Allergen-specific T-cell tolerance induction with allergen-derived long synthetic peptides: results of a phase I trial

CD4+CD25-mTGFbeta+ T cells induced by nasal application of ovalbumin transfer tolerance in a therapeutic model of asthma

BACKGROUND

Intranasal administration of high amount of allergen was shown to induce tolerance and to reverse the allergic phenotype. However, mechanisms of tolerance induction via the mucosal route are still unclear.

OBJECTIVES

To characterize the therapeutic effects of intranasal application of ovalbumin (OVA) in a mouse model of bronchial inflammation as well as the cellular and molecular mechanisms leading to protection upon re-exposure to allergen.

METHODS

After induction of bronchial inflammation, mice were treated intranasally with OVA and re-exposed to OVA aerosols 10 days later. Bronchoalveolar lavage fluid (BALF), T cell proliferation and cytokine secretion were examined. The respective role of CD4(+)CD25(+) and CD4(+)CD25(-) T cells in the induction of tolerance was analysed.

RESULTS

Intranasal treatment with OVA drastically reduced inflammatory cell recruitment into BALF and bronchial hyperresponsiveness upon re-exposure to allergen. Both OVA- specific-proliferation of T cells, T(h)1 and T(h)2 cytokine production from lung and bronchial lymph nodes were inhibited. Transfer of CD4(+)CD25(-) T cells, which strongly expressed membrane-bound transforming growth factor β (mTGFβ), from tolerized mice protected asthmatic recipient mice from subsequent aerosol challenges. The presence of CD4(+)CD25(+)(Foxp3(+)) T cells during the process of tolerization was indispensable to CD4(+)CD25(-) T cells to acquire regulatory properties. Whereas the presence of IL-10 appeared dispensable in this model, the suppression of CD4(+)CD25(-)mTGFβ(+) T cells in transfer experiments significantly impaired the down-regulation of airways inflammation.

CONCLUSION

Nasal application of OVA in established asthma led to the induction of CD4(+)CD25(-)mTGFβ(+) T cells with regulatory properties, able to confer protection upon allergen re-exposure.

Antigen-specific immunotherapy of autoimmune and allergic diseases

Nearly a century has passed since the first report describing antigen-specific immunotherapy (antigen-SIT) was published. Research into the use of antigen-SIT in the treatment of both allergic and autoimmune disease has increased dramatically since, although its mechanism of action is only slowly being unravelled. It is clear though, from recent studies, that success of antigen-SIT depends on the induction of regulatory T (T reg) cell subsets that recognise potentially disease-inducing epitopes. The major challenge remaining for the widespread use of antigen-SIT is to safely administer high doses of immunodominant and potentially pathogenic epitopes in a manner that induces T cell tolerance rather than activation. This review illustrates that intelligent design of treatment agents and strategies can lead to the development of safe and effective antigen-SIT.

Regulatory CD4+ T cells in allergic asthma

Active suppression by regulatory T cells (T(regs)) appears to play a key role in the downregulation of T-cell responses to foreign antigens. Several subtypes of T(regs) have been described but their mechanisms of action remain unclear. Recent data demonstrate that the suppressive capacity of natural T(regs) could be associated with cytotoxicity due to the release of granzymes, which are capable of apoptosis induction in target effector T lymphocytes and in antigen-presenting cells, such as dendritic cells. The mechanism of such nonspecific T(regs) is discussed. Peptide immunotherapy is thought to induce regulatory cells capable of suppressing autoimmune and allergic diseases. We have recently optimized a vaccination strategy by which cytotoxic antigen-specific adaptive T(regs) can be elicited towards allergens involved in allergic asthma. Such a strategy could be of value in the treatment of allergic asthma.

Allergen immunotherapy: immunomodulatory treatment for allergic diseases

Allergen immunotherapy is currently the only immune-modifying treatment for allergic disease. At the present time it is indicated for the treatment of allergic rhinitis, asthma and venom hypersensitivity. Efficacy appears to be dose dependent, and the immunological mechanisms responsible for the clinical efficacy of immunotherapy are still being elucidated. Immunological changes associated with immunotherapy include induction of T regulatory cells, increase in allergen-specific immunoglobulin G4, increase in interleukin-10 production and downregulation of the T helper 2 response. The disadvantages of allergen immunotherapy include risk of adverse events and patient time and inconvenience. Risks of immunotherapy range from large local reactions to mild systemic reactions, such as rhinitis. Fatalities from immunotherapy injections have been reported at a rate of approximately one fatality per 2.5 million injections. Conventional subcutaneous immunotherapy build-up schedules involve administration of a single-dose increase each visit and it may take several months before a patient achieves the therapeutic maintenance dose. Accelerated schedules, such as rush and cluster, will allow the patient to achieve the maintenance dose sooner but there may be a greater risk of a systemic reaction. The current focus of immunotherapy research is to develop safer and more effective vaccines. Another approach to enhancing immunotherapy safety is through an alternative delivery method. Sublingual immunotherapy is clearly safer than subcutaneous immunotherapy, but further investigation is needed to determine optimal dose and appropriate patient selection.

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.

Regulatory T cells in many flavors control asthma

That regulatory T cells (Tregs) have a crucial role in controlling allergic diseases such as asthma is now undisputed. The cytokines most commonly implicated in Treg-mediated suppression of allergic asthma are transforming growth factor-beta (TGF-beta) and interleukin (IL)-10). In addition to naturally occurring Tregs, adaptive Tregs, induced in response to foreign antigens, have been shown in recent studies. The concept of inducible/adaptive Tregs (iTregs) has considerable significance in preventing asthma if generated early enough in life. This is because cytokines such as IL-4 and IL-6 inhibit Foxp3 induction in naive CD4+ T cells and therefore de novo generation of Tregs can be expected to be less efficient when it is concomitant with effector cell development in response to an allergen. However, if iTregs can be induced, the process of infectious tolerance would facilitate expansion of the iTreg pool as suggested in the recent literature. It is tempting to speculate that there is a window of opportunity in early life in the context of a relatively immature immune system that is permissive for the generation of iTregs specific to a spectrum of allergens that would regulate asthma for lifelong. The focus of this review is the relevance of nTregs and iTregs in controlling asthma from early life into adulthood, the mechanisms underlying Treg function, and the prospects for using our current concepts to harness the full potential of Tregs to limit disease development and progression.

