Design, engineering and in vitro evaluation of MHC class-II targeting allergy vaccines

Perspectives in Allergen-Specific Immunotherapy: Molecular Evolution of Peptide- and Protein-Based Strategies

Allergen-specific Immunotherapy (AIT), through repetitive subcutaneous or sublingual administrations of allergen extracts, represents up to now the unique treatment against allergic sensitizations. However, the clinical efficacy of AIT can be largely dependent on the quality of natural allergen extracts. Moreover, the long duration and adverse side effects associated with AIT negatively impact patient adherence. Tremendous progress in the field of molecular allergology has made possible the design of safer, shorter and more effective new immunotherapeutic approaches based on purified and characterized natural or recombinant allergen derivatives and peptides. This review will summarize the characteristics of these different innovative vaccines including their effects in preclinical studies and clinical trials.

Molecular approaches to allergen-specific immunotherapy: Are we so far from clinical implementation?

Conventional allergen-specific immunotherapy (AIT), based on administrations of allergen extracts, represents up to now the unique protocol for the desensitization of allergic patients. Whereas the effectiveness of AIT was evidenced for the treatment of allergic rhinitis and allergic asthma, such strategy remains experimental for food allergies up to now. However, important issues are commonly associated with AIT as the quality of natural allergen extracts, the long duration and adverse side-effects which negatively affect successful desensitization together with the patient compliance. The rapid progression of molecular allergology made possible the quest of safer, shorter and more effective immunotherapeutic approaches. The aim of this review was to provide an update on these different innovative recombinant derivatives including their efficacy but also their limitations. Despite promising preclinical and early clinical studies, the absence of convincing data in large phase III trials precludes so far the translation of these immunotherapeutic candidates into the clinic.

Hydrophobic ligands influence the structure, stability, and processing of the major cockroach allergen Bla g 1

The cockroach allergen Bla g 1 forms a novel fold consisting of 12 amphipathic alpha-helices enclosing an exceptionally large hydrophobic cavity which was previously demonstrated to bind a variety of lipids. Since lipid-dependent immunoactivity is observed in numerous allergens, understanding the structural basis of this interaction could yield insights into the molecular determinants of allergenicity. Here, we report atomic modelling of Bla g 1 bound to both fatty-acid and phospholipids ligands, with 8 acyl chains suggested to represent full stoichiometric binding. This unusually high occupancy was verified experimentally, though both modelling and circular dichroism indicate that the general alpha-helical structure is maintained regardless of cargo loading. Fatty-acid cargoes significantly enhanced thermostability while inhibiting cleavage by cathepsin S, an endosomal protease essential for antigen processing and presentation; the latter of which was found to correlate to a decreased production of known T-cell epitopes. Both effects were strongly dependent on acyl chain length, with 18-20 carbons providing the maximal increase in melting temperature (~20 °C) while completely abolishing proteolysis. Diacyl chain cargoes provided similar enhancements to thermostability, but yielded reduced levels of proteolytic resistance. This study describes how the biophysical properties of Bla g 1 ligand binding and digestion may relate to antigen processing, with potential downstream implications for immunogenicity.

IgG4 but no IgG1 antibody production after intralymphatic immunotherapy with recombinant MAT-Feld1 in human

Allergy immunotherapy (AIT) mediates protection against allergen exposure in part due to allergen-specific antibodies. While immunization typically stimulated IgG1 and IgG2, AIT is often associated with production of IgG4. Here, twenty cat dander-sensitized patients were randomized to receive three injections of intralymphatic immunotherapy (ILIT) with MAT-Feld1 adsorbed to aluminum hydroxide or just aluminum hydroxide (placebo) in a double-blind setting (ClinicalTrials.gov NCT00718679). Whereas the clinical data, showing benefit of Mat-Feld1 ILIT was published in 2012 (Senti et al., J Allergy Clin Immunol, vol 129(5):1290-1296), the current study investigated the cat allergen-specific antibody responses. Blood was drawn prior to ILIT, as well as 1, 3, and 12 months after first ILIT. The sera were analyzed to characterize all IgG subclasses and IgE antibody responses. ILIT with MAT-Feld1 elicited high levels of total IgG that were maintained for at least 12 months. Interestingly, a strong increase in IgG4 and some increase in IgG2 were observed throughout the study, while production of cat-specific IgG1 and IgG3 was not stimulated by MAT-Feld1 ILIT. The IgE levels remained constant.

