Conversion of grass pollen allergen-specific human IgE into a protective IgG(1) antibody

Clonal evolution and stereotyped sequences of human IgE lineages in aeroallergen-specific immunotherapy

BACKGROUND

Allergic disease reflects specific inflammatory processes initiated by interaction between allergen and allergen-specific IgE. Specific immunotherapy (SIT) is an effective long-term treatment option, but the mechanisms by which SIT provides desensitization are not well understood.

OBJECTIVE

Our aim was to characterize IgE sequences expressed by allergen-specific B cells over a 3-year longitudinal study of patients with aeroallergies who were undergoing SIT.

METHODS

Allergen-specific IgE-expressing clones were identified by using combinatorial single-chain variable fragment libraries and tracked in PBMCs and nasal biopsy samples over a 3-year period with antibody gene repertoire sequencing. The characteristics of private IgE-expressing clones were compared with those of stereotyped or "public" IgE responses to the grass pollen allergen Phleum pratense (Phl p) 2.

RESULT

Members of the same allergen-specific IgE lineages were observed in nasal biopsy samples and blood, and lineages detected at baseline persisted in blood and nasal biopsy samples after 3 years of SIT, including B cells that express IgE. Evidence of progressive class switch recombination to IgG subclasses was observed after 3 years of SIT. A common stereotyped Phl p 2-specific antibody heavy chain sequence was detected in multiple donors. The amino acid residues enriched in IgE-stereotyped sequences from seropositive donors were analyzed with machine learning and k-mer motif discovery. Stereotyped IgE sequences had lower overall rates of somatic hypermutation and antigen selection than did single-chain variable fragment-derived allergen-specific sequences or IgE sequences of unknown specificity.

CONCLUSION

Longitudinal tracking of rare circulating and tissue-resident allergen-specific IgE+ clones demonstrates persistence of allergen-specific IgE+ clones, progressive class switch recombination to IgG subtypes, and distinct maturation of a stereotyped Phl p 2 clonotype.

Allergen immunotherapy: progress and future outlook

INTRODUCTION

Allergy, the immunological hypersensitivity to innocuous environmental compounds, is a global health problem. The disease triggers, allergens, are mostly proteins contained in various natural sources such as plant pollen, animal dander, dust mites, foods, fungi and insect venoms. Allergies can manifest with a wide range of symptoms in various organs, and be anything from just tedious to life-threatening. A majority of all allergy patients are self-treated with symptom-relieving medicines, while allergen immunotherapy (AIT) is the only causative treatment option.

AREAS COVERED

This review will aim to give an overview of the state-of-the-art allergy management, including the use of new biologics and the application of biomarkers, and a special emphasis and discussion on current research trends in the field of AIT.

EXPERT OPINION

Conventional AIT has proven effective, but the years-long treatment compromises patient compliance. Moreover, AIT is typically not offered in food allergy. Hence, there is a need for new, effective and safe AIT methods. Novel routes of administration (e.g. oral and intralymphatic), hypoallergenic AIT products and more effective adjuvants holds great promise. Most recently, the development of allergen-specific monoclonal antibodies for passive immunotherapy may also allow treatment of patients currently not treated or treatable.

Allergen desensitization reduces the severity of relapsed alopecia areata in dust-mite allergic patients

Atopy may be a facilitating factor in some alopecia areata (AA) patients with early disease onset and more severe/extensive AA. The underlying immune mechanisms are unknown, but allergen responses may support a pro-inflammatory environment that indirectly promotes AA. To investigate the long-term effect of allergen immunotherapy (AIT) against house dust mite (HDM) allergy on disease severity and prognosis for AA patients. An observational comparative effectiveness study was conducted on 69 AA patients with HDM allergy. 34 patients received conventional/traditional AA treatment (TrAA) plus AIT (AIT-TrAA), and 35 patients received TrAA alone. Serum total immunoglobulin E (tIgE), HDM specific IgE (sIgE), HDM specific IgG4 (sIgG4) and cytokines (IL-4, IL-5, IL-10, IL-12, IL-13, IL-33, IFNγ) were quantified in these patients, together with 58 non-allergic AA patients and 40 healthy controls. At the end of the 3-year desensitization course, the AIT-TrAA group presented with lower SALT scores than the TrAA group, especially in non-alopecia totalis/universalis (AT/U) patients and pre-adolescent AT/U patients (age ≤ 14). In patients with elevated tIgE levels before AIT, a decrease in tIgE was correlated to reduced extent of AA on completion of the AIT course. After desensitization, elevation of IL-5 and decrease of IL-33 were observed in HDM allergic-AA patients. Desensitization to HDM in allergic AA patients reduces the severity of relapse-related hair loss over the 3-year AIT treatment course, possibly via opposing Th2 dominance. This adjunctive treatment may help reduce disease severity and curtail the disease process in allergic patients with AA.

Antibody Conjugates Bispecific for Pollen Allergens and ICAM-1 with Potential to Prevent Epithelial Allergen Transmigration and Rhinovirus Infection

Allergy and rhinovirus (RV) infections are major triggers for rhinitis and asthma, causing a socioeconomic burden. As RVs and allergens may act synergistically to promote airway inflammation, simultaneous treatment strategies for both causative agents would be innovative. We have previously identified the transmembrane glycoprotein intercellular adhesion molecule 1 (ICAM-1) as an anchor for antibody conjugates bispecific for ICAM-1 and Phleum pratense (Phl p) 2, a major grass pollen allergen, to block allergen transmigration through the epithelial barrier. Since ICAM-1 is a receptor for the major group RVs, we speculated that our bispecific antibody conjugates may protect against RV infection. Therefore, we created antibody conjugates bispecific for ICAM-1 and the major grass pollen allergen Phl p 5 and analyzed their capacity to affect allergen penetration and RV infection. Bispecific antibody conjugates significantly reduced the trans-epithelial migration of Phl p 5 and thus the basolateral Phl p 5 concentration and allergenic activity as determined by humanized rat basophilic leukemia cells and inhibited RV infection of cultured epithelial cells. A reduction in allergenic activity was obtained only through the prevention of allergen transmigration because the Phl p 5-specific IgG antibody did not block the allergen-IgE interaction. Our results indicate the potential of allergen/ICAM-1-specific antibody conjugates as a topical treatment strategy for allergy and RV infections.