Tolerance induction after specific immunotherapy with pollen allergoids adjuvanted by monophosphoryl lipid A in children

Specific immunotherapy (SIT) is a well-established and clinically effective treatment for allergic diseases. A pollen allergoid formulated with the T helper type 1 (Th1)-inducing adjuvant monophosphoryl lipid A (MPL) facilitates short-term SIT. Little is known about mechanisms of tolerance induction in this setting. In a prospective study, 34 patients allergic to grass pollen (25 male, nine female, median age 10.2 years) received a total of 44 SIT courses (20 in the first, 24 in the second) with MPL-adjuvanted pollen allergoids. Immunogenicity was measured by levels of specific immunoglobulin G (IgG(grass)) and IgG4(grass) by antibody blocking properties on basophil activation, and by induction of CD4(+), CD25(+) and forkhead box P3 (FoxP3(+)) regulatory T cells (T(reg)). Specific IgG and IgG4 levels increased only slightly in the first year of SIT. In the second year these changes reached significance (P < 0.0001). In keeping with these findings, we were able to show an increase of T(reg) cells and a decreased release of leukotrienes after the second year of treatment. In the first year of treatment we found little evidence for immunological changes. A significant antibody induction was seen only after the second course of SIT. Short-course immunotherapy with pollen allergoids formulated with the Th1-inducing adjuvant MPL needs at least two courses to establish tolerance.

Humoral and cell-mediated immunity to MSP3 peptides in adults immunized with MSP3 in malaria endemic area, Burkina Faso

We performed a single-blind, randomized phase 1 trial of the long synthetic peptide (LSP) of merozoite surface protein-3 (MSP3) in adults living in Burkina Faso. Thirty eligible volunteers were randomized to receive either the MSP3-LSP candidate vaccine or tetanus toxoid vaccine as a control. A dose of each vaccine was administered on days 0, 28 and 112 and the vaccine was formulated with aluminium hydroxide. Humoral immune responses were assessed by ELISA at days 0, 28, 56, 112, 140, 252 and 365 and cell-mediated immune responses by lymphoproliferation assay and by ELISA on days 0, 56 and 140. IgG responses to four peptides of MSP3 were similar in both vaccine groups. Higher IgG concentrations were recorded after the beginning of malaria high transmission season in both vaccine groups. The lymphocyte proliferation and the production of IFN-γ in response to stimulation with the four overlapping peptides increased following vaccination in the MSP3-LSP vaccine group, but did not change appreciably in the control group. In contrast to natural infection, MSP3-LSP did not boost humoral responses to the four overlapping peptides of MSP3 to any detectable degree in our semi-immune adult. MSP3-LSP may be more immunogenic in young children with little or no acquired immunity.

CD4+CD25+ T cell depletion impairs tolerance induction in a murine model of asthma

BACKGROUND

Regulatory T cells (Tregs) are key players in controlling the development of airway inflammation. However, their role in the mechanisms leading to tolerance in established allergic asthma is unclear.

OBJECTIVE

To examine the role of Tregs in tolerance induction in a murine model of asthma.

METHODS

Ovalbumin (OVA) sensitized asthmatic mice were depleted or not of CD25(+) T cells by anti-CD25 PC61 monoclonal antibody (mAb) before intranasal treatment (INT) with OVA, then challenged with OVA aerosol. To further evaluate the respective regulatory activity of CD4(+)CD25(+) and CD4(+)CD25(-) T cells, both T cell subsets were transferred from tolerized or non-tolerized animals to asthmatic recipients. Bronchoalveolar lavage fluid (BALF), T cell proliferation and cytokine secretion were examined.

RESULTS

Intranasal treatment with OVA led to increased levels of IL-10, TGF-beta and IL-17 in lung homogenates, inhibition of eosinophil recruitment into the BALF and antigen specific T cell hyporesponsiveness. CD4(+)CD25(+)Foxp3(+) T cells were markedly upregulated in lungs and suppressed in vitro and in vivo OVA-specific T cell responses. Depletion of CD25(+) cells before OVA INT severely hampered tolerance induction as indicated by a strong recruitment of eosinophils into BALF and a vigorous T cell response to OVA upon challenge. However, the transfer of CD4(+)CD25(-) T cells not only suppressed antigen specific T cell responsiveness but also significantly reduced eosinophil recruitment as opposed to CD4(+)CD25(+) T cells. As compared with control mice, a significantly higher proportion of CD4(+)CD25(-) T cells from OVA treated mice expressed mTGF-beta.

CONCLUSION

Both CD4(+)CD25(+) and CD4(+)CD25(-) T cells appear to be essential to tolerance induction. The relationship between both subsets and the mechanisms of their regulatory activity will have to be further analyzed.

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.

Analysis of helper T cell responses to Cry j 1-derived peptides in patients with nasal allergy: candidate for peptide-based immunotherapy of Japanese cedar pollinosis

BACKGROUND

Allergen specific immunotherapy is highly effective, but adverse events may occur during treatment. Peptide-based immunotherapy has been proposed as one of new strategies for reduction of allergic adverse reactions. We examined the possibility of candidate peptides for the development of peptide-based immunotherapy for Japanese cedar pollinosis.

METHODS

Twelve Cry j 1-specific T-cell lines were established from peripheral blood mononuclear cells (PBMC) of 12 patients with Japanese cedar pollinosis. Using these T-cell lines, 37 Cry j 1-derived overlapping peptides were assessed for their proliferative responses and cytokine production.

