Synthetic peptides, representing CD4+ T cell epitopes, derived from the primary sequence of allergen molecules have been used to down-regulate allergic inflammation in sensitised individuals. Treatment of allergic diseases with peptides may offer substantial advantages over treatment with native allergen molecules because of the reduced potential for cross-linking IgE bound to the surface of mast cells and basophils.
Methods and Findings
In this study we address the mechanism of action of peptide immunotherapy (PIT) in cat-allergic, asthmatic patients. Cell-division-tracking dyes, cell-mixing experiments, surface phenotyping, and cytokine measurements were used to investigate immunomodulation in peripheral blood mononuclear cells (PBMCs) after therapy. Proliferative responses of PBMCs to allergen extract were significantly reduced after PIT. This was associated with modified cytokine profiles generally characterised by an increase in interleukin-10 and a decrease in interleukin-5 production. CD4+ cells isolated after PIT were able to actively suppress allergen-specific proliferative responses of pretreatment CD4neg PBMCs in co-culture experiments. PIT was associated with a significant increase in surface expression of CD5 on both CD4+ and CD8+ PBMCs.
This study provides evidence for the induction of a population of CD4+ T cells with suppressor/regulatory activity following PIT. Furthermore, up-regulation of cell surface levels of CD5 may contribute to reduced reactivity to allergen.
Immunotherapy is one approach to treating cat allergy and asthma. One mechanism of action might be that it induces a population of CD4 positive T cells with suppressor activity
Allergy and asthma to cat (Felis domesticus) affects about 10% of the population in affluent countries. Immediate allergic symptoms are primarily mediated via IgE antibodies binding to B cell epitopes, whereas late phase inflammatory reactions are mediated via activated T cell recognition of allergen-specific T cell epitopes. Allergen-specific immunotherapy relieves symptoms and is the only treatment inducing a long-lasting protection by induction of protective immune responses. The aim of this study was to produce an allergy vaccine designed with the combined features of attenuated T cell activation, reduced anaphylactic properties, retained molecular integrity and induction of efficient IgE blocking IgG antibodies for safer and efficacious treatment of patients with allergy and asthma to cat. The template gene coding for rFel d 1 was used to introduce random mutations, which was subsequently expressed in large phage libraries. Despite accumulated mutations by up to 7 rounds of iterative error-prone PCR and biopanning, surface topology and structure was essentially maintained using IgE-antibodies from cat allergic patients for phage enrichment. Four candidates were isolated, displaying similar or lower IgE binding, reduced anaphylactic activity as measured by their capacity to induce basophil degranulation and, importantly, a significantly lower T cell reactivity in lymphoproliferative assays compared to the original rFel d 1. In addition, all mutants showed ability to induce blocking antibodies in immunized mice.The approach presented here provides a straightforward procedure to generate a novel type of allergy vaccines for safer and efficacious treatment of allergic patients.
Peptide-based allergen immunotherapy is a promising alternative to conventional allergy vaccine. However, the optimal composition of such vaccines, in terms of the choice of the appropriate peptides, has remained unclear. Knowledge of the epitope-specific T cell responses to allergens can give important information on the pathogenesis and regulation of allergic inflammation. In this study we sought to identify candidate allergen-epitopes that can be used to improve peptide-based allergen immunotherapy.
Tetramer Guided Epitope Mapping was first used to identify CD4+ T cell epitopes for group 1 and group 5 timothy grass pollen allergens. MHC class II tetramer technology was then used in an ex vivo approach to assess the grass pollen-specific CD4+ T cell responses in allergic and non-allergic individuals. The frequency, surface marker phenotype and cytokine profile of these cells were directly analysed by flow cytometry.
CD4+ T cell responses to Timothy grass allergens are directed to a broad range of epitopes characterized by defined immunodominance hierarchy patterns. We observed heterogeneity of phenotype within the allergen-specific CD4+ T cells that depends on the epitope for which the cells are specific. T cell epitopes associated with production of IL-10 or IFN-g are recognized at low frequencies in both allergic and healthy individuals. In contrast, allergy-associated epitopes are only recognized in allergic individuals by high frequency, terminally differentiated allergen-specific CD4+ T cells, which are susceptible to deletion by repeated stimulation with high doses of antigen. Allergen-specific immunotherapy caused significant changes in the epitopes hierarchy of the grass pollen allergen-specific memory CD4 T cell pool.