Review: The Nose as a Route for Therapy. Part 2 Immunotherapy

The nose provides a route of access to the body for inhalants and fluids. Unsurprisingly it has a strong immune defense system, with involvement of innate (e.g., epithelial barrier, muco- ciliary clearance, nasal secretions with interferons, lysozyme, nitric oxide) and acquired (e.g., secreted immunoglobulins, lymphocytes) arms. The lattice network of dendritic cells surrounding the nostrils allows rapid uptake and sampling of molecules able to negotiate the epithelial barrier. Despite this many respiratory infections, including SARS-CoV2, are initiated through nasal mucosal contact, and the nasal mucosa is a significant "reservoir" for microbes including Streptococcus pneumoniae, Neisseria meningitidis and SARS -CoV-2. This review includes consideration of the augmentation of immune defense by the nasal application of interferons, then the reduction of unnecessary inflammation and infection by alteration of the nasal microbiome. The nasal mucosa and associated lymphoid tissue (nasopharynx-associated lymphoid tissue, NALT) provides an important site for vaccine delivery, with cold-adapted live influenza strains (LAIV), which replicate intranasally, resulting in an immune response without significant clinical symptoms, being the most successful thus far. Finally, the clever intranasal application of antibodies bispecific for allergens and Intercellular Adhesion Molecule 1 (ICAM-1) as a topical treatment for allergic and RV-induced rhinitis is explained.

Linear Epitope Binding Patterns of Grass Pollen-Specific Antibodies in Allergy and in Response to Allergen-Specific Immunotherapy

Allergic diseases affect many individuals world-wide and are dependent on the interaction between allergens and antibodies of the IgE isotype. Allergen-specific immunotherapy (AIT) can alter the development of the disease, e.g., through induction of allergen-specific IgG that block allergen-IgE interactions. The knowledge of epitopes recognized by allergy-causing and protective antibodies are limited. Therefore, we developed an allergome-wide peptide microarray, aiming to track linear epitope binding patterns in allergic diseases and during AIT. Here, we focused on immune responses to grass pollen allergens and found that such epitopes were commonly recognized before initiation of AIT and that AIT commonly resulted in increased antibody production against additional epitopes already after 1 year of treatment. The linear epitope binding patterns were highly individual, both for subjects subjected to and for individuals not subjected to AIT. Still, antibodies against some linear epitopes were commonly developed during AIT. For example, the two rigid domains found in grass pollen group 5 allergens have previously been associated to a diversity of discontinuous epitopes. Here, we present evidence that also the flexible linker, connecting these domains, contains regions of linear epitopes against which antibodies are developed during AIT. We also describe some commonly recognized linear epitopes on Phl p 2 and suggest how antibodies against these epitopes may contribute to or prevent allergy in relation to a well-defined stereotyped/public IgE response against the same allergen. Finally, we identify epitopes that induce cross-reactive antibodies, but also antibodies that exclusively bind one of two highly similar variants of a linear epitope. Our findings highlight the complexity of antibody recognition of linear epitopes, with respect to both the studied individuals and the examined allergens. We expect that many of the findings in this study can be generalized also to discontinuous epitopes and that allergen peptide microarrays provide an important tool for enhancing the understanding of allergen-specific antibodies in allergic disease and during AIT.

Structural Phylogeny of Different Allergens May Reveal Common Epitopic Footprint

BACKGROUND

The incidence of allergy is increasing at an alarming rate for the last few decades.

OBJECTIVE

Our present study is focused on finding out the structurally homologous motifs present in different proteinaceous allergens Methods: Significant number of protein sequences and their corresponding structures of various pollen, fungal, bacterial, and food allergens were retrieved, and the sequence and structural identity were analyzed.

RESULTS

Intra- and inter-sequence and their structural analysis of the proteinaceous allergens, resulted in no significant relationships among them. A few, but not negligible number of high structural similarities were observed within different groups of allergens from fungus, angiosperms, and animals (Aves and Mammalia).

CONCLUSION

Our in silico study on thirty-six different allergens showed a significant level of structural similarities among themselves, regardless of their sequences.

Past, present, and future of allergen immunotherapy vaccines

Allergen-specific immunotherapy (AIT) is an allergen-specific form of treatment for patients suffering from immunoglobulin E (IgE)-associated allergy; the most common and important immunologically mediated hypersensitivity disease. AIT is based on the administration of the disease-causing allergen with the goal to induce a protective immunity consisting of allergen-specific blocking IgG antibodies and alterations of the cellular immune response so that the patient can tolerate allergen contact. Major advantages of AIT over all other existing treatments for allergy are that AIT induces a long-lasting protection and prevents the progression of disease to severe manifestations. AIT is cost effective because it uses the patient´s own immune system for protection and potentially can be used as a preventive treatment. However, broad application of AIT is limited by mainly technical issues such as the quality of allergen preparations and the risk of inducing side effects which results in extremely cumbersome treatment schedules reducing patient´s compliance. In this article we review progress in AIT made from its beginning and provide an overview of the state of the art, the needs for further development, and possible technical solutions available through molecular allergology. Finally, we consider visions for AIT development towards prophylactic application.

Nanobodies-Useful Tools for Allergy Treatment?

In the last decade single domain antibodies (nanobodies, VHH) qualified through their unique characteristics have emerged as accepted and even advantageous alternative to conventional antibodies and have shown great potential as diagnostic and therapeutic tools. Currently nanobodies find their main medical application area in the fields of oncology and neurodegenerative diseases. According to late-breaking information, nanobodies specific for coronavirus spikes have been generated these days to test their suitability as useful therapeutics for future outbreaks. Their superior properties such as chemical stability, high affinity to a broad spectrum of epitopes, low immunogenicity, ease of their generation, selection and production proved nanobodies also to be remarkable to investigate their efficacy for passive treatment of type I allergy, an exaggerated immune reaction to foreign antigens with increasing global prevalence.