RESULTS

Four peptides corresponding to the Cry j 1 sequence were able to induce proliferative responses to more than one T-cell line: p61-80 (3/12; 25.0%); p115-132 (2/12; 16.6%); p206-225 (4/12; 33.3%); and p337-353 (5/12; 41.7%). Furthermore, T-cell lines generated from 11 of 12 donors (91.7%) responded to at least one of these four peptides. On the other hand, the pattern of cytokine production from Cry j 1-specific T-cell lines varied. Moreover, cytokine production patterns by stimulation with Cry j 1 peptide did not reflect those by stimulation with Cry j 1 protein.

CONCLUSIONS

Our results suggest four Cry j 1-derived peptides (p61-80, p115-132, p206-225 and p337-353) may be considered to be the immunodominant T-cell epitopes of the Cry j 1 molecule, and can be useful for the design of peptide-based immunotherapy for the management of Japanese cedar pollinosis.

Advances in hymenoptera venom immunotherapy

PURPOSE OF REVIEW

Venom immunotherapy is highly effective treatment, capable of improving health-related quality of life. This overview examines advances in various aspects of this treatment.

RECENT FINDINGS

New findings on the immunological mechanisms of the early and long-term efficacy of venom immunotherapy have been made. The decision to start and then to stop venom immunotherapy is best made on an individual case basis and should take into account medical and other factors, like the influence on patient quality of life. Venoms for use in immunotherapy should be selected according to the geographical distribution of each species and partial cross-reactivity between certain types of venom. Rapid protocols seem to be as safe as slower ones, though the major incidence of bee venom immunotherapy side-effects remains. Patients suffering from mast cell diseases seem to be at greater risk for an adverse reaction during treatment, without influencing its efficacy that much until the immunotherapy is actually ongoing. A number of new strategies for venom immunotherapy, mostly based on genetic engineering, have been described, and so far only a few have been used in humans.

SUMMARY

Although there has been progress in the past few years, much remains to be accomplished.

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

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

Immunotherapy with allergen peptides

Specific allergen immunotherapy (SIT) is disease-modifying and efficacious. However, the use of whole allergen preparations is associated with frequent allergic adverse events during treatment. Many novel approaches are being designed to reduce the allergenicity of immunotherapy preparations whilst maintaining immunogenicity. One approach is the use of short synthetic peptides which representing dominant T cell epitopes of the allergen. Short peptides exhibit markedly reduced capacity to cross link IgE and activate mast cells and basophils, due to lack of tertiary structure. Murine pre-clinical studies have established the feasibility of this approach and clinical studies are currently in progress in both allergic and autoimmune diseases.

Immunology of anaphylaxis: lessons from murine models

The use of animal models is increasing, and mice are suitable animals to use in exploring systemic anaphylaxis based on the similarity between human and mouse immune systems. Two anaphylaxis pathways have been characterized in mice, which may help in understanding some of the discrepancies found in humans. In addition, cytokine studies are raising new concepts that may put together some of the puzzling mechanisms described in this disease. Finally, the study of the mechanisms that parasitic infections use to evade the human immune system and the scene in which a parasite induces clinical anaphylaxis are opening new insights in the immunology pathways and new strategies to fight against this exclusive disease.

Defining the T cell antigen proteome of wasp venom

BACKGROUND

While modulation of T cell function is believed to be important in the successful acquisition of clinical tolerance during venom immunotherapy, little is known of the role of wasp venom specific T cell antigens.

OBJECTIVE

We sought comprehensively to characterize the T cell proteome for wasp venom to facilitate the future development of T cell-based immunotherapeutic approaches.

METHODS

Using peripheral blood mononuclear cells from wasp venom-allergic individuals and IL-4 ELISPOT analysis, we characterized T cell responses to whole venom and gel filtration/ion exchange-fractionated venom. Reactive fractions were purified and identified using highly sensitive electrospray ion-trap mass spectrometry.

RESULTS

Wasp venom-allergic individuals have detectable whole wasp venom-specific T cells directly ex vivo, which show rapid IL-4 effector function. T cell responses to gel filtration/ion exchange fractionated venom were dominated by responses to phospholipase A(1), hyaluronidase and antigen 5.

CONCLUSION

Although it is likely that there are many T cell antigens within wasp venom, the main responses are to proteins coincident with the known IgE-binding proteins.

Update on the current status of peptide immunotherapy

The use of synthetic peptide fragments of allergen molecules holds promise for the delivery of effective immunotherapy without IgE-mediated adverse events. Early studies were associated with frequent induction of allergic symptoms after treatment, mostly related to activation of allergen-specific effector T cells with high doses of peptides. More recently, low doses of peptides have been shown to modify clinical and laboratory surrogates without inducing adverse events. Studies are ongoing to define the optimal dose, dose interval, and route of administration. Current results indicate that treatment with peptides modulates the immune response by reducing T(H)2 responses to allergen and increasing IL-10 production and the activity of allergen-specific regulatory T cells. Further studies are required in larger numbers of subjects and with peptides derived from a variety of allergens.

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

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

Potential of an altered peptide ligand of lipocalin allergen Bos d 2 for peptide immunotherapy

BACKGROUND

Peptide immunotherapy is a promising alternative for treating allergic diseases. One way to enhance the efficacy of peptide immunotherapy is to use altered peptide ligands (APLs) that contain amino acid substitutions compared with the natural peptide.

OBJECTIVE

To evaluate the potential of an APL of the immunodominant epitope of lipocalin allergen Bos d 2 for peptide immunotherapy.

METHODS

Peripheral blood CD4(+) T-cell responses of 8 HLA-DR4-positive subjects to the natural ligand of Bos d 2 (p127-142) or to an APL (pN135D) were analyzed by MHC class II tetramer staining after in vitro expansion with the peptides. Long-term T-cell lines (TCLs) were induced with the peptides, and the cytokine production, cross-reactivity, and T-cell receptor Vbeta subtype expression of the TCLs were analyzed.

