Neutrophil Extracellular Traps in Asthma: Friends or Foes?

Asthma is a chronic inflammatory disease characterized by variable airflow limitation and airway hyperresponsiveness. A plethora of immune and structural cells are involved in asthma pathogenesis. The roles of neutrophils and their mediators in different asthma phenotypes are largely unknown. Neutrophil extracellular traps (NETs) are net-like structures composed of DNA scaffolds, histones and granular proteins released by activated neutrophils. NETs were originally described as a process to entrap and kill a variety of microorganisms. NET formation can be achieved through a cell-death process, termed NETosis, or in association with the release of DNA from viable neutrophils. NETs can also promote the resolution of inflammation by degrading cytokines and chemokines. NETs have been implicated in the pathogenesis of various non-infectious conditions, including autoimmunity, cancer and even allergic disorders. Putative surrogate NET biomarkers (e.g., double-strand DNA (dsDNA), myeloperoxidase-DNA (MPO-DNA), and citrullinated histone H3 (CitH3)) have been found in different sites/fluids of patients with asthma. Targeting NETs has been proposed as a therapeutic strategy in several diseases. However, different NETs and NET components may have alternate, even opposite, consequences on inflammation. Here we review recent findings emphasizing the pathogenic and therapeutic potential of NETs in asthma.

Repetitive nasal allergen challenge in allergic rhinitis: Priming and Th2-type inflammation but no evidence of remodelling.

BACKGROUND: Local tissue eosinophilia and Th2 cytokines are characteristic features of seasonal allergic rhinitis. Airway remodelling is a feature of asthma whereas evidence for remodelling in allergic rhinitis (AR) is conflicting. OBJECTIVE: By use of a novel human repetitive nasal allergen challenge (RAC) model, we evaluated the relationship between allergic inflammation and features of remodelling in AR. METHODS: Twelve patients with moderate-severe AR underwent 5 alternate day challenges with diluent which after 4 weeks were followed by 5 alternate day challenges with grass pollen extract. Nasal symptoms, Th1/Th2 cytokines in nasal secretion and serum were evaluated. Nasal biopsies were taken 24 hours after the 1st and 5th challenges with diluent and with allergen. Sixteen healthy controls underwent a single challenge with diluent and with allergen. Using immunohistochemistry, epithelial and submucosal inflammatory cells and remodelling markers were evaluated by computed image analysis. RESULTS: There was an increase in early and late-phase symptoms after every allergen challenge compared to diluent (both P < .05) with evidence of both clinical and immunological priming. Nasal tissue eosinophils and IL-5 in nasal secretion increased significantly after RAC compared to corresponding diluent challenges (P < .01, P = .01, respectively). There was a correlation between submucosal mast cells and the early-phase clinical response (r = 0.79, P = .007) and an association between epithelial eosinophils and IL-5 concentrations in nasal secretion (r = 0.69, P = .06) in allergic rhinitis. No differences were observed after RAC with regard to epithelial integrity, reticular basement membrane thickness, glandular area, expression of markers of activation of airway remodelling including α-SMA, HSP-47, extracellular matrix (MMP7, 9 and TIMP-1), angiogenesis and lymphangiogenesis for AR compared with healthy controls. CONCLUSION: Novel repetitive nasal allergen challenge in participants with severe persistent seasonal allergic rhinitis resulted in tissue eosinophilia and increases in IL-5 but no structural changes. Our data support no link between robust Th2-inflammation and development of airway remodelling in AR.

Toll-Like Receptor Agonists as Adjuvants for Allergen Immunotherapy.