Mapping Human Monoclonal IgE Epitopes on the Major Dust Mite Allergen Der p 2

IgE Abs drive the symptoms of allergic disease upon cross-linking allergens on mast cells or basophils. If the IgE binding sites on the allergens could be identified, it may be useful for creating new forms of immunotherapy. However, direct knowledge of the human IgE (hIgE) epitopes is limited because of the very low frequency of IgE-producing B cells in blood. A new hybridoma technology using human B cells from house dust mite-allergic patients was used to identify four Der p 2-specific hIgE mAbs. Their relative binding sites were assessed and compared by immunoassays with three previously studied murine IgG mAbs. Immunoassays showed that the recognition of Der p 2 by the first three hIgE was inhibited by a single murine IgG, but the fourth hIgE recognized a different epitope from all the other mAbs. The functional ability of the hIgE that bind different epitopes to cross-link Der p 2 was demonstrated in a mouse model of passive systemic anaphylaxis. Nuclear magnetic resonance analyses of Der p 2 in complex with IgG and IgE Abs were used to identify specific residues in the epitopes. To our knowledge, the combination of immunoassays to distinguish overlapping epitopes and nuclear magnetic resonance analyses to identify specific residues involved in Ab binding provided the first epitope mapping of hIgE mAbs to an allergen. The technologies developed in this study will be useful in high-resolution mapping of human epitopes on other Ags and the design of improved therapeutics.

Quantification, epitope mapping and genotype cross-reactivity of hepatitis B preS-specific antibodies in subjects vaccinated with different dosage regimens of BM32

Background

Chronic hepatitis B virus (HBV) infections are a global health problem. There is a need for therapeutic strategies blocking continuous infection of liver cells. The grass pollen allergy vaccine BM32 containing the preS domain of the large HBV surface protein (LHBs) as immunogenic carrier induced IgG antibodies in human subjects inhibiting HBV infection in vitro. Aim of this study was the quantification, epitope mapping and investigation of HBV genotype cross-reactivity of preS-specific antibodies in subjects treated with different dosage regimens of BM32

Methods

Hundred twenty eight grass pollen allergic patients received in a double-blind, placebo-controlled trial five monthly injections of placebo (aluminum hydroxide, n= 34) or different courses of BM32 (2 placebo + 3 BM32, n= 33; 1 placebo + 4 BM32, n= 30; 5 BM32, n= 31). Recombinant Escherichia coli-expressed preS was purified. Overlapping peptides spanning preS and the receptor-binding sites from consensus sequences of genotypes A–H were synthesized and purified. Isotype (IgM, IgG, IgA, IgE) and IgG subclass (IgG₁-IgG₄) responses to preS and peptides were determined by ELISA at baseline, one and four months after the last injection. IgG₁ and IgG₄ subclass concentrations specific for preS and the receptor-binding site were measured by quantitative ELISA.

Findings

Five monthly injections induced the highest levels of preS-specific IgG consisting mainly of IgG₁ and IgG₄, with a sum of median preS-specific IgG₁ and IgG₄ concentrations of >135 μg/ml reaching up to 1.8 mg/ml. More than 20% of preS-specific IgG was directed against the receptor-binding site. BM32-induced IgG cross-reacted with the receptor-binding domains from all eight HBV genotypes A-H.

Interpretation

BM32 induces high levels of IgG₁ and IgG₄ antibodies against the receptor binding sites of all eight HBV genotypes and hence might be suitable for therapeutic HBV vaccination.

Funding

This study was supported by the PhD program IAI (KPW01212FW), by Viravaxx AG and by the Danube-ARC funded by the Government of Lower Austria. Rudolf Valenta is a recipient of a Megagrant of the Government of the Russian Federation, grant No 14.W03.31.0024.

Molecular profiling of allergen-specific antibody responses may enhance success of specific immunotherapy

BACKGROUND

House dust mites (HDMs) are among the most important allergen sources containing many different allergenic molecules. Analysis of patients from a double-blind, placebo-controlled allergen-specific immunotherapy (AIT) study indicated that patients may benefit from AIT to different extents depending on their molecular sensitization profiles.

OBJECTIVE

Our aim was to investigate in a real-life setting whether stratification of patients with HDM allergy according to molecular analysis may enhance AIT success.

METHODS

Serum and nasal secretion samples from patients with HDM allergy (n = 24) (at baseline, 7, 15, 33, and 52 weeks) who had received 1 year of treatment with a well-defined subcutaneous AIT form (Alutard SQ 510) were tested for IgE and IgG reactivity to 15 microarrayed HDM allergen molecules with ImmunoCAP Immuno-solid-phase Allergen Chip technology. IgG subclass levels to allergens and peptides were determined by ELISA, and IgG blocking was assessed by basophil activation. In vitro parameters were related to reduction of symptoms determined by combined symptom medication score and visual analog scale score.

RESULTS

Alutard SQ 510 induced protective IgG mainly against Dermatophagoides pteronyssinus (Der p) 1 and Der p 2 and to a lesser extent to Der p 23, but not to the other important allergens such as Der p 5, Der p 7, and Der p 21, showing better clinical efficacy in patients sensitized only to Der p 1 and/or Der p 2 as compared with patients having additional IgE specificities.

CONCLUSION

Stratification of patients with HDM allergy according to molecular sensitization profiles and molecular monitoring of AIT-induced IgG responses may enhance the success of AIT.

Structural Analysis of Recent Allergen-Antibody Complexes and Future Directions

PURPOSE OF REVIEW

Allergen-antibody complexes are extremely valuable in describing the detailed molecular features of epitopes. This review summarizes insights gained from recently published co-structures and what obstacles impede the acquisition of further data.

RECENT FINDINGS

Structural epitope data helped define the epitopes of two anti-Fel d 1 antibodies undergoing phase I clinical trials, providing a greater level of detail than was possible through hydrogen-deuterium exchange protection studies. Separately, a human camelid-like antibody structure with lysozyme described several unique features in a long variable loop that interacted with the active site cleft of Gal d 4. Finally, a co-structure conclusively demonstrated that Phl p 7 could function as a superantigen and that an antibody could simultaneously recognize two epitopes. These remarkable assertions would not have been possible without visualization of the complex. Only three new complexes have appeared in the last few years, suggesting that there are major impediments to traditional production and crystallization. The structural data was extremely valuable in describing epitopes. New techniques like cryo-EM may provide an alternative to crystallography.

Allergen-specific immunotherapy induces regulatory T cells in an atopic dermatitis mouse model

BACKGROUND

Several studies have demonstrated that allergen-specific immunotherapy (SIT) can be an effective treatment for atopic dermatitis (AD). However, there is no relevant mouse model to investigate the mechanism and validate the novel modality of SIT in AD.