Allergen extracts for immunotherapy: to mix or not to mix?

Allergen immunotherapy (AIT) is established as a curative treatment for allergic rhinitis, asthma, as well as insect venom allergy. AIT is based on the administration of natural allergen extracts via the subcutaneous or sublingual routes to reorient the immune system towards tolerogenic mechanisms. In this regard, since many patients are poly-allergic, mixtures of allergen extracts are often used with a potential risk to cause allergen degradation, thereby affecting treatment efficacy. Herein, we discuss the advantages and drawbacks of mixing homologous (i.e., related) or heterogeneous (i.e., unrelated) allergen extracts. We provide evidence for incompatibilities between mixes of grass pollen and house dust mite extracts containing bodies and feces, and summarize critical points to consider when mixing allergen extracts for AIT.

Intralymphatic immunotherapy

Gold Standard allergen-specific immunotherapy is associated with low efficacy because it requires either many subcutaneous injections of allergen or even more numerous sublingual allergen administrations to achieve amelioration of symptoms. Intralymphatic vaccination can maximize immunogenicity and hence efficacy. We and others have demonstrated that as few as three low dose intralymphatic allergen administrations are sufficient to effectively alleviate symptoms. Results of recent prospective and controlled trials suggest that this strategy may be an effective form of allergen immunotherapy.

The contribution of biotechnology toward progress in diagnosis, management, and treatment of allergic diseases

'Biotechnology' has been intuitively used by humans since thousands of years for the production of foods, beverages, and drugs based on the experience without any scientific background. However, the golden era of this discipline emerged only during the second half of the last century. Incredible progresses have been achieved on all fields starting from the industrialization of the production of foods to the discovery of antibiotics, the decipherment of the genetic code, and rational approaches to understand and define the status we now call 'healthy'. The extremely complex interactions between genetic background, life style, and environmental factors influencing our continuously increasing life span have become more and more evident and steadily generate new questions which are only partly answered. Here, we try to summarize the contribution of biotechnology to our understanding, control, and cure of IgE-mediated allergic diseases. We are aware that a review of such a vast topic can never cover all aspects of the progress achieved in the different fields.

Immune regulation by intralymphatic immunotherapy with modular allergen translocation MAT vaccine

BACKGROUND

Allergen-specific immunotherapy (SIT) faces problems related to side effects and limited efficacy. Direct administration of allergen extracts into lymph nodes induces increased specific IgG production and T-cell responses using significantly lower allergen doses.

METHODS

In this study, mechanisms of immune regulation by MAT vaccines in vitro and in allergen-SIT of cat-allergic rhinitis patients, who received 3 inguinal intra-lymph node injections of MAT-Fel d 1 vaccine, were investigated in PBMC and cell cultures for specific T-cell proliferation, Fel d 1-tetramer-specific responses, and multiple immune regulatory molecules.

RESULTS

MAT-Fel d 1 vaccine was efficiently internalized by antigen-presenting cells. This was followed by precaspase 1 cleavage to caspase 1 and secretion of IL-1β, indicating inflammasome activation. Mat-Fel d 1 induced specific T-cell proliferation and an IL-10- and IFN-γ-dominated T-cell responses with decreased Th2 cytokines at 100 times lower doses than Fel d 1. Induction of immune tolerance by MAT-Fel d 1-ILIT involved multiple mechanisms of immune suppression. Early Fel d 1-specific T-cell activation was followed by full T-cell unresponsiveness to allergen after 1 year in the MAT-Fel d 1 group, characterized by increased allergen-specific T regulatory cells, decreased circulating Fel d 1 tetramer-positive cells, increased IL-10 and FOXP3 expression, and change in the HR2/HR1 ratio toward HR2.

