vaccinations. One innovative method is the transcutaneous immunization (TCI) system.

AREAS COVERED

Two major strategies for TCI are discussed in this review. One is to promote antigen permeation of the skin barrier by patch systems or nanoparticles. The other is the delivery of antigens into the skin by electroporation and microneedles in order to physically overcome the skin barrier. Moreover, adjuvant development for TCI is discussed.

EXPERT OPINION

Many different approaches have been developed for TCI, which have the potential to be effective, easy-to-use and painless methods of vaccination. However, in practical terms, the guidelines concerning the manufacturing processes and clinical trial evaluation of the procedures have not kept pace with the development of these novel formulations. The accumulation of information regarding skin characteristics and the properties of TCI devices will help refine TCI system development guidelines and thus lead to the improvement of transcutaneous vaccination.

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.

Transcutaneous immunization with a Vibrio cholerae O1 Ogawa synthetic hexasaccharide conjugate following oral whole-cell cholera vaccination boosts vibriocidal responses and induces protective immunity in mice

A shortcoming of currently available oral cholera vaccines is their induction of relatively short-term protection against cholera compared to that afforded by wild-type disease. We were interested in whether transcutaneous or subcutaneous boosting using a neoglycoconjugate vaccine made from a synthetic terminal hexasaccharide of the O-specific polysaccharide of Vibrio cholerae O1 (Ogawa) coupled to bovine serum albumin as a carrier (CHO-BSA) could boost lipopolysaccharide (LPS)-specific and vibriocidal antibody responses and result in protective immunity following oral priming immunization with whole-cell cholera vaccine. We found that boosting with CHO-BSA with immunoadjuvantative cholera toxin (CT) or Escherichia coli heat-labile toxin (LT) following oral priming with attenuated V. cholerae O1 vaccine strain O395-NT resulted in significant increases in serum anti-V. cholerae LPS IgG, IgM, and IgA (P < 0.01) responses as well as in anti-Ogawa (P < 0.01) and anti-Inaba (P < 0.05) vibriocidal titers in mice. The LPS-specific IgA responses in stool were induced by transcutaneous (P < 0.01) but not subcutaneous immunization. Immune responses following use of CT or LT as an adjuvant were comparable. In a neonatal mouse challenge assay, immune serum from boosted mice was associated with 79% protective efficacy against death. Our results suggest that transcutaneous and subcutaneous boosting with a neoglycoconjugate following oral cholera vaccination may be an effective strategy to prolong protective immune responses against V. cholerae.

Clinical study of transcutaneous vaccination using a hydrogel patch for tetanus and diphtheria

Transcutaneous immunization (TCI) is a non-invasive and easy-to-use vaccination method. We demonstrated the efficacy and safety of a transcutaneous vaccine formulation using a hydrogel patch in animal experiments. In the present study, we performed a clinical study to apply our TCI formulation for vaccination against tetanus and diphtheria in human. The TCI device was a hydrogel patch (antigen-free) applied to the left brachial medial skin of 22 healthy volunteers for 48 h. Next, the hydrogel patch, containing 2 mg tetanus toxoid (TT) and 2 mg diphtheria toxoid (DT) as the TCI formulation, was applied to 27 healthy volunteers for 24 h and some volunteers were vaccinated again by TCI formulation. For safety assessment, the patch application site was observed to assess local adverse events, and systemic adverse events were determined by a blood test. The antigen-free hydrogel patch and TCI formulation containing TT and DT did not induce local or systemic severe adverse events. For vaccine efficacy estimation, toxoid-specific serum antibody titers were determined by ELISA and the toxin-neutralizing activity of the induced antibody was evaluated in a passive-challenge experiment. The anti-TT IgG titer and the anti-DT IgG titer increased, and a significant effect was detected by paired t-test. The antibody titers were maintained at higher level than that before vaccination for at least 1 year. Moreover, toxoid-specific antibodies were produced by the second vaccination in some subjects. Antibodies induced by application of the TCI formulation neutralized the toxin and prevented toxic death in mice. In addition, changes in the skin condition due to application of the TCI formulation were observed under in vivo confocal Raman spectroscopy. The amount of water and patch components in the stratum corneum increased after application of the TCI formulation, suggesting that the change in the skin condition was related to antigen penetration. These data indicate that this easy-to-use TCI system induces an immune response without severe adverse reactions in humans. This easy-to-use and safe TCI formulation enables mass treatment in an outbreak setting and increased vaccination rates in developing countries, and will greatly contribute to worldwide countermeasures against infectious diseases.

