Strategies for converting allergens into hypoallergenic vaccine candidates

Immunotherapies in the treatment of immunoglobulin E‑mediated allergy: Challenges and scope for innovation (Review)

Immunoglobulin E (IgE)‑mediated allergy or hypersensitivity reactions are generally defined as an unwanted severe symptomatic immunological reaction that occurs due to shattered or untrained peripheral tolerance of the immune system. Allergen‑specific immunotherapy (AIT) is the only therapeutic strategy that can provide a longer‑lasting symptomatic and clinical break from medications in IgE‑mediated allergy. Immunotherapies against allergic diseases comprise a successive increasing dose of allergen, which helps in developing the immune tolerance against the allergen. AITs exerttheirspecial effectiveness directly or indirectly by modulating the regulator and effector components of the immune system. The number of success stories of AIT is still limited and it canoccasionallyhave a severe treatment‑associated adverse effect on patients. Therefore, the formulation used for AIT should be appropriate and effective. The present review describes the chronological evolution of AIT, and provides a comparative account of the merits and demerits of different AITs by keeping in focus the critical guiding factors, such as sustained allergen tolerance, duration of AIT, probability of mild to severe allergic reactions and dose of allergen required to effectuate an effective AIT. The mechanisms by which regulatory T cells suppress allergen‑specific effector T cells and how loss of natural tolerance against innocuous proteins induces allergy are reviewed. The present review highlights the major AIT bottlenecks and the importantregulatory requirements for standardized AIT formulations. Furthermore, the present reviewcalls attention to the problem of 'polyallergy', which is still a major challenge for AIT and the emerging concept of 'component‑resolved diagnosis' (CRD) to address the issue. Finally, a prospective strategy for upgrading CRD to the next dimension is provided, and a potential technology for delivering thoroughly standardized AIT with minimal risk is discussed.

Prediction of Epitope-Based Peptide Vaccine Against the Chikungunya Virus by Immuno-informatics Approach

BACKGROUND

Chikungunya is an arthropod-borne viral disease characterized by abrupt onset of fever frequently accompanied by joint pain, which has been identified in over 60 countries in Africa, the Americas, Asia, and Europe.

METHODS

Regardless of the availability of molecular knowledge of this virus, no definite vaccine or other remedial agents have been developed yet. In the present study, a combination of B-cell and T-cell epitope predictions, followed by molecular docking simulation approach has been carried out to design a potential epitope-based peptide vaccine, which can trigger a critical immune response against the viral infections.

RESULTS

A total of 52 sequences of E1 glycoprotein from the previously reported isolates of Chikungunya outbreaks were retrieved and examined through in silico methods to identify a potential B-cell and T-cell epitope. From the two separate epitope prediction servers, five potential B-cell epitopes were selected, among them "NTQLSEAHVEKS" was found highly conserved across strains and manifests high antigenicity with surface accessibility, flexibility, and hydrophilicity. Similarly, two highly conserved, non-allergenic, non-cytotoxic putative T-cell epitopes having maximum population coverage were screened to bind with the HLA-C 12*03 molecule. Molecular docking simulation revealed potential T-cell based epitope "KTEFASAYR" as a vaccine candidate for this virus.

CONCLUSION

A combination of these B-cell and T-cell epitope-based vaccine can open up a new skyline with broader therapeutic application against Chikungunya virus with further experimental and clinical investigation.

Characterization of a hybrid protein designed with segments of allergens from Blomia tropicalis and Dermatophagoides pteronyssinus

BACKGROUND

Sensitization to allergens of the house dust mites Dermatophagoides pteronyssinnus and Blomia tropicalis is an important risk factor for asthma and allergic diseases. Allergen-specific immunotherapy is currently based on natural allergen extracts, however, in the last years recombinant allergens with different modifications have shown promising immunological properties that may be advantageously applied for developing novel allergy vaccines.

METHODS

A hybrid molecule (MAVAC-BD-2) containing epitopes of B. tropicalis (Blo t 5, Blo t 8 and Blo t 10) and D. pteronyssinus (Der p 1, Der p 2, Der p 7 and Der p 8) allergens was constructed, expressed in Escherichia coli and purified by affinity chromatography. Its folding was analyzed by circular dichroism. Antibody reactivities were evaluated by ELISA and non-denaturing dot blot assays using a battery of sera from mite allergic patients and non-allergic subjects. ELISA inhibition and dot blot assays with monoclonal antibodies were used to detect B-cell epitopes. Human basophil activation and induction of IgG-blocking antibodies in mice immunized with the hybrid protein were also evaluated.

RESULTS

MAVAC-BD-2, expressed as a 22.8 kDa protein, showed a lower frequency and strength of IgE reactivity compared to Blo t 5, Der p 1, Der p 2 and the extracts of B. tropicalis and D. pteronyssinus. MAVAC-BD-2 inhibited 26% of IgE reactivity to Der p 2 and Blo t 5, reacted with anti-Der p 1 and anti-Der p 2 monoclonal antibodies and did not induce relevant basophil activation. MAVAC-BD-2 immunized mice produced specific antibodies that reacted against mite extracts and the purified allergens, as well as IgG antibodies that blocked the human IgE reactivity to mite extracts.

CONCLUSION

MAVAC-BD-2 has hypoallergenic characteristics and in mice induces IgG antibodies that block the human IgE reactivity to mite extracts.