CONCLUSIONS

This study demonstrates the induction of allergen tolerance after 3 intra-lymph node injections of MAT-Fel d 1 vaccine, mediated by increased cellular internalization of the allergen, activation of inflammasome, and generation of allergen-specific peripheral T-cell tolerance.

Mechanisms of immune tolerance to allergens in children

Because the prevalence of allergic diseases has significantly increased in recent years, understanding the causes and mechanisms of these disorders is of high importance, and intense investigations are ongoing. Current knowledge pinpoints immune tolerance mechanisms as indispensable for healthy immune response to allergens in daily life. It is evident that development and maintenance of allergens-pecific T cell tolerance is of vital importance for a healthy immune response to allergens. Such tolerance can be gained spontaneously by dose-dependent exposures to allergens in nature or by allergen-specific immunotherapy. Allergen-specific immunotherapy induces regulatory T cells with the capacity to secrete interleukin-10 and transforming growth factor-β, limits activation of effector cells of allergic inflammation (such as mast cells and basophils), and switches antibody isotype from IgE to the noninflammatory type IgG4. Although allergen-specific immunotherapy is the only method of tolerance induction in allergic individuals, several factors, such as long duration of treatment, compliance problems, and life-threatening side effects, have limited widespread applicability of this immunomodulatory treatment. To overcome these limitations, current research focuses on the introduction of allergens in more efficient and safer ways. Defining the endotypes and phenotypes of allergic diseases might provide the ability to select ideal patients, and novel biomarkers might ensure new custom-tailored therapy modalities.

Mammalian-derived respiratory allergens - implications for diagnosis and therapy of individuals allergic to furry animals

Furry animals cause respiratory allergies in a significant proportion of the population. A majority of all mammalian allergens are spread as airborne particles, and several have been detected in environments where furry animals are not normally kept. The repertoire of allergens from each source belongs to a restricted number of allergen families. Classification of allergen families is particularly important for the characterization of allergenicity and cross-reactivity of allergens. In fact, major mammalian allergens are taken from only three protein families, i.e. the secretoglobin, lipocalin and kallikrein families. In particular, the lipocalin superfamily harbours major allergens in all important mammalian allergen sources, and cross-reactivity between lipocalin allergens may explain cross-species sensitization between mammals. The identification of single allergen components is of importance to improve diagnosis and therapy of allergic patients using component-resolved diagnostics and allergen-specific immunotherapy (ASIT) respectively. Major disadvantages with crude allergen extracts for these applications emphasize the benefits of careful characterization of individual allergens. Furthermore, detailed knowledge of the characteristics of an allergen is crucial to formulate attenuated allergy vaccines, e.g. hypoallergens. The diverse repertoires of individual allergens from different mammalian species influence the diagnostic potential and clinical efficacy of ASIT to furry animals. As such, detailed knowledge of individual allergens is essential for adequate clinical evaluation. This review compiles current knowledge of the allergen families of mammalian species, and discusses how this information may be used for improved diagnosis and therapy of individuals allergic to mammals.

Novel developments in the mechanisms of immune tolerance to allergens

Allergy is the result of a disbalanced immune response to environmental innocuous antigens. Despite of accumulating data to define the pathomechanisms that take place in case of allergic diseases a detailed understanding of sequence of events that lead to the "normal" scenario of tolerance development are still under debate. Allergen-specific immunotherapy is the only causal treatment of allergic diseases. It modifies the immune response to a particular antigen to achieve tolerance against the symptom-causing allergen. This process is considered to mirror physiological peripheral tolerance induction. A number of immunological changes have been described to occur under allergen immunotherapy, including the generation of allergen-specific regulatory T cells, the induction of allergen-specific IgG4, an increase in the Th1/Th2 cytokine ratio and decreased activation and function of effector cells such as mast cells, basophils and eosinophils.

Intralymphatic immunotherapy for cat allergy induces tolerance after only 3 injections

BACKGROUND

Subcutaneous allergen-specific immunotherapy frequently causes allergic side effects and requires 30 to 80 injections over 3 to 5 years.