METHODS

NC/Nga mice with induced AD-like skin lesions received a subcutaneous injection of SIT (an extract of the house dust mite Dermatophagoides farinae [DfE]) or placebo for 5 weeks). Clinical and histological improvements of AD-like skin lesions were examined. The responses of local and systemic regulatory T (Treg) cells, natural killer (NK) cells, B cells, serum immunoglobulin, and T-cell cytokine response to DfE were evaluated to determine the underlying mechanism of the observed results.

RESULTS

Specific immunotherapy significantly improved AD-like skin lesions. Histologically, SIT decreased epidermal thickness and reduced inflammatory cell infiltration, especially that of eosinophils. Concomitantly, SIT suppressed Th2 responses and induced local infiltration of Treg cells into the skin. Also, SIT induced the immunoglobulin G4 and attenuated allergen-specific immunoglobulin E. Furthermore, SIT induced local and systemic IL-10-producing Treg cells and regulatory NK cells.

CONCLUSION

We established a SIT model on AD mice and showed that our model correlates well with previous reports about SIT-treated patients. Also, we revealed NK cells as another possible resource of IL-10 in SIT. Based on our results, we suggest our SIT model as a useful tool to investigate mechanism of action of SIT and to validate the efficacy of new SIT modalities for the treatment of AD.

Next-Generation of Allergen-Specific Immunotherapies: Molecular Approaches

PURPOSE OF REVIEW

The aim of this article is to discuss how allergen-specific immunotherapy (AIT) can be improved through molecular approaches. We provide a summary of next-generation molecular AIT approaches and of their clinical evaluation. Furthermore, we discuss the potential of next generation molecular AIT forms for the treatment of severe manifestations of allergy and mention possible future molecular strategies for the secondary and primary prevention of allergy.

RECENT FINDINGS

AIT has important advantages over symptomatic forms of allergy treatment but its further development is limited by the quality of the therapeutic antigen preparations which are derived from natural allergen sources. The field of allergy diagnosis is currently undergoing a dramatic improvement through the use of molecular testing with defined, mainly recombinant allergens which allows high-resolution diagnosis. Several studies demonstrate that molecular testing in early childhood can predict the development of symptomatic allergy later on in life. Clinical studies indicate that molecular AIT approaches have the potential to improve therapy of allergic diseases and may be used as allergen-specific forms of secondary and eventually primary prevention for allergy.

Contributions and Future Directions for Structural Biology in the Study of Allergens

Allergy is defined as an inappropriate immune response to something normally considered harmless. The symptomatic immune response is driven by IgE antibodies directed against allergens. The study of allergens has contributed significantly to our understanding of allergic disease in 3 main areas. First, identifying allergens as the cause of symptoms and developing allergen standards has led to many advances in exposure assessment and patient diagnostics. Second, a biochemical understanding of allergens has suggested a number of hypotheses related to the mechanisms of allergic sensitization. And finally, studies of allergen-antibody interactions have contributed to understanding the cross-reactivity of allergens, mapping patient epitopes, and the development of hypoallergens. In this review, a few select cases are highlighted where structural biology, in particular, has contributed significantly to allergen research and provided new avenues for investigation.

Antibodies and superantibodies in patients with chronic rhinosinusitis with nasal polyps

Background

Chronic rhinosinusitis with nasal polyps is associated with local immunoglobulin hyperproduction and the presence of IgE antibodies against Staphylococcus aureus enterotoxins (SAEs). Aspirin-exacerbated respiratory disease is a severe form of chronic rhinosinusitis with nasal polyps in which nearly all patients express anti-SAEs.

Objectives

We aimed to understand antibodies reactive to SAEs and determine whether they recognize SAEs through their complementarity-determining regions (CDRs) or framework regions.

Methods

Labeled staphylococcal enterotoxin (SE) A, SED, and SEE were used to isolate single SAE-specific B cells from the nasal polyps of 3 patients with aspirin-exacerbated respiratory disease by using fluorescence-activated cell sorting. Recombinant antibodies with “matched” heavy and light chains were cloned as IgG₁, and those of high affinity for specific SAEs, assayed by means of ELISA and surface plasmon resonance, were recloned as IgE and antigen-binding fragments. IgE activities were tested in basophil degranulation assays.

Results

Thirty-seven SAE-specific, IgG- or IgA-expressing B cells were isolated and yielded 6 anti-SAE clones, 2 each for SEA, SED, and SEE. Competition binding assays revealed that the anti-SEE antibodies recognize nonoverlapping epitopes in SEE. Unexpectedly, each anti-SEE mediated SEE-induced basophil degranulation, and IgG₁ or antigen-binding fragments of each anti-SEE enhanced degranulation by the other anti-SEE.

Conclusions

SEEs can activate basophils by simultaneously binding as antigens in the conventional manner to CDRs and as superantigens to framework regions of anti-SEE IgE in anti-SEE IgE-FcεRI complexes. Anti-SEE IgG₁s can enhance the activity of anti-SEE IgEs as conventional antibodies through CDRs or simultaneously as conventional antibodies and as “superantibodies” through CDRs and framework regions to SEEs in SEE–anti-SEE IgE-FcεRI complexes.

Single B-cell deconvolution of peanut-specific antibody responses in allergic patients

BACKGROUND

The frequencies, cellular phenotypes, epitope specificity, and clonal diversity of allergen-specific B cells in patients with food allergy are not fully understood but are of major pathogenic and therapeutic significance.

OBJECTIVE

We sought to characterize peanut allergen-specific B-cell populations and the sequences and binding activities of their antibodies before and during immunotherapy.

METHODS

B cells binding fluorescently labeled Ara h 1 or Ara h 2 were phenotyped and isolated by means of flow cytometric sorting from 18 patients at baseline and 13 patients during therapy. Fifty-seven mAbs derived from allergen-binding single B cells were evaluated by using ELISA, Western blotting, and peptide epitope mapping. Deep sequencing of the B-cell repertoires identified additional members of the allergen-specific B-cell clones.

RESULTS

Median allergen-binding B-cell frequencies were 0.0097% (Ara h 1) or 0.029% (Ara h 2) of B cells in baseline blood from allergic patients and approximately 3-fold higher during immunotherapy. Five of 57 allergen-specific cells belonged to clones containing IgE-expressing members. Almost all allergen-specific antibodies were mutated, and binding to both conformational and linear allergen epitopes was detected. Increasing somatic mutation of IgG4 members of a clone was seen in immunotherapy, whereas IgE mutation levels in the clone did not increase.

