Recombinant allergens with reduced allergenicity but retaining immunogenicity of the natural allergens: hybrids of yellow jacket and paper wasp venom allergen antigen 5s

Biological and Inflammatory Effects of Antigen 5 from Polybia paulista (Hymenoptera, Vespidae) Venom in Mouse Intraperitoneal Macrophages

The social wasp Polybia paulista (Hymenoptera, Vespidae) is highly aggressive, being responsible for many medical occurrences. One of the most allergenic components of this venom is Antigen 5 (Poly p 5). The possible modulation of the in vitro immune response induced by antigen 5 from P. paulista venom, expressed recombinantly (rPoly p 5), on BALB/c mice peritoneal macrophages, activated or not with LPS, was assessed. Here, we analyzed cell viability changes, expression of the phosphorylated form of p65 NF-κB subunit, nitric oxide (NO), proinflammatory cytokines production, and co-stimulatory molecules (CD80, CD86). The results suggest that rPoly p 5 does not affect NO production nor the expression of co-stimulatory molecules in mouse peritoneal macrophages. On the other hand, rPoly p 5 induced an increase in IL-1β production in non-activated macrophages and a reduction in the production of TNF-α and MCP-1 cytokines in activated macrophages. rPoly p 5 decreased the in vitro production of the phosphorylated p65 NF-κB subunit in non-activated macrophages. These findings suggest an essential role of this allergen in the polarization of functional M2 macrophage phenotypes, when analyzed in previously activated macrophages. Further investigations, mainly in in vivo studies, should be conducted to elucidate Polybia paulista Ag5 biological role in the macrophage functional profile modulation.

Structural Aspects of the Allergen-Antibody Interaction

The development of allergic disease involves the production of IgE antibodies upon allergen exposure in a process called sensitization. IgE binds to receptors on the surface of mast cells and basophils, and subsequent allergen exposure leads to cross-linking of IgE antibodies and release of cell mediators that cause allergy symptoms. Although this process is quite well-understood, very little is known about the epitopes on the allergen recognized by IgE, despite the importance of the allergen-antibody interaction for the allergic response to occur. This review discusses efforts to analyze allergen-antibody interactions, from the original epitope mapping studies using linear peptides or recombinant allergen fragments, to more sophisticated technologies, such as X-ray crystallography and nuclear magnetic resonance. These state-of-the-art approaches, combined with site-directed mutagenesis, have led to the identification of conformational IgE epitopes. The first structures of an allergen (egg lysozyme) in complex with Fab fragments from IgG antibodies were determined in the 1980s. Since then, IgG has been used as surrogate for IgE, due to the difficulty of obtaining monoclonal IgE antibodies. Technical developments including phage display libraries have contributed to progress in epitope mapping thanks to the isolation of IgE antibody constructs from combinatorial libraries made from peripheral blood mononuclear cells of allergic donors. Most recently, single B cell antibody sequencing and human hybridomas are new breakthrough technologies for finally obtaining human IgE monoclonal antibodies, ideal for epitope mapping. The information on antigenic determinants will facilitate the design of hypoallergens for immunotherapy and the investigation of the fundamental mechanisms of the IgE response.

Egg Allergy: Diagnosis and Immunotherapy

Hypersensitivity or an allergy to chicken egg proteins is a predominant symptomatic condition affecting 1 in 20 children in Australia; however, an effective form of therapy has not yet been found. This occurs as the immune system of the allergic individual overreacts when in contact with egg allergens (egg proteins), triggering a complex immune response. The subsequent instantaneous inflammatory immune response is characterized by the excessive production of immunoglobulin E (IgE) antibody against the allergen, T-cell mediators and inflammation. Current allergen-specific approaches to egg allergy diagnosis and treatment lack consistency and therefore pose safety concerns among anaphylactic patients. Immunotherapy has thus far been found to be the most efficient way to treat and relieve symptoms, this includes oral immunotherapy (OIT) and sublingual immunotherapy (SLIT). A major limitation in immunotherapy, however, is the difficulty in preparing effective and safe extracts from natural allergen sources. Advances in molecular techniques allow for the production of safe and standardized recombinant and hypoallergenic egg variants by targeting the IgE-binding epitopes responsible for clinical allergic symptoms. Site-directed mutagenesis can be performed to create such safe hypoallergens for their potential use in future methods of immunotherapy, providing a feasible standardized therapeutic approach to target egg allergies safely.

Ole e 15 and its human counterpart -PPIA- chimeras reveal an heterogeneous IgE response in olive pollen allergic patients

Olive pollen is a major cause of immunoglobulin E (IgE)-mediated allergy in Mediterranean countries. It is expected to become a worldwide leading allergenic source because olive cultivation is increasing in many countries. Ole e 15 belongs to the cyclophilin pan-allergen family, which includes highly cross-reactive allergens from non-related plant, animal and mold species. Here, the amino acid differences between Ole e 15 and its weak cross-reactive human homolog PPIA were grafted onto Ole e 15 to assess the contribution of specific surface areas to the IgE-binding. Eight Ole e 15-PPIA chimeras were produced in E. coli, purified and tested with 20 sera from Ole e 15-sensitized patients with olive pollen allergy by ELISA experiments. The contribution of linear epitopes was analyzed using twelve overlapping peptides spanning the entire Ole e 15 sequence. All the patients displayed a diverse reduction of the IgE-reactivity to the chimeras, revealing a highly polyclonal and patient-specific response to Ole e 15. IgE-epitopes are distributed across the entire Ole e 15 surface. Two main surface areas containing relevant conformational epitopes have been characterized. This is the first study to identify important IgE-binding regions on the surface of an allergenic cyclophilin.