Toll-like receptors (TLRs) are essential components of innate immunity and provide defensive inflammatory responses to invading pathogens. Located within the plasma membranes of cells and also intracellular endosomes, TLRs can detect a range of pathogen associated molecular patterns from bacteria, viruses and fungi. TLR activation on dendritic cells can propagate to an adaptive immune response, making them attractive targets for the development of both prophylactic and therapeutic vaccines. In contrast to conventional adjuvants such as aluminium salts, TLR agonists have a clear immunomodulatory profile that favours anti-allergic T lymphocyte responses. Consequently, the potential use of TLRs as adjuvants in Allergen Immunotherapy (AIT) for allergic rhinitis and asthma remains of great interest. Allergic Rhinitis is a Th2-driven, IgE-mediated disease that occurs in atopic individuals in response to exposure to otherwise harmless aeroallergens such as pollens, house dust mite and animal dander. AIT is indicated in subjects with allergic rhinitis whose symptoms are inadequately controlled by antihistamines and nasal corticosteroids. Unlike anti-allergic drugs, AIT is disease-modifying and may induce long-term disease remission through mechanisms involving upregulation of IgG and IgG4 antibodies, induction of regulatory T and B cells, and immune deviation in favour of Th1 responses that are maintained after treatment discontinuation. This process takes up to three years however, highlighting an unmet need for a more efficacious therapy with faster onset. Agonists targeting different TLRs to treat allergy are at different stages of development. Synthetic TLR4, and TLR9 agonists have progressed to clinical trials, while TLR2, TLR5 and TLR7 agonists been shown to have potent anti-allergic effects in human in vitro experiments and in vivo in animal studies. The anti-allergic properties of TLRs are broadly characterised by a combination of enhanced Th1 deviation, regulatory responses, and induction of blocking antibodies. While promising, a durable effect in larger clinical trials is yet to be observed and further long-term studies and comparative trials with conventional AIT are required before TLR adjuvants can be considered for inclusion in AIT. Here we critically evaluate experimental and clinical studies investigating TLRs and discuss their potential role in the future of AIT.

Allergen-specific IgG+ memory B cells are temporally linked to IgE memory responses.

BACKGROUND: IgE is the least abundant immunoglobulin and tightly regulated, and IgE-producing B cells are rare. The cellular origin and evolution of IgE responses are poorly understood. OBJECTIVE: The cellular and clonal origin of IgE memory responses following mucosal allergen exposure by sublingual immunotherapy (SLIT) were investigated. METHODS: In a randomized double-blind, placebo-controlled, time course SLIT study, PBMCs and nasal biopsy samples were collected from 40 adults with seasonal allergic rhinitis at baseline and at 4, 8, 16, 28, and 52 weeks. RNA was extracted from PBMCs, sorted B cells, and nasal biopsy samples for heavy chain variable gene repertoire sequencing. Moreover, mAbs were derived from single B-cell transcriptomes. RESULTS: Combining heavy chain variable gene repertoire sequencing and single-cell transcriptomics yielded direct evidence of a parallel boost of 2 clonally and functionally related B-cell subsets of short-lived IgE+ plasmablasts and IgG+ memory B cells. Mucosal grass pollen allergen exposure by SLIT resulted in highly diverse IgE and IgGE repertoires. These were extensively mutated and appeared relatively stable as per heavy chain isotype, somatic hypermutations, and clonal composition. Single IgGE+ memory B-cell and IgE+ preplasmablast transcriptomes encoded antibodies that were specific for major grass pollen allergens and able to elicit basophil activation at very low allergen concentrations. CONCLUSION: For the first time, we have shown that on mucosal allergen exposure, human IgE memory resides in allergen-specific IgG+ memory B cells. These cells rapidly switch isotype, expand into short-lived IgE+ plasmablasts, and serve as a potential target for therapeutic intervention.

Hymenoptera Venom Allergy: How Does Venom Immunotherapy Prevent Anaphylaxis From Bee and Wasp Stings?