Comparison of the immunogenicity and safety of a split-virion, inactivated, trivalent influenza vaccine (Fluzone®) administered by intradermal and intramuscular route in healthy adults

The aim of the study was to determine whether reduced doses of trivalent inactivated influenza vaccine (TIV) administered by the intradermal (ID) route generated similar immune responses to standard TIV given intramuscularly (IM) with comparable safety profiles. Recent changes in immunization recommendations have increased the number of people for whom influenza vaccination is recommended. Thus, given this increased need and intermittent vaccine shortages, means to rapidly expand the vaccine supply are needed. Previously healthy subjects 18-64 years of age were randomly assigned to one of four TIV vaccine groups: standard 15 μg HA/strain TIV IM, either 9 μg or 6 μg HA/strain of TIV ID given using a new microinjection system (BD Soluvia™ Microinjection System), or 3 μg HA/strain of TIV ID given by Mantoux technique. All vaccines contained A/New Caledonia (H1N1), A/Wyoming (H3N2) and B/Jiangsu strains of influenza. Sera were obtained 21 days after vaccination and hemagglutination inhibition (HAI) assays were performed and geometric mean titers (GMT) were compared among the groups. Participants were queried immediately following vaccination regarding injection pain and quality of the experience. Local and systemic reactions were collected for 7 days following vaccination and compared. Ten study sites enrolled 1592 subjects stratified by age; 18-49 years [N=814] and 50-64 years [N=778]. Among all subjects, for each of the three vaccine strains, the GMTs at 21 days post-vaccination for both the 9 μg and the 6 μg doses of each strain given ID were non inferior to GMTs generated after standard 15 μg doses/strain IM. However, for the 3 μg ID dose, only the A/Wyoming antigen produced a GMT that was non-inferior to the standard IM dose. Additionally, in the subgroup of subjects 50-64 years of age, the 6μg dose given ID induced GMTs that were inferior to the standard IM TIV for the A/H1N1 and B strains. No ID dose produced a GMT superior to that seen after standard IM TIV. Local erythema and swelling were significantly more common in the ID groups but the reactions were mild to moderate and short-lived. No significant safety issues related to intradermal administration were identified. Participants given TIV ID provided favorable responses to questions about their experiences with ID administration. In conclusion, for the aggregated cohorts of adults 18-64 years of age, reduced doses (6 μg and 9 μg) of TIV delivered ID using a novel microinjection system stimulated comparable HAI antibody responses to standard TIV given IM. The reduced 3 μg dose administered ID by needle and syringe, as well as the 6 μg ID for subjects aged 50-64 years of age generated poorer immune responses as compared to the 15 μg IM dose.

Hydration effects on skin microstructure as probed by high-resolution cryo-scanning electron microscopy and mechanistic implications to enhanced transcutaneous delivery of biomacromolecules

Although hydration is long known to improve the permeability of skin, penetration of macromolecules such as proteins is limited and the understanding of enhanced transport is based on empirical observations. This study uses high-resolution cryo-scanning electron microscopy to visualize microstructural changes in the stratum corneum (SC) and enable a mechanistic interpretation of biomacromolecule penetration through highly hydrated porcine skin. Swollen corneocytes, separation of lipid bilayers in the SC intercellular space to form cisternae, and networks of spherical particulates are observed in porcine skin tissue hydrated for a period of 4-10 h. This is explained through compaction of skin lipids when hydrated, a reversal in the conformational transition from unilamellar liposomes in lamellar granules to lamellae between keratinocytes when the SC skin barrier is initially established. Confocal microscopy studies show distinct enhancement in penetration of fluorescein isothiocyanate-bovine serum albumin (FITC-BSA) through skin hydrated for 4-10 h, and limited penetration of FITC-BSA once skin is restored to its natively hydrated structure when exposed to the environment for 2-3 h. These results demonstrate the effectiveness of a 4-10 h hydration period to enhance transcutaneous penetration of large biomacromolecules without permanently damaging the skin.

Stabilization of influenza vaccine enhances protection by microneedle delivery in the mouse skin

Background

Simple and effective vaccine administration is particularly important for annually recommended influenza vaccination. We hypothesized that vaccine delivery to the skin using a patch containing vaccine-coated microneedles could be an attractive approach to improve influenza vaccination compliance and efficacy.