Chinese Society of Allergy Guidelines for Diagnosis and Treatment of Allergic Rhinitis

Allergic rhinitis (AR) is a global health problem that causes major illnesses and disabilities worldwide. Epidemiologic studies have demonstrated that the prevalence of AR has increased progressively over the last few decades in more developed countries and currently affects up to 40% of the population worldwide. Likewise, a rising trend of AR has also been observed over the last 2-3 decades in developing countries including China, with the prevalence of AR varying widely in these countries. A survey of self-reported AR over a 6-year period in the general Chinese adult population reported that the standardized prevalence of adult AR increased from 11.1% in 2005 to 17.6% in 2011. An increasing number of Journal Articles and imporclinical trials on the epidemiology, pathophysiologic mechanisms, diagnosis, management and comorbidities of AR in Chinese subjects have been published in international peer-reviewed journals over the past 2 decades, and substantially added to our understanding of this disease as a global problem. Although guidelines for the diagnosis and treatment of AR in Chinese subjects have also been published, they have not been translated into English and therefore not generally accessible for reference to non-Chinese speaking international medical communities. Moreover, methods for the diagnosis and treatment of AR in China have not been standardized entirely and some patients are still treated according to regional preferences. Thus, the present guidelines have been developed by the Chinese Society of Allergy to be accessible to both national and international medical communities involved in the management of AR patients. These guidelines have been prepared in line with existing international guidelines to provide evidence-based recommendations for the diagnosis and management of AR in China.

Adjuvants for allergy immunotherapeutics

Allergic diseases are reaching epidemic proportions in developed countries. In particular, food allergy is increasing in prevalence and severity, thus becoming an important socioeconomic burden. Numerous cell types and cell populations, which form an intricate and balanced network, are involved in an immune response. This balance is occasionally disturbed, leading to the onset of different diseases, such as allergic diseases. Antihistamines and corticosteroids provide some degree of relief from the symptoms of allergic conditions. However, the only treatment that can revert the disease is immunotherapy. Nevertheless, specific immunotherapy has at least 2 major drawbacks: it is time-consuming, and it can produce local and even systemic allergic side effects. Immunotherapy's potential goes beyond our current knowledge of the immune response; nevertheless, we can still design strategies to reach a safer immune modulation for treating allergies. This review deals with the use of adjuvants to reduce the undesirable side effects associated with specific allergen immunotherapy. For example, nanoparticles used as immunoadjuvants are offering promising results in preclinical assays.

Modified Allergens for Immunotherapy

PURPOSE OF REVIEW

During the past few decades, modified allergens have been developed for use in allergen-specific immunotherapy (AIT) with the aim to improve efficacy and reduce adverse effects. This review aims to provide an overview of the different types of modified allergens, their mechanism of action and their potential for improving AIT.

RECENT FINDINGS

In-depth research in the field of allergen modifications as well as the advance of recombinant DNA technology have paved the way for improved diagnosis and research on human allergic diseases. A wide range of structurally modified allergens has been generated including allergen peptides, chemically altered allergoids, adjuvant-coupled allergens, and nanoparticle-based allergy vaccines. These modified allergens show promise for the development of AIT regimens with improved safety and long-term efficacy. Certain modifications ensure reduced IgE reactivity and retained T cell reactivity, which facilities induction of immune tolerance to the allergen. To date, multiple clinical trials have been performed using modified allergens. Promising results were obtained for the modified cat, grass and birch pollen, and house dust mite allergens. The use of modified allergens holds promise for improving AIT efficacy and safety. There is however a need for larger clinical studies to reliably assess the added benefit for the patient of using modified allergens for AIT.

Chinese Guideline on allergen immunotherapy for allergic rhinitis

The present document is based on a consensus reached by a panel of experts from Chinese Society of Allergy (CSA) and Chinese Allergic Rhinitis Collaborative Research Group (C2AR2G). Allergen immunotherapy (AIT), has increasingly been used as a treatment for allergic rhinitis (AR) globally, as it has been shown to provide a long-term effect in improving nasal and ocular symptoms, reducing medication need, and improving quality of life. AIT is currently the only curative intervention that can potentially modify the immune system in individuals suffering from AR and prevent the development of new sensitization and the progression of disease from AR to asthma. Although the use of AIT is becoming more acceptable in China, to date no AR immunotherapy guideline from China is available for use by the international community. This document has thus been produced and covers the main aspects of AIT undertaken in China; including selection of patients for AIT, the allergen extracts available on the Chinese market, schedules and doses of allergen employed in different routes of AIT, assessment of effect and safety, patients' administration and follow-up, and management of adverse reactions. The Chinese guideline for AR immunotherapy will thus serve as a reference point by doctors, healthcare professionals and organizations involved in the AIT of AR in China. Moreover, this guideline will serve as a source of information for the international community on AIT treatment strategies employed in China.

Heterologous Expression, Purification and Immunoreactivity of the Antigen 5 from Polybia paulista Wasp Venom

Polybia paulista (Hymenoptera: Vespidae) is responsible for a high number of sting accidents and anaphylaxis events in Southeast Brazil, Argentina and Paraguay. The specific detection of allergy to the venom of this wasp is often hampered by the lack of recombinant allergens currently available for molecular diagnosis. Antigen 5 (~23 kDa) from P. paulista venom (Poly p 5) is a highly abundant and glycosylated allergenic protein that could be used for development of component-resolved diagnosis (CRD). Here, we describe the cloning and heterologous expression of the antigen 5 (rPoly p 5) from P. paulista venom using the eukaryotic system Pichia pastoris. The expression as a secreted protein yielded high levels of soluble rPoly p 5. The recombinant allergen was further purified to homogeneity (99%) using a two-step chromatographic procedure. Simultaneously, the native form of the allergen (nPoly p 5) was purified from the wasp venom by Ion exchange chromatography. The rPoly p 5 and nPoly p 5 were then submitted to a comparative analysis of IgE-mediated immunodetection using sera from patients previously diagnosed with sensitization to wasp venoms. Both rPoly p 5 and nPoly p 5 were recognized by specific IgE (sIgE) in the sera of the allergic individuals. The high levels of identity found between nPoly p 5 and rPoly p 5 by the alignment of its primary sequences as well as by 3-D models support the results obtained in the immunoblot. Overall, we showed that P. pastoris is a suitable system for production of soluble rPoly p 5 and that the recombinant allergen represents a potential candidate for molecular diagnosis of P.paulista venom allergy.

