Effects of peptide therapy on ex vivo T-cell responses

Peptide-based immunotherapy: a novel strategy for allergic disease

The T-cell component of the antigen-specific immune response is the target of various novel interventions to modify chronic immunologic disorders, such as allergic diseases. Recent clinical trials have evaluated the safety and efficacy of therapeutic vaccines consisting of short, synthetic, allergen-derived peptides, corresponding to T-cell epitopes from the eliciting antigen. The main advantage of such an approach is the reduction in systemic, immunoglobulin E-mediated adverse events compared with existing whole allergen immunotherapy, often referred to as 'allergy shots'. T-cell peptide epitopes, although capable of inducing immunologic tolerance, are short linear structures that have reduced ability to cross-link mast cell- and basophil-bound immunoglobulin E. The precise mechanism of tolerance induction remains incompletely defined. However, recent data indicate that peptide therapy induces/expands a population of antigen-specific regulatory T-cells. A novel form of treatment combining efficacy with a substantially decreased occurrence of adverse events is likely to have a major impact on the management and prevalence of allergic diseases. Furthermore, the principles of epitope-specific therapy hold promise for the development of therapeutic vaccines for the treatment of autoimmune diseases.

Fel d 1-airway inflammation prevention and treatment by co-immunization vaccine via induction of CD4+CD25-Foxp3+ Treg cells

Pet allergens are major causes for asthma and allergic rhinitis. Fel d 1 protein, a key pet allergen from domestic cat, can sensitize host and trigger asthma attack. In this study, we report that co-immunization with recombinant Fel d 1 protein (rFel d 1) plus plasmid DNA that contains Fe1 d 1 gene was effective in preventing and treating the natural Fel d 1 (nFel d 1) induced allergic airway inflammation in mice. A population of T regulatory cells (iTreg) exhibiting a CD4+CD25-Foxp3+ phenotype and expressing IL-10 and TGF-β was induced by this co-immunization strategy. Furthermore, after adoptive transfers of the iTreg cells, mice that were pre-sensitized and challenged with nFel d 1 exhibited less signs of allergic inflammation, AHR and a reduced allergic immune response. These data indicate that co-immunization with DNA and protein mixture vaccine may be an effective treatment for cat allergy.

Structure-based prediction of Major Histocompatibility Complex (MHC) epitopes

Because of the enormous diversity of both MHC proteins and peptide epitopes, computational epitope prediction methods are needed in order to supplement limited experimental data. These prediction methods are useful for guiding experiments and have many potential biomedical applications. Unlike popular sequence-based methods, structure-based epitope prediction methods can predict epitopes for multiple MHC types with highly distinct peptide binding propensities. In this chapter, we describe in detail our previously developed structure-based epitope prediction methods for both class I and class II MHC proteins. We also discuss the relative advantages and disadvantages of sequence-based versus structure-based methods and how to evaluate prediction performance.

An aerobiological perspective in allergy and asthma

Allergic diseases are amongst the most common chronic disorders worldwide. Today, more than 300 million of the population is known to suffer from one or other allergic ailments affecting the socio-economic quality of life. Major causative agents implicated are pollen grains, fungal spores, dust mites, insect debris, animal epithelia, etc. Several aerobiological studies have been conducted in different parts of the world to ascertain aerial concentration and seasonality of pollen grains and fungi. Especially from clinical point of view, it is important to know the details about the pollen season and pollen load in the atmosphere. The flowering time of higher plants are events that come periodically in each season, but the time of blooming may differ from year to year, in different geographic locations. Based on differences recorded in several years of observations in airborne pollen, pollen calendars are drawn as an aid to allergy diagnosis and management. This review article emphasises on various aerobiological parameters of environmental pollen from different parts of the world with special emphasis from India. The role of aerobiology in the diagnosis and management of allergic diseases is reviewed briefly in this article.

Peptide and recombinant immunotherapy

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

Allergic rhinitis: an update on disease, present treatments and future prospects

Allergic rhinitis (AR) is an inflammation of nasal mucosa mediated by IgE-associated processes occurring independently, or concurrently with asthma. AR is characterized by sensitization-formation and expression of antigen specific IgE, followed by inflammation in two phases. The early phase response involves cross linking of IgE molecules leading to degranulation of mast cells and release of preformed mediators such as histamine and tryptase, or newly synthesized mediators such as prostaglandins and leukotrienes. The late phase response is predominated by the presence of eosinophils, lymphocytes, cytokines, and adhesion molecules. Newer insights reveal that the whole phenomenon of immunological inflammation is intricately knit with neural pathways, which strongly influence the process. Furthermore, AR can impact psychological health and vice versa. Classical pharmacotherapy of AR includes use of oral or topical antihistamines, oral antileukotrienes, topical corticosteroids, mast cell stabilizers, decongestants, and an anticholinergic agent. Among immunomodulatory treatments, immunotherapy is gaining widespread use, while antibody treatment is restricted mainly to resistant cases. Several small molecules with improved safety profile, or targeting novel mechanisms are in the clinical research. Newer antihistamines and corticosteroids with improved safety profile and antagonists of the prostaglandin D(2) (CRTH2) receptors are likely to be available for clinical use in the near future. Lack of properly validated animal models and complexities associated with clinical evaluation are some of the challenges facing the researchers in AR. Comprehensive understanding of immunological and neurological processes in AR would facilitate the future quest for more effective and safer management of this disease.