Methodology/Principal Findings

Solid microneedle arrays coated with inactivated influenza vaccine were prepared for simple vaccine delivery to the skin. However, the stability of the influenza vaccine, as measured by hemagglutination activity, was found to be significantly damaged during microneedle coating. The addition of trehalose to the microneedle coating formulation retained hemagglutination activity, indicating stabilization of the coated influenza vaccine. For both intramuscular and microneedle skin immunization, delivery of un-stabilized vaccine yielded weaker protective immune responses including viral neutralizing antibodies, protective efficacies, and recall immune responses to influenza virus. Immunization using un-stabilized vaccine also shifted the pattern of antibody isotypes compared to the stabilized vaccine. Importantly, a single microneedle-based vaccination using stabilized influenza vaccine was found to be superior to intramuscular immunization in controlling virus replication as well as in inducing rapid recall immune responses post challenge.

Conclusions/Significance

The functional integrity of hemagglutinin is associated with inducing improved protective immunity against influenza. Simple microneedle influenza vaccination in the skin produced superior protection compared to conventional intramuscular immunization. This approach is likely to be applicable to other vaccines too.

Transdermal immunization with low-pressure-gene-gun mediated chitosan-based DNA vaccines against Japanese encephalitis virus

DNA vaccine is a milestone in contemporary vaccine development. It has considerably offset many shortcomings in conventional vaccines. Although DNA vaccines applied through 'traditional' high-pressure gene guns generally elicit high titers of protective immunity, such a practice however requires enormous investment in daunting instruments that often discourage vaccines due to an inevitable pain-eliciting effect. In this study, we exploited a less expensive yet low-pressure-gene-gun that can alleviate such phobia of pain. DNA vaccines were prepared by using the associative feature of cationic chitosan and anionic DNAs. The optimized N/P ratio is 3. The formulized complex sizes to nano-scale. The vaccine complexes were tested in C3H/HeN mice. The expression of GFP reporter gene was observable and traceable in epidermis and spleen over 3 days. The expressions of GFP and the activation of dendritic cells (DCs) were evident and co-localized in hair follicles and epidermis. C3H/HeN mice immunized with the developed chitosan-JEV DNA vaccines can elicit desired JEV specific antibodies, whereby the mice maintained high survival rates against 50xLD(50) JEV challenge. The low-pressure-gene-gun mediated chitosan-based JEV DNA vaccines have proven to be convenient and efficacious, thereby with high capacity in deployment for future prophylaxis against JEV outbreaks.

Development and psychometric validation of a self-administered questionnaire assessing the acceptance of influenza vaccination: the Vaccinees' Perception of Injection (VAPI) questionnaire

BACKGROUND

Influenza is among the most common infectious diseases. The main protection against influenza is vaccination. A self-administered questionnaire was developed and validated for use in clinical trials to assess subjects' perception and acceptance of influenza vaccination and its subsequent injection site reactions (ISR).

METHODS

The VAPI questionnaire was developed based on interviews with vaccinees. The initial version was administered to subjects in international clinical trials comparing intradermal with intramuscular influenza vaccination. Item reduction and scale construction were carried out using principal component and multitrait analyses (n = 549). Psychometric validation of the final version was conducted per country (n = 5,543) and included construct and clinical validity and internal consistency reliability. All subjects gave their written informed consent before being interviewed or included in the clinical studies.

RESULTS

The final questionnaire comprised 4 dimensions ("bother from ISR"; "arm movement"; "sleep"; "acceptability") grouping 16 items, and 5 individual items (anxiety before vaccination; bother from pain during vaccination; satisfaction with injection system; willingness to be vaccinated next year; anxiety about vaccination next year). Construct validity was confirmed for all scales in most of the countries. Internal consistency reliability was good for all versions (Cronbach's alpha ranging from 0.68 to 0.94), as was clinical validity: scores were positively correlated with the severity of ISR and pain.

CONCLUSION

The VAPI questionnaire is a valid and reliable tool, assessing the acceptance of vaccine injection and reactions following vaccination.