The ability to evaluate epitope-specific T cell responses to allergens can give important information on the pathogenesis and regulation of allergic inflammation and could be of great use in designing peptide-based allergy vaccination strategies. Some epitopes may play a prominent role in driving a protective response, while others may directly impair the pathogenic response.
Effective immunotherapy for peanut allergy is hampered by a lack of understanding of peanut-reactive CD4+ T cells
To identify, characterize and track Ara h 1-reactive cells in peanut allergic subjects using Ara h 1-specific class II tetramers.
Tetramer Guided Epitope Mapping (TGEM) was used to identify the antigenic peptides within the peanut allergen Ara h 1. Subsequently, HLA class II/Ara h 1-specific tetramers were used to determine the frequency and phenotype of Ara h 1-reactive T cells in peanut-allergic subjects. Cytokine profiles of Ara h 1-reactive T cells were also determined.
Multiple Ara h 1 epitopes with defined HLA restriction were identified. Ara h 1-specific CD4+ T cells were detected in all of the peanut-allergic subjects tested. Ara h 1-reactive T cells in allergic subjects expressed CCR4 but did not express CRTH2. The percentage of Ara h1-reactive cells that expressed the β7 integrin was low compared to total CD4+ T cells. Ara h 1- reactive cells that secreted IFN-γ, IL-4, IL-5, IL-10 and IL-17 were detected.
In peanut-allergic individuals, Ara h 1-reactive T cells occurred at moderate frequencies, were predominantly CCR4+ memory cells and produced IL-4. Class II tetramers can be readily used to detect Ara h 1-reactive T cells in the peripheral blood of peanut allergic subjects without in vitro expansion and would be effective for tracking peanut-reactive CD4+ T cells during immunotherapy.
Food allergy; Peanut; Ara h 1; T cells; Class II tetramers
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.
allergy; epitope; IL-10; immunological tolerance; immunotherapy; peptide; regulatory T cell; T cell
One of the concerns of allergen-specific immunotherapy is the possible boost of inflammatory allergen-specific T lymphocytes. To address this problem, treatment with B cell epitopes devoid of allergen-specific T cell epitopes would be a promising alternative.
In this study, we examined the therapeutic potency of a single mimotope, mimicking a structural IgE epitope of grass pollen allergen Phl p 5 in an established memory mouse model of acute allergic asthma.
In the experimental set-up, BALB/c mice were primed with intraperitoneal injections of recombinant Phl p 5a (rPhl p 5a) and subsequently aerosol challenged with the nebulized allergen. Mice developed signs of bronchial asthma including hypereosinophilia around bronchi, goblet cell hyperplasia and enhanced mucus production.
When the mice were subsequently treated with the grass pollen mimotope coupled to keyhole limpet haemocyanin, bronchial eosinophilic inflammation and mucus hypersecretion decreased. Further, a decrease of Th2 cytokines IL-4 and IL-5 could be observed in the bronchoalveolar lavage (BAL). In contrast to rPhl p 5a, the mimotope was in vitro not able to stimulate splenocytes to proliferation or IL-5 production. Despite not affecting the levels of pre-existing IgE, vaccination with the single mimotope thus rendered anti-inflammatory effects in a mouse model of acute asthma.
From our data, we conclude that vaccination with a mimotope peptide representing a single IgE epitope of the allergen Phl p 5a and being devoid of allergen-specific T cell epitopes is able to down-regulate inflammation in acute asthma.