Immunotherapy with peptides

Specific allergen immunotherapy is clinically effective and disease modifying. It has a duration of effect that exceeds the treatment period and prevents both the progression of allergic rhinitis to asthma and the acquisition of new allergic sensitizations. However, immunotherapy is associated with a high frequency of adverse events related to the allergenicity of vaccines. Allergenicity is conferred by the presence of intact B-cell epitopes that crosslink allergen-specific IgE on effector cells. The use of linear peptide sequences representing fragments of the native allergen is one approach to reduce allergenicity. Preclinical models of peptide immunotherapy have demonstrated efficacy in both autoimmunity and allergy. Translation of this technology into the clinic has gained momentum in recent years based on encouraging results from early clinical trials. To date, efforts have focused on two major allergens, but vaccines to a broader range of molecules are currently in clinical development. Mechanistically, peptide immunotherapy appears to work through the induction of adaptive, allergen-specific regulatory T cells that secrete the immunoregulatory cytokine IL-10. There is also evidence that peptide immunotherapy targeting allergen-specific T cells can indirectly modulate allergen-specific B-cell responses. Peptide immunotherapy may provide a safe and efficacious alternative to conventional subcutaneous and/or sublingual approaches using native allergen preparations.

Clinical practice: Allergen-specific immunotherapy in children: facts and FAQs

Allergen-specific immunotherapy (SIT) in its various application forms represents the main treatment approach of IgE-mediated allergic diseases in adults and children. Despite this clear recommendation, many particularities of products, patient characteristics, and product availability in different countries hamper the use of allergen-specific immunotherapy in particular in children. The frequently asked questions by parents, patients, and physicians are the backbone of this review. Thus, the potentials and limitations of allergen-specific immunotherapy in children and adolescents will be highlighted. IgE-mediated allergic diseases are affecting about 20% of the population. They manifest commonly early in life, and hence, the use of SIT should be considered also early in the course of the disease.

T cell epitope-based allergy vaccines

Specific immunotherapy (SIT) with extracts containing intact allergen molecules is clinically efficacious, but associated with frequent adverse events related to the allergic sensitization of the patient. As a result, treatment is initiated in an incremental dose fashion which ultimately achieves a plateau (maintenance dose) that may be continued for several years. Reduction of allergic adverse events may allow safer and more rapid treatment Thus, many groups have developed and evaluated strategies to reduce allergenicity whilst maintaining immunogenicity, the latter being required to achieve specific modulation of the immune response. Peptide immunotherapy can be used to target T and/or B cells in an antigen-specific manner. To date, only approaches that target T cells have been clinically evaluated. Short, synthetic peptides representing immunodominant T cell epitopes of major allergens are able to modulate allergen-specific T cell responses in the absence of IgE cross linking and activation of effector cells. Here we review clinical and mechanistic studies associated with peptide immunotherapy targeting allergy to cats or to bee venom. 

Update in the mechanisms of allergen-specific immunotheraphy

Allergic diseases represent a complex innate and adoptive immune response to natural environmental allergens with Th2-type T cells and allergen-specific IgE predominance. Allergen-specific immunotherapy is the most effective therapeutic approach for disregulated immune response towards allergens by enhancing immune tolerance mechanisms. The main aim of immunotherapy is the generation of allergen nonresponsive or tolerant T cells in sensitized patients and downregulation of predominant T cell- and IgE-mediated immune responses. During allergen-specific immunotherapy, T regulatory cells are generated, which secrete IL-10 and induce allergen-specific B cells for the production of IgG4 antibodies. These mechanisms induce tolerance to antigens that reduces allergic symptoms. Although current knowledge highlights the role of T regulatory cell-mediated immunetolerance, definite mechanisms that lead to a successful clinical outcomes of allergen-specific immunotherapy still remains an open area of research.