RESULTS

CD4(+) T cells specific for both p127-142 and pN135D were readily detected in peripheral blood after a single in vitro stimulation. Whereas the TCLs induced with p127-142 were T(H)2/T(H)0-deviated, those induced with pN135D were T(H)1/T(H)0-deviated and highly cross-reactive with p127-142. Moreover, the pN135D-induced TCLs appeared to use a broader repertoire of T-cell receptor Vbeta subtypes than those induced with p127-142.

CONCLUSION

An APL of an immunodominant allergen epitope was able to induce a novel T(H)1-deviated T-cell population cross-reactive with the natural epitope in vitro. This cell population could have a therapeutic immunomodulatory function in vivo through bystander suppression.

CLINICAL IMPLICATIONS

These results support the idea that altered peptide ligands may be used to enhance the efficacy of peptide immunotherapy.

Peptide immunotherapy for allergic diseases

Specific allergen immunotherapy has been widely practised for almost 100 years. Whilst this approach is disease-modifying and efficacious, the use of whole allergen preparations is associated with an unacceptably high prevalence of allergic adverse events during treatment. Many approaches to reduce the allergenicity of immunotherapy preparations whilst maintaining immunogenicity are under development. One such approach is the use of short synthetic peptides which represent major T-cell epitopes of the allergen. Major potential advantages of this approach include markedly reduced capacity to cross-link immunoglobulin-E and activate mast cells and basophils, and ease of manufacture and standardization. Promising results in preclinical studies have led to the translation of this approach to clinical studies in humans. Peptide immunotherapy is currently under development for allergic and autoimmune diseases.

Cry-consensus peptide, a novel peptide for immunotherapy of Japanese cedar pollinosis, induces Th1-predominant response in Cry j 1-sensitized B10.S mice

Cry-consensus peptide (CCP) is a newly designed peptide for peptide-based immunotherapy of Japanese cedar pollinosis but its mechanism of efficacy is unknown. We investigated the effect of CCP on Cry j 1-specific Th1/Th2 response in a mice model. Subcutaneous injection of CCP decreased Cry j 1-specific IgE and IgG1 in blood slightly, but the IgG2a level was increased significantly in a dose dependent manner. Splenocytes from these mice were stimulated with Cry j 1 in vitro. This inhibited IL-4, IL-5 and IL-10 secretion significantly, but IFN-gamma secretion was increased. In vitro CCP stimulation of splenocytes from Cry j 1-sensitized mice induced more marked Th1-predominancy of cytokine production than native allergen stimulation. Taken together, these data suggest that one of the mechanisms of CCP is dependent on the modulation of the antigen-specific Th1/Th2 response.

Functional Analysis of Birch Pollen Allergen Bet v 1-Specific Regulatory T Cells

Allergen-specific immunotherapy using peptides is an efficient treatment for allergic diseases. Recent studies suggest that the induction of CD4+ regulatory T (Treg) cells might be associated with the suppression of allergic responses in patients after allergen-specific immunotherapy. Our aim was to identify MHC class II promiscuous T cell epitopes for the birch pollen allergen Bet v 1 capable of stimulating Treg cells with the purpose of inhibiting allergic responses. Ag-reactive CD4+ T cell clones were generated from patients with birch pollen allergy and healthy volunteers by in vitro vaccination of PBMC using Bet v 1 synthetic peptides. Several CD4+ T cell clones were induced by using 2 synthetic peptides (Bet v 1(141-156) and Bet v 1(51-68)). Peptide-reactive CD4+ T cells recognized recombinant Bet v 1 protein, indicating that these peptides are produced by the MHC class II Ag processing pathway. Peptide Bet v 1(141-156) appears to be a highly MHC promiscuous epitope since T cell responses restricted by numerous MHC class II molecules (DR4, DR9, DR11, DR15, and DR53) were observed. Two of these clones functioned as typical Treg cells (expressed CD25, GITR, and Foxp3 and suppressed the proliferation and IL-2 secretion of other CD4+ T cells). Notably, the suppressive activity of these Treg cells required cell-cell contact and was not mediated through soluble IL-10 or TGF-beta. The identified promiscuous MHC class II epitope capable of inducing suppressive Treg responses may have important implication for the development of peptide-based Ag-specific immunotherapy to birch pollen allergy.

Prospects for peptide-based immunotherapy for dog allergy

PURPOSE OF REVIEW

Tolerance to ubiquitous environmental substances, allergens, can be accomplished with specific immunotherapy. Conducting therapy with allergen peptides helps to avoid immediate allergic reactions. Dogs are a source of important indoor allergens, which necessitates the development of effective modes of therapy against the allergy they cause.

RECENT FINDINGS

The human T-cell epitopes of the major dog allergen Can f 1 were determined recently. They were found to be distributed in seven epitope regions along the molecule. For the peptide immunotherapy of dog allergy, using a pool of seven peptides, one from each of the epitope regions of Can f 1, seems at present to be the best approach. As Can f 1 is not as immunodominant as the main allergens of some other mammals, it remains to be seen whether peptides from other dog allergens should be included in the pool.

SUMMARY

The use of a pool of seven peptides from the T-cell epitope regions of Can f 1 is likely to be feasible for treating dog allergy in a great majority of Caucasian populations. In the future, patient-tailored preparations of variants of the T-cell epitope-containing peptides may offer a way to enhance the efficacy of peptide-based immunotherapy.

Immunoregulation by targeting T cells in the treatment of allergy and asthma

T-cell responses to allergens are crucial in determining the choice between health and disease. Th2 responses drive synthesis of IgE and the recruitment, maturation, survival and effector function of accessory cells such as eosinophils, basophils and mast cells. Allergen-specific strategies for targeting T-cell responses in established allergic diseases have been employed with success for almost a century. Recently, new insight into the mechanism of action of such approaches has revealed modulation of the delicate and complex regulatory mechanisms including suppression of Th2 responses through antagonistic Th1 responses and regulation through IL-10 and TGFbeta production.

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.