Recombinant Allergens in Structural Biology, Diagnosis, and Immunotherapy

The years 1988-1995 witnessed the beginning of allergen cloning and the generation of recombinant allergens, which opened up new avenues for the diagnosis and research of human allergic diseases. Most crystal and solution structures of allergens have been obtained using recombinant allergens. Structural information on allergens allows insights into their evolutionary biology, illustrates clinically observed cross-reactivities, and makes the design of hypoallergenic derivatives for allergy vaccines possible. Recombinant allergens are widely used in molecule-based allergy diagnosis such as protein microarrays or suspension arrays. Recombinant technologies have been used to produce well-characterized, noncontaminated vaccine components with known biological activities including a variety of allergen derivatives with reduced IgE reactivity. Such recombinant hypoallergens as well as wild-type recombinant allergens have been used successfully in several immunotherapy trials for more than a decade to treat birch and grass pollen allergy. As a more recent application, the development of antibody repertoires directed against conformational epitopes during immunotherapy has been monitored by recombinant allergen chimeras. Although much progress has been made, the number and quality of recombinant allergens will undoubtedly increase and keep improving our knowledge in basic scientific investigations, diagnosis, and therapy of human allergic diseases.

Chimeras of Bet v 1 and Api g 1 reveal heterogeneous IgE responses in patients with birch pollen allergy

BACKGROUND

Characterization of IgE-binding epitopes of allergens and determination of their patient-specific relevance is crucial for the diagnosis and treatment of allergy.

OBJECTIVE

We sought to assess the contribution of specific surface areas of the major birch pollen allergen Bet v 1.0101 to binding IgE of individual patients.

METHODS

Four distinct areas of Bet v 1 representing in total 81% of its surface were grafted onto the scaffold of its homolog, Api g 1.0101, to yield the chimeras Api-Bet-1 to Api-Bet-4. The chimeras were expressed in Escherichia coli and purified. IgE binding of 64 sera from Bet v 1-sensitized subjects with birch pollen allergy was determined by using direct ELISA. Specificity was assessed by means of inhibition ELISA.

RESULTS

rApi g 1.0101, Api-Bet-1, Api-Bet-2, Api-Bet-3, and Api-Bet-4 bound IgE from 44%, 89%, 80%, 78%, and 48% of the patients, respectively. By comparing the amount of IgE binding to the chimeras and to rApi g 1.0101, 81%, 70%, 75%, and 45% of the patients showed significantly enhanced IgE binding to Api-Bet-1, Api-Bet-2, Api-Bet-3, and Api-Bet-4, respectively. The minority (8%) of the sera revealed enhanced IgE binding exclusively to a single chimera, whereas 31% showed increased IgE binding to all 4 chimeras compared with rApi g 1.0101. The chimeras inhibited up to 70% of IgE binding to rBet v 1.0101, confirming the specific IgE recognition of the grafted regions.

CONCLUSION

The Bet v 1-specific IgE response is polyclonal, and epitopes are spread across the entire Bet v 1 surface. Furthermore, the IgE recognition profile of Bet v 1 is highly patient specific.

A naturally occurring hypoallergenic variant of vespid Antigen 5 from Polybia scutellaris venom as a candidate for allergen-specific immunotherapy

Stings by insects from the Hymenoptera order are known to cause life-threatening allergic reactions and impair life quality. Despite the effectiveness of conventional vespid venom immunotherapy, more standardized and safer allergy vaccines are required and recombinant hypoallergenic variants are important clinical tools. Antigen 5 is a major allergen of vespid venoms and it was previously reported that Antigen 5 from Polybia scutellaris (Poly s 5) could be a hypoallergenic variant. In this work we assess the immunological behavior and allergenic activity of Poly s 5 in order to explore its suitability for specific immunotherapy. With this aim, recombinant Poly s 5 was expressed in Pichia pastoris and the presence of cross-reactive epitopes with Pol a 5, a known allergenic Antigen 5, was investigated both at the IgG and IgE levels, by ELISA assays and a basophil-mediator release assay respectively. A molecular model was also built to better understand the relationship between immunological and structural aspects. In mice, Poly s 5 induced IgG antibodies which cross-reacted with Pol a 5. However, Poly s 5 induced only minimal amounts of IgE and was a poor inducer of basophil-mediator release, even when the cells were sensitized with Pol a 5-specific IgE. Moreover, Poly s 5-specific serum showed a specific protective activity and was able to inhibit the Pol a 5-induced basophil degranulation. Structural analysis from the molecular model revealed that a few amino acid substitutions in the N-terminal region of Poly s 5 should lead to an alteration of the surface topography and electrostatic potential of the epitopes which could be responsible for its hypoallergenic behavior. These findings, taken as a whole, show that Poly s 5 is likely a naturally occurring hypoallergenic Antigen 5 variant.

Mechanisms underlying allergy vaccination with recombinant hypoallergenic allergen derivatives

Hundred years ago therapeutic vaccination with allergen-containing extracts has been introduced as a clinically effective, disease-modifying, allergen-specific and long-lasting form of therapy for allergy, a hypersensitivity disease affecting more than 25% of the population. Today, the structures of most of the disease-causing allergens have been elucidated and recombinant hypoallergenic allergen derivatives with reduced allergenic activity have been engineered to reduce side effects during allergen-specific immunotherapy (SIT). These recombinant hypoallergens have been characterized in vitro, in experimental animal models and in clinical trials in allergic patients. This review provides a summary of the molecular, immunological and preclinical evaluation criteria applied for this new generation of allergy vaccines. Furthermore, we summarize the mechanisms underlying SIT with recombinant hypoallergens which are thought to be responsible for their therapeutic effect.