Towards universal structure-based prediction of class II MHC epitopes for diverse allotypes

The binding of peptide fragments of antigens to class II MHC proteins is a crucial step in initiating a helper T cell immune response. The discovery of these peptide epitopes is important for understanding the normal immune response and its misregulation in autoimmunity and allergies and also for vaccine design. In spite of their biomedical importance, the high diversity of class II MHC proteins combined with the large number of possible peptide sequences make comprehensive experimental determination of epitopes for all MHC allotypes infeasible. Computational methods can address this need by predicting epitopes for a particular MHC allotype. We present a structure-based method for predicting class II epitopes that combines molecular mechanics docking of a fully flexible peptide into the MHC binding cleft followed by binding affinity prediction using a machine learning classifier trained on interaction energy components calculated from the docking solution. Although the primary advantage of structure-based prediction methods over the commonly employed sequence-based methods is their applicability to essentially any MHC allotype, this has not yet been convincingly demonstrated. In order to test the transferability of the prediction method to different MHC proteins, we trained the scoring method on binding data for DRB1*0101 and used it to make predictions for multiple MHC allotypes with distinct peptide binding specificities including representatives from the other human class II MHC loci, HLA-DP and HLA-DQ, as well as for two murine allotypes. The results showed that the prediction method was able to achieve significant discrimination between epitope and non-epitope peptides for all MHC allotypes examined, based on AUC values in the range 0.632-0.821. We also discuss how accounting for peptide binding in multiple registers to class II MHC largely explains the systematically worse performance of prediction methods for class II MHC compared with those for class I MHC based on quantitative prediction performance estimates for peptide binding to class II MHC in a fixed register.

MultiRTA: a simple yet reliable method for predicting peptide binding affinities for multiple class II MHC allotypes

Background

The binding of peptide fragments of antigens to class II MHC is a crucial step in initiating a helper T cell immune response. The identification of such peptide epitopes has potential applications in vaccine design and in better understanding autoimmune diseases and allergies. However, comprehensive experimental determination of peptide-MHC binding affinities is infeasible due to MHC diversity and the large number of possible peptide sequences. Computational methods trained on the limited experimental binding data can address this challenge. We present the MultiRTA method, an extension of our previous single-type RTA prediction method, which allows the prediction of peptide binding affinities for multiple MHC allotypes not used to train the model. Thus predictions can be made for many MHC allotypes for which experimental binding data is unavailable.

Results

We fit MultiRTA models for both HLA-DR and HLA-DP using large experimental binding data sets. The performance in predicting binding affinities for novel MHC allotypes, not in the training set, was tested in two different ways. First, we performed leave-one-allele-out cross-validation, in which predictions are made for one allotype using a model fit to binding data for the remaining MHC allotypes. Comparison of the HLA-DR results with those of two other prediction methods applied to the same data sets showed that MultiRTA achieved performance comparable to NetMHCIIpan and better than the earlier TEPITOPE method. We also directly tested model transferability by making leave-one-allele-out predictions for additional experimentally characterized sets of overlapping peptide epitopes binding to multiple MHC allotypes. In addition, we determined the applicability of prediction methods like MultiRTA to other MHC allotypes by examining the degree of MHC variation accounted for in the training set. An examination of predictions for the promiscuous binding CLIP peptide revealed variations in binding affinity among alleles as well as potentially distinct binding registers for HLA-DR and HLA-DP. Finally, we analyzed the optimal MultiRTA parameters to discover the most important peptide residues for promiscuous and allele-specific binding to HLA-DR and HLA-DP allotypes.

Conclusions

The MultiRTA method yields competitive performance but with a significantly simpler and physically interpretable model compared with previous prediction methods. A MultiRTA prediction webserver is available at http://bordnerlab.org/MultiRTA.

Epitope-specific T-cell responses and allergic phenotypes: implications for T-cell peptide therapy

In the 1990s, elucidation of the primary amino acid sequence of several major allergens using molecular cloning techniques opened the door to T-cell epitope mapping studies. Such analyses underscored the complexity of the allergen-specific T-cell repertoire and the challenges to using allergen-derived peptides to identify epitope-specific differences associated with allergic and nonallergic responses. This review highlights important factors that may influence the nature of epitope-specific T-cell responses observed in vitro. These include the properties of the allergen, genetics of the host and selection of patients with defined allergic phenotypes based on serum antibody profiles and skin test reactivity. By taking these factors into account, T-cell epitope-specific differences associated with distinct allergic phenotypes can be identified. Observations at the T-cell epitope level undermine the Th1/Th2 paradigm as a model for the development of allergic versus nonallergic responses. Instead, they support the mounting data that point to a network of interactions between T helper cells and regulatory T cells, which controls the allergic response. The ability of peptides that localize to polypeptide chain 2 of the major cat allergen, Fel d 1, to preferentially induce interleukin-10 and interferon-gamma is discussed. Mechanisms whereby specific allergen-derived peptides may modify the T-cell repertoire and influence the immune outcome are also outlined. Further investigation of allergen-derived T-cell epitopes is warranted in order to optimize the design of peptide vaccines for the treatment of allergic disease.