Advances in patent applications related to allergen immunotherapy

INTRODUCTION

Allergies are among the most prevalent chronic diseases worldwide. Allergen-specific immunotherapy is used as an alternative treatment to pharmacotherapy. These immunotherapies are performed with crude extracts, which have disadvantages when compared to the new approaches, among them are recombinant proteins and hypoallergens. This review aims to assess immunotherapy for allergies through patent application analysis spanning recent decades.

AREAS COVERED

Patents referring to allergen immunotherapies used in allergy treatment. Data were obtained from the Espacenet® website, using the Cooperative Patent Classification (CPC) system. Two-hundred-and-one patent applications were analyzed, taking into consideration their classification by the type of technology and applicant.

EXPERT OPINION

Allergen-specific immunotherapy represents the only potentially curative therapeutic intervention for the treatment of allergic diseases. The extract-based immunotherapy is being replaced by the use of recombinant allergens, highlighting the hypoallergenic forms, which have low IgE-binding while retaining T-cell reactivity. It is expected that the development of hypoallergens will expand the scope of allergen-specific immunotherapy, especially if associated with alternative systems for expression and delivery systems with future potential. Furthermore, these new developments will likely address the problem of long-term protocols in allergen-specific immunotherapy, thus allowing better patient adherence and compliance.

Mucosal delivery of allergen peptides expressed by Lactococcus lactis inhibit allergic responses in a BALB/c mouse model

Allergen-specific immunotherapy (SIT) is considered to be the only curative treatment of allergy, but its safety is always affected by immunologic properties and quality of allergen. Recombinant allergen derivative could be a potential therapeutic strategy, but clinical studies showed that macromolecular derivatives could not avoid T cell-mediated side effects. In this study, five Der p2-derived peptides (DPs) containing major T cell epitopes of Der p2 were first artificially synthesized. Compared with Der p2 macromolecular derivative DM, these DPs not only fully eliminated IgE-binding capacity but also reduced T cells reactivity, suggesting these DPs could be better therapeutic molecules. For their application in vivo, Lactococcus lactis was engineered to express these DPs, and their protective effects were evaluated in BALB/c mice models. Western blot showed that all DPs could be produced in the recombinant strains. Mucosal delivery of these strains could inhibit Der p2-induced allergic responses in Der p2-sensitized mice, characterized by a reduction in specific IgE antibody and lung inflammatory responses. These protective effects were associated with an increase of specific IgG2a in serum and regulatory T cells in the mesenteric lymph nodes. On the whole, the suppressive effect induced by the DP mixture could be better than single DP, but a bit weaker than DM. These DPs could be promising candidate molecules for active vaccination and induction of tolerance, and thus promote the development of non-allergenic peptide in the treatment and prevention of allergy.

A folded and immunogenic IgE-hyporeactive variant of the major allergen Phl p 1 produced in Escherichia coli

BACKGROUND

Group 1 grass pollen allergens are a major cause of allergic disease. Specific immunotherapy involving controlled administration of allergens can be used as a disease-modifying treatment for such disease. Recombinant allergen variants with reduced IgE binding capacity may be used as component in such vaccines, as they may induce fewer treatment side effects than materials currently in use. A mutated variant of the immunodominant C-terminal domain of the group 1 grass pollen allergen Phl p 1 was recently established through an approach that used a set of human monoclonal IgE as a guide to identify mutations that disturbed IgE-allergen interactions. Further analysis of this domain is required to establish its potential for use in treatment.

METHODS

GST-tagged wild-type and mutated C-terminal domains of Phl p 1 were produced in Escherichia coli TUNER(DE3). The products were purified by affinity chromatography on immobilized glutathione. GST was removed by enzymatic cleavage and tag-free products were purified by size exclusion chromatography. Products were assessed by SDS-PAGE, circular dichroism spectroscopy, differential scanning fluorimetry and dynamic light scattering. Rats were immunized with GST-tagged and tag-free mutated C-terminal domain of Phl p 1. Antigen-binding properties of induced antibodies were assessed by immunochemical analysis.

RESULTS

The mutated domain has a structure very similar to that of the wild-type domain as determined by circular dichroism, but a reduced thermal stability. Immunization of rats demonstrates that this IgE-hyporeactive domain, despite its three sequence modifications (K8A, N11A, D55A), is able to induce antibodies that substantially block the binding of allergic subjects' IgE to the wild-type allergen.

CONCLUSIONS

It is concluded that this IgE-hyporeactive molecule can be produced in folded form and that it is able to induce an antibody response that efficiently competes with IgE recognition of Phl p 1. These findings suggest that it, or a further evolved variant thereof, is a candidate for use as a component in specific immunotherapy against grass pollen allergy.

Recombinant house dust mite allergens

House dust mites (HDM) are a globally important source of allergen responsible for the sensitization of more than 50% of allergic patients. Specific immunotherapy with HDM extracts is effective but allergen extracts cannot be fully standardized and severe side-effects can occur during the protracted course of treatment. The introduction of molecular biological techniques into allergy research allowed the indentification of more than 20 groups of HDM allergens. Recombinant HDM allergens can be produced in defined concentrations and consistent quality and allow the development of vaccines for HDM allergy with reduced allergenic activity and retained immunogenicity. The immunotherapy trials in pollen allergic patients with recombinant pollen allergens/hypoallergenic allergen derivatives have shown that this treatment is effective and indicated that recombinant HDM vaccines might improve immunotherapy of HDM allergic patients. Here we report the steps for the development of vaccines for HDM allergy. After selection of the most prevalent HDM species, the panel of allergens to be included into a therapeutic vaccine for HDM allergy needs to be determined. HDM allergens with high IgE-binding frequency and clinical relevance will be modified into hypoallergenic variants and evaluated for their allergenic activity and immunogenicity. Derivatives with reduced allergenic activity but with retained immunogenicity would be good candidates for a HDM vaccine for safe and efficient immunotherapy.

