Clinical manifestations of the release of histamine and other inflammatory mediators

Mechanisms and Predictive Biomarkers of Allergen Immunotherapy in the Clinic

Allergen immunotherapy (AIT) remains to be the only disease-modifying treatment for IgE-mediated allergic diseases such as allergic rhinitis. It can provide long-term clinical benefits when given for 3 years or longer. Mechanisms of immune tolerance induction by AIT are underscored by the modulation of several compartments within the immune system. These include repair of disruption in epithelial barrier integrity, modulation of the innate immune compartment that includes regulatory dendritic cells and innate lymphoid cells, and adaptive immune compartments such as induction of regulatory T and B cells. Altogether, these are also associated with the dampening of allergen-specific TH2 and T follicular helper cell responses and subsequent generation of blocking antibodies. Although AIT is effective in modifying the immune response, there is a lack of validated and clinically relevant biomarkers that can be used to monitor desensitization, efficacy, and the likelihood of response, all of which can contribute to accelerating personalized medication and increasing patient care. Candidate biomarkers comprise humoral, cellular, metabolic, and in vivo biomarkers; however, these are primarily studied in small trials and require further validation. In this review, we evaluate the current candidates of biomarkers of AIT and how we can implement changes in future studies to help us identify clinically relevant biomarkers of safety, compliance, and efficacy.

Allergic Rhinitis and Treatment Modalities: A Review of Literature

Allergic rhinitis is a highly prevalent disease affecting the quality of life of millions of patients. Immunotherapy, medication, and allergen avoidance are all part of the treatment for allergic rhinitis. Allergic rhinitis causes an increase in inflammation throughout the body. As a result, asthma, chronic hyperplastic eosinophilic sinusitis, nasal polyposis, and serous otitis media are all associated with allergic rhinitis. Treatment that is effective should target systemic inflammation and its underlying causes. It has a negative impact on work productivity and academic achievement in both children and adults. Understanding the pathophysiology of allergic rhinitis, how it relates to its comorbid disorders, and how different therapy choices affect the pathophysiology of both allergic rhinitis and its related comorbidities are essential for providing effective treatment. As the quality of air around us is changing, there is an increased chance of allergies. Along with nasal and ocular symptoms that are directly linked to the allergic process, these symptoms' interference with sleep results in daytime tiredness and a decreased quality of life. In this paper, we look at pathogenesis, causes, signs, symptoms, and treatment modalities in patients with allergic rhinitis.

Comparative nasal airflow with loratadine-pseudoephedrine and fluticasone nasal spray for allergic rhinitis

BACKGROUND

Although it is known that oral antihistamine-pseudoephedrine combination tablets have a faster onset than intranasal corticosteroid sprays in the treatment of allergic rhinitis after the first dose, the magnitude of change has not been measured in a comparative manner. Furthermore, the sensation of sprayed liquid in the nose may lead patients to mistakenly believe that intranasal steroid sprays work instantly.

OBJECTIVE

To evaluate, numerically, nasal airflow changes provided by a single dose of loratadine-pseudoephedrine tablet (LP) and fluticasone propionate nasal spray (FP) in participants experiencing allergic rhinitis symptoms, including nasal congestion.

METHODS

This single-center, double-blinded, placebo-controlled, crossover study evaluated objective nasal airflow changes in patients with a documented sensitivity to ragweed pollen. Participants were randomized to receive 1 of 4 treatment sequences, and their peak nasal inspiratory flow (PNIF) was measured in a span of 4 hours after pollen exposure in an environmental exposure unit.

RESULTS

Average change in PNIF was 31% with LP in the course of the study, significantly greater than with placebo and FP (12% and 15%, respectively; P < .001). Nevertheless, FP did not produce a significant change compared with its placebo. At hour one post-dose, LP had a clinically significant 31% increase in PNIF, whereas FP only yielded an 8.6% increase (P < .001). Measurable nasal airflow improvements are associated with the opening of nasal passages, allowing congested patients to breathe more freely.

CONCLUSION

A single dose of LP quickly and significantly (P < .001) improved nasal airflow after ragweed pollen challenge in an environmental exposure unit. Comparatively, FP did not display this same benefit.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03443843.