CONCLUSION

Most peanut allergen-binding B cells isolated by means of antigen-specific flow sorting express mutated and isotype-switched antibodies. Immunotherapy increases their frequency in the blood, and even narrowly defined allergen epitopes are recognized by numerous distinct B-cell clones in a patient. The results also suggest that oral immunotherapy can stimulate somatic mutation of allergen-specific IgG4.

Multiple independent IgE epitopes on the highly allergenic grass pollen allergen Phl p 5

Background

Group 5 allergens are small proteins that consist of two domains. They belong to the most potent respiratory allergens.

Objective

To determine the binding sites and to study allergic patients' IgE recognition of the group 5 allergen (Phl p 5) from timothy grass pollen using human monoclonal IgE antibodies that have been isolated from grass pollen allergic patients.

Methods

Using recombinant isoallergens, fragments, mutants and synthetic peptides of Phl p 5, as well as peptide-specific antibodies, the interaction of recombinant human monoclonal IgE and Phl p 5 was studied using direct binding and blocking assays. Cross-reactivity of monoclonal IgE with group 5 allergens in several grasses was studied and inhibition experiments with patients' polyclonal IgE were performed.

Results

Monoclonal human IgE showed extensive cross-reactivity with group 5 allergens in several grasses. Despite its small size of 29 kDa, four independent epitope clusters on isoallergen Phl p 5.0101, two in each domain, were recognized by human IgE. Isoallergen Phl p 5.0201 carried two of these epitopes. Inhibition studies with allergic patients' polyclonal IgE suggest the presence of additional IgE epitopes on Phl p 5.

Conclusions & Clinical Relevance

Our results reveal the presence of a large number of independent IgE epitopes on the Phl p 5 allergen explaining the high allergenic activity of this protein and its ability to induce severe allergic symptoms. High-density IgE recognition may be a general feature of many potent allergens and form a basis for the development of improved diagnostic and therapeutic procedures in allergic disease.

A milestone in house dust-mite-allergen immunotherapy: the new sublingual tablet S-524101 (actair)

Subcutaneous allergen-specific immunotherapy has long been used in the treatment of allergic rhinitis and/or asthma and its efficacy has been confirmed. However, due to the discomfort of injections and the risk of severe adverse reactions, alternative routes of allergen administration have emerged. Delivery of allergens through the mucosal route had been proposed and investigated thoroughly, confirming the sublingual route to be the most efficacious. Later, the efficacy and safety of this route have been documented by numerous controlled trials both for house dust mite (HDM) and pollens. Recently, sublingual orodispersable grass pollen allergen tablets were in use followed by the newly developed HDM allergen tablets with satisfactory clinical results: Moreover, very recently 1 year of HDM tablet treatment was demonstrated to exert its clinical efficacy 1 year after discontinuation of tablet IT. The persistence of efficacy after only 1 year of treatment is a new and promising era. Currently, Sublingual Immunotherapy is the most easily administered and safe treatment option until more immunogenic, less allergenic and more efficient allergen extracts are developed.

The molecular basis of peanut allergy

Peanut allergens can trigger a potent and sometimes dangerous immune response in an increasing number of people. The molecular structures of these allergens form the basis for understanding this response. This review describes the currently known peanut allergen structures and discusses how modifications both enzymatic and non-enzymatic affect digestion, innate immune recognition, and IgE interactions. The allergen structures help explain cross-reactivity among allergens from different sources, which is useful in improving patient diagnostics. Surprisingly, it was recently noted that similar short peptide sequences among unrelated peanut allergens could also be a source of cross-reactivity. The molecular features of peanut allergens continue to inform predictions and provide new research directions in the study of allergic disease.

Characterization of an anti-Bla g 1 scFv: epitope mapping and cross-reactivity

Bla g 1 is a major allergen from Blatella germanica and one of the primary allergens used to assess cockroach allergen exposure. The epitope of an anti-Bla g 1 scFv was mapped in order to better understand cross reactivity with other group 1 cockroach allergens and patient IgE epitopes. X-ray crystallography was used to determine the structure of the scFv. The scFv epitope on Bla g 1 was located by alanine scanning site-directed mutagenesis and ELISA. Twenty-six rBla g 1-GST alanine mutants were evaluated for variations in binding to the scFv compared to the wild type allergen. Six mutants showed a significant difference in scFv binding affinity. These mutations clustered to form a discontinuous epitope mainly comprising two helices of Bla g 1. The allergen-scFv complex was modeled based on the results, and the epitope region was found to have low sequence similarity with Per a 1, especially among the residues identified as functionally important for the scFv binding to Bla g 1. Indeed, the scFv failed to bind Per a 1 in American cockroach extract. The scFv was unable to inhibit the binding of IgE antibodies from a highly cockroach allergic patient to Bla g 1. Based on the surface area of Bla g 1 occluded by the scFv, putative regions of patient IgE-Bla g 1 interactions can be inferred. This scFv could be best utilized as a capture antibody in an IgE detection ELISA, or to differentiate Bla g 1 from Per a 1 in environmental exposure assays.

Advances in allergen-microarray technology for diagnosis and monitoring of allergy: the MeDALL allergen-chip

Allergy diagnosis based on purified allergen molecules provides detailed information regarding the individual sensitization profile of allergic patients, allows monitoring of the development of allergic disease and of the effect of therapies on the immune response to individual allergen molecules. Allergen microarrays contain a large variety of allergen molecules and thus allow the simultaneous detection of allergic patients' antibody reactivity profiles towards each of the allergen molecules with only minute amounts of serum. In this article we summarize recent progress in the field of allergen microarray technology and introduce the MeDALL allergen-chip which has been developed for the specific and sensitive monitoring of IgE and IgG reactivity profiles towards more than 170 allergen molecules in sera collected in European birth cohorts. MeDALL is a European research program in which allergen microarray technology is used for the monitoring of the development of allergic disease in childhood, to draw a geographic map of the recognition of clinically relevant allergens in different populations and to establish reactivity profiles which are associated with and predict certain disease manifestations. We describe technical advances of the MeDALL allergen-chip regarding specificity, sensitivity and its ability to deliver test results which are close to in vivo reactivity. In addition, the usefulness and numerous advantages of allergen microarrays for allergy research, refined allergy diagnosis, monitoring of disease, of the effects of therapies, for improving the prescription of specific immunotherapy and for prevention are discussed.