Tracking antigen-specific T-cells during clinical tolerance induction in humans

Allergen immunotherapy presents an opportunity to define mechanisms of induction of clinical tolerance in humans. Significant progress has been made in our understanding of changes in T cell responses during immunotherapy, but existing work has largely been based on functional T cell assays. HLA-peptide-tetrameric complexes allow the tracking of antigen-specific T-cell populations based on the presence of specific T-cell receptors and when combined with functional assays allow a closer assessment of the potential roles of T-cell anergy and clonotype evolution. We sought to develop tools to facilitate tracking of antigen-specific T-cell populations during wasp-venom immunotherapy in people with wasp-venom allergy. We first defined dominant immunogenic regions within Ves v 5, a constituent of wasp venom that is known to represent a target antigen for T-cells. We next identified HLA-DRB1*1501 restricted epitopes and used HLA class II tetrameric complexes alongside cytokine responses to Ves v 5 to track T-cell responses during immunotherapy. In contrast to previous reports, we show that there was a significant initial induction of IL-4 producing antigen-specific T-cells within the first 3–5 weeks of immunotherapy which was followed by reduction of circulating effector antigen-specific T-cells despite escalation of wasp-venom dosage. However, there was sustained induction of IL-10-producing and FOXP3 positive antigen-specific T cells. We observed that these IL-10 producing cells could share a common precursor with IL-4-producing T cells specific for the same epitope. Clinical tolerance induction in humans is associated with dynamic changes in frequencies of antigen-specific T-cells, with a marked loss of IL-4-producing T-cells and the acquisition of IL-10-producing and FOXP3-positive antigen-specific CD4+ T-cells that can derive from a common shared precursor to pre-treatment effector T-cells. The development of new approaches to track antigen specific T-cell responses during immunotherapy can provide novel insights into mechanisms of tolerance induction in humans and identify new potential treatment targets.

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.

[Allergen-specific Immunotherapy for children and adolescents - a review on available products in Austria]

A pediatric consensus report on allergen-specific immunotherapy for children and adolescents is presented for Austria. Products on the market in Austria are presented and categorised according to studies performed on the target population of children and adolescents, their effectiveness and indication. In general, more clinical studies on children and adolescents are mandatory for most of the available allergen-specific immunotherapeutics. In addition, the use of allergen-specific immunotherapy in general should be promoted as the exclusive treatment with long-lasting effects in type I allergies in particular in children.

Therapeutic manipulation of immune tolerance in allergic disease

Immune tolerance - the adaptation of the immune system to external antigens or allergens - might be therapeutically manipulated to restore normal immunity in conditions such as allergy, asthma and autoimmune diseases. The field of allergen-specific immunotherapy is experiencing exciting and novel developments for the treatment of allergic and autoimmune diseases, and recent insights into the reciprocal regulation and counter-balance between different T-cell subsets is foreseen to facilitate new strategies for immunointervention. This Review highlights current knowledge of immunomodulatory therapies for the manipulation of immune tolerance and highlights recent approaches to improve allergen-specific immunotherapy for the treatment of allergic diseases.

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.

Clinical presentation and time course in hypersensitivity reactions to beta-lactams

BACKGROUND

beta-lactam hypersensitivity reactions are classified as immediate or nonimmediate. Diagnosis is usually based upon skin tests and provocation challenges.

OBJECTIVE

The time course of the reactions in proven beta-lactam hypersensitivities was studied and then correlated with the symptoms to determine the relationship between the clinical presentations and the time course.

METHOD

All of the patients who consulted between 1996 and 2004 for a suspected beta-lactam hypersensitivity reaction were studied. Two hundred and ten patients with a proven hypersensitivity reaction diagnosed according to the European Network on Drug Allergy were included in the present study.

RESULTS

Of the patients, 36.7% had urticaria as a single symptom, 19.1% anaphylaxis without shock, 17.6% anaphylactic shock and 19.1% maculopapular exanthema. Anaphylactic shock and anaphylaxis mostly occurred within 1 h after drug administration. Exanthema mainly occurred after 24 h. Urticaria as a single symptom occurred at any time. A firm diagnosis was determined using immediate-reading skin prick (10.0%) and intradermal tests (38.1%), late-reading skin tests (19.1%) or provocation tests (32.9%).

CONCLUSION AND CLINICAL IMPLICATION

Depending on the time course of the reaction, three clinical groups were identified: anaphylaxis and anaphylactic shock (immediate reaction); maculopapular exanthema (late reaction) as well as urticaria (immediate and late reaction).

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.

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.

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.

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.

Basophil interleukin 4 and interleukin 13 production is suppressed during the early phase of rush immunotherapy

BACKGROUND

Studies using rush immunotherapy (RIT) have shown that rapid protection can be achieved using protocols allowing a fast increment of allergen dose. We examined the early effects of RIT on basophil numbers and expression of CD203c, production of interleukin (IL)-4 and IL-13 and histamine release by basophils in the peripheral blood of patients treated with immunotherapy and controls.