OBJECTIVE

We sought to improve immunotherapy by using intralymphatic allergen administration (intralymphatic immunotherapy [ILIT]) and by targeting allergen to the MHC class II pathway.

METHODS

Recombinant major cat dander allergen Fel d 1 was fused to a translocation sequence (TAT) and to part of the human invariant chain, generating a modular antigen transporter (MAT) vaccine (MAT-Fel d 1). In a randomized double-blind trial ILIT with MAT-Fel d 1 in alum was compared with ILIT with placebo (saline in alum) in allergic patients (ClinicalTrials.govNCT00718679).

RESULTS

ILIT with MAT-Fel d 1 elicited no adverse events. After 3 placebo injections within 2 months, nasal tolerance increased less than 3-fold, whereas 3 intralymphatic injections with MAT-Fel d 1 increased nasal tolerance 74-fold (P < .001 vs placebo). ILIT with MAT-Fel d 1 stimulated regulatory T-cell responses (P = .026 vs placebo) and increased cat dander-specific IgG(4) levels by 5.66-fold (P = .003). The IgG(4) response positively correlated with IL-10 production (P < .001).

CONCLUSION

In a first-in-human clinical study ILIT with MAT-Fel d 1 was safe and induced allergen tolerance after 3 injections.

Treatment of allergic asthma: modulation of Th2 cells and their responses

Atopic asthma is a chronic inflammatory pulmonary disease characterised by recurrent episodes of wheezy, laboured breathing with an underlying Th2 cell-mediated inflammatory response in the airways. It is currently treated and, more or less, controlled depending on severity, with bronchodilators e.g. long-acting beta agonists and long-acting muscarinic antagonists or anti-inflammatory drugs such as corticosteroids (inhaled or oral), leukotriene modifiers, theophyline and anti-IgE therapy. Unfortunately, none of these treatments are curative and some asthmatic patients do not respond to intense anti-inflammatory therapies. Additionally, the use of long-term oral steroids has many undesired side effects. For this reason, novel and more effective drugs are needed. In this review, we focus on the CD4+ Th2 cells and their products as targets for the development of new drugs to add to the current armamentarium as adjuncts or as potential stand-alone treatments for allergic asthma. We argue that in early disease, the reduction or elimination of allergen-specific Th2 cells will reduce the consequences of repeated allergic inflammatory responses such as lung remodelling without causing generalised immunosuppression.

Intralymphatic immunotherapy: from the rationale to human applications

Allergen specific immunotherapy (SIT) is the only treatment of IgE mediated allergies that is causative and has a long-term effect. Classically, SIT requires numerous subcutaneous injections of the allergen during 3-5 years. Over the last decade sublingual allergen applications have established as an alternative, but treatment duration could not be shortened. This review focuses on direct administration of vaccines in general and of allergens in particular into lymph nodes with the aim to enhance immunotherapy. Several studies have found that direct injection of antigens into lymph nodes enhanced immune responses. Recently we have focused on intralymphatic allergen administration in order to enhance SIT. Data in mouse models and in clinical trials showed that intralymphatic allergen administration strongly enhanced SIT, so that the number of allergen injections could be reduced to three, and the allergen dose could be reduced 10-100 fold. Intralymphatic injections proved easy, practically painless and safe. In mice and men, intralymphatic immunotherapy injecting allergens into a subcutaneous lymph node markedly enhances the protective immune response, so that both the dose and number of allergen injections can be reduced, making SIT safer and faster, which enhances patient convenience and compliance.

Intralymphatic immunotherapy

PURPOSE OF REVIEW

IgE-mediated allergy can be treated by subcutaneous allergen-specific immunotherapy (SCIT). However, the percentage of allergic patients undergoing SCIT is low, mainly due to the long duration of the therapy and the risk of severe systemic allergic reactions associated with the allergen administration. Typically, SCIT requires dozens of subcutaneous allergen injections that stretch over 3-5 years. Over the last decade, sublingual immunotherapy has been established as an alternative to SCIT, but treatment duration and dosing frequencies could not be reduced. Recently, immunotherapy by direct administration of the allergen into lymph nodes [intralymphatic immunotherapy (ILIT)] has proven a promising alternative and this method is the focus of the present review.