Information technologies for vaccine research

Vaccinology is a combinatorial science which studies the diversity of pathogens and the human immune system, and formulations that can modulate immune responses and prevent or cure disease. Huge amounts of data are produced by genomics and proteomics projects and large-scale screening of pathogen-host and antigen-host interactions. Current developments in computational vaccinology mainly support the analysis of antigen processing and presentation and the characterization of targets of immune response. Future development will also include systemic models of vaccine responses. Immunomics, the large-scale screening of immune processes which includes powerful immunoinformatic tools, offers great promise for future translation of basic immunology research advances into successful vaccines.

Immunotherapy with a recombinant hybrid molecule alleviates allergic responses more efficiently than an allergenic cocktail or pollen extract in a model of chenopodium album allergy

BACKGROUND

The aim of this study is to assess the therapeutic potential of a recombinant hybrid molecule (rHM) alongside an allergenic cocktail from recombinant wild-type allergens as well as pollen extract on Chenopodium album allergy, using a BALB/c mouse model.

METHODS

The BALB/c mice had already been sensitized to C. album via intraperitoneal injections of alum-adsorbed allergenic cocktail and immunotherapy procedure was followed by subcutaneous injections of the rHM, allergenic cocktail and pollen extract at weekly intervals. Humoral immune responses were determined via measurement of specific antibodies in serum. Splenocytes of immunized mice were stimulated in vitro and then proliferation responses, cytokine secretion and mRNA expression of genes involved in immunotherapy were examined by ELISA and real-time PCR.

RESULTS

Sensitized mice were identified with high specific IgE against allergenic cocktail when compared with healthy mice. Immunotherapy with the rHM induced the highest ratio of the IgG2a/IgG1 levels compared to allergenic cocktail or C. album pollen extract. The rHM was able to induce proliferative responses as well as the allergenic cocktail in cultured splenocytes. Immunotherapy with the rHM significantly improved secretion of IFN-γ and IL-10, while secretion of IL-13 rapidly diminished. Interestingly, mRNA expression of GATA3 was strongly decreased in rHM-treated mice whereas mRNA expression of T-bet and Foxp3 was significantly increased.

CONCLUSION

Our results prove that immunotherapy with the rHM effectively controlled allergic responses by shifting from a Th2-like immune response to a Th1-dominated immune response.

Recent developments with B-cell epitope identification for predictive studies

This review discusses currently available methods for predicting B-cell epitopes on proteins. The use of animals for assessing protein immunogenicity is addressed primarily to highlight the differences in B- and T-cell epitope recognition between species. These differences have to be considered when interpreting potential B-cell epitopes identified by the methods addressed here. "In vitro alternatives" focuses on the strengths and limitations of peptide-based technologies. Three types of computer-based methods for identifying potential B-cell epitopes are discussed: (i) methods applying physico-chemical and structural propensity scales for predicting linear epitopes from the primary structure of a protein, (ii) comparative methods basing prediction upon amino acid sequence and structural similarities between antigenically known and unknown proteins, and (iii) a method combining structural features with a B-cell epitope motif database for predicting linear and conformational antigenic determinants. With respect to human safety, the usefulness of antibody-based tests is limited to comparative studies between an antigenically known protein and variants thereof. Similarly, computer-based methods using data mining can address similarities in B-cell epitope profiles between related proteins, if a proper cut off can be defined for the minimal amino acid sequence similarity required for obtaining an acceptable accuracy. Among the physico-chemical and structural scales, scales identifying in a protein hairpin and non-specific turns seem useful for predicting epitopes with a continuous primary binding site. When conformational epitopes have to be identified as well, a novel computer-based tool seems to be the most promising alternative to X-ray crystallography. However, both methods remain to be extensively evaluated and validated. Thus, promising tools for B-cell epitope identification have been developed. But, no validated method for B-cell epitope identification on antigenically unknown proteins is available yet.

Allergen-specific immunotherapy with recombinant allergens

Subcutaneous immunotherapy is a well-documented treatment of allergic rhinitis and asthma. The major limitation is the risk of anaphylactic side effects. The documentation of clinical efficacy is based on crude allergenic extracts sometimes containing varying amounts of individual allergens including allergens to which the patient may not be sensitized. The introduction of recombinant allergens offer a possibility to use well-defined molecules with consistent pharmaceutical quality defined in mass units. The proof-of-concept of the clinical efficacy of recombinant allergens is based on two studies published as full articles. One study applied a mixture of five Phleum pratense major allergens in a maximum dose of 40 μg protein. The clinical efficacy showed a significant efficacy with about 40% reduction in disease severity. The second study compared a commercial birch extract with both recombinant Bet v 1 and purified Bet v 1 in dosages of 15 μg allergen. The clinical effect was around 60% additional efficacy. Systemic side effects occurred more frequently with grass allergens. A third study used hypoallergenic fragments and a trimer of Bet v 1. The study did not show efficacy and a rather high frequency of systemic side effects. The advantages of using recombinant allergens for immunotherapy are obvious but more large-scale clinical studies are needed before the overall value in terms of efficacy and safety can be determined.