METHODS

Twelve patients treated with RIT and 4 untreated controls were included in the study. Any adverse events were evaluated during the incremental phase of RIT. Mononuclear cells were isolated before the start of RIT and 3 days, 1 week, 4 weeks and 3 months after the beginning of the treatment. Histamine release upon allergen stimulation, expression of CD203c and allergen-induced production of IL-4 and IL-13 by basophils were examined.

RESULTS

Significant decreases in blood basophil count (p = 0.02) were observed early in the treatment, returning to baseline values 1 week after the start of RIT. Similarly, histamine release decreased at day 3 (p = 0.02), but returned to pretreatment levels after 1 week. Also, the percentage of IL-4+ and IL-13+ basophils and levels of CD203c expression were markedly reduced early in the treatment. IL-4 and IL-13 production correlated with histamine release and CD203c expression. Histamine release and production of IL-4 and IL-13 by basophils before the treatment correlated with the severity of adverse events during the incremental phase of RIT.

CONCLUSION

We report the decrease in blood basophil numbers, their lower activation status and the reduced production of IL-4 and IL-13 early in the course of RIT. This early suppression of basophil activation could be one mechanism behind the protective effect of RIT.

The DR4-DQ8 haplotype and a specific T cell receptor Vbeta T cell subset are associated with absence of allergy to Can f 1

BACKGROUND

The significance of specific T cell receptor (TCR) Vbeta subtypes and human leucocyte antigen (HLA) class II alleles for the development of allergy to lipocalin allergens such as the major dog allergen Can f 1 is not clear at present.

OBJECTIVE

To characterize the TCR Vbeta usage in the Can f 1-specific T cell lines and the HLA class II genotypes of Can f 1-allergic and non-allergic subjects.

METHODS

T cell lines were induced with recombinant Can f 1 from the peripheral blood mononuclear cells of 12 non-atopic dog owners and 26 dog-allergic patients. Thirteen of the dog-allergic subjects were sensitized to Can f 1. Expression of the TCR Vbeta subtypes on CD4(+) T cells in the T cell lines was measured by flow cytometry. The subjects were HLA genotyped for DRB1, DQB1 and DPB1 loci.

RESULTS

Can f 1-specific T cell lines were obtained from 18 subjects, with either positive (n=8) or negative (n=10) skin prick tests (SPTs) to recombinant Can f 1. The frequency of TCR Vbeta5.1(+) T cells was significantly higher in the T cell lines of subjects with negative SPTs to the allergen. Moreover, DR4-DQ8 haplotype was over-represented among these subjects.

CONCLUSION

The DR4-DQ8 haplotype and the TCR Vbeta5.1(+) CD4(+) T cells may be protective against allergy to Can f 1.

Mechanisms of allergen specific immunotherapy--T-cell tolerance and more

Specific immune suppression and induction of tolerance are essential processes in the regulation and circumvention of immune defence. The balance between allergen-specific T-regulatory (Treg) cells and T helper 2 cells appears to be decisive in the development of allergic and healthy immune response against allergens. Treg cells consistently represent the dominant subset specific for common environmental allergens in healthy individuals. In contrast, there is a high frequency of allergen-specific T helper 2 cells in allergic individuals. A decrease in interleukin (IL)-4, IL-5 and IL-13 production by allergen-specific CD4+ T cells due to the induction of peripheral T cell tolerance is the most essential step in allergen-specific immunotherapy (SIT). Suppressed proliferative and cytokine responses against the major allergens are induced by multiple suppressor factors, such as cytokines like IL-10 and transforming growth factor (TGF)-beta and cell surface molecules like cytotoxic T lymphocyte antigen-4, programmed death-1 and histamine receptor 2. There is considerable rationale for targeting T cells to increase efficacy of SIT. Such novel approaches include the use of modified allergens produced using recombinant DNA technology and adjuvants or additional drugs, which may increase the generation of allergen-specific peripheral tolerance. By the application of the recent knowledge in Treg cells and related mechanisms of peripheral tolerance, more rational and safer approaches are awaiting for the future of prevention and cure of allergic diseases.

Targets in allergy-directed immunotherapy

Allergic diseases such as asthma, atopic dermatitis, rhinitis and urticaria are immunological disorders affecting almost one third of the population in industrialised countries. Therapeutic or prophylactic approaches to turn around the increasing prevalence of these diseases have been intensively investigated. Allergen-specific immunotherapy has been applied in clinical practice for many decades, although varying results and occasional severe side effects have called for more effective and safer vaccines. Recent advances in our knowledge of immunological mechanisms have created several options to comply with these demands. This article will focus on some of the most promising new developments.