RECENT FINDINGS

Several studies on animals and on humans have shown that direct injection into lymph nodes enhanced immune responses to protein, peptide, and naked DNA vaccines. Moreover, ILIT strongly improved allergen immunotherapy, so that the number of allergen administrations as well as the allergen dose could be reduced. As ILIT was also well tolerated, practically painless, and easy to perform, patient compliance was improved as compared with SCIT.

SUMMARY

Direct ILIT into a subcutaneous lymph node markedly enhances protective immune responses, so that both the dose and the number of allergen injections can be reduced, making ILIT safer and faster than other forms of immunotherapy, and most importantly, this enhances patient convenience and compliance.

Modular antigen-translocation as a novel vaccine strategy for allergen-specific immunotherapy

PURPOSE OF REVIEW

The purpose of the present review is to describe recent approaches aimed at improving the treatment of allergic diseases through allergen-specific immunotherapy (SIT). Special emphasis will be given to the approach based on specific targeting of the major histocompatibility complex (MHC) class-II antigen-presentation pathway.

RECENT FINDINGS

It is well recognized that IgE-mediated allergic diseases including rhinitis, atopic eczema and allergic asthma are increasing worldwide to a pandemic dimension. The only curative treatment remains allergen-SIT, which, however, requires a long treatment time of 3-5 years with up to 80 injections to confer protection. Recent findings strongly indicate that the treatment time and the number of injections could be drastically reduced by turning immunotherapy to a true vaccination. Direct injection of allergen extracts into the inguinal lymph nodes and targeting the MHC class-II antigen-presentation pathway by recombinant modular antigen-translocating vaccines have the potential to cure allergic diseases in a very short time.

SUMMARY

The mechanisms of allergic inflammation can be divided into four distinct stages: T cell activation, organ-selective homing, survival/reactivation and effector functions. On the basis of this new knowledge several novel concepts aimed at treating allergic diseases have been developed. The area of allergen-SIT is experiencing exciting developments. Reciprocal regulation of effector and regulatory T cell subsets is being more and more used to develop novel strategies for immunomodulation.

Effects of food processing on food allergens

Food allergies are on the rise in Western countries. With the food allergen labeling requirements in the US and EU, there is an interest in learning how food processing affects food allergens. Numerous foods are processed in different ways at home, in institutional settings, and in industry. Depending on the processing method and the food, partial or complete removal of the offending allergen may be possible as illustrated by reduction of peanut allergen in vitro IgE immunoreactivity upon soaking and blanching treatments. When the allergen is discretely located in a food, one may physically separate and remove it from the food. For example, lye peeling has been reported to produce hypoallergenic peach nectar. Protein denaturation and/or hydrolysis during food processing can be used to produce hypoallergenic products. This paper provides a short overview of basic principles of food processing followed by examples of their effects on food allergen stability. Reviewed literature suggests assessment of processing effects on clinically relevant reactivity of food allergens is warranted.

Targeting the MHC class II pathway of antigen presentation enhances immunogenicity and safety of allergen immunotherapy

BACKGROUND

Current s.c. allergen-specific immunotherapy (SIT) leads to amelioration of IgE-mediated allergy, but it requires numerous allergen injections over several years and is frequently associated with severe side-effects. The aim of this study was to test whether modified recombinant allergens can improve therapeutic efficacy in SIT while reducing allergic side-effects.

METHODS

The major cat allergen Fel d 1 was fused to a TAT-derived protein translocation domain and to a truncated invariant chain for targeting the MHC class II pathway (MAT-Fel d 1). The immunogenicity was evaluated in mice, while potential safety issues were assessed by cellular antigen stimulation test (CAST) using basophils from cat-dander-allergic patients.

RESULTS

MAT-Fel d 1 enhanced induction of Fel d 1-specific IgG2a antibody responses as well as the secretion of IFN-gamma and IL-2 from T cells. Subcutaneous allergen-specific immunotherapy of mice using the modified Fel d 1 provided stronger protection against anaphylaxis than SIT with unmodified Fel d 1, and MAT-Fel d 1 caused less degranulation of human basophils than native Fel d 1.