IgE-binding epitopes: a reappraisal

Here, we discuss various questions related to IgE epitopes: What are the technical possibilities and pitfalls, what is currently known, how can we put this information into hypothetical frameworks and the unavoidable question: how useful is this information for patient care or allergenicity prediction? We discuss the information obtained by (i) 3D structures of allergen-antibody complexes; (ii) analysis of allergen analogues; (iii) mimics without obvious structural similarity; (iv) mAbs competing with IgE; (v) repertoire analysis of cloned IgEs, and other developments. Based on limited data, four suggestions are presented in the literature: (i) IgE might be more cross-reactive than IgG; (ii) IgE might be more often directed to immunologically 'uninviting' surfaces; (iii) IgE epitopes may tend to cluster and (iv) IgE paratopes might have a higher intrinsic flexibility. While these are not proven facts, they still can generate hypotheses for future research. The hypothesis is put forward that the IgE repertoire of switched B-cells is less influenced by positive selection, because positive selection might not be able to rescue IgE-switched B cells. While this might be of interest for the discussion about mechanisms leading to allergen-sensitization, we need to be modest in answering the 'clinical relevance' question. Current evidence indicates the IgE-epitope repertoire is too big to make specific IgE epitopes a realistic target for diagnosis, treatment or allergenicity prediction. In-depth analysis of a few selected IgE epitope-peptides or mimitopes derived from allergen-sequences and from random peptide libraries, respectively, might well prove rewarding in relation to diagnosis and prognosis of allergy, particularly food allergy.

Peptide and recombinant immunotherapy

Because of the need to standardize allergen immunotherapy and the desire to reduce allergic adverse events during therapy, a transition to recombinant/synthetic hypoallergenic approaches is inevitable. Evidence supports the notion that effective therapy can be delivered using a limited panel of allergens or even epitopes, weakening the argument that all allergens must be present for optimal efficacy. Moreover, standardized products will allow direct comparisons between studies and, for the first time, immunotherapy studies will be truly blinded, allowing an accurate assessment of the actual treatment effect that can be achieved with this form of intervention.

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.

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.

Characterization of a cashew allergen, 11S globulin (Ana o 2), conformational epitope

Both linear and conformational epitopes likely contribute to the allergenicity of tree nut allergens, yet, due largely to technical issues, few conformational epitopes have been characterized. Using the well studied recombinant cashew allergen, Ana o 2, an 11S globulin or legumin, we identified a murine monoclonal antibody which recognizes a conformational epitope and competes with patient IgE Ana o 2-reactive antibodies. This epitope is expressed on the large subunit of Ana o 2, but only when associated with an 11S globulin small subunit. Both Ana o 2 and the homologous soybean Gly m 6 small subunits can foster epitope expression, even when the natural N-terminal to C-terminal subunit order is reversed in chimeric molecules. The epitope, which is also expressed on native Ana o 2, is readily susceptible to destruction by physical and chemical denaturants.

Dialyzed venom skin tests for identifying yellow jacket-allergic patients not detected using standard venom

BACKGROUND

The chance of a nonspecific intradermal skin test response at venom concentrations greater than 1.0 microg/mL limits the diagnostic range and can interfere with the diagnosis of some affected patients.

OBJECTIVE

To compare the diagnostic ranges and clinical detection rates of skin tests using dialyzed yellow jacket venom (DYJV) and undialyzed YJV (UYJV), particularly in patients who have had negative venom skin test results.

METHODS

Both DYJV and UYJV from the same original lot were diluted from 100 microg/mL to skin test concentrations of 0.01, 0.1, 1.0, 3.0, and 10 microg/mL. Participants included 10 nonallergic controls, 20 patients with a positive history and positive skin test results using UYJV, and 24 patients with a positive history but negative skin test results using UYJV (17 of whom had a positive IgE anti-YJV serology).

RESULTS

Dialyzed venom skin test results were positive at 10 microg/mL or less in 79% of patients with a positive history but negative skin test reactions using UYJV. The dialyzed venom skin test results showed a half-log shift to the left from the undialyzed venom results in linear regression analysis, indicating a greater detection rate with skin tests using DYJV. Results of skin tests with dialyzed venom were positive in 3 of 4 patients who had negative undialyzed venom skin test results and who experienced a systemic reaction to challenge stings.

CONCLUSIONS

The DYJV improves the ability of skin tests to detect yellow jacket allergy and should be subject to further study.

Comprehensive 3D-modeling of allergenic proteins and amino acid composition of potential conformational IgE epitopes

Similarities in sequences and 3D structures of allergenic proteins provide vital clues to identify clinically relevant immunoglobulin E (IgE) cross-reactivities. However, experimental 3D structures are available in the Protein Data Bank for only 5% (45/829) of all allergens catalogued in the Structural Database of Allergenic Proteins (SDAP, http://fermi.utmb.edu/SDAP). Here, an automated procedure was used to prepare 3D-models of all allergens where there was no experimentally determined 3D structure or high identity (95%) to another protein of known 3D structure. After a final selection by quality criteria, 433 reliable 3D models were retained and are available from our SDAP Website. The new 3D models extensively enhance our knowledge of allergen structures. As an example of their use, experimentally derived "continuous IgE epitopes" were mapped on 3 experimentally determined structures and 13 of our 3D-models of allergenic proteins. Large portions of these continuous sequences are not entirely on the surface and therefore cannot interact with IgE or other proteins. Only the surface exposed residues are constituents of "conformational IgE epitopes" which are not in all cases continuous in sequence. The surface exposed parts of the experimental determined continuous IgE epitopes showed a distinct statistical distribution as compared to their presence in typical protein-protein interfaces. The amino acids Ala, Ser, Asn, Gly and particularly Lys have a high propensity to occur in IgE binding sites. The 3D-models will facilitate further analysis of the common properties of IgE binding sites of allergenic proteins.

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.

Genetically engineered hybrid proteins from Parietaria judaica pollen for allergen-specific immunotherapy

BACKGROUND

Despite the use of conventional allergen-specific immunotherapy in clinical practice, more defined, efficient, and safer allergy vaccines are required.

OBJECTIVE

The aim of the study was to obtain hypoallergenic molecules by deleting B-cell epitopes, which could potentially be applied to Parietaria judaica pollen allergy treatment.