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.

Future of allergen-specific immunotherapy

Allergen-specific immunotherapy (SIT) has been used for almost a century as a desensitising therapy for allergic diseases. Administration of appropriate concentrations of allergen extracts has been shown to be reproducibly effective when patients are carefully selected. The disadvantage with allergen extracts is that they consist of nonallergenic or even toxic proteins, and can induce severe side effects including anaphylaxis and death. Several strategies have been developed to tackle this issue. With the introduction of recombinant DNA technology and peptide chemistry, it became possible to produce SIT vaccines with reduced allergenic activity. In addition, current understanding of immunological mechanisms of SIT, particularly the role of regulatory T cells in allergen-specific peripheral tolerance, may enable novel treatment strategies.

Peptide-based vaccination: where do we stand?

PURPOSE OF REVIEW

Allergen-specific immunotherapy represents the only causative approach towards allergy treatment. Specific immunotherapy can, however, include allergic reactions and occasionally life-threatening anaphylaxis. Peptides have been evaluated as a potential therapeutic approach in atopic allergic disease because they have the potential to inhibit T-cell function but not induce anaphylaxis.

RECENT FINDINGS

Data from early clinical trials of peptide vaccination revealed that therapy was associated with a modest improvement in allergic disease, and was accompanied by a high frequency of adverse reactions. More recent studies have demonstrated improved clinical outcomes, improved safety, and have defined the mechanisms of adverse events observed in earlier studies. Mechanisms of peptide vaccination include the hyporesponsiveness of allergen-specific responses and the induction of regulatory T cells and cytokines. Novel peptide design has allowed the generation of fragments that contain T-cell stimulatory epitopes, lack B cell epitopes, and can induce protective IgG responses in both mice and humans. Other approaches have focused on hypoallergenic B-cell epitopes that induce inhibitory IgG antibodies. Peptides that specifically induce regulatory cytokine production would also enhance peptide vaccines. Several recent studies have described immunodominant epitopes from major allergens that may form candidate peptides for use in peptide vaccination.

SUMMARY

The manipulation of peptide epitopes may provide a strategy for the rational design of peptide allergy vaccines further improving safety and efficacy.

Prevention and treatment of hymenoptera venom allergy: guidelines for clinical practice

Based on the knowledge of the living conditions and habitat of social Aculeatae a series of recommendations have been formulated which can potentially greatly minimize the risk of field re-sting. After a systemic sting reaction, patients should be referred to an allergy specialist for evaluation of their allergy, and if necessary venom immunotherapy (VIT). An emergency medical kit should be supplied, its use clearly demonstrated and repeatedly practised until perfected. This should be done under the supervision of a doctor or a trained nurse. Epinephrine by intramuscular injection is regarded as the treatment of choice for acute anaphylaxis. H1-antihistamines alone or in combination with corticosteroids may be effective in mild to moderate reactions confined to the skin and may support the value of treatment with epinephrine in full-blown anaphylaxis. Up to 75% of the patients with a history of systemic anaphylactic sting reaction develop systemic symptoms once again when re-stung. Venom immunotherapy is a highly effective treatment for individuals with a history of systemic reaction and who have specific IgE to venom allergens. The efficacy of VIT in yellow jacket venom allergic patients has been demonstrated also by assessing health-related quality of life. If both skin tests and serum venom specific IgE turn negative, VIT may be stopped after 3 years. After VIT lasting 3-5 years, most patients with mild to moderate anaphylactic symptoms remain protected following discontinuation of VIT even with positive skin tests. Longer term or lifelong treatment should be considered in high-risk patients. Because of the small but relevant risk of re-sting reactions, in these patients, emergency kits, including epinephrine auto-injectors, should be discussed with every patient when stopping VIT.

T regulatory cells in allergy: novel concepts in the pathogenesis, prevention, and treatment of allergic diseases

The identification of T regulatory (T(Reg)) cells as key regulators of immunologic processes in peripheral tolerance to allergens has opened an important era in the prevention and treatment of allergic diseases. Both naturally occurring CD4(+)CD25(+) T(Reg) cells and inducible populations of allergen-specific IL-10-secreting T(R)1 cells inhibit allergen-specific effector cells in experimental models. Allergen-specific T(Reg) cell responses contribute to the control of allergic inflammation in several ways. Skewing of allergen-specific effector T cells to a T(Reg) phenotype appears to be a crucial event in the development of a healthy immune response to allergens and successful outcome in allergen-specific immunotherapy. The increased levels of IL-10 and TGF-beta produced by T(Reg) cells can potently suppress IgE production while simultaneously increasing the production of the noninflammatory antibody isotypes IgG4 and IgA, respectively. T(Reg) cells directly or indirectly suppress effector cells of allergic inflammation, such as mast cells, basophils, and eosinophils, and contribute to remodeling in asthma and atopic dermatitis. In addition, mediators of allergic inflammation that trigger cyclic AMP-associated G protein-coupled receptors, such as histamine receptor 2, might play a role in peripheral tolerance mechanisms against allergens. Current strategies for drug development and allergen-specific immunotherapy exploit these observations with the potential to provide cure for allergic diseases.