The regulation of allergy and asthma

Allergic diseases and asthma are caused by exaggerated T-helper 2 (Th2)-biased immune responses in genetically susceptible individuals. Tolerance to allergens is a mechanism that normally prevents such responses, but the specific immunological events that mediate tolerance in this setting are poorly understood. A number of recent studies indicate that regulatory T cells (Tregs) play an important role in controlling such Th2-biased responses. Tregs involved in regulating allergy and asthma consist of a family of related types of T cells, including natural CD25+ Tregs as well as inducible forms of antigen-specific adaptive Tregs. Impaired expansion of natural and/or adaptive Tregs is hypothesized to lead to the development of allergy and asthma, and treatment to induce allergen-specific Tregs could provide curative therapies for these problems.

Induction of interleukin-10 and suppressor of cytokine signalling-3 gene expression following peptide immunotherapy

BACKGROUND

Allergen-derived (T cell epitope) peptides may be safer for immunotherapy than native allergen, as they do not cross-link immunoglobulin (Ig)E. However, HLA polymorphism results in multiple potential epitopes. Synthetic peptides of phospholipase (PL) A(2) were selected for a peptide vaccine, on the basis of binding affinity for commonly expressed HLA-DR molecules.

OBJECTIVE

To evaluate treatment with an HLA-DR-based PLA(2) peptide vaccine in subjects with mild honeybee allergy in an open, controlled study.

METHODS

Twelve volunteers with allergy to bee venom received nine intradermal injections of PLA(2) peptides, with six untreated subjects serving as controls. Outcome was assessed by the size of the late-phase cutaneous reaction to allergen, peripheral blood mononuclear cell (PBMC) proliferation, cytokine release, and expression of genes associated with immune regulation.

RESULTS

Subjects receiving peptides showed a decrease in the magnitude of the late-phase cutaneous reaction to bee venom compared with controls (P=0.03). The proliferation of venom-stimulated PBMCs decreased in treated subjects compared with controls (P=0.01). Peptide treatment reduced the production of IL-13 by PLA(2)-stimulated PBMCs (P<0.01) and IFN-gamma (P<0.01), and increased the production of IL-10 (P=0.02). Transcription of the suppressor of cytokine signalling (Socs)3 gene was significantly increased following therapy. A transient, but modest, increase in allergen-specific IgG was also observed.

CONCLUSION

HLA-DR-based T cell epitopes modify surrogate markers associated with successful immunotherapy and induction of immune regulation, supporting the concept that this form of treatment may be efficacious in human allergic disease.

Inhibition of the allergic response by regulatory T cells

PURPOSE OF REVIEW

Allergic diseases are caused by the overdevelopment of T-helper type 2 biased immune responses in susceptible individuals. A number of recent studies indicate that regulatory T cells play an important role in controlling such T-helper type 2 biased responses not only in animal models, but in humans as well, and these will be reviewed in this article.

RECENT FINDINGS

A family of regulatory cells appears to be involved in regulating allergies. Both naturally occurring CD4CD25 regulatory T cells and inducible forms of antigen-specific regulatory T cells, both expressing the transcription factor foxp3, have been shown to inhibit the inappropriate immune responses involved in allergic diseases. Impaired expansion of natural or adaptive regulatory T cells is hypothesized to lead to the development of allergy, and treatment to induce allergen-specific regulatory T cells could provide curative therapies for allergy and asthma.

SUMMARY

Allergen-specific regulatory T cells play an important role in controlling the development of allergy and asthma.

Heat denaturation, a simple method to improve the immunotherapeutic potential of allergens

Allergen-specific immunotherapy (SIT) leads to a long-term amelioration of IgE- and Th2-mediated allergic diseases. However, SIT efficiency is low, with years of treatment along with frequent allergic side effects. The goal of this study was to reduce the side effects by destroying IgE-binding epitopes, i.e. by heat-denaturation, while preserving the therapeutic effect. Mice were immunised with bee venom, birch pollen, grass pollen or cat hair allergens, or with ovalbumin. Heat-denatured allergens bound less IgE but enhanced Th1-dependent IgG2a production as measured by ELISA. The strong IgG2a antibody responses also prevented allergic anaphylaxis in mice, as measured by body temperature drop after a challenge with a high allergen dose. We found that optimal heat-denaturation of allergens left a small proportion in the native conformation to sufficiently stimulate B cells, while non-B cell-mediated effects were probably amplified. The enhanced immunogenicity of heat-denatured allergens is likely explained by enhanced antigen presentation to T cells due to the particulate nature of heat-denatured proteins. This enables Th1 skewing of the immune response with strong production of IgG2a in mice. Therefore, heat-denaturation represents probably the simplest way to enhance the efficiency of SIT while reducing its side effects.

Molecular approaches for new vaccines against allergy

Type I allergy represents an important health problem that is currently affecting approximately 25% of the population in Western countries. Immunotherapy, the only causative treatment of Type I allergy, is currently performed with crude allergen extracts, which contain unpredictable amounts of allergenic, as well as nonallergenic, components. The application of molecular biology for allergen characterization has revealed the molecular nature of the most common allergens and allowed the production of recombinant allergens that equal natural allergens. Based on this knowledge, several different strategies to improve immunotherapy have become available. Until now, T-cell peptides, selected wild-type-like recombinant allergens and genetically modified hypoallergenic allergen derivatives have been evaluated in clinical trials in patients. Immunotherapy based on T-cell peptides has focused on allergen-specific T-cell responses, whereas genetically modified recombinant allergen molecules offer the advantage of combining T-cell and B-cell epitopes. Genetically modified recombinant birch pollen derivatives (Bet v 1-fragments, Bet v 1-trimer) have been evaluated in a double-blind, placebo-controlled, multicenter study. Vaccination with the Bet v 1-derivatives improved symptoms of birch pollen allergy, induced a healthy allergen-specific immunoglobulin G response and led to a significant reduction of seasonally induced boosts of immunoglobulin E.

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.