CONCLUSION

MAT-Fel d 1 allergen enhanced protective antibody and Th1 responses in mice, while reducing human basophil degranulation. Immunotherapy using MAT-Fel d 1 allergen therefore has the potential to enhance SIT efficacy and safety, thus, shortening SIT. This should increase patient compliance and lower treatment costs.

Allergen-related approaches to immunotherapy

Allergic diseases, including asthma, rhinitis and eczema, represent a major health burden worldwide. Mainstay treatments are allergen avoidance where feasible and pharmacotherapy for symptom relief. For selected patients, allergen-specific immunotherapy (SIT) offers the prospect of long lasting clinical efficacy. SIT involves the administration of allergen extract using a standardized regimen, usually subcutaneously or increasingly sublingually. However, application of this potentially curative treatment is restricted, largely due to the risk of serious adverse events, especially in asthmatics and for potent allergens such as peanut, seafood and latex. New insights into immunological mechanisms underlying effective SIT and molecular characterization of allergens and their recognition by the immune system suggest strategies for refinement of SIT. Selective targeting of allergen-specific T cells, especially regulatory T cells, is likely to be pivotal for efficacy. Recombinant allergens lacking IgE reactivity and small T cell epitope-based peptides are being trialled clinically with evidence of efficacy without serious IgE-mediated adverse reactions. Adjuvants, either co-administered or incorporated into a recombinant allergen vaccine to target tolerogenic dendritic cells may also increase efficacy. The safer sublingual route of allergen administration is attracting interest and different allergen forms may be optimal for inducing tolerance by this route. Defined allergen-derived molecules or peptides offer ease of standardization and, coupled with appropriate targeting of immunoregulatory mechanisms, will result in more widespread clinical use of SIT. Adjunct therapies such as anti-IgE antibody and corticosteroids may minimize the likelihood of adverse reactions in those with severe allergic disease who would most benefit from this treatment.

Allergy vaccines: dreams and reality

Allergy, extrinsic asthma and atopic eczema derive from deregulated immune responses against innocuous antigens. The incidence of atopic diseases is actually affecting approximately 30% of the population in industrialized countries. Although much progress has been achieved in the development of efficient symptomatic treatments for allergic diseases, the only curative treatment remains allergen-specific immunotherapy. In contrast to classical vaccines, which elicit strong host immune responses after one or a few injections, allergen-specific immunotherapy might require a long treatment time of 3-5 years with up to 80 injections to confer some protection. The reality is that 'allergy vaccines' achieve beneficial effects through immunomodulation, which takes a long time to establish. The dream would be to develop highly efficient allergy vaccines able to cure the disease with a few injections.

GATA3-driven Th2 responses inhibit TGF-beta1-induced FOXP3 expression and the formation of regulatory T cells

Transcription factors act in concert to induce lineage commitment towards Th1, Th2, or T regulatory (T_reg) cells, and their counter-regulatory mechanisms were shown to be critical for polarization between Th1 and Th2 phenotypes. FOXP3 is an essential transcription factor for natural, thymus-derived (nT_reg) and inducible T_reg (iT_reg) commitment; however, the mechanisms regulating its expression are as yet unknown. We describe a mechanism controlling iT_reg polarization, which is overruled by the Th2 differentiation pathway. We demonstrated that interleukin 4 (IL-4) present at the time of T cell priming inhibits FOXP3. This inhibitory mechanism was also confirmed in Th2 cells and in T cells of transgenic mice overexpressing GATA-3 in T cells, which are shown to be deficient in transforming growth factor (TGF)-β–mediated FOXP3 induction. This inhibition is mediated by direct binding of GATA3 to the FOXP3 promoter, which represses its transactivation process. Therefore, this study provides a new understanding of tolerance development, controlled by a type 2 immune response. IL-4 treatment in mice reduces iT_reg cell frequency, highlighting that therapeutic approaches that target IL-4 or GATA3 might provide new preventive strategies facilitating tolerance induction particularly in Th2-mediated diseases, such as allergy.