Hymenoptera stings may cause both local and systemic allergic reactions and even life threatening anaphylaxis. Along with pharmaceutical drugs and foods, hymenoptera venom is one of the most common causes of anaphylaxis in humans. To date, no parameter has been identified that may predict which sensitized people will have a future systemic sting reaction (SSR), however some risk factors, such as mastocytosis and age >40 years are known. Venom immunotherapy (VIT) is the most effective method of treatment for people who had SSR, which is shown to be effective even after discontinuation of the therapy. Development of peripheral tolerance is the main mechanism during immunotherapy. It is mediated by the production of blocking IgG/IgG4 antibodies that may inhibit IgE dependent reactions through both high affinity (FcεRI) and low affinity (FcεRII) IgE receptors on mast cells, basophils and B cells. The generation of antigen specific regulatory T cells produces IL-10 and suppresses Th2 immunity and the immune responses shift toward a Th1-type response. B regulatory cells are also involved in the production of IL-10 and the development of long term immune tolerance. During VIT the number of effector cells in target organs also decreases, such as mast cells, basophils, innate type 2 lymphocytes and eosinophils. Several meta-analyses and randomized controlled studies have proved that VIT is effective for preventing SSR to a sting and improves the quality of life. In this review, the risk of SSR in venom allergy and how VIT changed this risk are discussed.

Immunologic mechanisms of a short-course of Lolium perenne peptide immunotherapy: A randomized, double-blind, placebo-controlled trial.

BACKGROUND: A 3-week short-course of adjuvant-free hydrolysates of Lolium perenne peptide (LPP) immunotherapy for rhinoconjunctivitis with or without asthma over 4 physician visits is safe, well tolerated, and effective. OBJECTIVE: We sought to investigate immunologic mechanisms of LPP immunotherapy in a subset of patients who participated in a phase III, multicenter, randomized, double-blind, placebo-controlled trial (clinical.govNCT02560948). METHODS: Participants were randomized to receive LPP (n = 21) or placebo (n = 11) for 3 weeks over 4 visits. Grass pollen-induced basophil, T-cell, and B-cell responses were evaluated before treatment (visit [V] 2), at the end of treatment (V6), and after the pollen season (V8). RESULTS: Combined symptom and rescue medication scores (CSMS) were lower during the peak pollen season (-35.1%, P = .03) and throughout the pollen season (-53.7%, P = .03) in the LPP-treated group compared with those in the placebo-treated group. Proportions of CD63+ and CD203cbrightCRTH2+ basophils were decreased following LPP treatment at V6 (10 ng/mL, P < .0001) and V8 (10 ng/mL, P < .001) compared to V2. No change in the placebo-treated group was observed. Blunting of seasonal increases in levels of grass pollen-specific IgE was observed in LPP-treated but not placebo-treated group. LPP immunotherapy, but not placebo, was associated with a reduction in proportions of IL-4+ TH2 (V6, P = .02), IL-4+ (V6, P = .003; V8, P = .004), and IL-21+ (V6, P = .003; V8, P = .002) follicular helper T cells. Induction of FoxP3+, follicular regulatory T, and IL-10+ regulatory B cells were observed at V6 (all P < .05) and V8 (all P < .05) in LPP-treated group. Induction of regulatory B cells was associated with allergen-neutralizing IgG4-blocking antibodies. CONCLUSION: For the first time, we demonstrate that the immunologic mechanisms of LPP immunotherapy are underscored by immune modulation in the T- and B-cell compartments, which is necessary for its effect.

Broad IgG repertoire in patients with chronic rhinosinusitis with nasal polyps regulates proinflammatory IgE responses.

BACKGROUND: Chronic rhinosinusitis with nasal polyps (CRSwNP) is often characterized by local production of polyclonal IgE idiotypes. Although tissue IgE concentrations can be in the range of several thousand kilounits per liter, the regulatory mechanisms by which IgE-mediated inflammation is controlled in patients with nasal polyps are not well understood. OBJECTIVE: We sought to determine whether locally induced IgG antibodies in patients with nasal polyps can inhibit an IgE-mediated proallergic response. METHODS: Nasal polyp homogenates were collected from patients with grass pollen allergy with CRSwNP and nonallergic control subjects. IgE levels were measured using the Immuno Solid-phase Allergen Chip assay. IgE-containing nasal polyp homogenates with or without IgG depletion were evaluated for their capacity to promote IgE-facilitated allergen presentation, basophil activation, and histamine release. Local IgE and IgG repertoires were evaluated using Immunoglobulin 454 sequencing. RESULTS: We show that IgG plays a key role in controlling IgE-mediated inflammatory responses in patients with nasal polyps. Depletion of IgG from nasal homogenates resulted in an increase in CD23-mediated IgE-facilitated allergen binding to B cells but also enhanced FcεRI-mediated allergen-driven basophil activation and histamine release. A similar response was observed in relation to specific IgE antibodies to Staphylococcus aureus enterotoxins. The capacity of IgG in nasal polyps to limit IgE-mediated inflammation is based on the fact that IgG repertoires widely share the antigen targets with the IgE repertoires in both allergic and nonallergic subjects. CONCLUSION: Polyclonal IgE idiotypes in patients with CRSwNP are functional, promote IgE-mediated proallergic inflammation, and are partially antagonized by corresponding IgG idiotypes. This is most likely due to the fact that IgE and IgG clonotypes are widely shared in patients with nasal polyps.