100 years of hyposensitization: history of allergen-specific immunotherapy (ASIT)

Hundred years ago, Leonhard Noon and John Freeman published their pioneering works on allergen-specific immunotherapy (ASIT) using grass pollen extracts. To honor their contribution to the development of ASIT as the only causal treatment of IgE-mediated allergies, we review the history of ASIT that started with the anecdotal descriptions of ASIT performed by the ancient king Mithridates (132-63 B.C.) and Jenner's development of a cowpox vaccine. Following Noon's and Freeman's first controlled human trials, ASIT was performed by a large number of modalities and with a myriad of pharmacologic preparations. These developments range from early aqueous pollen extracts and whole bee extracts to chemically modified allergens (allergoids) and various recombinant allergens. In addition to allergen-specific immunotherapy, non-specific immune response modifiers have been used in the past or are in the developmental stage. Also, currently many innovative experimental approaches of ASIT are studied in animal models and human in vitro systems and will hopefully further broaden the range of allergies that can be treated by ASIT, with enhanced efficacy and further reduced side-effects.

The current state of recombinant allergens for immunotherapy

PURPOSE OF REVIEW

Subcutaneous immunotherapy is a well documented treatment of allergic rhinitis and asthma. The majority of the disadvantages of the treatment are related to the poor quality of the natural allergen extracts which can contain varying amounts of individual allergens including allergens to which the patient may not be sensitized. Recombinant allergens offer a possibility to use well defined molecules with consistent pharmaceutical quality defined in mass units. The proof of concept of the clinical efficacy of recombinant allergens is based on two studies published as full articles.

RECENT FINDINGS

One study applied a mixture of five Phleum pratense major allergens in a maximum dose of 40mcg protein. The clinical efficacy showed a significant efficacy with 40% reduction in disease severity. The second study compared a commercial birch extract with both recombinant Bet v 1 and purified Bet v 1 in dosages of 15mcg allergen. The clinical effect was 60% additional efficacy. Systemic side effects occurred more frequently with grass allergens. A third study used hypoallergenic fragments and a trimer of Bet v 1. The study did not show efficacy and a rather high frequency of systemic side effects.

SUMMARY

The advantages of using recombinant allergens for immunotherapy are obvious but more studies on a large scale are needed before the overall value in terms of efficacy and safety can be assessed. Clinical trials are also necessary for new combined vaccines based on recombinant allergens that in experimental studies have shown greatly enhanced immunogenicity and low allergen-specific reactivity.

Treatment with a Fel d 1 hypoallergen reduces allergic responses in a mouse model for cat allergy

BACKGROUND

  A hypoallergen of the major cat allergen Fel d 1, recombinant (r) Fel d 1 (DTE III), was previously shown to have retained T-cell reactivity and strongly reduced IgE-binding capacity compared to unmodified rFel d 1. Here, we evaluated the therapeutic capacity of rFel d 1 (DTE III) in a mouse model for cat allergy.

METHODS

  Mice were subcutaneously (s.c.) sensitized with rFel d 1 and subsequently treated (s.c.) with 50 or 200 μg rFel d 1 (DTE III), or 50 μg rFel d 1, prior to intranasal challenge with cat dander extract. Airway hyperreactivity (AHR), cells and cytokines in bronchoalveolar lavage fluid, splenocyte in vitro response, and serum immunoglobulins were analyzed. Seven cat-allergic patients and ten healthy controls were tested for skin prick test (SPT) reactivity to rFel d 1 (DTE III) and rFel d 1.

RESULTS

  Mice treated with 50 and 200 μg rFel d 1 (DTE III), and 50 μg rFel d 1, produced increased serum levels of rFel d 1-specific IgG1 and IgG2a compared to sham-treated mice. IgG from all treatment groups could block binding of patients' IgE to rFel d 1. The 200 μg rFel d 1 (DTE III) treatment tended to reduce AHR. All mice tolerated treatment with rFel d 1 (DTE III), in contrast to only four of ten treated with rFel d 1. Compared to rFel d 1, the hypoallergen showed a tendency of reduced SPT reactivity.

CONCLUSION

  The rFel d 1 (DTE III) hypoallergen might be a promising candidate for application in immunotherapy of cat allergy with improved safety and efficacy.

Genetic engineering of trimers of hypoallergenic fragments of the major birch pollen allergen, Bet v 1, for allergy vaccination

An immunotherapy trial performed in allergic patients with hypoallergenic recombinant fragments, comprising aa 1-74 and 75-160 of the major birch pollen allergen, Bet v 1, has indicated that the induction of allergen-specific IgG responses may be an important mechanism of this treatment. To investigate whether the immunogenicity of the rBet v 1 fragments can be increased, recombinant trimers of the fragments were produced. For this purpose, DNA trimers of rBet v 1 aa 1-74 as well as of rBet v 1 aa 75-160 were subcloned into expression plasmid pET 17b, expressed in Escherichia coli and purified. The fragments as well as the fragment trimers showed a reduced IgE-binding capacity and allergenic activity compared to rBet v 1 wildtype when tested in allergic patients. Both rBet v 1 aa 75-160 monomer and trimer induced high titers of allergen-specific IgG1 Abs in mice. Interestingly, rBet v 1 aa 1-74 trimer induced a much higher IgG(1) response to rBet v 1 than rBet v 1 aa 1-74 monomer. Consequently, IgG Abs induced with the rBet v 1 aa 1-74 trimer inhibited birch pollen allergic patients' IgE-binding 10-fold more efficiently than IgG Abs induced with the monomer. Our data show that the immunogenicity of allergy vaccines can be increased by oligomerization.