Peptide therapy for allergic diseases: basic mechanisms and new clinical approaches

Desensitising allergen immunotherapy has been practised for many decades. Although time consuming, this form of therapy is antigen-specific and disease-modifying, in contrast to palliative pharmacotherapy. However, the use of allergen extracts containing native allergen molecules frequently results in allergic adverse reactions to treatment. Several strategies to reduce the allergenicity of therapeutic preparations, while maintaining their therapeutic benefit, are being developed. Peptide immunotherapy is one such approach. Short synthetic peptides, comprising T cell epitopes of major allergens, were unable to crosslink allergen-specific IgE molecules on basophils in vitro. Treatment of allergic volunteers with allergen peptides resulted in reduced skin, lung and nasal sensitivity to allergen challenge and improved their subjective ability to tolerate allergen exposure. Peptides reduced pro-inflammatory cytokine secretion from peripheral blood cells, whilst increasing the immunosuppressive cytokine IL-10. Furthermore, peptide therapy was associated with the induction of a population of CD4+ T cells with a suppressive functional phenotype. Thus, peptide therapy may be suitable for the antigen-specific treatment of allergic diseases.

A major allergen gene-fusion protein for potential usage in allergen-specific immunotherapy

BACKGROUND

Specific immunotherapy is a common treatment of allergic diseases and could potentially be applied to other immunologic disorders. Despite its use in clinical practice, more defined and safer allergy vaccine preparations are required. Differences between epitopes of IgE that recognize the 3-dimensional structure of allergens and T cells that recognize linear amino acid sequences provide a suitable tool for novel vaccine development for specific immunotherapy.

OBJECTIVE

The aim of the study was to delete B-cell epitopes and prevent IgE crosslinking, but to preserve T-cell epitopes by fusion of 2 major allergens of bee venom because of a change in the conformation.

METHODS

By genetic engineering, we produced a fusion protein composed of the 2 major bee venom allergens: phospholipase A 2 (Api m 1) and hyaluronidase (Api m 2).

RESULTS

The Api m [1/2] fusion protein induced T-cell proliferation and both T H 1-type and T H 2-type cytokine responses. In contrast, IgE reactivity was abolished, and profoundly reduced basophil degranulation and type 1 skin test reactivity was observed. Pretreatment of mice with Api m [1/2] fusion protein significantly suppressed the development of specific IgE as well as other antibody isotypes after immunization with the native allergen.

CONCLUSION

The novel fusion protein of 2 major allergens bypasses IgE binding and mast cell/basophil IgE FcepsilonRI crosslinking and protects from IgE development.

Identification of peptides containing T-cell epitopes of Japanese cedar (Cryptomeria japonica) pollen allergen (Cry j 1) in dogs

Japanese cedar (Cryptomeria japonica, CJ) pollen has been known to cause atopic dermatitis in dogs in Japan. However, since the mechanism of the CJ antigen recognition is not well understood in dogs, it is difficult to develop effective immunotherapy for atopic dermatitis caused by sensitization to CJ pollen. In order to aim at development of a peptide immunotherapy, we tried to identify T-cell epitopes of a major allergen of CJ pollen, Cry j 1, in dogs sensitive to CJ pollen allergen. Peripheral blood mononuclear cells (PBMCs) obtained from 22 dogs experimentally sensitized to CJ pollen allergen and 5 atopic dogs sensitive to CJ pollen allergen were used for mapping of T-cell epitopes of Cry j 1 using 35 kinds of synthesized overlapping peptides of Cry j 1. Reactive peptides were identified based on the results of blastogenic responses of PBMCs against the peptides when the stimulation indices were beyond 2.0. Three reactive peptides were identical in a relatively high population of experimental dogs, which were Nos. 8 (p71-90) (41%), 10 (p91-110) (50%), and 11 (p101-120) (41%). It was considered that these synthesized peptides should contain T-cell epitopes of Cry j 1 in the dogs. However, there were no reactive peptides identical among the five atopic dogs spontaneously sensitive to CJ pollen. The population of dogs experimentally sensitized to CJ pollen antigen will be used in order to investigate effects of a peptide immunotherapy using the reactive peptides. The results in atopic dogs sensitive to CJ pollen antigen will also provide useful information on necessity to develop a tailor-made immunotherapy using reactive peptides in each dog.