METHODS

Three hybrid molecules (Q1, Q2, and Q3) derived from fragments of the 2 major P judaica pollen allergens, Par j 1 and Par j 2, were engineered by means of PCR. Hybrid structures were compared with their natural components by means of circular dichroism, and their biologic activities were compared by using T-cell proliferation assays. Their IgE-binding activity was determined with Western blotting, skin prick tests, and enzyme allergosorbent and ELISA inhibition tests.

RESULTS

The hybrid proteins, especially Q2 and Q3, revealed significantly reduced IgE reactivity compared with the natural allergens, as well as with the whole P judaica extract. Furthermore, in vivo skin prick tests showed that the hybrid proteins had a significantly lower potency to induce cutaneous reactions than the whole P judaica extract. Two (Q1 and Q2) of the 3 hybrid proteins induced a comparable T-cell proliferation response as that produced by the whole extract and natural allergens.

CONCLUSION

Considering its reduced anaphylactogenic potential, together with its conserved T-cell reactivity, the engineered Q2 protein could be used in safe and shortened schedules of allergen-specific immunotherapy against P judaica pollen allergy.

CLINICAL IMPLICATIONS

Recombinant hybrid Q2 is able to induce T-cell proliferation, thus evidencing a potential therapeutic effect. Its reduced IgE-binding capacity envisages an excellent safety profile.

A recombinant allergen chimer as novel mucosal vaccine candidate for prevention of multi-sensitivities

BACKGROUND

As conventional immunotherapy is less efficacious in patients with allergic multi-sensitivities compared with mono-sensitized subjects, new intervention strategies are needed. Therefore, an allergen chimer was genetically engineered for treatment of multi-sensitization with birch and grass pollen on the basis of mucosal tolerance induction.

METHODS

The major birch pollen allergen Bet v 1 served as a scaffold for N- and C-terminal linkage of the immunodominant peptides of the grass pollen allergens Phl p 1 and Phl p 5 and this new construct was cloned and expressed in Escherichia coli. After purification, physicochemical and immunological characterization the chimer was used for intranasal tolerance induction prior to poly-sensitization with Bet v 1, Phl p 1 and Phl p 5.

RESULTS

The immunological characterization revealed that the conformation of Bet v 1 within the chimer was comparable to that of natural as well as recombinant Bet v 1. The chimer was immunogenic in mice for T and B cell responses to the three allergens. Intranasal application of the chimer prior to poly-sensitization significantly suppressed humoral and cellular allergen-specific Th2 responses and prevented development of airway inflammation upon allergen challenge. Moreover, local allergen-specific IgA antibodies were induced by the chimer. The mechanisms of poly-tolerance induction seemed to be mediated by regulatory cytokines, since TGF-beta and IL-10 mRNA in splenocytes were upregulated and tolerance was transferable with these cells.

CONCLUSION

The data indicate that such allergen chimers harboring several unrelated allergens or allergen peptides could serve as mucosal polyvalent vaccines for prevention of multi-sensitivities.

Immunological mechanisms of allergen-specific immunotherapy

Allergen-specific immunotherapy has been carried out for almost a century and remains one of the few antigen-specific treatments for inflammatory diseases. The mechanisms by which allergen-specific immunotherapy exerts its effects include the modulation of both T-cell and B-cell responses to allergen. There is a strong rationale for improving the efficacy of allergen-specific immunotherapy by reducing the incidence and severity of adverse reactions mediated by IgE. Approaches to address this problem include the use of modified allergens, novel adjuvants and alternative routes of administration. This article reviews the development of allergen-specific immunotherapy, our current understanding of its mechanisms of action and its future prospects.

Hymenoptera venom allergens

Hymenoptera venoms each contain a variety of protein allergens. The major components have all been characterized, and most of the amino acid sequences are known. This article concentrates on the use of contemporary techniques including cloning, mass spectrometry and genomics in the characterization of venom allergens, and newer separation techniques for protein isolation. Examples of the use of these techniques with venom proteins are presented.

Bacterial fermentation of recombinant major wasp allergen Antigen 5 using oxygen limiting growth conditions improves yield and quality of inclusion bodies

A process for bacterial expression and purification of the recombinant major wasp allergen Antigen 5 (Ves v 5) was developed to produce protein for diagnostic and therapeutic applications for type 1 allergic diseases. Special attention was focused on medium selection, fermentation conditions, and efficient refolding procedures. A soy based medium was used for fermentation to avoid peptone from animal origin. Animal-derived peptone required the use of isopropyl-beta-D-thiogalactopyranoside (IPTG) for the induction of expression. In the case of soy peptone, a constitutive expression was observed, suggesting the presence of a component that mimics IPTG. Batch cultivation at reduced stirrer speed caused a reduced biomass due to oxygen limitation. However, subsequent purification and processing of inclusion bodies yielded significantly higher amount of product. Furthermore, the protein composition of the inclusion bodies differed. Inclusion bodies were denatured and subjected to diafiltration. Detailed monitoring of diafiltration enabled the determination of the transition point. Final purification was conducted using cation-exchange and size-exclusion chromatography. Purified recombinant Ves v 5 was analyzed by RP-HPLC, CD-spectroscopy, SDS-PAGE, and quantification ELISA. Up to 15 mg highly purified Ves v 5 per litre bioreactor volume were obtained, with endotoxin concentrations less than 20 EU mg(-1) protein and high comparability to the natural counterpart. Analytical results confirm the suitability of the recombinant protein for diagnostic and clinical applications. The results clearly demonstrate that not only biomass, but especially growth conditions play a key role in the production of recombinant Ves v 5. This has an influence on inclusion body formation, which in turn influences the renaturation rate and absolute product yield. This might also be true for other recombinant proteins that accumulate as inclusion bodies in Escherichia coli.

Molecular design of allergy vaccines

Recombinant-allergen-based diagnostic tests enable the dissection and monitoring of the molecular reactivity profiles of allergic patients, resulting in more specific diagnosis, disease monitoring, prevention and therapy. In vitro experiments, animal studies and clinical trials in patients demonstrate that allergenic molecules can be engineered to induce different immune responses ranging from tolerance to vigorous immunity. The available data thus suggest that molecular engineering of the disease-related antigens is a technology that may be applicable not only for the design of allergy vaccines but also for the design of vaccines against infectious diseases, autoimmunity and cancer.