4-CMTB Ameliorates Ovalbumin-Induced Allergic Asthma through FFA2 Activation in Mice

Free fatty acid receptor 2 (FFA2, also known as GPR43), a G-protein-coupled receptor, has been known to recognize short-chain fatty acids and regulate inflammatory responses. FFA2 gene deficiency exacerbated disease states in several models of inflammatory conditions including asthma. However, in vivo efficacy of FFA2 agonists has not been tested in allergic asthma. Thus, we investigated effect of 4-chloro-α-(1-methylethyl)-N-2-thiazoylylbenzeneacetanilide (4-CMTB), a FFA2 agonist, on antigen-induced degranulation in RBL-2H3 cells and ovalbumin-induced allergic asthma in BALB/c mice. Treatment of 4-CMTB inhibited the antigen-induced degranulation concentration-dependently. Administration of 4-CMTB decreased the immune cell numbers in the bronchoalveolar lavage fluid and suppressed the expression of inflammatory Th2 cytokines (IL-4, IL-5, and IL-13) in the lung tissues. Histological studies revealed that 4-CMTB suppressed mucin production and inflammation in the lungs. Thus, results proved that FFA2 functions to suppress allergic asthma, suggesting 4-CMTB activation of FFA2 as a therapeutic tool for allergic asthma.

Immunological Responses and Biomarkers for Allergen-Specific Immunotherapy Against Inhaled Allergens

Long-term efficacy that occurs with allergen immunotherapy of proven value is associated with decreases in IgE-dependent activation of mast cells and tissue eosinophilia. This suppression of type 2 immunity is accompanied by early induction of regulatory T cells, immune deviation in favor of T_H1 responses, and induction of local and systemic IgG, IgG₄, and IgA antibodies. These "protective" antibodies can inhibit allergen-IgE complex formation and consequent mast cell triggering and IgE-facilitated T_H2-cell activation. Recent studies have highlighted the importance of innate responses mediated by type 2 dendritic cells and innate lymphoid cells in allergic inflammation. These cell types are under the regulation of cytokines such as thymic stromal lymphopoietin and IL-33 derived from the respiratory epithelium. Novel subsets of regulatory cells induced by immunotherapy include IL-35-producing regulatory T cells, regulatory B cells, a subset of T follicular regulatory cells, and IL-10-producing group 2 innate lymphoid cells. These mechanisms point to biomarkers that require testing for their ability to predict clinical response to immunotherapy and to inform novel approaches for better efficacy, safety, and long-term tolerance.

Altered chromatin landscape in circulating T follicular helper and regulatory cells following grass pollen subcutaneous and sublingual immunotherapy

BACKGROUND

Allergen-specific immunotherapy is a disease-modifying treatment that induces long-term T-cell tolerance.

OBJECTIVE

We sought to evaluate the role of circulating CXCR5⁺PD-1⁺ T follicular helper (cT_FH) and T follicular regulatory (T_FR) cells following grass pollen subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT) and the accompanying changes in their chromatin landscape.

METHODS

Phenotype and function of cT_FH cells were initially evaluated in the grass pollen-allergic (GPA) group (n = 28) and nonatopic healthy controls (NAC, n = 13) by mathematical algorithms developed to manage high-dimensional data and cell culture, respectively. cT_FH and T_FR cells were further enumerated in NAC (n = 12), GPA (n = 14), SCIT- (n = 10), and SLIT- (n = 8) treated groups. Chromatin accessibility in cT_FH and T_FR cells was assessed by assay for transposase-accessible chromatin sequencing (ATAC-seq) to investigate epigenetic mechanisms underlying the differences between NAC, GPA, SCIT, and SLIT groups.

RESULTS

cT_FH cells were shown to be distinct from T_H2- and T_H2A-cell subsets, capable of secreting IL-4 and IL-21. Both cytokines synergistically promoted B-cell class switching to IgE and plasma cell differentiation. Grass pollen allergen induced cT_FH-cell proliferation in the GPA group but not in the NAC group (P < .05). cT_FH cells were higher in the GPA group compared with the NAC group and were lower in the SCIT and SLIT groups (P < .01). Time-dependent induction of IL-4, IL-21, and IL-6 was observed in nasal mucosa following intranasal allergen challenge in the GPA group but not in SCIT and SLIT groups. T_FR and IL-10⁺ cT_FH cells were induced in SCIT and SLIT groups (all, P < .01). ATAC-seq analyses revealed differentially accessible chromatin regions in all groups.