epitope-specific immunotherapy; grass pollen allergy; mimotopes
Intradermal administration of short overlapping peptides derived from chain 1 of the cat allergen Fel d 1 (FC1P) that did not cross-link IgE, elicited isolated late asthmatic reactions with no visible early or late cutaneous response in 9/40 cat-allergic asthmatics. Four of the nine were human histocompatibility leukocyte antigen DR13–positive, as compared with only 1/31 nonreactors. The other five reactors expressed either DR1 or DR4. To confirm major histocompatibility complex restriction, fibroblast cell lines transfected with HLA-DR molecules were used to present FC1Ps to cat allergen–specific T cell lines derived from subjects before peptide injection. FC1P3 (peptide 28–44 of Fel d 1 chain 1) was recognized in the context of DR13 alleles (DRB1*1301, 1302) and induced specific T cell proliferation and IL-5 production. T cells from a DR1+ responder proliferated and produced IL-5 in the presence of FC1P3 and DR1 (DRB1*0101) fibroblast cell lines, whereas T cells from a DR4+ subject recognized FC1P2 (peptide 22–37) when presented by DRB1*0405. We conclude that short, allergen-derived peptides can directly initiate a major histocompatibility complex–restricted, T cell–dependent late asthmatic reaction, without the requirement for an early IgE/mast cell–dependent response, in sensitized asthmatic subjects.
T lymphocyte; Fel d 1; allergen; allergy; human histocompatibility leukocyte antigen
Subjects with allergic asthma develop isolated late asthmatic reactions after inhalation of allergen‐derived T cell peptides. Animal experiments have shown that airway hyperresponsiveness (AHR) is CD4+ cell‐dependent. It is hypothesised that peptide inhalation produces increases in non‐specific AHR and a T cell‐dominant bronchial mucosal inflammatory response.
Bronchoscopy, with bronchial biopsies and bronchoalveolar lavage (BAL), was performed in 24 subjects with cat allergy 6 h after aerosol inhalation of short overlapping peptides derived from Fel d 1, the major cat allergen. Biopsy specimens and BAL fluid were studied using immunohistochemistry and ELISA.
Twelve of the 24 subjects developed an isolated late asthmatic reaction without a preceding early (mast cell/histamine‐dependent) reaction characteristic of whole allergen inhalation. These responders had significant between‐group differences (responders vs non‐responders) in the changes (peptide vs diluent) in AHR (p = 0.007) and bronchial mucosal CD3+ (p = 0.005), CD4+ (p = 0.006) and thymus‐ and activation‐regulated chemokine (TARC)+ (p = 0.003) but not CD8+ or CD25+ cells or eosinophils, basophils, mast cells and macrophages. The between‐group difference for neutrophils was p = 0.05 but with a non‐significant within‐group value (peptide vs diluent, responders, p = 0.11). In BAL fluid there was a significant between‐group difference in TARC (p = 0.02) but not in histamine, tryptase, basogranulin, C3a or C5a, leukotrienes C4/D4/E4, prostaglandins D2 or F2α.
Direct activation of allergen‐specific airway T cells by peptide inhalation in patients with atopic asthma leads to increased AHR with local increases in CD3+ and CD4+ cells and TARC but no significant changes in eosinophils or basophil/mast cell products. These findings support previous animal experiments which showed a CD4+ dependence for AHR.
Bee venom phospholipase A2 (PLA) is the major allergen in bee sting allergy. It displays three peptide and a glycopeptide T cell epitopes, which are recognized by both allergic and non-allergic bee venom sensitized subjects. In this study PLA- and PLA epitope-specific T cell and cytokine responses in PBMC of bee sting allergic patients were investigated before and after 2 mo of rush immunotherapy with whole bee venom. After successful immunotherapy, PLA and T cell epitope peptide-specific T cell proliferation was suppressed. In addition the PLA- and peptide-induced secretion of type 2 (IL-4, IL-5, and IL-13), as well as type 1 (IL-2 and IFN-gamma) cytokines were abolished, whereas tetanus toxoid-induced cytokine production and proliferation remained unchanged. By culturing PBMC with Ag in the presence of IL-2 or IL-15 the specifically tolerized T cell response could be restored with respect to specific proliferation and secretion of the type 1 T cell cytokines, IL-2 and IFN-gamma. In contrast, IL-4, IL-5, and IL-13 remained suppressed. Treatment of tolerized T cells with IL-4 only partially restored proliferation and induced formation of distinct type 2 cytokine pattern. In spite of the allergen-specific tolerance in T cells, in vitro produced anti-PLA IgE and IgG4 Ab and their corresponding serum levels slightly increased during immunotherapy, while the PLA-specific IgE/IgG4 ratio changed in favor of IgG4. These findings indicate that bee venom immunotherapy induces a state of peripheral tolerance in allergen-specific T cells, but not in specific B cells. The state of T cell tolerance and cytokine pattern can be in vitro modulated by the cytokines IL-2, IL-4, and IL-15, suggesting the importance of microenvironmental cytokines leading to success or failure in immunotherapy.