Genetically engineered vaccines

The application of recombinant DNA technology to allergen research has provided the sequence information and genetic material to produce new types of allergy vaccines. One general strategy has been to use the knowledge to produce synthetic peptides that represent selected T-cell or B-cell epitopes. The production of genetically engineered allergens provides an alternative strategy to construct hypoallergenic vaccines, which can provide a better and less selected representation of the epitopes. Many strategies have been used to produce such hypoallergens, and their ability to reduce allergenicity has been amply demonstrated by skin and nasal provocation tests. The retention of T cell-stimulating activity has also been demonstrated, and a consistent feature of the vaccines has been, despite the reduced immunoglobulin E (IgE)-binding reactivity, the ability to induce anti-allergen IgG antibody. The lead hypoallergens have been polypeptide fragments and trimeric constructs of the birch allergen Bet v 1. A clinical trial with these medicaments has shown the ability to modify IgE and IgG antibody production, skin test reactivity, and symptom scores. This is the first trial of a recombinant allergy vaccine, and it has set a benchmark for further studies. A new generation of hypoallergens is now being produced based on the detailed knowledge of the tertiary structures of the allergens and of the T-cell and B-cell epitopes. The modifications have been made to change the topography of the allergens while retaining a stable, folding structure. In the case of Bet v 1, tertiary structures of hypoallergens have been determined. Structurally modeled hypoallergens have been produced for pollen, venom, food, and latex allergens, with promising characteristics from preclinical studies.

Characterization of the human T cell response to antigen 5 from Vespula vulgaris (Ves v 5)

BACKGROUND

The T cell reactivity to the major allergen of bee venom, phospholipase A2, has been thoroughly characterized. In contrast, only little is known about the human cellular response to major allergens from wasp venom.

OBJECTIVE

To characterize the human T cell response to antigen 5 from Vespula vulgaris, Ves v 5.

METHODS

Recombinant Ves v 5 was used to establish allergen-specific T cell lines (TCL) and T cell clones (TCC) from the peripheral blood of vespid-allergic and non-allergic individuals. Ves v 5-specific TCL were mapped for T cell epitopes using overlapping synthetic peptides representing the complete amino acid sequence of Ves v 5. Ves v 5-specific TCC were analysed for antigen-induced secretion of IL-4, IFN-gamma and IL-10.

RESULTS

Seventeen distinct T cell epitopes were recognized by allergic individuals among which Ves v 5(181-192) was identified as a dominant T cell epitope. Partially different epitopes were observed in TCL from non-allergic subjects and the dominant epitope Ves v 5(181-192) was not prevalent in these cultures. Ves v 5-specific TCC isolated from allergic individuals did not show the typical T helper type 2 (Th2)-like cytokine profile in response to specific stimulation, i.e. high amounts of IL-4 and low IFN-gamma. TCC from non-allergic individuals showed a Th1-like cytokine pattern.

CONCLUSIONS

Our findings provide evidence that the allergic T cell response to Ves v 5 is not Th2-dominated and that different immunogenic sites on this major wasp venom allergen are recognized by allergic and non-allergic individuals.

Crystal Structures of Recombinant Human Purple Acid Phosphatase With and Without an Inhibitory Conformation of the Repression Loop

The crystal structure of human purple acid phosphatase recombinantly expressed in Escherichia coli (rHPAP(Ec)) and Pichia pastoris (rHPAP(Pp)) has been determined in two different crystal forms, both at 2.2A resolution. In both cases, the enzyme crystallized in its oxidized (inactive) state, in which both Fe atoms in the dinuclear active site are Fe(III). The main difference between the two structures is the conformation of the enzyme "repression loop". Proteolytic cleavage of this loop in vivo or in vitro results in significant activation of the mammalian PAPs. In the crystals obtained from rHPAP(Ec), the carboxylate side-chain of Asp145 of this loop acts as a bidentate ligand that bridges the two metal atoms, in a manner analogous to a possible binding mode for a phosphate ester substrate in the enzyme-substrate complex. The carboxylate side-chain of Asp145 and the neighboring Phe146 side-chain thus block the active site, thereby inactivating the enzyme. In the crystal structure of rHPAP(Pp), the enzyme "repression loop" has an open conformation similar to that observed in other mammalian PAP structures. The present structures demonstrate that the repression loop exhibits significant conformational flexibility, and the observed alternate binding mode suggests a possible inhibitory role for this loop.

The major human structural IgE epitope of the Brazil nut allergen Ber e 1: a chimaeric and protein microarray approach

A protein microarray system containing different dilutions of 77 related and non-related proteins was used to show that IgE from subjects allergic to Brazil nut specifically recognise the seed 2S albumin protein (Ber e 1). Further, correctly folded chimaeric 2S albumin proteins containing structural epitope replacement were constructed and directed to the secretion pathway of the methylotropic yeast Pichia pastoris. Through the use of a chimaeric protein microarray system together with sera from a panel of 18 well-characterised Brazil nut allergic subjects, a structural IgE epitope of Ber e 1 was mapped to a helix-loop-helix region. The same structural region has been previously reported as the immunodominant region in related food allergens by different techniques. In conclusion, the combination of chimaeric proteins and protein microarrays will greatly facilitate the screening of a large number of individuals for a particular structural epitope and help to further our understanding of how proteins are recognised by the adaptive immune system.

Distribution of vespid species in Europe

PURPOSE OF REVIEW

Knowledge of the different stinging vespids found in various parts of Europe and their venom cross-reactivity is important in order to improve the venoms available for diagnostic and therapeutic purposes.

RECENT FINDINGS

In recent years the amino acid sequences of different vespid venom allergens have been determined. Comparison of these sequences has led to an improved taxonomical classification of vespids compared with that based on morphological differences. However, the distribution of vespids in Europe is still based on a very good but somewhat old study carried out in the 1970s. Most recent epidemiological studies focus on the type of reaction produced rather than the insect responsible.