Antiapoptotic serine protease inhibitors contribute to survival of allergenic TH2 cells.

BACKGROUND: The mechanisms that regulate maintenance of persistent TH2 cells and potentiate allergic inflammation are not well understood. OBJECTIVE: The function of serine protease inhibitor 2A (Spi2A) was studied in mouse TH2 cells, and the serine protease inhibitor B3 (SERPINB3) and SERPINB4 genes were studied in TH2 cells from patients with grass pollen allergy. METHODS: Spi2A-deficient TH2 cells were studied in in vitro culture or in vivo after challenge of Spi2A knockout mice with ovalbumin in alum. Expression of SERPINB3 and SERPINB4 mRNA was measured in in vitro-cultured TH2 cells and in ex vivo CD27-CD4+ cells and innate lymphoid cell (ILC) 2 from patients with grass pollen allergy by using quantitative PCR. SERPINB3 and SERPINB4 mRNA levels were knocked down in cultured CD27-CD4+ cells with small hairpin RNA. RESULTS: There were lower levels of in vitro-polarized TH2 cells from Spi2A knockout mice (P < .005) and in vivo after ovalbumin challenge (P < .05), higher levels of apoptosis (Annexin V positivity, P < .005), and less lung allergic inflammation (number of lung eosinophils, P < .005). In vitro-polarized TH2 cells from patients with grass pollen allergy expressed higher levels of both SERPINB3 and SERPINB4 mRNA (both P < .05) compared with unpolarized CD4 T cells. CD27-CD4+ from patients with grass pollen allergy expressed higher levels of both SERPINB3 and SERPINB4 mRNA (both P < .0005) compared with CD27+CD4+ cells. ILC2 expressed higher levels of both SERPINB3 and SERPINB4 mRNA (both P < .0005) compared with ILC1. Knockdown of either SERPINB3 or SERPINB4 mRNA (both P < .005) levels resulted in decreased viability of CD27-CD4+ compared with control transduced cells. CONCLUSION: The Serpins Spi2A in mice and SERPINB3 and SERPINB4 in allergic patients control the viability of TH2 cells. This provides proof of principle for a therapeutic approach for allergic disease through ablation of allergic memory TH2 cells through SERPINB3 and SERPINB4 mRNA downregulation.

Reduced need for surgery in severe nasal polyposis with mepolizumab: Randomized trial.

BACKGROUND: Patients with eosinophilic nasal polyposis frequently require surgery, and recurrence rates are high. OBJECTIVE: We sought to assess the efficacy and safety of mepolizumab versus placebo for severe bilateral nasal polyposis. METHODS: This randomized, double-blind, placebo-controlled trial recruited patients aged 18 to 70 years with recurrent nasal polyposis requiring surgery. Patients received 750 mg of intravenous mepolizumab or placebo every 4 weeks for a total of 6 doses in addition to daily topical corticosteroid treatment. The primary end point was the number of patients no longer requiring surgery at Week 25 based on a composite end point of endoscopic nasal polyp score and nasal polyposis severity visual analog scale (VAS) score. Secondary end points included change in nasal polyposis severity VAS score, endoscopic nasal polyp score, improvement in individual VAS symptoms (rhinorrhea, mucus in throat, nasal blockage, and sense of smell), patient-reported outcomes, and safety. RESULTS: One hundred five patients received mepolizumab (n = 54) or placebo (n = 51). A significantly greater proportion of patients in the mepolizumab group compared with the placebo group no longer required surgery at Week 25 (16 [30%] vs 5 [10%], respectively; P = .006). There was a significant improvement in nasal polyposis severity VAS score, endoscopic nasal polyp score, all individual VAS symptom scores, and Sino-Nasal Outcome Test patient-reported outcome score in the mepolizumab compared with placebo groups. Mepolizumab's safety profile was comparable with that of placebo. CONCLUSION: In patients with recurrent nasal polyposis receiving topical corticosteroids who required surgery, mepolizumab treatment led to a greater reduction in the need for surgery and a greater improvement in symptoms than placebo.