CONCLUSIONS

For the first time, we showed dysregulation of cT_FH cells in the GPA group compared to NAC, SCIT, and SLIT groups and induction of T_FR and IL-10⁺ cT_FH cells following SCIT and SLIT. Changes in the chromatin landscape were observed following allergen-specific immunotherapy in cT_FH and T_FR cells.

EAACI Allergen Immunotherapy User's Guide

Allergen immunotherapy is a cornerstone in the treatment of allergic children. The clinical efficiency relies on a well-defined immunologic mechanism promoting regulatory T cells and downplaying the immune response induced by allergens. Clinical indications have been well documented for respiratory allergy in the presence of rhinitis and/or allergic asthma, to pollens and dust mites. Patients who have had an anaphylactic reaction to hymenoptera venom are also good candidates for allergen immunotherapy. Administration of allergen is currently mostly either by subcutaneous injections or by sublingual administration. Both methods have been extensively studied and have pros and cons. Specifically in children, the choice of the method of administration according to the patient's profile is important. Although allergen immunotherapy is widely used, there is a need for improvement. More particularly, biomarkers for prediction of the success of the treatments are needed. The strength and efficiency of the immune response may also be boosted by the use of better adjuvants. Finally, novel formulations might be more efficient and might improve the patient's adherence to the treatment. This user's guide reviews current knowledge and aims to provide clinical guidance to healthcare professionals taking care of children undergoing allergen immunotherapy.

Association between allergic and nonallergic rhinitis and obstructive sleep apnea

PURPOSE OF REVIEW

Allergic rhinitis and nonallergic rhinitis (NAR) are common disorders, which have been considered as potential risk factors for obstructive sleep apnea (OSA). This review summarizes the proposed underlying pathophysiological mechanisms to provide a better understanding of the relationship between these conditions.

RECENT FINDINGS

In adults, allergic rhinitis and NAR may be considered as symptoms potentiating, rather than risk potentiating factors in the pathophysiology of OSA, whereas in children, these are considered to be independent predictors for sleep-disordered breathing (SDB) and failure of adeno-tonsillectomy, the recommended first-line therapy for children with OSA. Current advances suggest IL-6 may be important in regulating the sleep-wake cycle, and serum soluble IL-6 receptor (sIL-6R) levels may reflect the severity of OSA. Elevated Th17/Treg ratio correlates positively with apnea-hypopnea index of OSA patients, and Th17 and Treg imbalances caused by allergic rhinitis and OSA, respectively, may possibly promote each other, leading to further imbalance. Moreover, obesity is a strong risk factor for OSA, and leptin plays an important role in ventilatory function and upper airway obstruction. The variant trigeminocardiac reflex and nasotrigeminal reflex may also be involved in the association between rhinitis and OSA.

SUMMARY

Allergic rhinitis/NAR and OSA are closely associated, and each condition can be detrimental to the other. Thus, clinicians should pay attention to the potential presence of allergic rhinitis/NAR in OSA patients and vice versa.

Expression of substance P, vasoactive intestinal peptide and heat shock protein 70 in nasal mucosal smears of patients with allergic rhinitis: investigation using a liquid-based method

OBJECTIVE

The aim of this study was to investigate expression of the neuropeptides substance P, vasoactive intestinal peptide and heat shock protein 70 in the nasal mucosa cells of patients with seasonal allergic rhinitis, in order to obtain more information on the pathophysiological and immunological role of these markers in allergic rhinitis.

MATERIAL AND METHODS

Nasal epithelium specimens obtained from 42 patients with allergic rhinitis were studied, using Shandon's Papspin liquid-based cytology method. Smears were immunostained with antibodies against substance P, vasoactive intestinal peptide and heat shock protein 70, and the results were correlated with the clinical features of seasonal allergic rhinitis.