Possible therapeutic potential of a recombinant group 2 grass pollen allergen-specific antibody fragment

The induction of blocking IgG antibodies that compete with IgE for allergen binding is one important mechanism of allergen-specific immunotherapy. The application of blocking antibodies may be an alternative treatment strategy. A synthetic gene coding for a single-chain fragment (ScFv) specific for the major timothy grass pollen allergen Phl p 2 was inserted into plasmid pCANTAB 5 E, and the recombinant ScFv was expressed in Escherichia coli and purified by affinity chromatography. The ScFv was tested for allergen binding by ELISA, and its association and dissociation were measured by surface plasmon resonance (Biacore) technology. The ability of the ScFv to inhibit allergic patients' IgE binding to Phl p 2 and Phl p 2-induced basophil degranulation was studied by ELISA competition and basophil activation (CD203c) assays. We report the expression, purification, biochemical and immunological characterization of a monomeric single-chain fragment (ScFv) of human origin specific for the major timothy grass pollen allergen, Phl p 2. The Phl p 2-ScFv showed high affinity binding to the allergen and blocked the binding of allergic patients' polyclonal IgE to Phl p 2 up to 98%. Furthermore, it inhibited allergen-induced basophil activation. The Phl p 2-ScFv inhibited allergic patients' IgE binding to Phl p 2 as well as Phl p 2-induced basophil activation and might be useful for passive immunotherapy of grass pollen allergy.

The human IgE repertoire

IgE is a key mediator in allergic diseases. However, in strong contrast to other antibody isotypes, many details of the composition of the human IgE repertoire are poorly defined. The low levels of human IgE in the circulation and the rarity of IgE-producing B cells are important reasons for this lack of knowledge. In this review, we summarize the current knowledge on these repertoires both in terms of their complexity and activity, i.e. knowledge which despite the difficulties encountered when studying the molecular details of human IgE has been acquired in recent years. We also take a look at likely future developments, for instance through improvements in sequencing technology and methodology that allow the isolation of additional allergen-specific human antibodies mimicking IgE, as this certainly will support our understanding of human IgE in the context of human disease in the years to come.

Determination of allergen specificity by heavy chains in grass pollen allergen-specific IgE antibodies

BACKGROUND

Affinity and clonality of allergen-specific IgE antibodies are important determinants for the magnitude of IgE-mediated allergic inflammation.

OBJECTIVE

We sought to analyze the contribution of heavy and light chains of human allergen-specific IgE antibodies for allergen specificity and to test whether promiscuous pairing of heavy and light chains with different allergen specificity allows binding and might affect affinity.

METHODS

Ten IgE Fabs specific for 3 non-cross-reactive major timothy grass pollen allergens (Phl p 1, Phl p 2, and Phl p 5) obtained by means of combinatorial cloning from patients with grass pollen allergy were used to construct stable recombinant single chain variable fragments (ScFvs) representing the original Fabs and shuffled ScFvs in which heavy chains were recombined with light chains from IgE Fabs with specificity for other allergens by using the pCANTAB 5 E expression system. Possible ancestor genes for the heavy chain and light chain variable region-encoding genes were determined by using sequence comparison with the ImMunoGeneTics database, and their chromosomal locations were determined. Recombinant ScFvs were tested for allergen specificity and epitope recognition by means of direct and sandwich ELISA, and affinity by using surface plasmon resonance experiments.

RESULTS

The shuffling experiments demonstrate that promiscuous pairing of heavy and light chains is possible and maintains allergen specificity, which is mainly determined by the heavy chains. ScFvs consisting of different heavy and light chains exhibited different affinities and even epitope specificity for the corresponding allergen.

CONCLUSION

Our results indicate that allergen specificity of allergen-specific IgE is mainly determined by the heavy chains. Different heavy and light chain pairings in allergen-specific IgE antibodies affect affinity and epitope specificity and thus might influence clinical reactivity to allergens.

Strategies to query and display allergy-derived epitope data from the immune epitope database

The recognition of specific epitopes on allergens by antibodies and T cells is a key element in allergic processes. Analysis of epitope data may be of interest for basic immunopathology or for potential application in diagnostics or immunotherapy. The Immune Epitope Database (IEDB) is a freely available repository of epitope data from infectious disease agents, as well as epitopes defined for allergy, autoimmunity, and transplantation. The IEDB curates the experiments associated with each epitope and thus provides a variety of different ways to search the data. This review aims to demonstrate the utility of the IEDB and its query strategies, including searching by epitope structure (peptidic/nonpeptidic), by assay methodology, by host, by the allergen itself, or by the organism from which the allergen was derived. Links to tools for visualization of 3-D structures, epitope prediction, and analyses of B and T cell reactivity by host response frequency score are also highlighted.

Passive immunization with allergen-specific IgG antibodies for treatment and prevention of allergy

IgE antibody-mediated allergies affect more than 25% of the population worldwide. To investigate therapeutic and preventive effects of passive immunization with allergen-specific IgG antibodies on allergy in mouse models we used clinically relevant pollen allergens. In a treatment model, mice were sensitized to the major birch pollen allergen Bet v 1 and to the major grass pollen allergens, Phl p 1 and Phl p 5 and then received passive immunization with rabbit IgG antibodies specific for the sensitizing or an unrelated allergen. In a prevention model, mice obtained passive immunization with allergen-specific rabbit IgG before sensitization. Kinetics of the levels of administered IgG antibodies, effects of administered allergen-specific IgG on allergen-specific IgE reactivity, the development of IgE and IgG responses and on immediate allergic reactions were studied by ELISA, rat basophil leukaemia degranulation assays and skin testing, respectively. Treated mice showed an approximately 80% reduction of allergen-specific IgE binding and basophil degranulation which was associated with the levels of administered allergen-specific IgG antibodies. Preventive administration of allergen-specific IgG antibodies suppressed the development of allergen-specific IgE and IgG1 antibody responses as well as allergen-induced basophil degranulation and skin reactivity. Our results show that passive immunization with allergen-specific IgG antibodies is effective for treatment and prevention of allergy to clinically important pollen allergens in a mouse model and thus may pave the road for the clinical application of allergen-specific antibodies in humans.