Peanut allergy is a life-threatening condition; there is currently no cure. While whole allergen extracts are used for specific immunotherapy for many allergies, they can cause severe reactions and even fatalities in peanut allergy.
To identify short, HLA-degenerate CD4+ T cell epitope-based peptides of the major peanut allergen Ara h 1 that target allergen-specific T cells without causing IgE-mediated inflammatory cell activation, as candidates for safe peanut-specific immunotherapy.
Ara h 1-specific CD4+ T cell lines (TCL) were generated from peripheral blood mononuclear cells (PBMC) of peanut-allergic subjects using CFSE-based methodology. T cell epitopes were identified using CFSE and thymidine-based proliferation assays. Epitope HLA-restriction was investigated using blocking antibodies, HLA-genotyping and epitope prediction algorithms. Functional peanut-specific IgE reactivity to peptides was assessed by basophil activation assay.
A total of 145 Ara h 1-specific TCL were generated from 18 HLA-diverse peanut-allergic subjects. The TCL recognized 20-mer peptides throughout Ara h 1. Nine 20-mers containing the most frequently recognized epitopes were selected and their recognition confirmed in 18 additional peanut-allergic subjects. Ten core epitopes were mapped within these 20-mers. These were HLA-DQ and/or HLA–DR restricted, with each presented on at least two different HLA-molecules. Seven short (≤ 20 aa) non-basophil-reactive peptides encompassing all core epitopes were designed and validated in peanut-allergic donor PBMC T cell assays.
Conclusions and Clinical Relevance
Short CD4+ T cell epitope-based Ara h 1 peptides were identified as novel candidates for a safe, T cell targeted peanut-specific immunotherapy for HLA-diverse populations.
Ara h 1; CD4+ T cell; Immunotherapy; peanut allergy; peptide; T cell epitope
Recent advances in immunology have greatly increased our understanding of immunological tolerance. In particular, there has been a resurgence of interest in mechanisms of immune regulation. Immune regulation refers to the phenomenon, previously known as immune suppression, by which excessive responses to infectious agents and hypersensitivities to otherwise innocuous antigens such as self antigens and allergens are avoided. We now appreciate that various distinct cell types mediate immune suppression and that some of these may be induced by appropriate administration of antigens, synthetic peptides and drugs of various types. The induction of antigen specific immunotherapy for treatment of autoimmune and allergic diseases remains the ‘holy grail’ for treatment of these diseases. This goal comes ever closer as understanding of the mechanisms of immune suppression and in particular antigen specific immunotherapy increases. Here we review evidence that immune suppression is mediated by various different subsets of CD4 T cells.
Autoimmunity; allergy; T-cell; cytokine; immune regulation; antigen; peptide
Environmental factors play an important role in the rise and manifestation of allergic conditions in genetically predisposed subjects. Increased exposure to indoor/outdoor allergens is a significant factor in the development of allergic sensitization and asthma. Recently, strong relationships between the immune response to several highly purified allergens and specific human leukocyte antigen (HLA)-DQ and -DR haplotypes have been reported. The major antigens from clinically important allergens have been cloned and sequenced. However, whether innate structural features of major allergens or peculiar immune recognition of these molecules contribute to the overly robust immune responses is not known. We generated and used transgenic (tg) mice expressing single HLA class II transgene(s) to characterize the allergen epitopes presented by particular HLA class II molecules. Next, we generated in vivo models for asthma in the HLA tg mice by intranasal challenge with allergenic extracts. Furthermore, we used a single epitope to induce an allergic lung inflammation. Our system offers a sophisticated technique for systematically identifying the genetic (individual human class II) and antigenic (individual allergenic epitopes) basis of asthma sensitivity and has important implications for new treatment strategies.