Peptide Immunotherapy

Synthetic peptides representing T-cell epitopes of allergens and autoantigens have been employed to induce antigen-specific tolerance in vivo in experimental models and the clinical setting. Delivery of peptides orally or by injection leads to reduced reactivity to antigen accompanied by the induction of T cells with a regulatory phenotype. Peptide therapy may provide a safe, effective, and economically viable approach for disease-modifying therapy in autoimmune and allergic diseases.

Efficacy and safety of allergen-specific immunotherapy in rhinitis, rhinoconjunctivitis, and bee/wasp venom allergies

The prevalence of allergic diseases, such as rhinoconjunctivitis, is increasing worldwide, particularly in Westernized countries, where more than 30% of the population is affected. Insect venom allergy is also very common, affecting up to 5% of the population. Allergen-specific immunotherapy is the only immunomodulatory treatment that may alter the natural course of allergic disease, for example by preventing the development of asthma in rhinitic patients. Nonetheless, the risk-benefit ratio for subcutaneous immunotherapy has changed little from when it was first developed a century ago. However, the rapid evolution of new developments, including new methods of administration and new forms of antigen to stimulate the immune system, now offers improvements in both the safety and the efficacy of specific immunotherapy. These developments include the sublingual administration of the relevant antigens, which has a superior safety profile than the original subcutaneous route. This may enable higher dosages to be used over shorter treatment periods, with a lower risk of anaphylactic reactions. Improvements in the purity, specificity, and immunogenicity of the antigens, often as a result of advances in biotechnology, coupled with the development of new adjuvants, may further increase the efficacy of this form of treatment. This review describes and discusses these new developments in the context of the many recent advances in our understanding of the mechanisms by which immunotherapy appears to act.

IgG-blocking antibodies inhibit IgE-mediated anaphylaxis in vivo through both antigen interception and Fc gamma RIIb cross-linking

Although it has long been hypothesized that allergen immunotherapy inhibits allergy, in part, by inducing production of IgG Abs that intercept allergens before they can cross-link mast cell Fc epsilonRI-associated IgE, this blocking Ab hypothesis has never been tested in vivo. In addition, evidence that IgG-allergen interactions can induce anaphylaxis by activating macrophages through Fc gammaRIII suggested that IgG Ab might not be able to inhibit IgE-mediated anaphylaxis without inducing anaphylaxis through this alternative pathway. We have studied active and passive immunization models in mice to approach these issues and to determine whether any inhibition of anaphylaxis observed was a direct effect of allergen neutralization by IgG Ab or an indirect effect of cross-linking of Fc epsilonRI to the inhibitory IgG receptor Fc gammaRIIb. We demonstrate that IgG Ab produced during the course of an immune response or administered passively can completely suppress IgE-mediated anaphylaxis; that these IgG blocking Abs inhibit IgE-mediated anaphylaxis without inducing Fc gammaRIII-mediated anaphylaxis only when IgG Ab concentration is high and challenge allergen dose is low; that allergen epitope density correlates inversely with the allergen dose required to induce both IgE- and Fc gammaRIII-mediated anaphylaxis; and that both allergen interception and Fc gammaRIIb-dependent inhibition contribute to in vivo blocking Ab activity.

Phase I malaria vaccine trial with a long synthetic peptide derived from the merozoite surface protein 3 antigen

The C-terminal conserved region of Plasmodium falciparum merozoite surface protein 3 (MSP3) is the trigger antigen of a protective immune response mediated by cytophilic antibodies. In an open, randomized, two-adjuvant (Montanide ISA 720, aluminum hydroxide) phase I clinical trial we evaluated the safety and immunogenicity of increasing doses of a long synthetic peptide construct spanning the conserved region of MSP3 targeted by biologically active antibodies (MSP3-LSP). Thirty-five healthy volunteers were randomized to receive three subcutaneous injections on days 0, 30, and 120. Of the 100 injections given, 10 caused severe local reactions, 62 caused transient mild to moderate local reactions, and 28 caused no reaction. On the basis of preestablished exclusion criteria, use of the Montanide formulation led to withdrawal of five volunteers after the second injection. This led to a reduction in the subsequent vaccine doses in four of the groups. No vaccine-related serious adverse events occurred throughout the trial. After the third injection, volunteers displayed a marked specific anti-MSP3-LSP antibody response (23/30 individuals, compared with 29/34 individuals for plasma from an area where malaria is endemic), an anti-native MSP3 antibody response (19/30 individuals), a T-cell-antigen-specific proliferative response (26/30 individuals), and gamma interferon production (25/30 individuals). In conclusion, the MSP3-LSP vaccine was immunogenic with both adjuvants, although it was unacceptably reactogenic when it was combined with Montanide. The potential usefulness of the candidate vaccine is supported by the induction of a strong cytophilic response (i.e., the type of anti-MSP3 antibodies involved in antibody-dependent, monocyte-mediated protective mechanisms in areas where malaria is endemic).

Immunotherapy of hypersensitivity to hymenoptera venom

Insect sting allergy is a common condition with a risk of life-threatening anaphylaxis. After a severe reaction, the fear of being restung can significantly reduce quality of life. Venom immunotherapy (VIT) is a highly effective treatment of the underlying type I-sensitisation. This review addresses the mechanisms of immune modulation by VIT and outlines current clinical application. Although highly effective in the majority of patients, VIT fails in a few individuals. It can also cause systemic allergic side effects, restricting its application to physicians trained in the treatment of anaphylaxis. This review discusses several new strategies to overcome these problems, which are presently a promising focus of research. These include the use of new adjuvants, of recombinant and genetically engineered venom allergens, as well as vaccination with peptides.

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.