SUMMARY

The genera Vespula, Dolichovespula and Vespa are found all over Europe, but the genus Polistes, although present in central Europe, is not found in the UK and only represents a specific clinical problem in areas around the Mediterranean sea. Although there are significant differences in the distribution of stings, the genus Vespula predominates over Polistes and Vespa throughout Europe, except in Mediterranean areas. The different species of Polistes in Europe show a great similarity in the sequences of their venom allergens, but the similarity to their American counterparts is less marked. Vespula allergens show up to 95% sequence identity and almost complete cross-reactivity. There is also great cross-reactivity among the genera Vespula, Vespa and Dolichovespula. This identity of amino acid sequences confirms the latest morphological taxonomy of Hymenoptera and opens the way for the use of recombinant hybrids of different species in venom immunotherapy.

Mechanisms of immunotherapy: IgG revisited

PURPOSE OF REVIEW

This paper will review historical and recent evidence for the induction of 'blocking' IgG antibodies during successful specific immunotherapy.

RECENT FINDINGS

Specific immunotherapy is frequently associated with a rise in allergen-specific IgG4 antibodies and a modest reduction in specific IgE titres, although this does not always correlate with clinical efficacy. There is accumulating evidence that specific immunotherapy also influences the blocking activity on IgE-mediated responses by IgG4, and cellular assays are commonly used to investigate these changes. Recently, a novel assay, which detects allergen-IgE binding using flow cytometry, has been used to detect 'functional' specific immunotherapy-induced changes in IgG antibody activity. Results suggest that successful specific immunotherapy is associated with an increase in IgG blocking activity that is not solely dependent on the quantity of IgG antibodies.

SUMMARY

Successful immunotherapy is associated with quantitative and qualitative changes in the allergen-specific IgG antibody response. The induction of IgG antibodies with blocking activity may have a protective role not only through the inhibition of allergen-induced, IgE-mediated release of inflammatory mediators from mast cells and basophils, but also through the inhibition of IgE-facilitated antigen presentation to T cells. Qualitative changes in the allergen-specific IgG antibody response may possibly be an important mechanism underlying the clinical efficacy of specific immunotherapy. Monitoring changes in blocking activity using cellular assays may give an early indication of the potential success of treatment.

Alteration of the tertiary structure of the major bee venom allergen Api m 1 by multiple mutations is concomitant with low IgE reactivity

We have engineered a recombinant form of the major bee venom allergen (Api m 1) with the final goal of reducing its IgE reactivity. This molecule (Api mut) contains 24 mutations and one deletion of 10 amino acids. The successive introduction of these sequence modifications led to a progressive loss of specific IgE and IgG reactivity and did not reveal any immunodominant epitopes. However, Api mut exhibited a clear loss of reactivity for Api m 1-specific IgE and IgG. Injection of Api mut into mice induced specific antibody production. This humoral response was as high as that induced by the Api m 1 but the cross-reactivity of the antibodies was weak. As inferred by far UV circular dichroism, this mutant was correctly folded. However, near UV circular dichroism and denaturation curves of Api mut showed that it exhibits a dynamic tertiary structure and that it is a highly flexible molecule. Finally, as all the sequence modifications have been introduced outside the human and murine T cell epitope regions, we investigated its T cell properties in mice. We showed that Api mut-specific T lymphocytes induced in vivo were stimulated in vitro by both proteins. These data provide new insights in the design of hypoallergenic molecules.

The recombinant major allergen of Parietaria judaica and its hypoallergenic variant: in vivo evaluation in a murine model of allergic sensitization

BACKGROUND

Par j 1 represents the major allergenic component of Parietaria judaica pollen. Its three-dimensional structure is stabilized by four disulphide bridges. A family of three-dimensional mutants of the recombinant Par j 1 (rPar j 1) allergen, showing reduced allergenicity and retained T cell recognition has been recently developed by site-directed mutagenesis.

OBJECTIVE

To develop and characterize a murine model of IgE sensitization to rPar j 1. To evaluate similarities between the murine model and the human IgE response. To investigate in this model the recognition of a hypoallergenic mutant of Par j 1, and to study the immune responses elicited in mice by the mutant itself.

METHODS

BALB/c mice were sensitized by two intraperitoneal immunizations with rPar j 1 in alum on days 0 and 21. Allergen-specific serum IgE and IgG responses were studied by direct ELISA and immunoblotting, ELISA inhibition and competitive ELISA. Cell proliferation was evaluated in splenocyte cultures.

RESULTS

Sensitization with rPar j 1 induced high levels of IgE and IgG1 vs. low levels of IgG2a. Mouse antibodies specific to rPar j 1 were able to compete with human IgE for recognition of rPar j 1. IgE from mice immunized with rPar j 1 showed a significantly reduced binding activity towards the hypoallergenic variant rPjC, which lacks three disulphide bridges. On the contrary, rPjC was recognized by IgG1 and IgG2a antibodies as well as rPar j 1. The proliferative response to rPjC by splenocytes from mice immunized with rPar j 1 was comparable to that stimulated by rPar j 1. Immunization with rPjC induced low levels of IgE antibodies to the rPjC itself, while IgG and proliferative responses were similar to those induced by rPar j 1.

CONCLUSION

Conformational variants of allergens, displaying reduced allergenicity accompanied by retained IgG and T cell recognition, offer a safe, specific and flexible approach to immunotherapy of type I allergy. Our mouse model of IgE sensitization to a recombinant allergen, mimicking the human response to its native counterpart, could provide valuable information for pre-clinical testing of such hypoallergenic molecules.

Can we genetically engineer safer and more effective immunotherapy reagents?

PURPOSE OF REVIEW

Progress in allergen-specific immunotherapy, the only causative form of allergy treatment, was limited by the lack of defined allergen molecules for vaccine formulation. Today the genetic informations for the most common allergens have been obtained. Here we review recombinant allergen-based technologies for the improvement of diagnosis and therapy of allergy.