Functional and immunological characterization of a natural polymorphic variant of a heat-labile toxin (LT-I) produced by enterotoxigenic Escherichia coli (ETEC)

Heat-labile toxins (LT) encompass at least 16 natural polymorphic toxin variants expressed by wild-type enterotoxigenic Escherichia coli (ETEC) strains isolated from human beings, but only one specific form, produced by the reference ETEC H10407 strain (LT1), has been intensively studied either as a virulence-associated factor or as a mucosal/transcutaneous adjuvant. In the present study, we carried out a biological/immunological characterization of a natural LT variant (LT2) with four polymorphic sites at the A subunit (S190L, G196D, K213E, and S224T) and one at the B subunit (T75A). The results indicated that purified LT2, in comparison with LT1, displayed similar in vitro toxic activities (adenosine 3',5'-cyclic monophosphate accumulation) on mammalian cells and in vivo immunogenicity following delivery via the oral route. Nonetheless, the LT2 variant showed increased adjuvant action to ovalbumin when delivered to mice via the transcutaneous route while antibodies raised in mice immunized with LT2 displayed enhanced affinity and neutralization activity to LT1 and LT2. Taken together, the results indicate that the two most frequent LT polymorphic forms expressed by wild ETEC strains share similar biological features, but differ with regard to their immunological properties.

Dendrimeric Aβ1–15 is an effective immunogen in wildtype and APP-tg mice

Immunization of humans and APP-tg mice with full-length beta-amyloid (Abeta) results in reduced cerebral Abeta levels. However, due to adverse events in the AN1792 trial, alternative vaccines are required. We investigated dendrimeric Abeta1-15 (dAbeta1-15), which is composed of 16 copies of Abeta1-15 peptide on a branched lysine core and thus, includes an Abeta-specific B cell epitope but lacks the reported T cell epitope. Immunization by subcutaneous, transcutaneous, and intranasal routes of B6D2F1 wildtype mice led to anti-Abeta antibody production. Antibody isotypes were mainly IgG1 for subcutaneous or transcutaneous immunization and IgG2b for intranasal immunization, suggestive of a Th2-biased response. All Abeta antibodies preferentially recognized an epitope in Abeta1-7. Intranasal immunization of J20 APP-tg mice resulted in a robust humoral immune response with a corresponding significant reduction in cerebral plaque burden. Splenocyte proliferation against Abeta peptide was minimal indicating the lack of an Abeta-specific cellular immune response. Anti-Abeta antibodies bound monomeric, oligomeric, and fibrillar Abeta. Our data suggest that dAbeta1-15 may be an effective and potentially safer immunogen for Alzheimer's disease (AD) vaccination.

Transcutaneous immunization with Clostridium difficile toxoid A induces systemic and mucosal immune responses and toxin A-neutralizing antibodies in mice

Clostridium difficile is the leading cause of nosocomial infectious diarrhea. C. difficile produces two toxins (A and B), and systemic and mucosal anti-toxin A antibodies prevent or limit C. difficile-associated diarrhea. To evaluate whether transcutaneous immunization with formalin-treated C. difficile toxin A (CDA) induces systemic and mucosal anti-CDA immune responses, we transcutaneously immunized three cohorts of mice with CDA with or without immunoadjuvantative cholera toxin (CT) on days 0, 14, 28, and 42. Mice transcutaneously immunized with CDA and CT developed prominent anti-CDA and anti-CT immunoglobulin G (IgG) and IgA responses in serum and anti-CDA and anti-CT IgA responses in stool. Sera from immunized mice were able to neutralize C. difficile toxin A activity in an in vitro cell culture assay. CDA itself demonstrated adjuvant activity and enhanced both serum and stool anti-CT IgA responses. Our results suggest that transcutaneous immunization with CDA toxoid may be a feasible immunization strategy against C. difficile, an important cause of morbidity and mortality against which current preventative strategies are failing.

Immunization onto bare skin with synthetic peptides: immunomodulation with a CpG-containing oligodeoxynucleotide and effective priming of influenza virus-specific CD4+ T cells

Exploiting the immune system of the skin for vaccine administration offers an attractive alternative to the currently used invasive immunization procedures. In this study we report that a synthetic peptide representing a T-helper (Th) epitope from influenza virus haemagglutinin (aa 307--319) can be an effective immunogen when coapplied with cholera toxin (CT) onto bare skin. Proliferation of both peptide- and influenza virus-specific CD4+ T cells was measured in lymphocyte cultures from spleens and regional lymph nodes. The presence of the CpG oligodeoxynucleotide 1826 in the peptide/CT formulation, enhanced the proliferation of peptide- and virus-specific T cells as measured by the conventional [(3)H]thymidine uptake and interleukin (IL)-2 assays. Furthermore, the bias towards Th2-type of responses stimulated by CT was shifted towards Th1 as demonstrated (i) by the increase of interferon-gamma and decrease of IL-4 cytokine levels measured in culture supernatants, (ii) by the predominance of IG2a anti-CT antibodies in the serum, and (iii) by the down-regulation of total serum IgE antibody levels. These findings demonstrate the potential of the bare skin as a non-invasive route for administration of small molecular size peptide antigens. Furthermore, with the selection and combination of the appropriate type of adjuvants, immune responses can be modulated towards the desired type of Th phenotype.