From allergen genes to allergy vaccines

IgE-mediated allergy is a hypersensitivity disease affecting more than 25% of the population. The structures of the most common allergens have been revealed through molecular cloning technology in the past two decades. On the basis of this knowledge of the sequences and three-dimensional structures of culprit allergens, investigators can now analyze the immune recognition of allergens and the mechanisms of allergic inflammation in allergic patients. Allergy vaccines have been constructed that are able to selectively target the aberrant immune responses in allergic patients via different pathways of the immune system. Here we review various types of allergy vaccines that have been developed based on allergen structures, results from their clinical application in allergic patients, and future strategies for allergen-specific immunotherapy and allergy prophylaxis.

Directed evolution of chemotaxis inhibitory protein of Staphylococcus aureus generates biologically functional variants with reduced interaction with human antibodies

Chemotaxis inhibitory protein of Staphylococcus aureus (CHIPS) is a protein that binds and blocks the C5a receptor (C5aR) and formylated peptide receptor, thereby inhibiting the immune cell recruitment associated with inflammation. If CHIPS was less reactive with existing human antibodies, it would be a promising anti-inflammatory drug candidate. Therefore, we applied directed evolution and computational/rational design to the CHIPS gene in order to generate new CHIPS variants displaying lower interaction with human IgG, yet retaining biological function. The optimization was performed in four rounds: one round of random mutagenesis to add diversity into the CHIPS gene and three rounds of DNA recombination by Fragment INduced Diversity (FIND). Every round was screened by phage selection and/or ELISA for decreased interaction with human IgG and retained C5aR binding. The mean binding of human anti-CHIPS IgG decreased with every round of evolution. For further optimization, new amino acid substitutions were introduced by rational design, based on the mutations identified during directed evolution. Finally, seven CHIPS variants with low interaction with human IgG and retained C5aR blocking capacity could be identified.

Relevance of IgE binding to short peptides for the allergenic activity of food allergens

BACKGROUND

Analysis of IgE antibody binding to epitopes provides information for food allergy diagnosis and management and construction of hypoallergenic candidate vaccines, but the contribution of sequential epitopes to functionally relevant IgE binding is not fully understood.

OBJECTIVES

We sought to study the impact of IgE-binding peptides described as major sequence epitopes in the literature on IgE-binding capacity of 2 selected food allergens.

METHODS

IgE-binding peptides of the food allergens Ara h 2 (peanut) and Pen a 1 (shrimp) were identified. Synthetic soluble peptides representing the identified sequences were assessed for their capacity to inhibit IgE binding to the parent allergens by means of ELISA and in mediator release assay. The IgE-binding capacity of unfolded recombinant (r) Ara h 2 was analyzed. A hybrid tropomyosin carrying the IgE-binding regions of Pen a 1 grafted into the structural context of the nonallergenic mouse tropomyosin was applied in ELISA inhibition experiments and ImmunoCAP analysis.

RESULTS

Although IgE-binding peptides representing sections of the allergen sequences were detected, no relevant capacity to inhibit the IgE binding to the parent allergen in ELISA or basophil activation test was observed. Unfolded rAra h 2 showed reduced IgE-binding capacity compared with folded rAra h 2 and failed to elicit mediator release. Hybrid tropomyosin bound less IgE than rPen a 1 in ImmunoCAP analysis and revealed marginal inhibitory capacity.

CONCLUSION

Peptides identified as major sequence epitopes on Pen a 1 and Ara h 2 show little contribution to the IgE binding of the allergens studied.

Immunomodulatory effects of egg white enzymatic hydrolysates containing immunodominant epitopes in a BALB/c mouse model of egg allergy

Egg has ben documented as a rich source for the supply of biologically active peptides. This study characterizes the immunomodulatory effects of an egg white enzymatic hydrolysate (EWH) using a BALB/c mouse model of egg allergy. Mice were orally sensitized to egg white and subsequently gavaged with EWH. ELISA results indicated significant reductions of both serum histamine and specific IgE titers in EWH-fed mice, accompanied by a repression of both IL-4 and IFN-gamma production in spleen cell cultures. Similarly, real-time RT-PCR analyses highlighted decreased mRNA expression of IFN-gamma and IL-12 (Th1-biased), as well as lower ratios of IL-4 and IL-13 mRNA (Th2-biased). On the other hand, increased intestinal expressions of TGF-beta and FOXp3 mRNA were determined in EWH-fed mice, suggesting induction of local regulatory mechanisms. The presence of immunodominant epitopes was proposed to be responsible for the immunomodulatory effects observed.

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.

From allergen genes to new forms of allergy diagnosis and treatment

Type I allergy represents an important health problem that affects more than 25% of the population in industrialized countries. Specific immunotherapy is one of the few causative treatment approaches for type I allergy and is currently performed with crude allergen extracts, which consist of a mixture of allergenic and nonallergenic components, are difficult to standardize and cannot be applied according to the patient's reactivity profile. With the introduction of molecular biological techniques into allergy research, a large panel of individual recombinant allergens has become available. Recombinant allergens can be used for improved diagnosis of allergy to determine the patient's sensitization profile, which is a prerequisite to select the allergens for patient-tailored immunotherapy. They allow the elucidation of the properties of allergens and of the mechanisms of allergy as well as of the mechanisms of immunotherapy. Moreover, recombinant allergens allow the development of hypoallergenic allergen derivatives with reduced allergenic activity and retained immunogenicity. First immunotherapy trials with hypoallergenic allergen derivatives have shown that this treatment might improve immunotherapy in the near future. This review summarizes the results, which were obtained with recombinant allergens and hypoallergenic allergen derivatives. The experiences from the in vitro and in vivo evaluation of the hypoallergenic derivatives and from clinical studies as well as the contribution of hypoallergenic derivatives to develop new treatment strategies and possibly prophylactic vaccination strategies are discussed.