Genes of tolerance

Activation-induced cell death, anergy and/or immune response modulation by T-regulatory cells (T(Reg)) are essential mechanisms of peripheral T-cell tolerance. There is growing evidence that anergy, tolerance and active suppression are not entirely distinct, but rather, represent linked mechanisms possibly involving the same cells and multiple suppressor mechanisms. Skewing of allergen-specific effector T cells to T(Reg) cells appears as a crucial event in the control of healthy immune response to allergens and successful allergen-specific immunotherapy. The T(Reg) cell response is characterized by abolished allergen-induced specific T-cell proliferation and suppressed T helper 1 (Th1)- and Th2-type cytokine secretion. In addition, mediators of allergic inflammation that trigger cAMP-associated G-protein coupled receptors, such as histamine receptor 2 may contribute to peripheral tolerance mechanisms. The increased levels of interleukin-10 (IL-10) and transforming growth factor-beta (TGF-beta) that are produced by T(Reg) cells potently suppress immunoglobulin E (IgE) production, while simultaneously increasing production of noninflammatory isotypes IgG4 and IgA, respectively. In addition, T(Reg) cells directly or indirectly suppress effector cells of allergic inflammation such as mast cells, basophils and eosinophils. In conclusion, peripheral tolerance to allergens is controlled by multiple active suppression mechanisms. It is associated with regulation of antibody isotypes and effector cells to the direction of a healthy immune response and opens a window for novel therapies of allergic diseases.

T-cell immunotherapy of allergic disease: the role of CD8+ T cells

PURPOSE OF REVIEW

The scope of this review is to place recent advances in T-cell immunotherapy into an account of our understanding of the potential role of CD8+ T cells in the pathogenesis of allergic disease.

RECENT FINDINGS

Studies over the last year suggest that changes in CD8+ T-cell function may represent key events in successful T-cell immunotherapy. The first human human leukocyte antigen class I allergen epitopes have now been described and will provide further insights into the role of allergen-specific CD8+ T cells.

SUMMARY

The coupling of recent technical advances in the study of antigen-specific T cells with the knowledge of human allergen class I epitopes will promote rapid progress in the field, with potential consequences for the diagnosis, monitoring and immunotherapeutic treatment of affected individuals.

Allergen immunotherapy with cat allergen peptides

Desensitising therapy for allergic diseases has changed little over almost a century of practice. Administration of increasing doses of extracts of allergen source material has been shown to be reproducibly effective when patients are carefully selected and appropriate concentrations of allergen employed. However, specific immunotherapy is limited by the interaction of specific IgE with allergen, leading to a relatively high frequency of adverse events including anaphylaxis and death. Several strategies have been developed to tackle this issue. Most of these rely on reducing the allergenicity of the treatment, whilst maintaining the immunogenicity. The use of short, synthetic peptide sequences corresponding to T-cell epitopes from the allergen has been shown to modify surrogate markers of allergy including cutaneous responses to allergen challenge and ex vivo parameters of T-cell activation. This review discusses recent advances in our understanding of the mechanisms and potential efficacy of this form of therapy.

Peptide immunotherapy for allergic disease

The only disease-modifying treatment available for IgE-mediated disease is specific immunotherapy, but the retention of B cell epitopes in whole allergen preparations confers a risk of IgE-mediated systemic reactions to their administration. Compelling evidence for the central role of T cells in allergic disease suggests that IgE-binding epitopes could be removed from such therapy, improving safety without affecting efficacy. Short, allergen-derived peptides lack the conformational determinants required for IgE crosslinking and are, therefore, an attractive therapeutic possibility. However, human leukocyte antigen (HLA) polymorphism means that T cell peptide epitopes present a huge diversity, which makes the design of peptide-based vaccines problematic. Over the past 10 years, advances in our understanding of epitope selection and major histocompatibility complex (MHC)-peptide-T cell receptor interactions have taken this therapy forward to early clinical trials with human volunteers.

Anti-T-cell strategies in the treatment of allergic disease

Specific allergen immunotherapy (SIT) has been shown to be effective in modulating allergic responses in diseases such as rhinitis and asthma. However, the ability of whole allergen to cross link mast cell bound IgE, resulting in release of mediators such as histamine, has limited the application of this therapy to carefully selected patients who have failed conventional pharmacotherapy. The use of peptide sequences corresponding to T cell epitopes of the allergen has been postulated as an alternative to SIT in which high molar doses of T cell epitope can be delivered over a shorter time period and with improved safety. Using peptides from the sequence of the major cat allergen, Fel d 1, we have demonstrated the ability to induce transient T cell activation, resulting in isolated late asthmatic reactions, which are followed by prolonged periods of allergen-specific hyporesponsiveness, both to peptide re-challenge and to cutaneous challenge with whole allergen. Thus, peptide therapy may prove safe and efficacious in the treatment of allergic diseases.