Intradermal grass pollen immunotherapy increases TH2 and IgE responses and worsens respiratory allergic symptoms.

BACKGROUND: Repeated low-dose grass pollen intradermal allergen injection suppresses allergen-induced cutaneous late-phase responses comparably with conventional subcutaneous and sublingual immunotherapy. OBJECTIVE: We sought to evaluate the efficacy and safety of grass pollen intradermal immunotherapy in the treatment of allergic rhinitis. METHODS: We randomly assigned 93 adults with grass pollen-induced allergic rhinitis to receive 7 preseasonal intradermal allergen injections (containing 7 ng of Phl p 5 major allergen) or a histamine control. The primary end point was daily combined symptom-medication scores during the 2013 pollen season (area under the curve). Analysis was by intention to treat. Skin biopsy specimens were collected after intradermal allergen challenges, and late-phase responses were measured 4 and 7, 10, or 13 months after treatment. RESULTS: There was no significant difference in the primary end point between treatment arms (active, n = 46; control, n = 47; median difference, 14; 95% CI, -172.5 to 215.1; P = .80). Among secondary end points, nasal symptoms were worse in the intradermal treatment group, as measured based on daily (median difference, 35; 95% CI, 4.0-67.5; P = .03) and visual analog scale (median difference, 53; 95% CI, -11.6 to 125.2; P = .05) scores. In a per-protocol analysis intradermal immunotherapy was further associated with worse asthma symptoms and fewer symptom-free days. Intradermal immunotherapy increased serum Phleum pratense-specific IgE levels (P = .001) compared with those in the control arm. T cells cultured from biopsy specimens of subjects undergoing intradermal immunotherapy had higher expression of the TH2 surface marker CRTH2 (P = .04) and lower expression of the TH1 marker CXCR3 (P = .01), respectively. Late-phase responses remained inhibited 7 months after treatment (P = .03). CONCLUSION: Intradermal allergen immunotherapy suppressed skin late-phase responses but was not clinically effective and resulted in worsening of respiratory allergic symptoms.

Geohistorical records indicate no impact of the Deepwater Horizon oil spill on oyster body size.

Documentation of the near- and long-term effects of the Deepwater Horizon (DWH) oil spill, one of the largest environmental disasters in US history, is still ongoing. We used a novel before-after-control-impact analysis to test the hypothesis that average body size of intertidal populations of the eastern oyster (Crassostrea virginica) inhabiting impacted areas in Louisiana decreased due to increased stress/mortality related to the oil spill. Time-averaged death assemblages of oysters were used to establish a pre-spill baseline of body-size structure for four impacted and four control locations along a 350 km stretch of Louisiana's coastline. Post-spill body sizes were then measured from live oysters at each site in order to evaluate the differences in body size between oiled (i.e. impact) and unoiled (i.e. control) locations before and after the spill. Our results indicate that average body size of oysters remained relatively unchanged after the oil spill. There were also no temporal patterns in temperature, salinity or disease prevalence that could have explained our results. Together, these findings suggest that oysters either recovered rapidly following the immediate impact of the DWH oil spill, or that its impact was not severe enough to influence short-term population dynamics of the oyster beds.

Omalizumab reduces bronchial mucosal IgE and improves lung function in non-atopic asthma.