Biotechnology-based allergy diagnosis and vaccination

The diagnosis and immunotherapy currently applied to allergic diseases involve the use of crude extracts of the allergen source without defining the allergy-eliciting molecule(s). Advances in recombinant DNA technology have made identification, cloning, expression and epitope mapping of clinically significant allergens possible. Recombinant allergens that retain the immunological features of natural allergens form the basis of accurate protein-chip-based methods for diagnosing allergic conditions. The ability to produce rationally designed hypoallergenic forms of allergens is leading to the development of novel and safe forms of allergy vaccines with improved efficacy. The initial clinical tests on recombinant-allergen-based vaccine preparations have provided positive results, and ongoing developments in areas such as alternative routes of vaccine delivery will enhance patient compliance.

Production of Recombinant Peanut Allergen Ara h 2 using Lactococcus lactis

Background

Natural allergen sources can supply large quantities of authentic allergen mixtures for use as immunotherapeutics. However, such extracts are complex, difficult to define, vary from batch to batch, which may lead to unpredictable efficacy and/or unacceptable levels of side effects. The use of recombinant expression systems for allergen production can alleviate some of these issues. Several allergens have been tested in high-level expression systems and in most cases show immunereactivity comparable to their natural counterparts. The gram positive lactic acid bacterium Lactococcus lactis is an attractive microorganism for use in the production of protein therapeutics. L. lactis is considered food grade, free of endotoxins, and is able to secrete the heterologous product together with few other native proteins. Hypersensitivity to peanut represents a serious allergic problem. Some of the major allergens in peanut have been described. However, for therapeutic usage more information about the individual allergenic components is needed. In this paper we report recombinant production of the Ara h 2 peanut allergen using L. lactis.

Results

A synthetic ara h 2 gene was cloned into an L. lactis expression plasmid containing the P170 promoter and the SP310mut2 signal sequence. Flask cultures grown overnight showed secretion of the 17 kDa Ara h 2 protein. A batch fermentation resulted in 40 mg/L recombinant Ara h 2. Purification of Ara h 2 from the culture supernatant was done by hydrophobic exclusion and size separation. Mass spectrometry and N-terminal analysis showed a recombinant Ara h 2 of full length and correctly processed by the signal peptidase. The immunological activity of recombinant Ara h 2 was analysed by ELISA using antibodies specific for native Ara h 2. The recombinant Ara h 2 showed comparable immunereactivity to that of native Ara h 2.

Conclusion

Recombinant production of Ara h 2 using L. lactis can offer high yields of secreted, full length and immunologically active allergen. The L. lactis expression system can support recombinant allergen material for immunotherapy and component resolved allergen diagnostics.

Intranasal immunization with a dominant T-cell epitope peptide of a major allergen of olive pollen prevents mice from sensitization to the whole allergen

Mucosal tolerance induction with vaccines based on peptides representing T-cell epitopes of allergens is a promising way for treating allergic diseases. Ole e 1 is the main allergen of olive pollen, which is an important cause of allergy in Mediterranean countries. The aim of this study was to evaluate the ability of the peptide T109-K130 containing a dominant T-cell epitope of Ole e 1, to modulate the allergen-specific immune response in a prophylactic mouse model. Mice were intranasally treated with the peptide 1 week prior to sensitization with Ole e 1. Blood, lungs and spleens were collected and analysed for immune response. Intranasal pretreatment of mice with the peptide led to suppress serum specific IgE, IgG1 and IgG2a antibody levels, and markedly reduced proliferative T-cell response and Th2-cytokine production, but increased IFN-gamma secretion in spleen cell cultures. Increased mRNA IL-10 levels were observed in lungs from pretreated mice. Pathologic alterations of the lung associated with airway inflammation (peribronchial/perivascular infiltrates, eosinophilia and mucus production) were significantly suppressed after pretreatment. Similar results were obtained when mice were sensitized 10 weeks after treatment. Our results demonstrate that intranasal administration of a single T-cell peptide protects mice against subsequent sensitization to the allergen, possibly via IFN-gamma and IL-10. This study emphasizes the usefulness of nasal peptide T-based vaccines against allergy.

Use of multiple peptides containing T cell epitopes is a feasible approach for peptide-based immunotherapy in Can f 1 allergy

We have previously shown that the major dog allergen Can f 1 contains seven T cell epitope regions, none of which was preferentially recognized. To identify the immune characteristics of Can f 1 epitopes and to verify their suitability for peptide-based allergen immunotherapy, short-term T cell lines were generated with epitope-containing peptides from peripheral blood mononuclear cells of Can f 1 skinprick test-positive allergic and healthy control subjects. The lines were examined for their proliferative capacity and cytokine production upon stimulation with the allergen peptide, a homologous peptide from human tear lipocalin (TL) and Can f 1 and TL proteins. Can f 1 peptides induced proliferation of T cells and gave rise to T cell lines with comparable efficiencies. In particular, the T cell lines of allergic subjects induced with p33-48 and p107-122 favoured the production of interferon-gamma and interleukin-10, respectively. A greater number of Can f 1-specific T cell lines were generated from allergic than from healthy individuals. Two p107-122-induced Can f 1-specific T cell lines also reacted to a homologous peptide of human TL. Our results suggest that several T cell epitope-containing peptides should be used in combination for specific immunotherapy in Can f 1 allergy.