RESULTS

A positive reaction for substance P, vasoactive intestinal peptide and heat shock protein 70 was observed in 73.8, 66.7 and 69.0 per cent of the allergic rhinitis mucosal smears, respectively. The Pearson chi-square test showed that 40.5 per cent of the immunostained smears had a positive reaction for one or two of the markers studied (i.e. substance P, vasoactive intestinal peptide or heat shock protein 70), and that 47.6 per cent of the smears had a positive reaction for all the markers (p < 0.0001).

CONCLUSIONS

We found a high level of expression of substance P and vasoactive intestinal peptide in the nasal mucosa smears of patients suffering from allergic rhinitis. This indicates a role for these neuropeptides in the neuroregulation of immunity and hypersensivity in this disease. Furthermore, expression of heat shock protein 70 may contribute to the development of allergic rhinitis.

The importance of rhinitis on sleep, daytime somnolence, productivity and fatigue

PURPOSE OF REVIEW

The goal of treatment of allergic rhinitis should include improvement of daytime and nighttime symptoms, sleep, and quality of life. Congestion from allergic rhinitis is associated with decreased learning and productivity at work and school and a reduced quality of life. The release of inflammatory mediators and activation of inflammatory cells results in nasal congestion, causing disrupted sleep and subsequent daytime somnolence.

RECENT FINDINGS

This review presents evidence that allergic rhinitis causes sleep disruption, and discusses the pathophysiology of this process. The medications used to treat allergic rhinitis and their ability to improve sleep in patients with allergic rhinitis are reviewed.

SUMMARY

Some allergic rhinitis medications can be sedating; therefore, it is important to treat allergic rhinitis with medications that improve symptoms while producing few adverse effects. Medications such as the second-generation antihistamines and anticholinergic drugs are well tolerated, but have little effect on congestion. Intranasal corticosteroids reduce congestion, improve sleep and sleep problems, and reduce daytime sleepiness, fatigue, and inflammation. Recently, montelukast, a leukotriene receptor antagonist, has been added to the therapies approved for allergic rhinitis. Montelukast significantly improves both daytime and nighttime symptoms.

Pathophysiology of nasal obstruction and meta-analysis of early and late effects of levocetirizine

Nasal obstruction, also referred to as congestion, blockage or stuffiness, is a crucial symptom in allergic rhinitis (AR) and may affect sleep as well as quality of life. Early- and late-phase-allergic reactions both contribute to nasal obstruction, although it primarily represents a major symptom in the chronic allergic reaction. A complex network of inflammatory and neurogenic phenomena relates to chronic nasal obstruction, including the subepithelial accumulation of inflammatory cells, particularly mast cells and eosinophils, and the release of neuropeptides. Nasal obstruction is a difficult-to-treat symptom. Vasoconstrictors (decongestants) and intranasal corticosteroids, due to their anti-inflammatory properties, have mainly been used for relieving the nasal passages from the congested mucosa. However, there is accumulating evidence recently that the latest-generation potent antihistamines have decongestant properties in AR. This paper aims to review the pathophysiologic background of nasal obstruction and the evidence for an antihistamine, levocetirizine, in relieving nasal congestion. A meta-analysis on the early and late effects of levocetirizine on nasal obstruction under artificial and natural allergen exposure conditions is presented, demonstrating convincingly that levocetirizine shows a consistent effect on nasal obstruction as early as over the first 2 h and sustained over 6 weeks.

Nasal allergies and beyond: a clinical review of the pharmacology, efficacy, and safety of mometasone furoate

Mometasone furoate nasal spray (MFNS; Nasonex, Schering-Plough Corporation, Kenilworth, NJ, USA) is an effective and well-tolerated intranasal corticosteroid approved for the prophylactic treatment of seasonal allergic rhinitis, and the treatment of perennial allergic rhinitis. MFNS is a potent molecule with a rapid onset of action and excellent safety and efficacy profiles. Having recently received approval for the treatment of nasal polyposis, data indicate that MFNS may also be effective in rhinosinusitis.