Omalizumab therapy of non-atopic asthmatics reduces bronchial mucosal IgE and inflammation and preserves/improves lung function when disease is destabilised by staged withdrawal of therapy.18 symptomatic, non-atopic asthmatics were randomised (1:1) to receive omalizumab or identical placebo treatment in addition to existing therapy for 20 weeks. Bronchial biopsies were collected before and after 12-14 weeks of treatment, then the patients destabilised by substantial, supervised reduction of their regular therapy. Primary outcome measures were changes in bronchial mucosal IgE+ cells at 12-14 weeks, prior to regular therapy reduction, and changes in lung function (forced expiratory volume in 1 s) after destabilisation at 20 weeks. Quality of life was also monitored.Omalizumab but not placebo therapy significantly reduced median total bronchial mucosal IgE+ cells (p<0.01) but did not significantly alter median total mast cells, plasma cells, B lymphocytes, eosinophils and plasmablasts, although the latter were difficult to enumerate, being distributed as disperse clusters. By 20 weeks, lung function declined in the placebo-treated patients but improved in the omalizumab treated patients, with significant differences in absolute (p=0.04) and % predicted forced expiratory volume in 1 s (p=0.015).Omalizumab therapy of non-atopic asthmatics reduces bronchial mucosal IgE+ mast cells and improves lung function despite withdrawal of conventional therapy.

IL-25/IL-33-responsive TH2 cells characterize nasal polyps with a default TH17 signature in nasal mucosa.

BACKGROUND: Chronic rhinosinusitis with nasal polyposis (CRSwNP) in Western countries is characterized by eosinophilia, IgE production, and TH2 cytokine expression. Type 2 innate lymphoid cells from polyps produce IL-5 and IL-13 in response to IL-25 and IL-33, although the relevance of this axis to local mucosal T-cell responses is unknown. OBJECTIVE: We sought to investigate the role of the IL-25/IL-33 axis in local mucosal T-cell responses in patients with CRSwNP. METHODS: Polyp tissue and blood were obtained from patients undergoing nasal polypectomy. Control nasal biopsy specimens and blood were obtained from healthy volunteers. Tissue was cultured in a short-term explant model. T-cell surface phenotype/intracellular cytokines were assessed by means of flow cytometry. T-cell receptor variable ß-chain analysis was performed with the immunoSEQ assay. Microarrays were performed for gene expression analysis. RESULTS: IL-25 receptor (IL-17RB)-expressing TH2 effector cells were identified in nasal polyp tissue but not the healthy nasal mucosa or periphery. IL-17RB(+)CD4(+) polyp-derived TH2 cells coexpressed ST2 (IL-33 receptor) and responded to IL-25 and IL-33 with enhanced IL-5 and IL-13 production. Within IL-17RB(+)CD4(+) T cells, several identical T-cell receptor variable ß-chain complementarity-determining region 3 sequences were identified in different subjects, suggesting clonal expansion driven by a common antigen. Abundant IL-17-producing T cells were observed in both healthy nasal mucosal and polyp populations, with TH17-related genes the most overexpressed compared with peripheral blood T cells. CONCLUSION: IL-25 and IL-33 can interact locally with IL-17RB(+)ST2(+) polyp T cells to augment TH2 responses in patients with CRSwNP. A local TH17 response might be important in healthy nasal mucosal immune homeostasis.

Severe Persistent Allergic Rhinitis. Inflammation but No Histologic Features of Structural Upper Airway Remodeling.