Immunomodulatory potential of heteroclitic analogs of the dominant T-cell epitope of lipocalin allergen Bos d 2 on specific T cells

Peptide-based allergen immunotherapy is a novel alternative for conventional allergen immunotherapy. Here, we have characterized the immunomodulatory potential of heteroclitic peptide analogs of the immunodominant epitope of lipocalin allergen Bos d 2 on specific human T-cell clones. The TCR affinity of Bos d 2-specific T-cell clones for the natural peptide ligand and its heteroclitic analogs was assessed with fluorescent-labeled MHC class II tetramers. The activation and cytokine production of the clones were analyzed upon stimulation with the different ligands. Moreover, the capacity of the heteroclitic analogs to induce hyporesponsiveness and cell death was examined. The T-cell clones F1-9 and K3-2 bound MHC class II tetramers loaded with the heteroclitic peptide analogs of the immunodominant epitope of Bos d 2 with increased affinity. At similar peptide concentrations, stimulation of the clones with the heteroclitic analogs favored increased IFN-gamma/IL-4 and IFN-gamma/IL-5 ratios in comparison with stimulation with the natural peptide ligand. Moreover, the T-cell clones stimulated with the heteroclitic analogs exhibited an increased susceptibility to cell death or hyporesponsiveness upon re-stimulation. Our results suggest that heteroclitic analogs of a T-cell epitope of an allergen may enhance the efficacy of peptide-based allergen immunotherapy.

The protein composition of honeybee venom reconsidered by a proteomic approach

Pure honeybee venom samples were submitted to two-dimensional gel electrophoresis. A total of 49 excised spots were analyzed by mass spectrometry; 39 of them resulted in the identification of 6 different known bee venom proteins and of 3 proteins that have not been described in such samples before. The first new venom protein has a platelet-derived and vascular endothelial growth factor family domain, the second protein shows no homologies with any known protein and the third matches a hypothetical protein similar to major royal jelly protein 8.

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.

Peptide-based therapeutic vaccines for allergic and autoimmune diseases

Allergic and autoimmune diseases are forms of immune hypersensitivity that increasingly cause chronic ill health. Most current therapies treat symptoms rather than addressing underlying immunological mechanisms. The ability to modify antigen-specific pathogenic responses by therapeutic vaccination offers the prospect of targeted therapy resulting in long-term clinical improvement without nonspecific immune suppression. Examples of specific immune modulation can be found in nature and in established forms of immune desensitization. Understanding and exploiting common mechanisms such as the ability to induce antigen-specific regulatory cells should allow the development of effective therapeutic strategies for both forms of immunopathology. Targeting pathogenic T cells using vaccines consisting of synthetic peptides representing T cell epitopes is one such strategy that is currently being evaluated with encouraging results. Future challenges in the development of therapeutic vaccines include selection of appropriate antigens and peptides, optimization of peptide dose and route of administration and identifying strategies to induce bystander suppression.

Oral administration of a T cell epitope inhibits symptoms and reactions of allergic rhinitis in Japanese cedar pollen allergen-sensitized mice

Although the concept of a T cell epitope in specific immunoprophylaxis was proposed more than a decade ago, it had not been well demonstrated since then that a T cell epitope inhibits symptoms and reactions of allergic disease in animal models. In this study, we have established a system to evaluate symptoms and reactions of allergic rhinitis in mice, and investigated whether oral administration of a T cell epitope relieves sensitized mice of allergic rhinitis. P2-246-259 (RAEVSYVHVNGAKF) is a BALB/c mouse T-cell epitope of Cry j 2, which is a major Japanese cedar (Cryptomeria japonica) pollen allergen. Mice were administered orally with 200 microg/animal of P2-246-259 four times within 2 weeks before sensitization, and sensitized intranasally with Cry j 2 twice. Of the cardinal symptoms of allergic rhinitis, we assessed sneezing and airway obstruction, but could not estimate rhinorrhea or pruritus. Sneezing frequency was significantly increased by challenge with Cry j 2. Concerning allergic reactions, vascular permeability of the nasal mucosa in the early phase and hyperreactivity to histamine in the late phase were also exacerbated by the challenge. These symptoms and reactions of allergic rhinitis were significantly inhibited by oral administration of P2-246-259. These results indicate utility of mice as models for allergic rhinitis; furthermore, the effects of P2-246-259 on allergic rhinitis imply that oral administration of a T cell epitope is a promising approach for specific immunoprophylaxis.

T regulatory-1 cells induce IgG4 production by B cells: role of IL-10

The study was aimed to find out whether T cells with a regulatory profile could regulate the secretion of IgG4. Using tetanus Ag we found that PBMC of healthy human donors responded to exogenous IL-10 by down-regulating IgG1 and increasing IgG4 secretion. IgE was not affected. To investigate the direct effect of IL-10-producing T cells on B cells, we generated T cell clones (TCC) with two different cytokine profiles: first, IL-10high, IL-2low, IL-4low TCC, and second, IL-10low, IL-2high, IL-4high. The T cell-dependent Ab secretion was measured by coculturing purified CD19+ B cells and the TCC. Interestingly, we found that IgG4 production in the coculture correlated with the TCC production of IL-10 (r2 = 0.352, p = 0.0001), but not with IL-2, IL-4, nor IFN-gamma. IgE showed only a trend with regard to IL-4. Further, there was decreased Ab secretion in the absence of T-B cell contact. IL-10 also induced IgG4 when added to a Th1 TCC-B cell coculture system. The present study thus shows that in T-B cell coculture, IL-10, if induced by the TCC or added to the system, down-regulates the immune response by inducing IgG4 secretion. This establishes a direct implication of IL-10 in humoral hyporesponsiveness, particularly in compartments where the T-B cell interplay determines the subsequent immune response. The correlation between IgG4 and IL-10 (r2 = 0.352) indicates that IL-10 is an important but not the only factor for IgG4 induction.

Potential role of interleukin-10-secreting regulatory T cells in allergy and asthma

Allergic diseases are caused by aberrant T-helper-2 immune responses in susceptible individuals. Both naturally occurring CD4(+)CD25(+) regulatory T cells and inducible populations of antigen-specific interleukin-10-secreting regulatory T cells inhibit these inappropriate immune responses in experimental models. This article discusses the evidence that regulatory T-cell function might be impaired in allergic and asthmatic disease and that certain therapeutic regimens might function, at least in part, to promote regulatory T-cell generation. Current research strategies seek to exploit these observations to improve the generation of allergen-specific regulatory T-cell populations with the potential to provide the safe and long-term alleviation of disease symptoms.