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.
dendritic cells; mucosal tolerance; regulatory T cells; allergen-specific immunotherapy
Asthma and rhinitis are often co-morbid conditions. As rhinitis often precedes asthma it is possible that effective treatment of allergic rhinitis may reduce asthma progression.
The aim of our study is to investigate history of allergic rhinitis as a risk factor for asthma and the potential effect of allergen immunotherapy in attenuating the incidence of asthma.
Hospital-referred non-asthmatic adults, aged 18–40 years between 1990 and 1991, were retrospectively followed up until January and April 2000. At the end of follow up, available subjects were clinically examined for asthma diagnosis and history of allergen specific immunotherapy, second-hand smoking and the presence of pets in the household. A total of 436 non-asthmatic adults (332 subjects with allergic rhinitis and 104 with no allergic rhinitis nor history of atopy) were available for final analyses.
The highest OR (odds ratio) associated with a diagnosis of asthma at the end of follow-up was for the diagnosis of allergic rhinitis at baseline (OR, 7.8; 95%CI, 3.1–20.0 in the model containing the covariates of rhinitis diagnosis, sex, second-hand smoke exposure, presence of pets at home, family history of allergic disorders, sensitization to Parietaria judaica; grass pollen; house dust mites; Olea europea: orchard; perennial rye; and cat allergens). Female sex, sensitization to Parietaria judaica and the presence of pets in the home were also significantly predictive of new onset asthma in the same model. Treatment with allergen immunotherapy was significantly and inversely related to the development of new onset asthma (OR, 0.53; 95%CI, 0.32–0.86).
In the present study we found that allergic rhinitis is an important independent risk factor for asthma. Moreover, treatment with allergen immunotherapy lowers the risk of the development of new asthma cases in adults with allergic rhinitis.
We investigated the molecular determinants of allergen-derived T cell epitopes in humans utilizing the Phleum pratense (Timothy grass) allergens (Phl p). PBMCs from allergic individuals were tested in ELISPOT assays with overlapping peptides spanning known Phl p allergens. A total of 43 distinct antigenic regions were recognized, illustrating the large breadth of grass-specific T cell epitopes. Th2 cytokines (as represented by IL-5) were predominant, whereas IFN-γ, IL-10, and IL-17 were detected less frequently. Responses from specific immunotherapy treatment individuals were weaker and less consistent, yet similar in epitope specificity and cytokine pattern to allergic donors, whereas nonallergic individuals were essentially nonreactive. Despite the large breadth of recognition, nine dominant antigenic regions were defined, each recognized by multiple donors, accounting for 51% of the total response. Multiple HLA molecules and loci restricted the dominant regions, and the immunodominant epitopes could be predicted using bioinformatic algorithms specific for 23 common HLA-DR, DP, and DQ molecules. Immunodominance was also apparent at the Phl p Ag level. It was found that 52, 19, and 14% of the total response was directed to Phl p 5, 1, and 3, respectively. Interestingly, little or no correlation between Phl p-specific IgE levels and T cell responses was found. Thus, certain intrinsic features of the allergen protein might influence immunogenicity at the level of T cell reactivity. Consistent with this notion, different Phl p Ags were associated with distinct patterns of IL-5, IFN-γ, IL-10, and IL-17 production.
Allergic asthma is a disease characterized by persistent allergen-driven airway inflammation, remodeling, and airway hyperresponsiveness. CD4+ T-cells, especially T-helper type 2 cells, play a critical role in orchestrating the disease process through the release of the cytokines IL-4, IL-5, and IL-13. Allergen-specific immunotherapy (SIT) is currently the only treatment with a long-term effect via modifying the natural course of allergy by interfering with the underlying immunological mechanisms. However, although SIT is effective in allergic rhinitis and insect venom allergy, in allergic asthma it seldom results in complete alleviation of the symptoms. Improvement of SIT is needed to enhance its efficacy in asthmatic patients. Herein, the immunoregulatory mechanisms underlying the beneficial effects of SIT are discussed with the ultimate aim to improve its treatment efficacy.