Bcl6 regulates Th2 type cytokine productions by mast cells activated by FcepsilonRI/IgE cross-linking

Bcl6-deficient (Bcl6-/-) mice displayed Th2 type inflammation, which caused by abnormality of non-lymphoid cells. However, initiators for the Th2 type inflammation were not clear. In order to elucidate the initiators, we investigated property and function of mast cells derived from Bcl6-/- mice. Mast cells were developed from bone marrow cells cultured with IL-3 (BMMCs). Although the development of BMMCs from Bcl6-/- mice was similar to that from wild-type mice, proliferation of Bcl6-/- BMMCs stimulated with IL-3 was slightly lower than that of wild-type BMMCs. When these BMMCs were stimulated by FcepsilonRI/IgE cross-linking, Bcl6-/- BMMCs produced Th2 cytokines more than wild-type BMMCs did. Thus, Bcl6-/- mast cells are one of the initiators for Th2 type inflammation in Bcl6-/- mice, and Bcl6 may be a molecular target for Th2 type allergic diseases.

Identification of beta-tubulin isoform V as an autoantigen in allergic rhinitis by a proteomic approach

Autoantibodies to IgE and beta2-adrenergic receptor have been reported in patients with allergic rhinitis. To investigate whether autoimmunity in allergic rhinitis is directed to such limited molecules or directed to a wide range of self proteins, we here attempted to survey autoantigens/autoantibodies comprehensively, using proteomics. Specifically, we separated proteins extracted from peripheral blood mononuclear cells by 2-dimensional electrophoresis and then detected autoantigens by subsequent western blotting with sera from patients with allergic rhinitis. As a result, we detected multiple autoantigens, some of which were further identified by mass fingerprinting. Next, we confirmed antigenicity of one of the identified autoantigens, beta-tubulin isoform V (beta-tubV), using a recombinant protein and then measured prevalence of the anti-beta-tubV autoantibodies. As a result, 52% of the tested patients with allergic rhinitis were found to possess anti-beta-tubV autoantibodies. Our study indicates that autoimmunity is a common phenomena and beta-tubV is one of the major autoantigens in allergic rhinitis.

Optimising the management of allergic rhinitis: an Australian perspective

Allergic rhinitis (AR) is one of the most prevalent medical conditions. It has significant effects on quality of life and can have considerable socioeconomic effects. The traditional classification of perennial and seasonal rhinitis does not distinguish between provoking factors, nor does it indicate the most appropriate treatment. A more useful classification is based on symptoms, which may be intermittent or persistent, and vary widely in severity. The goal of management is to achieve optimal symptom control. Therapeutic options include allergen avoidance, pharmacotherapy and immunotherapy. Antihistamines and intranasal corticosteroids (INCS) have become the cornerstones of therapy. A variety of effective treatments are available for consumers to self-select, without the advice of a doctor or pharmacist. INCS are widely recognised as the most effective pharmacotherapy for AR, in both adults and children. The efficacy of various preparations is similar, but those with low systemic bioavailability are preferred for children and for patients who are also receiving inhaled, topical or systemic corticosteroids.

Histamine inhibits lipopolysaccharide-induced interleukin (IL)-18 production in human monocytes

Lipopolysaccharide (LPS) is an inducer of interleukin (IL)-18, which in turn plays important roles in immune responses. Previously, we reported that tumor necrosis factor (TNF)-alpha production could be detected in human peripheral blood mononuclear cells (PBMCs) treated with relatively low concentration of LPS (1 ng/ml), but that same concentration of LPS could not induce IL-18 production. In the present study, we found that LPS at relatively high concentrations (10-1000 ng/ml) induced IL-18 production in a concentration-dependent manner both in monocytes isolated from PBMC, and that histamine (10(-7) to 10(-4) M) inhibited IL-18 production induced by LPS. The studies using receptor subtype-selective agonists and antagonists suggested that the effect of histamine was mediated by H2 receptor but not by H1, H3 and H4 receptors. Therefore, the stimulation of H2 receptor might be beneficial in the treatment of sepsis through inhibiting LPS-elicited IL-18.

Influences of allergic rhinitis on sleep

BACKGROUND

Allergic rhinitis is classically characterized by sneezing, pruritus, rhinorrhea, and nasal congestion. These symptoms can lead to impaired nocturnal sleep, and this impairment results in daytime fatigue and somnolence, reducing both learning and work efficiency and decreasing quality of life.