Hypoallergenic mutants of Ole e 1, the major olive pollen allergen, as candidates for allergy vaccines

BACKGROUND

The C-terminal region of Ole e 1, a major allergen from olive pollen, is a dominant IgE-reactive site and offers a target for site-directed mutagenesis to produce variants with reduced IgE-binding capability.

OBJECTIVE

To evaluate in vitro and in vivo the immunogenic properties of three engineered derivatives of Ole e 1.

METHODS

One point (Y141A) and two deletion (135Delta10 and 140Delta5) mutants were generated by site-directed mutagenesis of Ole e 1-specific cDNA and produced in Pichia pastoris. Ole e 1 mutants were analysed for IgE reactivity by ELISA using sera from olive pollen-allergic patients. Their allergenicity was also investigated in both a mouse model of allergic sensitization and in basophil activation assays. IgG1 response was assayed by immunoblotting and competitive ELISA. T cell reactivity was evaluated by proliferation assays and cytokine production in splenocyte cultures.

RESULTS

The 135Delta10 mutant showed the strongest reduction in the IgE-binding capability of sera from olive pollen-allergic patients. Rat basophil leukaemia assays identified the deletion mutant 135Delta10 as the variant with the lowest beta-hexosaminidase-releasing capacity. Furthermore, the same 135Delta10 mutant induced the lowest IgE levels in a BALB/c mouse model of sensitization. All Ole e 1 mutants retained their allergen-specific T cell reactivity. Immunization of mice with the mutants induced IgG1 antibodies, which cross-reacted with Ole e 1 and Ole e 1-like allergens from ash, lilac and privet pollens. The ability of the human IgE to block the binding of anti-Ole e 1 mutant-specific mouse IgG1 antibodies to natural Ole e 1 demonstrated that Ole e 1 mutants are able to induce in vivo antibodies reactive to the natural allergen.

CONCLUSION

The 135Delta10 mutant with reduced allergenicity, intact T cell reactivity and capacity to induce blocking antibodies could provide a suitable candidate vaccine for efficient and safer therapy of olive pollen allergy.

A new recombinant mosquito salivary allergen, rAed a 2: allergenicity, clinical relevance, and cross-reactivity

BACKGROUND

Mosquito salivary proteins cause allergic reactions in humans. The allergenicity, clinical relevance, and species cross-reactivity of a new 37-kDa recombinant mosquito (Aedes aegypti) salivary allergen, rAed a 2, were evaluated.

METHODS

rAed a 2 was expressed using a baculovirus/insect cell system and purified. Its allergenicity was examined using an enzyme-linked immunosorbent assay (ELISA), ELISA inhibition tests, immunoblots, and skin tests. Epicutaneous tests with the allergen, mosquito whole body extracts, and mosquito bite tests were performed on 48 volunteers. Serum rAed a 2-specific immunoglobulin E (IgE) was measured in individuals with positive mosquito saliva-specific IgE and negative controls.

RESULTS

Both immunoblots and ELISAs demonstrated that rAed a 2 bound to the IgE of mosquito-allergic individuals. The binding could be inhibited by the addition of a natural mosquito preparation. Furthermore, rAed a 2 induced immediate and delayed skin reactions. Ten per cent of 31 participants with a positive mosquito bite test had positive skin reactions to rAed a 2, compared with 32% for mosquito whole body extract. None of the participants with a negative bite test showed positive reactions to either of the two extracts. Forty-three per cent of individuals with positive saliva-IgE had positive rAed a 2-IgE. rAed a 2 was a species-shared allergen, being present in the saliva of the 11 species studied.

CONCLUSIONS

rAed a 2 has identical antigenicity and biologic activity to its native form. It can be used in the diagnosis of mosquito allergy, and is an important species-shared antigen.

Engineered recombinant ovomucoid third domain can modulate allergenic response in Balb/c mice model

IgE-mediated allergic reactions to egg white are a serious health problem and ovomucoid being the dominant egg white allergen has been on focus in the past decade. Engineered hypoallergens with reduced reactivity for IgE antibodies are being examined to modulate the allergic response and develop prophylactic allergen vaccines. In this study, we evaluated the immunomodulatory effect of a genetic variant of the third domain of ovomucoid (GMFA) which showed reduced IgE binding with egg allergic patient's sera in comparison to the native form of the third domain of ovomucoid (DIII) in a murine model system. Balb/c mice were injected intraperitoneally with DIII and GMFA antigens. Allergen-specific serum IgG, IgG1, IgG2a, and IgE responses were evaluated using enzyme-linked immunosorbent assay. Splenocyte cytokine levels in the medium of the cultured cells were examined by ELISA and levels of IL-4, INF-gamma, and IL-12 (p70) cytokines were quantified. Neutralization with anti-IL-12 monoclonal antibody was assayed and cytokine levels with respect to GMFA mutant antigen stimulation were measured. GMFA mutant form was found to have significantly reduced levels of specific IgE when compared to the DIII suggesting a mutation-induced abrogation of the IgE binding epitope in mice. The increase in IgG2a levels in GMFA together with the decline of IgE and IgG1 points to a shift from a Th2 response to a Th1 dominated response. The cytokine profile showed a modulation of anti-allergic Th1 phenotype in GMFA from a proallergic Th2 response observed with DIII. Low levels of IL-4 and increased levels of INF-gamma and IL-12 were observed and anti-IL-12 monoclonal antibody restored the levels of IL-4 and suppressed levels of INF-gamma and IL-12 in the GMFA sensitized group. These results indicate that GMFA has a marked suppressive effect on the allergic response of ovomucoid and caused a shift towards a Th1 pathway, thereby modulating the Th1/Th2 cytokine balance and could be used as a potential hypoallergenic candidate for allergen-immunotherapy in the treatment of egg white allergy.