RECENT FINDINGS

Numerous strategies, including the genetic engineering of allergens for reduction of allergenic activity, have been developed to improve allergen-specific immunotherapy. Genetically modified allergen derivatives with reduced allergenic activity, preserved T cell epitope repertoire and retained immunogenicity have been characterized in vitro and in vivo.

SUMMARY

Based on the review of the recently published data we argue that it is possible to genetically engineer safer and more effective immunotherapy reagents.

Par j 1 and Par j 2, the major allergens from Parietaria judaica pollen, have similar immunoglobulin E epitopes

BACKGROUND

Parietaria judaica is the main cause of allergy in Mediterranean countries. The major allergens from P. judaica pollen, Par j 1 and Par j 2, have amino acid sequence identity of 45% and contain eight cysteine residues involved in disulphide bonds that compact the structure.

OBJECTIVE

The aim of the study was to identify IgE-binding epitopes on Par j 1 and Par j 2, the major allergens from P. judaica pollen and correlate them with the three-dimensional structure of the proteins.

METHODS

Overlapping peptides representing the complete length of Par j 1 and Par j 2 were synthesized on a cellulose-derivatized membrane. Sera from 17 P. judaica-allergenic patients were used to identify IgE-binding epitopes. Homology modelling of the three dimensional structure of both allergens was generated using the Swiss-Model software on the basis of previously reported crystal structures.

RESULTS

Five and eight IgE-binding epitopes were identified on Par j 1 and Par j 2 allergens, respectively. Both proteins belonged to the non-specific lipid transfer proteins (ns-LTP) family and therefore a three-dimensional model of both allergens was constructed on the basis of the maize ns-LTP crystal structure. Par j 1 and Par j 2 allergens have three similar allergenic epitopes with high homology and identical conformation.

CONCLUSION

Three similar IgE-epitopes of major allergens from P. judaica have been described. They could be good candidates for designing of IgE haptens as therapeutic agents with reduced anaphylactic side-effects or for developing hypoallergenic variants of these major allergens.

From allergen structure to new forms of allergen-specific immunotherapy

During the past decade, genetic information for most of the common allergens has been obtained. Using these genetic blueprints it has become possible to reconstruct, by recombinant DNA technology, almost complete repertoires of the relevant allergens and their epitopes. Recombinant allergens with the allergenic features of naturally occurring allergens have promoted allergy research and form the basis of new multiallergen tests for refined allergy diagnosis. Allergen derivatives with reduced allergenic activity have also been produced by recombinant DNA technology to increase safety and specificity of allergen-specific immunotherapy. These derivatives can be engineered to contain relevant T cell epitopes and to maintain those sequence motifs which are required for inducing protective antibody responses and therefore hold great promise for improving allergen-specific immunotherapy.

Structural and immunological aspects of Polybia scutellaris Antigen 5

Vespid venoms contain Antigen 5, an important allergen whose primary structure and immunological behavior have been extensively studied from venoms of vespids of the Northern Hemisphere. We report herein structural and immunological aspects of Antigen 5 from Polybia scutellaris subspecies rioplatensis (vulgar name: camoati) found in South America. Mast cell degranulation, histamine release, and IgE induction experiments performed in mice allow us to suggest that P. scutellaris Antigen 5 is a variant with reduced IgE response and anaphylactic activity. Sequence data indicate that the protein has a 72.5-90.3% similarity to that of members of the vespid Antigen 5 family with an already known primary structure. Moreover, results suggest that the protein-a new member of an extracellular protein superfamily-could be a good candidate for immunotherapy related to vespid allergy.

The major conformational IgE-binding epitopes of hevein (Hev b6.02) are identified by a novel chimera-based allergen epitope mapping strategy

A novel approach to localize and reconstruct conformational IgE-binding epitope regions of hevein (Hev b6.02), a major natural rubber latex allergen, is described. An antimicrobial protein (AMP) from the amaranth Amaranthus caudatus was used as an immunologically non-IgE-binding adaptor molecule to which terminal or central parts of hevein were fused. Hevein and AMP share a structurally identical core region but have different N-terminal and C-terminal regions. Only 1 of 16 hevein-allergic patients showed weak IgE binding to purified native or recombinant AMP. Chimeric AMP with the hevein N terminus was recognized by IgE from 14 (88%) patients, and chimeric AMP with the hevein C terminus was recognized by IgE from 6 (38%) patients. In contrast, chimeric AMP containing the hevein core region was recognized by IgE from only two patients. When both the N-terminal and C-terminal regions of hevein were fused with the AMP core, IgE from all 16 patients bound to the chimera. This chimera was also able to significantly inhibit (>70%) IgE binding to the native hevein. On the contrary, linear synthetic peptides corresponding to hevein regions in the AMP chimeras showed no significant IgE binding capacity in either enzyme-linked immunosorbent assay or inhibition enzyme-linked immunosorbent assay. These results suggest that the IgE binding ability of hevein is essentially determined by its N-terminal and C-terminal regions and that major IgE-binding epitopes of hevein are conformational. The chimera-based epitope mapping strategy described here provides a valuable tool for defining structural epitopes and creating specific reagents for allergen immunotherapy.

Can knowledge of the molecular structure of allergens improve immunotherapy?

Conventional immunotherapy may be associated with the development of adverse reactions, including anaphylaxis, due to the use of increasing doses of allergen. Standardization of extracts is necessary in order to assess the correct amount of allergen administered. In recent years, increased knowledge on the molecular structure of allergens has allowed the development of novel alternatives for immunotherapy. Initially, allergens were cloned and expressed as recombinant proteins in eukaryotic and prokaryotic systems. Crystallization of the purified proteins led to the elucidation of the tertiary structure of the allergen. Molecular biology techniques were used to construct modified allergens whose new IgE binding properties were studied. IgE antibody mapping combined with molecular modeling has allowed the recognition of IgE binding sites on the surface of the molecule. This information has been applied to the engineering of new modified allergens, with and without adjuvants, that retain immunogenicity but with reduced allergenicity. The use of these molecules for immunotherapy should allow the administration of greater doses of allergen, without the undesired side effects characteristic of conventional immunotherapy.