New strategies in the treatment and prevention of allergic diseases

Allergic diseases (AD) are more prevalent today than 30 years ago but over the same period, few novel efficacious drugs have been discovered to treat, control or even cure these disorders. Topical or systemic glucocorticosteroids combined with symptom-relieving medications, such as beta 2 -adrenoceptor agonists, leukotriene inhibitors or antihistamines, are still the mainstay of antiallergic treatment. Modified glucocorticosteroids with less adverse effects, better bronchodilators and new selective mediator inhibitors may improve symptom control in the future. Only specific immunotherapy has shown potential for long-lasting disease-modifying effects. Immunomodulation is a therapeutic goal, aiming to modify the dominant helper T cell Type 2 inflammation to a helper T cell Type 1 response using modified allergens, mycobacteria or CpG oligodeoxynucleotides. Humanised monoclonal anti-IgE antibodies are an exciting new immunomodulatory medication that are expected to reach the clinical practice and have recently been licensed in Australia and the US. Advances in molecular, cellular and genetic research of the immunopathophysiology of AD have led to the development of new antagonists for cytokines, chemokines, receptors, second messengers and transcription factors that may become available for clinical use in the next 10 years. Specific diets supplemented with antioxidants or probiotics need further study but offer promise as safe and cheap preventative medicine. The strong genetic component of AD and the Human Genome Project have opened a new field of research, and modification or replacement of target genes has a curative potential with exciting new therapeutic developments in the years ahead.

Antigen presentation of the immunodominant T-cell epitope of the major mugwort pollen allergen, Art v 1, is associated with the expression of HLA-DRB1∗01

BACKGROUND

Mugwort pollen allergens are the main cause of pollinosis in late summer in Europe. Ninety-five percent of patients allergic to mugwort are sensitized to the major allergen Art v 1. In contrast to other common pollen allergens that contain multiple T-cell epitopes, Art v 1 contains only 1 immunodominant T-cell epitope (Art v 1 25-36 ).

OBJECTIVE

To characterize the minimal epitope of Art v 1 25-36 and to investigate a possible association of Art v 1 reactivity with HLA class II phenotypes.

METHODS

Art v 1-specific T-cell lines and clones were established from 51 patients with clinically defined mugwort pollen allergy and IgE specific for Art v 1. To define minimal epitopes and binding sites within Art v 1 25-36 , truncated and single-substitution analog peptides were used for T-cell stimulation. To study HLA restriction, monoclonal anti-HLA antibodies and antigen-presenting cells with defined HLA-DRB and -DQB1 alleles were used. HLA typing of patients with allergy was performed by hybridization with sequence-specific oligonucleotides, PCR, and nucleotide sequencing.

RESULTS

In 96% of the patients, a cellular response to Art v 1 25-36 was obtained, and a core region of 5 to 10 amino acids containing 3 to 5 amino acids essential for T-cell reactivity was defined. The frequency of HLA-DRB1 * 01 in patients recognizing Art v 1 25-36 was significantly increased as compared with healthy controls (69% vs 21%; odds ratio, 8.45; P < 10 -6 ), and HLA-DRB1 * 01 was identified as the main restriction element for the presentation of the immunodominant epitope.

CONCLUSIONS

Allergy to Art v 1 is characterized by a uniform T-cell response. The disease is apparently associated with the HLA-DR1 phenotype. Therefore, mugwort pollinosis is an ideal candidate for a peptide-based immunotherapy.

Recombinant allergens for immunotherapy. Where do we stand?

PURPOSE OF REVIEW

This review is an update regarding the development of recombinant allergens from the laboratory bench to clinical applications. Special attention will be given to the potential improvement of allergen-specific immunotherapy through the use of recombinant allergens.

RECENT FINDINGS

Currently used therapeutic allergen extracts suffer from several important disadvantages and therefore may be replaced by recombinant allergens in the near future. Recent studies indicate that recombinant allergen-based diagnostic tests can be used for selection of patients for immunotherapy and to analyse the mechanisms underlying immunotherapy. Furthermore, recombinant and peptide technologies have been used for the generation of allergy vaccines with reduced allergenic activity. Applying the new technologies, the vaccines can be formulated to target either B cells or T cells, or both cell types. Very recently, encouraging results were obtained in an immunotherapy trial performed with genetically engineered allergens.

SUMMARY

Recombinant allergen-based diagnostic tests will improve the selection of patients for immunotherapy. The first immunotherapy trial with recombinant allergens provides information about mechanisms underlying immunotherapy and holds promise that new types of allergy vaccines based on recombinant allergens will become available soon.

Allergen immunotherapy in the prevention of asthma

PURPOSE OF REVIEW

Asthma is a disease causing significant morbidity and mortality. In the recent past, there has been an explosion of pharmacotherapeutic options attempting to control the disease. Unfortunately, none of the current options offers the promise of prevention or a permanent cure. However, there appear to be exciting, new data emerging to support the hypothesis that the prevention or early treatment of allergic rhinitis, such as with the use of allergen immunotherapy, may help mitigate the severity of bronchial symptoms and even prevent the development of asthma. In this paper, we review recent research published proposing immunotherapy as a means of preventing the development of, or at least ameliorating, allergic asthma.

RECENT FINDINGS

There is evidence that the upper and lower airways may be considered a single unit, with the nasal and bronchial mucosa having features in common. Epidemiological, pathophysiological and clinical studies have shown that they can be affected by similar inflammatory triggers, with interconnected mechanisms amplifying the inflammatory cascade. Allergic rhinitis is interrelated to, and is a risk factor for, the development of asthma. An evidence-based review validates the successful use of allergen immunotherapy in treating allergic rhinitis and asthma. There is promising evidence advocating its use in the prevention of clinical asthma.

SUMMARY

This article explores current research pertaining to the use of immunomodulation, such as by using allergen immunotherapy, to ameliorate and prevent the development of allergic asthma.