RATIONALE: Increases in airway smooth muscle, extracellular matrix, and vascularity are prominent features of airway remodeling in asthma, whereas the extent of such remodeling in patients with persistent allergic rhinitis (PAR) is unknown. OBJECTIVES: To test the hypothesis that upper airway remodeling is a feature of PAR. METHODS: Total nasal symptoms scores, nasal biopsies, and Th1 and Th2 cytokines from nasal lavage were assessed in subjects with severe PAR (n = 46) and healthy control subjects (n = 19). Angiolymphangiogenesis was examined using immunohistochemistry staining against CD31 (vascular endothelial cells), vascular endothelial growth factor-A, and D2-40 (lymphatic endothelial cells). Collagen and extracellular matrix proteins, such as heat shock protein-47 (markers of collagen synthesis), matrix metalloproteinase-9, and tissue inhibitor metalloproteinase-1, and α-smooth muscle actin (myofibroblasts) were evaluated as markers of activation of upper airway remodeling using image analysis, together with reticular basement membrane thickness, mucus gland area, collagen area, and submucosal effector inflammatory cells. MEASUREMENTS AND MAIN RESULTS: Total nasal symptoms scores, visual analog scale, and total quality of life were significantly higher in PAR compared with healthy control subjects (P < 0.0001). Nasal lavage cytokine levels of IL-4 (P < 0.01), IL-5, and IL-13 (P < 0.001, respectively) were significantly higher in PAR compared with healthy control subjects. In addition there was an increase in submucosal eosinophils (P = 0.06). No statistical difference in terms of angiogenesis, lymphangiogenesis, deposition of extracellular matrix, collagen markers, reticular basement membrane thickness, or glandular percentage area was observed between PAR and healthy control subjects. CONCLUSIONS: Our data suggest that tissue remodeling is not a feature of PAR and argues that in contrast to asthma, targeting remodeling in allergic rhinitis may not be appropriate as a therapeutic approach.

Influence of seasonal exposure to grass pollen on local and peripheral blood IgE repertoires in patients with allergic rhinitis.

BACKGROUND: Previous studies of immunoglobulin gene sequences in patients with allergic diseases using low-throughput Sanger sequencing have limited the analytic depth for characterization of IgE repertoires. OBJECTIVES: We used a high-throughput, next-generation sequencing approach to characterize immunoglobulin heavy-chain gene (IGH) repertoires in patients with seasonal allergic rhinitis (AR) with the aim of better understanding the underlying disease mechanisms. METHODS: IGH sequences in matched peripheral blood and nasal biopsy specimens from nonallergic healthy control subjects (n = 3) and patients with grass pollen-related AR taken in season (n = 3) or out of season (n = 4) were amplified and pyrosequenced on the 454 GS FLX+ System. RESULTS: A total of 97,610 IGH (including 8,135 IgE) sequences were analyzed. Use of immunoglobulin heavy-chain variable region gene families 1 (IGHV1) and 5 (IGHV5) was higher in IgE clonotypic repertoires compared with other antibody classes independent of atopic status. IgE repertoires measured inside the grass pollen season were more diverse and more mutated (particularly in the biopsy specimens) and had more evidence of antigen-driven selection compared with those taken outside of the pollen season or from healthy control subjects. Clonal relatedness was observed for IgE between the blood and nasal biopsy specimens. Furthermore in patients with AR, but not healthy control subjects, we found clonal relatedness between IgE and IgG classes. CONCLUSION: This is the first report that exploits next-generation sequencing to determine local and peripheral blood IGH repertoires in patients with respiratory allergic disease. We demonstrate that natural pollen exposure was associated with changes in IgE repertoires that were suggestive of ongoing germinal center reactions. Furthermore, these changes were more often apparent in nasal biopsy specimens compared with peripheral blood and in patients with AR compared with healthy control subjects.

Specific immunotherapy modifies allergen-specific CD4(+) T-cell responses in an epitope-dependent manner.

BACKGROUND: Understanding the mechanisms by which the immune system induces and controls allergic inflammation at the T-cell epitope level is critical for the design of new allergy vaccine strategies. OBJECTIVE: We sought to characterize allergen-specific T-cell responses linked with allergy or peripheral tolerance and to determine how CD4(+) T-cell responses to individual allergen-derived epitopes change over allergen-specific immunotherapy. METHODS: Timothy grass pollen (TGP) allergy was used as a model for studying grass pollen allergies. The breadth, magnitude, epitope hierarchy, and phenotype of the DR04:01-restricted TGP-specific T-cell responses in 10 subjects with grass pollen allergy, 5 nonatopic subjects, and 6 allergy vaccine-treated subjects was determined by using an ex vivo peptide-MHC class II tetramer approach. RESULTS: CD4(+) T cells in allergic subjects are directed to a broad range of TGP epitopes characterized by defined immunodominance hierarchy patterns and with distinct functional profiles that depend on the epitope recognized. Epitopes that are restricted specifically to either TH2 or TH1/TR1 responses were identified. Allergen-specific immunotherapy was associated with preferential deletion of allergen-specific TH2 cells and without a significant change in the frequency of TH1/TR1 cells. CONCLUSIONS: Preferential allergen-specific TH2 cell deletion after repeated high-dose antigen stimulation can be another independent mechanism to restore tolerance to allergen during immunotherapy.