allergic asthma; immunotherapy; dendritic cell; regulatory T cells; Th2 lymphocytes; hyperresponsiveness; eosinophilia; IgE; IL-10
Bla g allergens are major targets of IgE responses associated with cockroach allergies. However, little is known about corresponding T cell responses, despite their potential involvement in immunopathology and the clinical efficacy of Specific ImmunoTherapy (SIT). Bioinformatic predictions of the capacity of Bla g 1, 2, 4, 5, 6, and 7 peptides to bind HLA DR, DP and DQ molecules, and PBMC responses from 30 allergic donors, identified 25 T cell epitopes. Five immunodominant epitopes accounted for over half of the response. Bla g 5, the most dominant allergen, accounted for 65% of the response, and Bla g 6 accounted for 20%. Bla g 5 induced both IL-5 and IFN-γ responses, while Bla g 6 induced mostly IL-5 and, conversely, Bla g 2 induced only IFN-γ. Thus, responses to allergens within a source are independently regulated, suggesting a critical role for the allergen itself, and not extraneous stimulation from other allergens or co-presented immunomodulators. In comparing antibody with T cell responses for several donor/allergen combinations we detected IgE titers in the absence of detectable T cell responses, suggesting that unlinked T-B help might support development of IgE responses. Finally, SIT resulted in IL-5 down-modulation, which was not associated with development of IFN-γ or IL-10 responses to any of the Bla g derived peptides. In summary, the characteristics of T cell responses to Bla g allergens appear uncorrelated with IgE responses. Monitoring these responses may therefore yield important information relevant to understanding cockroach allergies and their treatment.
The main obstacle to elucidating the role of CD4+ T cells in allergen-specific immunotherapy has been the absence of an adequately sensitive approach to directly characterize rare allergen-specific T cells without introducing substantial phenotypic modifications by in vitro amplification.
To monitor in physiological conditions, the allergen-specific CD4+ T cells generated during natural pollen exposure and during allergy vaccine.
Alder pollen allergy was used as a model for studying seasonal allergies. Allergen-specific CD4+ T cells were tracked and characterized in twelve alder pollen-allergic, six non-allergic and nine allergy vaccine-treated individuals using peptide-MHC class II tetramers.
Allergen-specific CD4+ T cells were detected in all of the alder pollen-allergic and non-allergic subjects tested. Pathogenic responses (CRTH2 expression and TH2-cytokine production) are specifically associated with terminally differentiated (CD27−) allergen-specific CD4+ T cells, which dominate in allergic individuals but are absent in non-allergic individuals. In contrast, CD27 expressing allergen-specific CD4+ T cells are present at low frequencies in both allergic and non-allergic individuals and reflect classical features of the protective immune response with high expression of IL-10 and IFN-γ. Restoration of a protective response during allergen-specific immunotherapy appears to be due to the preferential deletion of pathogenic (CD27−) allergen-specific CD4+ T cells accompanied by IL-10 induction in surviving CD27+ allergen-specific CD4+ T cells.
Differentiation stage divides allergen-specific CD4+ T cells into two distinct subpopulations with unique functional properties and different fates during allergen-specific immunotherapy.
Immunotherapy; allergy; pollen; T cells; CD4; peptide-MHC class II tetramer; peripheral tolerance; differentiation stage; ex vivo
HDM allergy is associated with asthma, allergic rhinitis and atopic dermatitis. In many countries childhood asthma is predominantly found in HDM-allergic children with their probability of developing disease being proportional to their IgE antibody titers and the early development of Th2 responses. While the pathogenesis is complex and increasingly linked to infection the immunologically-based allergen immunotherapy and anti-IgE antibody therapy are highly beneficial. Immunotherapy could be a short-term treatment providing lifelong relief but the current regimens depend on repeated administration of allergen over years. Immunological investigations point to a contribution of responses outside the Th2 pathway and multiple potential but unproven control mechanisms. Over half of the IgE antibodies are directed to the group 1 and 2 allergens with most of remainder to the group 4, 5, 7 and 21 allergens. This hierarchy found in high and low responders provides a platform for introducing defined allergens into immunotherapy and defined reagents for investigation.