STUDY DESIGN

In addition, the mediators of AR, including histamine, leukotrienes, cytokines, and prostaglandins, may play a role in sleep regulation and, thus, may be directly involved in this impairment independent of nasal obstruction. Recumbency and/or diurnal variation augments turbinate swelling, causing nasal blockage during nocturnal sleep. Medications directed toward reversal of nasal congestion often concomitantly work through suppression of inflammatory mediators and constitute the primary therapy for sleep disturbance associated with allergic rhinitis. Some pharmaceutical interventions that reduce nasal congestion have adverse effects on sleep. Decongestants effectively reduce nasal congestion but frequently produce stimulatory effects and even insomnia. Antihistamines reduce sneezing and pruritus, but are less effective in relieving congestion. Earlier, "first-generation" antihistamines are associated with significant sedation. They also have anticholinergic properties, which can cause dry mouth and make mouth breathing even more uncomfortable in the allergic individual with nasal obstruction. The absence of anticholinergic properties in second-generation, largely nonsedating antihistamines limits their efficacy in rhinorrhea. Azelastine, a topical antihistamine, significantly reduces rhinorrhea and congestion and improves subjective sleep quality, but is also associated with increased sedation. Intranasal corticosteroids and oral leukotriene receptor antagonists effectively reduce rhinorrhea, congestion, and inflammatory mediators.

CONCLUSIONS

The efficacy of these medications at improving subjective sleep quality has been established through multiple randomized, double-blind, placebo-controlled clinical trials.

Desloratadine inhibits allergen-induced airway inflammation and bronchial hyperresponsiveness and alters T-cell responses in murine models of asthma

BACKGROUND

Histamine elicits many features of immediate hypersensitivity reactions. Recent evidence indicates that H1 receptors modulate immune responses to antigens. Desloratadine (DL), a new, long-acting, H1 receptor antagonist, has both a potent antihistaminic function and anti-inflammatory properties.

OBJECTIVE

We sought to evaluate the effect of DL on allergic-airway responses in mice after inhalation of the naturally occurring aeroallergen Aspergillus fumigatus (Af ) and to examine the effects of DL on specific immune responses to a defined protein antigen with the use of an ovalbumin (OVA) model of asthma.

METHODS

Mice were subjected either to repeated, intranasal application of Af extract or to intraperitoneal immunization with OVA, followed by inhalation challenge. DL or a control fluid was given daily throughout the sensitization process. Immunoglobulin E (IgE) levels, bronchoalveolar lavage-fluid cytokines and cytology, lung histology, and physiologic responses to methacholine were assessed in the allergen-treated mice. Anti-OVA IgE responses and OVA-driven T-cell cytokine production were examined.

RESULTS

Treatment with DL did not impair IgE production but did inhibit bronchial inflammation and bronchial hyperresponsiveness in both Af- and OVA-treated mice. This inhibition required that DL be administered concurrently with allergen sensitization, indicating that the attenuation of bronchial hyperresponsiveness and inflammation was not caused by anticholinergic receptor effects. OVA-responsive T cells from DL-treated mice exhibited depressed production of IL-4, IL-5, and IL-13 and normal amounts of interferon-gamma. The amounts of IL-5 and IL-13 were also diminished in the bronchoalveolar lavage fluid.

CONCLUSION

DL, given at the time of exposure to the allergen, inhibits T(H)2 responses, the induction of allergic pulmonary inflammation, and bronchial hyperresponsiveness. These results suggest that DL or similar agents given during times of antigen exposure might alter disease progression in patients with respiratory allergy.

Fexofenadine modulates T-cell function, preventing allergen-induced airway inflammation and hyperresponsiveness

BACKGROUND

Antihistamines have been evaluated for usefulness in the treatment of asthma for more than 50 years. Interest was limited until the introduction of newer compounds that were free of much of the dose-limiting sedation associated with the earlier drugs.

OBJECTIVE

In a murine model of allergen-induced airway inflammation and hyperresponsiveness, the efficacy of an H1 receptor antagonist to prevent allergic inflammation and altered airway function was evaluated.