Peptide-induced immune regulation by a promiscuous and immunodominant CD4T-cell epitope of Timothy grass pollen: a role of Cbl-b and Itch in regulation.

BACKGROUND: T-cell targeted peptide epitope tolerogens from grass pollen allergens may be useful in treating seasonal allergic rhinitis, but there is urgent need for optimisation of approaches from improved understanding of mechanism. OBJECTIVE: We sought to identify human leukocyte antigen (HLA)-DR1-restricted epitopes from the Timothy grass pollen allergen, Phleum pratense, and characterise T-cell immune regulation following intranasal administration of a single, immunodominant epitope. METHODS: T-cell epitopes within P pratense were identified using HLA-DR1 transgenic mice and tetramer-guided epitope mapping (TGEM) in HLA-DR1-positive individuals with grass allergy. An immunodominant epitope was tested in HLA-DR1 transgenics for impact on responses to whole Phl p5 b or peptide. Microarrays and quantitative PCR were used to characterise T-cell immunity. RESULTS: Peptide 26 (p26) was identified in HLA-DR1 transgenic mice and by TGEM analysis of HLA-DR1-positive individuals with grass allergy. p26 shows promiscuous binding to a wide range of HLA class II alleles, making it of relevance across immunogenetically diverse patients. The epitope is conserved in rye and velvet grass, making it applicable across a spectrum of grass pollen allergy. Intranasal pretreatment of mice with p26 results in significantly reduced T-cell responses. Transcriptomic array analysis in mice showed T-cell regulation in the intranasal treatment group associated with increased expression of members of the Cbl-b and Itch E3 ubiquitin ligase pathway. CONCLUSIONS: We defined an immunodominant P pratense epitope, p26, with broad binding across multiple HLA class II alleles. Intranasal treatment of mice with p26 results in T-cell regulation to whole allergen, involving the Cbl-b and Itch regulatory pathway.

Development of cockroach immunotherapy by the Inner-City Asthma Consortium.

BACKGROUND: Cockroach allergy is a key contributor to asthma morbidity in children living in urban environments. OBJECTIVE: We sought to document immune responses to cockroach allergen and provide direction for the development of immunotherapy for cockroach allergy. METHODS: Four pilot studies were conducted: (1) an open-label study to assess the safety of cockroach sublingual immunotherapy (SLIT) in adults and children; (2) a randomized, double-blind biomarker study of cockroach SLIT versus placebo in adults; (3) a randomized, double-blind biomarker study of 2 doses of cockroach SLIT versus placebo in children; and (4) an open-label safety and biomarker study of cockroach subcutaneous immunotherapy (SCIT) in adults. RESULTS: The adult SLIT trial (n = 54; age, 18-54 years) found a significantly greater increase in cockroach-specific IgE levels between the active and placebo groups (geometric mean ratio, 1.92; P < .0001) and a trend toward increased cockroach-specific IgG4 levels in actively treated subjects (P = .09) but no evidence of functional blocking antibody response. The pediatric SLIT trial (n = 99; age, 5-17 years) found significant differences in IgE, IgG, and IgG4 responses between both active groups and the placebo group but no consistent differences between the high- and low-dose groups. In the SCIT study the treatment resulted in significant changes from baseline in cockroach IgE, IgG4, and blocking antibody levels. The safety profile of cockroach immunotherapy was reassuring in all studies. CONCLUSIONS: The administration of cockroach allergen by means of SCIT is immunologically more active than SLIT, especially with regard to IgG4 levels and blocking antibody responses. No safety concerns were raised in any age group. These pilot studies suggest that immunotherapy with cockroach allergen is more likely to be effective with SCIT.