Dermatophagoides; Blomia; allergen; IgE; IgG; T-cell; immunotherapy; cytokine; asthma; house dust mite
► Allergen-specific immunotherapy is based on therapeutic vaccination with allergens. ► The genes encoding allergen molecules and their structures have been identified. ► Detailed knowledge of allergen structures and epitopes allows engineering new vaccines. ► These vaccines target different mechanisms of the allergic immune response. ► New allergy vaccines will increase safety, efficacy and convenience of immunotherapy and are currently tested in immunotherapy trials.
Vaccines aim to establish or strengthen immune responses but are also effective for the treatment of allergy. The latter is surprising because allergy represents a hyper-immune response based on immunoglobulin E production against harmless environmental antigens, i.e., allergens. Nevertheless, vaccination with allergens, termed allergen-specific immunotherapy is the only disease-modifying therapy of allergy with long-lasting effects. New forms of allergy diagnosis and allergy vaccines based on recombinant allergen-derivatives, peptides and allergen genes have emerged through molecular allergen characterization. The molecular allergy vaccines allow sophisticated targeting of the immune system and may eliminate side effects which so far have limited the use of traditional allergen extract-based vaccines. Successful clinical trials performed with the new vaccines indicate that broad allergy vaccination is on the horizon and may help to control the allergy pandemic.
Specific immunotherapy is the only treatment with the potential to prevent progression of the allergic disease and the potential to cure patients. The immunomodulatory ability of SQ-standardized house dust mite (HDM) subcutaneous immunotherapy (SCIT) was investigated in patients with allergic asthma.
Fifty-four adults with HDM-allergic asthma were randomized 1 : 1 to receive SQ-standardized HDM SCIT (ALK) or placebo for 3 years. At baseline, and after 1, 2 and 3 years of treatment, the lowest possible inhaled corticosteroid dose required to maintain asthma control was determined, followed by determinations of nonspecific and HDM-allergen-specific bronchial hyperresponsiveness, late asthmatic reaction (LAR), immediate and late-phase skin reactions, and immunological response.
SQ-standardized HDM SCIT provided a statistically significantly higher HDM-allergen tolerance (P < 0.05 vs placebo) in terms of a 1.6-fold increase in PD20 (HDM-allergen inhalation challenge), a 60-fold increase in skin test histamine equivalent HDM-allergen concentrations, reduced immediate- and reduced or abolished late-phase skin reactions, as well as fewer patients with LAR. PD20 (methacholine inhalation challenge) increased initially and was similar between groups. House dust mite SCIT induced an initial increase in serum HDM-allergen-specific IgE (P = 0.028 vs placebo), which then declined to baseline value. House dust mite SCIT induced an increase in components blocking IgE binding to allergen [ΔIgE-blocking factor: 0.31; 95% CI of (0.26; 0.37)] after 1 year that remained constant after 2 and 3 years (P < 0.0001 vs placebo).
SQ-standardized HDM SCIT induced a consistent immunomodulatory effect in adults with HDM-allergic asthma; the humoral immune response was changed and the HDM-allergen tolerance in lung and skin increased.
allergic asthma; bronchial hyperresponsiveness; house dust mite; immune response; immunotherapy
Allergic sensitisation usually begins early in life. The number of allergens a patient is sensitised to can increase over time and the development of additional allergic conditions is increasingly recognised. Targeting allergic disease in childhood is thus likely to be the most efficacious means of reducing the overall burden of allergic disease. Specific immunotherapy involves administering protein allergen to tolerise allergen reactive CD4+ T cells, thought key in driving allergic responses. Yet specific immunotherapy risks allergic reactions including anaphylaxis as a consequence of preformed allergen-specific IgE antibodies binding to the protein, subsequent cross-linking and mast cell degranulation. CD4+ T cells direct their responses to short "immunodominant" peptides within the allergen. Such peptides can be given therapeutically to induce T cell tolerance without facilitating IgE cross-linking. Peptide immunotherapy (PIT) offers attractive treatment potential for allergic disease. However, PIT has not yet been shown to be effective in children. This review discusses the immunological mechanisms implicated in PIT and briefly covers outcomes from adult PIT trials. This provides a context for discussion of the challenges for the application of PIT, both generally and more specifically in relation to children.