Advances in development of hypoallergenic latex immunotherapy

PURPOSE OF REVIEW

The characterization of clinically relevant latex allergens and the production of recombinant allergens is now well advanced, but this knowledge needs to be translated into new strategies for the safe and effective specific treatment of latex allergic diseases including asthma and anaphylaxis.

RECENT FINDINGS

The current status of latex allergy is discussed indicating a changing demographic paradigm. A new wave of latex allergy is emerging outside the healthcare setting with the widespread use of latex products. An increased prevalence in developing countries is also reported. Limited studies on current specific immunotherapy for latex allergy are reviewed, confirming the feasibility but demonstrating an unacceptable risk of adverse events. The characterization of latex allergens and the identification of B and T-cell epitopes point to rational strategies for the generation of hypoallergenic preparations for specific immunotherapy. Results to date for latex allergens are reviewed, including recombinant, chemical modification and synthetic peptide approaches. Candidate hypoallergenic preparations for targeting sensitization to the major allergens Hev b 1, Hev b 3, Hev b 5 and Hev b 6.01 have been identified. Further investigations of optimal regimens for the delivery of specific immunotherapy to induce regulatory T-cell function are warranted.

SUMMARY

The findings point to the selection of suitable hypoallergenic preparations for clinical trials of effective and safe latex allergy immunotherapy.

Antigen-specific targeting and elimination of EBV-transformed B cells by allergen toxins

BACKGROUND

With the exception of antigen-specific immunotherapy, current treatments for atopic diseases provide only symptomatic relief. Because of the increasing incidence of such diseases, the development of novel strategies and concepts for the treatment of allergies is urgently needed.

OBJECTIVE

Here we present a new approach for the treatment of atopic diseases. The strategy is comparable to the application of immunotoxins in cancer therapy, in which a cytotoxic peptide is coupled to a cancer cell-specific antibody fragment or ligand. In the case of so-called allergen toxins (ATs), the target cell-specific moiety is an allergen or allergen-derived fragment, which should be bound only by allergen-reactive cells. After receptor-mediated internalization, allergen-specific cells are killed, and the allergic pathogenesis is interrupted.

METHODS

Proof of the AT principle was shown by using a human ex vivo system in which EBV was used to transform human B cells specific for the timothy grass pollen allergen Phl p 5b. The AT is composed of the major B-cell and T-cell epitopes of the Phl p 5b (P5) allergen fused to a truncated form of the highly toxic Pseudomonas aeruginosa exotoxin A (ETA').

RESULTS

Allergen-specific and nonspecific B cells were challenged with P5-ETA', but only the Phl p 5b-reactive B cells showed selective binding and cytotoxicity.

CONCLUSION

This approach represents an initial step toward a novel therapeutic strategy in the treatment of atopic diseases.

Mucosal immunity and vaccines

There is currently great interest in developing mucosal vaccines against a variety of microbial pathogens. Mucosally induced tolerance also seems to be a promising form of immunomodulation for treating certain autoimmune diseases and allergies. Here we review the properties of the mucosal immune system and discuss advances in the development of mucosal vaccines for protection against infections and for treatment of various inflammatory disorders.

Tryptophan residue is essential for immunoreactivity of a diagnostically relevant peptide epitope of A. fumigatus

The role of tryptophan (Trp17) in immunoreactivity of P1, the diagnostically relevant peptide from a major allergen/antigen of Aspergillus fumigatus, was evaluated by chemically modifying tryptophanyl residue of P1. In BIAcore kinetic studies, unmodified P1 showed a 100-fold higher binding with ABPA (Allergic Bronchopulmonary Aspergillosis) patients' IgG [KD (equilibrium dissociation constant) = 2.74 e(-8) +/- 0.13 M] than the controls' IgG (KD = 2.97 e(-6) +/- 0.14 M), whereas chemically-modified P1 showed similar binding [KD patients' IgG = 3.25 e(-7) +/- 0.16 M, KD controls' IgG = 3.86 e(-7) +/- 0.19 M] indicating loss of specific immunoreactivity of P1 on tryptophan modification. Modified P1 showed loss of specific binding to IgE and IgG antibodies of ABPA patients in ELISA (Enzyme-Linked Immunosorbent Assay). The study infers that tryptophan residue (Trp17) is essential for immunoreactivity of P1.

The changing field of vaccine development in the genomics era

An improved understanding of the human immune system and the genetic make-up of pathogens, together with advances in instrumentation and bioinformatics, have provided new insights into the variation of immune responses to vaccines within the human population. Pathogen variation and the diversity of the immune system components within the human population make the design of universal vaccines difficult. New subunit vaccines that target immunologically similar subgroups of the human population and representative pathogen variants are emerging from research that combines immunomics, pathogen genomics, and high-throughput instrumentation.