Specific immune responses against foreign or autologous antigens are driven by specialized epitope-specific T cells, whose numbers expand upon recognition of antigen found on professional antigen-presenting cells. The subsequent maturation process involves the differentiation of certain T cell phenotypes such as pro-inflammatory cells (Th1, Th2, Th17) or regulatory T (T_reg) cells, which serve to keep the immune response in check. The current study focuses on the role of two key transcription factors—FOXP3 and GATA3—in controlling the commitment of these cells. We demonstrate that the Th2 cytokine IL-4 inhibits the induction of FOXP3 and thus inhibits the generation of inducible T_reg cells. We show that IL-4–induced GATA3 mediates FOXP3 inhibition by directly binding to a GATA element in the FOXP3 promoter. We hypothesize that therapeutic agents aimed at neutralizing IL-4 could be a novel strategy to facilitate inducible T_reg cell generation and thus promotion of tolerance in allergies and other Th2-dominated diseases.

It is shown that Th2 responses prevent the generation of inducible T_regs. This is mediated by IL-4 induction of GATA3, which binds directly to and represses the FOXP3 promoter. This mechanism is likely to be relevant in the induction of immunotolerance, particularly in allergic diseases.

Targeting the MHC II presentation pathway in allergy vaccine development

The worldwide increase in the incidence of allergic diseases and the limited efficacy of current vaccines require the development of new efficient vaccination strategies. Based on PTD (protein transduction domain) technology, we have engineered MAT (modular antigen translocation) molecules, aimed to enhance antigen presentation through intracellular targeting of the MHC II presentation pathway. MAT vaccines consist of a cloning cassette, which fuses Tat (transactivator of transcription) peptide to a truncated Ii (invariant chain), which is able to target antigens to the nascent MHC II molecules in the trans-Golgi compartment. To test the efficacy of intracellular targeting, we engineered arrays of MAT-fusions and compared the effects of recombinant allergens, Tat-conjugated allergens and MAT-conjugated allergens for the ability to stimulate T-cell proliferation and cytokine production in human PBMC (peripheral blood mononuclear cell) cultures derived from allergic individuals, and to elicit protective immune responses in mice. MAT-vaccines induced a strong proliferation of PBMCs at a low concentration and induced a Th2/Treg (regulatory T-cell) cell shift in the cytokine profile, reflecting those reported in successfully desensitized allergic individuals. In allergic mouse models, we showed that MAT-vaccines are highly efficient in desensitizing mice and protect them from anaphylactic shock. The technology is applicable not only for the treatment of allergies, but also for the development of preventive vaccines in general.

A protective allergy vaccine based on CpG- and protamine-containing PLGA microparticles

PURPOSE

Allergen-specific immunotherapy (SIT) requires dozens of subcutaneous injections over 3 to 5 years in order to control IgE-mediated hypersensitivity, which is a T-helper 2 (Th2)-associated pathology. This study investigates the use of poly(lactide-co-glycolide) (PLGA) microparticles combined with immunostimulatory oligodeoxynucleotide (CpG), as well as protamine in SIT.

MATERIALS AND METHODS

We prepared microparticle formulations with the major allergen of bee venom, phospholipase A2 (PLA2), and analyzed the effect of co-encapsulated or admixed CpG in both naïve and bee venom allergic mice.

RESULTS

Mice immunized with microparticles containing only PLA2 induced weak antibody responses. In contrast, the combination with CpG resulted in strong PLA2-specific antibody responses. The presence of CpG was required for the induction of the Th1-associated isotype IgG2a, and the titers of IgG2a in sensitized mice correlated with a better protection against an allergen challenge. The effect of CpG was further strengthened when protamine was co-encapsulated for complexation of CpG.

CONCLUSIONS

This study shows that allergen-specific immunotherapy with a PLGA-based allergen-delivery system in combination with CpG enhanced the induction of protective IgG2a immune responses. This may improve SIT compliance and shorten its duration.