Allergy; Children; Peptide Immunotherapy
Peptide immunotherapy using T-cell epitopes is expected to be an effective treatment for allergic diseases such as Japanese cedar (Cryptomeria japonica; Cj) pollinosis. To develop a treatment for pollen allergy by inducing oral tolerance, we generated genetically manipulated (GM) chickens by retroviral gene transduction, to produce a fusion protein of chicken egg white lysozyme and a peptide derived from seven dominant human T-cell epitopes of Japanese cedar pollen allergens (cLys-7crp). The transgene sequence was detected in all chickens transduced with the retroviral vector. Transduction efficiency in blood cells correlated to transgene expression. Western blot analysis revealed that cLys-7crp was expressed in the egg white of GM hens. Mice induced to develop allergic rhinitis by Cj pollinosis were fed with cLys-7crp-containing egg white produced by GM chickens. Total and Cj allergen (Cry j 1)-specific IgE levels were significantly decreased in allergic mice fed with cLys-7crp-containing egg white compared with allergic mice fed with normal egg white. These results suggest that oral administration of T-cell epitope-containing egg white derived from GM chickens is effective for the induction of immune tolerance as an allergy therapy.
Synthetic contiguous overlapping peptides (COPs) may represent an alternative to allergen extracts or recombinant allergens for allergen specific immunotherapy. In combination, COPs encompass the entire allergen sequence, providing all potential T cell epitopes, while preventing IgE conformational epitopes of the native allergen.
Individual COPs were derived from the sequence of Bet v 1, the major allergen of birch pollen, and its known crystal structure, and designed to avoid IgE binding. Three sets of COPs were tested in vitro in competition ELISA and basophil degranulation assays. Their in vivo reactivity was determined by intraperitoneal challenge in rBet v 1 sensitized mice as well as by skin prick tests in volunteers with allergic rhinoconjunctivitis to birch pollen.
The combination, named AllerT, of three COPs selected for undetectable IgE binding in competition assays and for the absence of basophil activation in vitro was unable to induce anaphylaxis in sensitized mice in contrast to rBet v 1. In addition no positive reactivity to AllerT was observed in skin prick tests in human volunteers allergic to birch pollen. In contrast, a second set of COPs, AllerT4-T5 displayed some residual IgE binding in competition ELISA and a weak subliminal reactivity to skin prick testing.
The hypoallergenicity of contiguous overlapping peptides was confirmed by low, if any, IgE binding activity in vitro, by the absence of basophil activation and the absence of in vivo induction of allergic reactions in mouse and human.
IgE; Peptides; Immunotherapy; Birch; Pollen
Allergen-specific desensitization is the only disease-modifying therapy currently available for the treatment of allergies. These therapies require application of allergen over several years and some may induce life-threatening anaphylactic reactions. An ideal vaccine for desensitization should be highly immunogenic and should alleviate allergic symptoms upon few injections while being nonreactogenic. We describe such a vaccine for the treatment of cat allergy, consisting of the major cat allergen Fel d1 coupled to bacteriophage Qβ-derived virus-like particles (Qβ–Fel d1). Qβ–Fel d1 was highly immunogenic, and a single vaccination was sufficient to induce protection against type I allergic reactions. Allergen-specific immunoglobulin G antibodies were shown to be the critical effector molecules and alleviated symptoms by two distinct mechanisms. Although allergen-induced systemic basophil degranulation was inhibited in an FcγRIIb-dependent manner, inhibition of local mast cell degranulation in tissues occurred independently of FcγRIIb. In addition, treatment with Qβ–Fel d1 abolished IgE memory responses upon antigen recall. Despite high immunogenicity, the vaccine was essentially nonreactogenic and vaccination induced neither local nor systemic anaphylactic reactions in sensitized mice. Moreover, Qβ–Fel d1 did not induce degranulation of basophils derived from human volunteers with cat allergies. These data suggest that vaccination with Qβ–Fel d1 may be a safe and effective treatment for cat allergy.