METHODS

Mice were sensitized and challenged to an allergen, ovalbumin, which elicited marked airway and tissue eosino-philia and airway hyperresponsiveness. Fexofenadine was administered before challenge, and airway responsiveness to inhaled methacholine, airway and tissue eosinophilia, bronchoalveolar lavage fluid cytokine levels, and serum IgE levels were assayed. In a second group of experiments, sensitized and challenged mice were treated or not treated with fexofenadine before challenge. T cells were isolated from the lungs and adoptively transferred into naive recipients before exposure to limited airway allergen challenge, and lung function and inflammation were evaluated.

RESULTS

Fexofenadine treatment of sensitized mice prevented the development of airway hyperresponsiveness in both the primary sensitization and challenge, as well as in the adoptive transfer experiments. These changes were accompanied by decreases in bronchoalveolar lavage and tissue eosinophilia, lymphocyte numbers, and T(H)2 cytokine production.

CONCLUSION

The results demonstrate the efficacy of an H1 receptor antagonist in preventing allergen-induced alterations in pulmonary inflammation and airway function. The data support the evaluation of drugs such as fexofenadine in the treatment of allergic asthma.

Human nasal allergen provocation for determination of true allergic rhinitis: methods for clinicians

The nasal provocation test (NPT) could be more extensively used in the diagnosis of allergic rhinitis by practicing physicians. However, the procedure has not been standardized, and has mainly been utilized for scientific purposes in the US. This review illustrates a wide variety of techniques and approaches to dosing and concentration of allergen extracts, and delivery systems. It also outlines the lack of a unified outcomes-evaluation system, including clinical symptom scores and nasal patency measurements, in different countries. NPT is a safe, simple, and useful method when conducted with the consideration of indications and contraindications. Standardized NPT has the potential to become a more frequently used additional clinical test in the diagnosis of allergic rhinitis.

Histamine polarizes human dendritic cells into Th2 cell-promoting effector dendritic cells

Allergic disorders are characterized by allergen-specific Th2-biased responses. Signals controlling Th2 cell polarization, especially those acting by polarizing dendritic cells (DC) into Th2-promoting DC (DC2), are not well known. Histamine, a mediator released by allergen-stimulated mast cells from allergic subjects, has been reported to activate human immature DC. We have therefore tested whether histamine affects DC polarization. We report here that histamine inhibits LPS-induced IL-12 production and polarizes uncommitted maturing DC into effector DC2. DC matured in the presence of histamine fail to produce IL-12 upon subsequent stimulation and prime Th2 responses, even in presence of IFN-gamma, a potent DC1-driving factor. All these effects are mediated through both H1 and H2 receptors. These data show that histamine is a potent DC2-polarizing factor and provide evidence for a novel mechanism that explains the initiation and maintenance of a predominant Th2 response in allergic disorders.

Mizolastine in the treatment of seasonal allergic rhinoconjunctivitis: a European clinical experience with 5408 patients managed in daily practice (PANEOS SAR Study)

BACKGROUND

Mizolastine, a potent H1 antihistamine with additional antiallergic properties, is marketed for the treatment of allergic rhinoconjunctivitis and urticaria. The objective was to investigate the safety and effectiveness of mizolastine under conditions of daily practice in patients with seasonal allergic rhinoconjunctivitis (SAR).

METHODS

In an open multicenter study, mizolastine 10 mg daily was administered for 14 days during the pollen season. Nasal and ocular symptoms, time to onset of symptom relief, and effect of the drug on diurnal alertness were evaluated. Safety was evaluated on the basis of self-reported adverse events (AE).

RESULTS

A total of 5408 patients (36+/-14 years of age, females=57%) with a history of SAR for 8+/-9 years were treated for a mean of 17.1+/-5.0 days. SAR symptoms improved in 93% and decreased by at least 50% in 86% of patients; 78% reported improvement after the first drug intake and 51% from the first hour. Sixty-nine percent considered mizolastine more effective than other antihistamines taken previously. The incidence of AE was low (3.8%).

CONCLUSION

The high responder rate, the rapid onset of action, and the low incidence of AE observed in this large multicenter study confirm the previously reported beneficial efficacy and safety of mizolastine in the management of SAR.