Simulated solar UVB exposure inhibits transcutaneous immunization to cholera toxin via an irradiated skin site in cattle

Transcutaneous immunization (TCI) is a new needle-free vaccination technology with the potential to reduce the risk of needle-borne disease transmission and carcass damage within the livestock industries. The principal antigen-presenting cell involved in TCI is thought to be the epidermal Langerhans cell. Langerhans cell function is inhibited by cutaneous ultraviolet-B radiation (UVB) exposure. Such exposure may inhibit TCI through sun exposed skin sites due to the phenomenon of local low dose photoimmunosuppression. TCI of cattle to cholera toxin (CT) resulted in the generation of a serum anti-CT-specific IgG(2) response. However, exposure of cattle to a sub-inflammatory dose of simulated solar UVB (2.43 x 10(3)J/m(2)) significantly (P<0.05) inhibited TCI to CT via irradiated skin sites.

Transcutaneous immunization: T cell responses and boosting of existing immunity

Transcutaneous immunization (TCI) is a novel immunization strategy by which antigen and adjuvant are applied topically to intact, hydrated skin to induce potent antibody and cell-mediated immune responses specific for both the antigen and the adjuvant. Using tetanus toxoid as a model antigen, we examined the T cell response to tetanus toxoid after topical immunization with a variety of adjuvants. TCI readily induced systemic antigen specific T cell responses with a mixed Th1/Th2 phenotype but with a Th2 bias. We also investigated whether priming by the intramuscular route, which is known to induce T cell memory, could be followed by a boosting immunization on the skin to induce secondary responses. TCI could augment existing immunity, but interestingly, this strategy induced potent responses only if the antibody titer was low at the time of TCI boosting. These and previous observations suggest that TCI follows known immunological principles that govern other routes of vaccine delivery. Furthermore, booster immunization using tetanus toxoid may provide a useful model for further development of important patch and formulation concepts for TCI, and act as an early candidate for validating product feasibility of TCI in humans.

Transcutaneous immunization: a human vaccine delivery strategy using a patch

Transcutaneous immunization, a topical vaccine application, combines the advantages of needle-free delivery while targeting the immunologically rich milieu of the skin. In animal studies, this simple technique induces robust systemic and mucosal antibodies against vaccine antigens. Here, we demonstrate safe application of a patch containing heat-labile enterotoxin (LT, derived from Escherichia coli) to humans, resulting in robust LT-antibody responses. These findings indicate that TCI is feasible for human immunization, and suggest that TCI may enhance efficacy as well as improve vaccine delivery.

Transcutaneous immunization with bacterial ADP-ribosylating exotoxins, subunits, and unrelated adjuvants

We have recently described a needle-free method of vaccination, transcutaneous immunization, consisting of the topical application of vaccine antigens to intact skin. While most proteins themselves are poor immunogens on the skin, we have shown that the addition of cholera toxin (CT), a mucosal adjuvant, results in cellular and humoral immune responses to the adjuvant and coadministered antigens. The present study explores the breadth of adjuvants that have activity on the skin, using diphtheria toxoid (DTx) and tetanus toxoid as model antigens. Heat-labile enterotoxin (LT) displayed adjuvant properties similar to those of CT when used on the skin and induced protective immune responses against tetanus toxin challenge when applied topically at doses as low as 1 microg. Interestingly, enterotoxin derivatives LTR192G, LTK63, and LTR72 and the recombinant CT B subunit also exhibited adjuvant properties on the skin. Consistent with the latter finding, non-ADP-ribosylating exotoxins, including an oligonucleotide DNA sequence, as well as several cytokines (interleukin-1beta [IL-1beta] fragment, IL-2, IL-12, and tumor necrosis factor alpha) and lipopolysaccharide also elicited detectable anti-DTx immunoglobulin G titers in the immunized mice. These results indicate that enhancement of the immune response to topical immunization is not restricted to CT or the ADP-ribosylating exotoxins as adjuvants. This study also reinforces earlier findings that addition of an adjuvant is important for the induction of robust immune responses to vaccine antigens delivered by topical application.