Subcutaneous versus sublingual immunotherapy for allergic rhinitis and/or asthma

Subcutaneous allergen-specific immunotherapy has long been used in allergic rhinitis and/or asthma and has been recognized to be efficacious. However, owing to the inconvenience of injection and the risk of serious side effects, alternative concepts inspiring the search for effective noninjective routes, namely sublingual administration of allergens, have emerged. Sublingual immunotherapy (SLIT) appears to be associated with a lower incidence of systemic reactions. The clinical efficacy of subcutaneous immunotherapy (SCIT) is well established for both rhinitis and asthma. Meta-analyses relating to its efficacy on asthma and rhinitis are available. SLIT has also been validated in this respect. Comparative clinical studies of SLIT versus SCIT are scarce demonstrating both routes to be clinically efficient. Knowledge of the exact mechanism of action of SLIT has been increasing in the last decade. In addition, recent studies have proved similarities of the immunological changes with the treatment of both routes. Further comparative clinical and immunological studies of SLIT versus SCIT are needed to confirm the long-term efficacy and to complete the knowledge of immunological mechanisms of both routes. Moreover, better understanding of the interaction of allergen and oral mucosal dendritic cells during SLIT may allow improved targeting of SLIT vaccines.

Immunological approaches for tolerance induction in allergy

Allergy is the consequence of an inappropriate inflammatory immune response generated against harmless environmental antigens. In allergic disorders such as asthma and rhinitis, the Th2 mediated phenotype is a result of loss of peripheral tolerance mechanisms. In cases such as these, approaches such as immunotherapy attempt to treat the underlying cause of allergic disease by restoring tolerance. Immunotherapy initiates many complex mechanisms within the immune system that result in initiation of innate immunity, activation of both cellular and humoral B cell immunity, as well as triggering T regulatory subsets which are major players in the establishment of peripheral tolerance. Though studies clearly demonstrate immunotherapy to be efficacious, research to improve this treatment is ongoing. Investigation of allergenicity versus immunogenicity, native versus modified allergens, and the use of adjuvant and modality of dosing are all current strategies for immunotherapy advancement that will be reviewed in this article.

Immunology in the Clinic Review Series; focus on allergies: basophils as biomarkers for assessing immune modulation

Allergen-specific immunotherapy is an effective clinical treatment for hypersensitivity to many allergens. Studies of basophils during immunotherapy have provided insight into underlying immune mechanisms and support the potential use of basophil activation as a biomarker of clinical outcomes. This review examines the evidence for different pathways of basophil modulation associated with various forms of immunotherapy. Better understanding the molecular mechanisms of basophil activation and desensitization and the relationship between suppression of these effector cells to clinical outcomes holds promise for further development and improvement in potential therapies for allergic diseases.

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.

Generation and epitope analysis of human monoclonal antibody isotypes with specificity for the Timothy grass major allergen Phl p 5a

The scarcity of monoclonal human IgE antibodies with specificity for defined allergens is a bottleneck for the molecular characterisation of allergens and their epitopes. Insights into the characteristics of such antibodies may allow for analyses of the molecular basis underlying allergenicity and cross-reactivity, standardisation of allergens as well as improvement of allergy diagnostics and therapeutics. Here we report the generation and application of the first set of authentic human IgG, IgE and IgA antibodies. On the basis of a Phl p 5a specific antibody fragment, a lambda light chain and the IgG1, IgG4, IgE, IgA1, and IgA2 heavy chains, the corresponding human immunoglobulins were constructed and produced in mammalian cells. In parallel, a murine hybridoma line with specificity for Phl p 5a was established, recloned and produced as human chimeric IgE. After purification, immunoreactivity of the antibodies with the allergen was assessed. Applicability in allergy diagnostics was confirmed by establishment of artificial human sera. Functionality of both antibodies was further demonstrated in receptor binding studies and mediator release assays using humanised rat basophil leukaemia cells (RBL-SX38) suggesting the presence of spatially separate epitopes. By using Phl p 5 fusion proteins and recombinant IgE in immunoblotting and mediator release assays we assigned the epitope of the authentic IgE to a looped stretch exclusively present in Phl p 5a. In summary, the Phl p 5-specific antibodies are the first full set of allergy-related antibody isotypes of their kind and represent valuable tools for studies of fundamental mechanisms and structure/function relationships in allergy.

Facilitated antigen presentation and its inhibition by blocking IgG antibodies depends on IgE repertoire complexity

BACKGROUND

The antibody repertoires of allergic subjects are characterized by the presence of allergen-specific IgE antibodies. We have previously shown that the composition of the IgE repertoire is critical for allergen-mediated activation of human effector cells. Activation of CD4(+) T cells in allergic subjects is highly potentiated by the process of facilitated antigen presentation (FAP), in which allergen in complex with IgE is taken up by B cells through the low-affinity IgE receptor CD23 and presented to T cells.

OBJECTIVE

We sought to investigate the influence of IgE repertoire complexity on the formation of IgE/allergen/CD23 complexes on B cells and subsequent T-cell activation.

METHODS

Using defined allergen-specific recombinant IgE and IgG antibodies, we investigated the influence of individual IgE affinity, IgE clonality, specific IgE concentration, and the ratio between IgE specificities on IgE/allergen/CD23 complex formation in vitro.

RESULTS

Although IgE affinity is an important factor, IgE clonality seems to be governing complex formation, especially with medium- and low-affinity IgE antibodies. We demonstrate that differences in allergen-specific IgE affinity correlate with the efficiency of subsequent T-cell activation. In addition, we show that the complexity of an IgE repertoire also affects the ability of allergen-specific IgG antibodies to block FAP.

CONCLUSION

The composition of allergen-specific IgE repertoires in individual patients, especially with respect to IgE clonality, might play an important role in the manifestation of allergic disease not only for the immediate allergic reaction through activation of basophils and mast cells but also for the exacerbation of allergic inflammation through recurring activation of allergen-specific T cells by FAP.

Passive immunization with allergen-specific antibodies

The induction of allergen-specific IgG antibodies has been identified as a major mechanism responsible for the reduction of allergic inflammation in allergic patients treated by allergen-specific immunotherapy. Several studies suggest that allergen-specific IgG antibodies induced by vaccination with allergens block mast cell and basophil degranulation, IgE-facilitated allergen presentation to T cells and IgE production. The availability of recombinant allergens and technologies for the production of recombinant human antibodies allows engineering of allergen-specific antibodies which can be used for passive immunization (i.e., therapy) and eventually for the prevention of allergy (i.e., prophylaxis). This chapter summarizes data supporting the possible use of allergen-specific antibodies for treatment and prophylaxis. Finally, concrete approaches for the treatment and prevention of allergy based on blocking antibodies are envisioned.