Histamine induces CD86 expression and chemokine production by human immature dendritic cells

Mast cells and immature dendritic cells (DC) are in close contact in peripheral tissues. Upon activation, mast cells release histamine, a mediator involved in the immediate hypersensitivity reaction. We therefore tested whether histamine could affect human DC activation and maturation. Histamine induces CD86 expression on immature DC in a dose-dependent (significant at 10(-7) M) and transient manner (maximal after 24-h stimulation). Histamine also transiently up-regulates the expression of the costimulatory and accessory molecules, CD40, CD49d, CD54, CD80, and MHC class II. As a consequence, immature DC exposed for 24 h to histamine stimulate memory T cells more efficiently than untreated DC. In addition, histamine induces a potent production of IL-6, IL-8, monocyte chemoattractant protein 1, and macrophage-inflammatory protein 1alpha by immature DC and also up-regulates IL-1beta, RANTES, and macrophage-inflammatory protein 1beta but not TNF-alpha and IL-12 mRNA expression. Histamine activates immature DC through both the H1 and H2 receptors. However, histamine-treated DC do not have a phenotype of fully mature cells, as they do neither show significant changes in the expression of the chemokine receptors, CCR5, CCR7 and CXC chemokine receptor 4, nor expression of CD83 de novo. These data demonstrate that histamine activates immature DC and induces chemokine production, thereby suggesting that histamine, via stimulation of resident DC, may participate locally in T cell stimulation and in the late inflammatory reaction associated with allergic disorders.

Nasal provocation testing: a review

OBJECTIVE

This review focuses on the uses of nasal provocation testing (NPT) for scientific investigations of the mechanisms of allergic and nonallergic rhinitis. It also describes the use of NPT as a diagnostic tool in clinical practice. The indications, contraindications, advantages, and limitations of different techniques for evaluation of nasal responses are reviewed. The paper familiarizes investigators with particulars of different nasal delivery systems, provocation agents, nasal patency measurements, secretion collection, and nasal lavage techniques.

DATA SOURCES

Relevant publications obtained from a literature review.

STUDY SELECTION

Relevant publications on the topics of NPT, allergic, and nonallergic rhinitis were critically evaluated.

RESULTS AND CONCLUSIONS

To date, NPT has been used primarily as a research tool for the investigation of allergic and nonallergic rhinitis with a wide variety of techniques depending on the specific scientific purposes. NPT will continue to provide useful information about the pathogenesis of airway diseases. Standardized nasal provocation testing has the potential to become a more frequently used clinical test in the diagnosis of allergic and occupational rhinitis and for determination of the appropriate and focused therapy.

Paediatric issues relating to the pharmacotherapy of allergic rhinitis

The prevalence of allergic rhinitis in children has risen significantly over the last two decades. Important comorbidities like asthma have grown in parallel due to a complex mix of environmental and genetic factors. These conditions have similar allergic inflammatory mechanisms, which raises the possibility of treating both conditions by targeting shared inflammatory mediators pharmacologically. The first line treatment for paediatric allergic rhinitis is a topical nasal corticosteroid or a non-sedating antihistamine. Available intranasal corticosteroids show superior symptom control to second-generation antihistamines. However, most topical steroids and non-sedating antihistamines have equivalent clinical efficacy within their respective classes, so the choice of agent depends on safety and tolerability. Ideally, topical nasal steroids should exhibit high local receptor binding affinity and low systemic bioavailability, allied with a lack of long-term growth suppression in children and adolescents. Regular use of topical steroids is advisable, but intermittent and prophylactic use is also effective. Second-generation antihistamines are effective and some have no adverse cardiac or sedative effects. Non-sedating antihistamine treatment can ameliorate rhinitis-induced decrements in learning. alpha-Adrenergic nasal decongestants provide short-term benefit, but topical agents can cause rebound symptoms. Prophylactic treatment with chromones is safe and effective, but multiple daily dosing is needed. Ipratroprium bromide nasal spray is useful as an intermittent therapy for mild disease or as add-on treatment, but its effect is limited to the control of rhinorrhoea. Children with allergic rhinitis should receive pharmacotherapy if allergen avoidance measures are ineffective, ideally with a topical intranasal steroid or a second-generation antihistamine.