Structural and immunologic cross-reactivity among filarial and mite tropomyosin: implications for the hygiene hypothesis

BACKGROUND

The hygiene hypothesis suggests that parasitic infection modulates host immune responses and decreases atopy. Other data suggest parasitic infections may induce allergic responsiveness.

OBJECTIVE

To assess the structural and immunologic relationships between the known Dermatophagoides pteronyssinus (Der p 10) tropomyosin allergen and filarial tropomyosin of Onchocerca volvulus (OvTrop).

METHODS

The molecular, structural, and immunologic relationships between OvTrop and Der p 10 were compared. Levels of OvTrop-specific and Der p 10-specific IgE, IgG, and IgG₄ in sera of filaria-infected and filarial-uninfected D pteronyssinus-atopic individuals were compared, as were the responses in nonhuman primates infected with the filarial parasite Loa loa. Cross-reactivity was compared by antigen-mediated depletion assays and functionality by passive basophil sensitization.

RESULTS

Filarial and mite tropomyosins were very similar, with 72% identity at the amino acid level, and overlapping predicted 3-dimensional structures. The prevalence of IgE and IgG to Der p 10 was increased in filaria-infected individuals compared with uninfected subjects. There was a strong correlation between serum levels of Ov- and Der p 10-tropomyosin-specific IgE, IgG, and IgG₄ (P < .0001; r > 0.79). Preincubation of sera from anti-Der p 10-positive subjects with OvTrop completely depleted IgE, IgG, and IgG₄ anti-Der p 10. Basophils sensitized with sera from individuals allergic to Der p 10 released histamine similarly when triggered with OvTrop or Der p 10. Primates experimentally infected with L loa developed IgE that cross-reacted with Der p 10.

CONCLUSION

Filarial infection induces strong cross-reactive antitropomyosin antibody responses that may affect sensitization and regulation of allergic reactivity.

Tracing antigen signatures in the human IgE repertoire

Allergen recognition by IgE antibodies is a key event in allergic inflammation.

In this study, the IgE IGHV repertoires of individuals with allergy to the major birch pollen allergen, Bet v 1, were analyzed over a four years period of allergen exposure by RT-PCR and sequencing of cDNA.

Approximately half of the IgE transcripts represented non-redundant sequences, which belonged to seventeen different IGHV genes. Most variable regions contained somatic mutations but also non-mutated sequences were identified. There was no evidence for relevant increases of somatic mutations over time of allergen exposure. Highly similar IgE variable regions were found after four years of allergen exposure in the same and in genetically non-related individuals.

Our results indicate that allergens select and shape a limited number of similar IgE variable regions in the human IgE repertoire.

Selection of recombinant IgE antibodies binding the beta-lactoglobulin allergen in a conformation-dependent manner

Cow's milk allergy (CMA) is a common food allergy, especially among infants and young children. Approximately 85% of milk-allergic children outgrow their allergy by the age of three but the remaining 15% remain allergic. Bovine beta-lactoglobulin (BLG) is one of the major allergens in cow's milk. There is a definite need for the specific and sensitive detection of allergenic substances. Validated methods are obligatory to demonstrate allergen contamination and even fatal hidden allergens and, thus, to prevent life-threatening conditions of allergic persons. In this study, we constructed human IgE scFv libraries from an adult milk-allergic patient and isolated the first recombinant IgE antibodies specific to a food allergen, BLG. The selection of the IgE antibody libraries with two distinct panning procedures resulted in the enrichment of four clones having different BLG-binding profiles; two of the clones recognize the native BLG whereas the other two recognize only the heat-denatured form of BLG. For further characterization, the scFv fragments were converted to Fab fragments with human IgG1 isotype. The D1 Fab fragment, binding native BLG with nanomolar affinity, also partially inhibited serum IgE binding to BLG. These BLG-specific IgE antibodies can be applied for the detection of both native and denatured BLG in cow's milk products and furthermore, for the optimization of manufacturing processes to develop safe hypoallergenic milk products.

A review of allergen-specific immunotherapy in human and veterinary medicine

This article reviews allergen-specific immunotherapy in human and veterinary medicine. Current hypotheses of possible mechanisms of actions are outlined. Indications, success rates, adverse effects and factors influencing outcome of therapy are discussed in humans, dogs, cats and horses.

Current immunological approaches for management of allergic rhinitis and bronchial asthma

A large population world over is affected with allergic diseases and asthma. Pharmacotherapy for allergic diseases and asthma is effective in controlling symptoms but on discontinuation of medication, symptoms reoccur. In contrast, immunotherapy modifies and corrects the underlying pathological immune responses in an antigen-specific manner. Immunotherapy shows an increase in IgG (blocking antibody) that competes with IgE for allergen, inhibiting the release of inflammatory mediators. Recent studies suggest that immunotherapy acts by modifying CD4+ T-cell responses either by immune deviation, T-cell anergy and/or both. Current immunological approaches for management of allergies and asthma involve immunization with native allergen, modified allergen, peptides/cDNA of allergen, anti-IgE, adjuvants coupled allergen, including immunostimulatory DNA sequences, cytokines, and bacterial products. These approaches modulate the immune response and are intended to give long-term benefit.

Nature of regulatory T cells in the context of allergic disease

Allergen-specific immunotherapy (SIT) is the cornerstone of the management of allergic diseases, which targets modification of the immunologic response, along with environmental allergen avoidance and pharmacotherapy. SIT is associated with improved tolerance to allergen challenge, with a decrease in immediate-phase and late-phase allergic inflammation. SIT has the potential to prevent development of new sensitizations and progression of allergic rhinitis to asthma. It has a role in cellular and humoral responses in a modified pattern. The ratio of T helper (Th)1 cytokines to Th2 cytokines is increased following SIT, and functional regulatory T cells are induced. Interleukin-10 production by monocytes, macrophages, and B and T cells is increased, as well as expression of transforming growth factor β. SIT is associated with increases in allergen-specific antibodies in IgA, IgG1, and IgG4 isotypes. These blocking-type immunoglobulins, particularly IgG4, may compete with IgE binding to allergen, decreasing the allergen presentation with the high- and low-affinity receptors for IgE (FcεRI and FcεRII, respectively). Additionally, SIT reduces the number of mast cells and eosinophils in the target tissues and release of mediators from these cells.