The effect of a histamine synthesis inhibitor on the immediate nasal allergic reaction

Immunopharmacology of Nasal Allergic Reactions

The technique of nasal provocation followed by lavage was used to study the pharmacology and pathophysiology of upper airway allergic reactions. The levels of histamine, TAME-esterase activity, kinins, and arachidonic acid metabolites were measured in the recovered nasal lavage fluid obtained during the early and, in certain cases, the late phase and rechallenge reactions to antigen. Leukocytes contained in the lavage were counted and differentiated. Topical application of azatadine and systemic administration of theophylline reduced both mediators and symptoms during the early reaction, probably by inhibiting antigen-induced mast cell activation. Pretreatment with aspirin decreased the concentration of cyclooxygenase products during the early reaction without ameliorating symptoms. Administration of systemic steroids ablated the increase of mediators and symptoms and the mucosal accumulation of eosinophils and mononuclear cells, but not of neutrophils during the late phase reaction, without affecting the mediators or symptoms of the early reaction, with the exception of kinins. Topical steroids reduced both the amount of mediators and the severity of symptoms during the early, late, and rechallenge reactions. The accumulation of eosinophils, basophils, neutrophils, and mononuclear cells during the late phase reaction was also significantly reduced. Thus, this nasal challenge model has helped us to gain insights into the pathophysiology of allergic reactions and the pharmacology of their treatment and can be used to examine the efficacy of pharmacologic agents designed for the treatment of such reactions.

Clinical and laboratory-based methods in the diagnosis of natural rubber latex allergy

The accurate diagnosis of hypersensitivity to natural rubber latex is the initial step in the effective management of individuals with latex allergy and in ensuring the quality of epidemiologic studies. The diagnostic algorithm used in the evaluation of an individual with suspected latex allergy begins with a comprehensive clinical history during which risk factors (atopy, food allergies, hand dermatitis) and temporal relationships between symptoms and natural rubber product exposure are identified. If type IV hypersensitivity is suspected because of the delayed nature (hours to days) and confinement of symptoms to the skin-latex product contact areas, patch testing can be conducted to confirm the presence of activated T cells with specificity for rubber chemicals. If type I hypersensitivity is suspected because of ocular, upper and lower airway, and/or systemic symptoms that have rapid onset (minutes) after a definable latex exposure, a confirmatory skin or blood test for IgE antibody may be conducted to verify a state of sensitization within the individual. The definitive diagnosis would then be made only after consideration of the individual's clinical history and confirmatory in vivo and/or in vitro laboratory test results. If discordance remains between highly convincing latex-associated symptoms as identified in the history and repetitively negative confirmatory IgE antibody test results, then one of several types of in vivo provocation tests may be performed for adjudication. This overview examines the current state of the art in both in vivo and in vitro diagnostic methods for latex-specific IgE antibody detection in skin and blood. The performance, advantages, and limitations of each diagnostic method are compared.

Diagnosis of natural rubber latex allergy

The accurate diagnosis of a latex-allergic individual begins with a comprehensive clinical history. Atopy, food allergies, hand dermatitis, and temporal relationships between allergic symptoms and natural rubber product exposure are risk factors that increase the suspicion of latex allergy. If symptoms are temporally delayed (hours-days) and confined to skin-latex product contact areas, Type IV hypersensitivity should be suspected and patch testing may be performed to identify activated T cells that are specific for selected rubber chemical additives. If ocular, upper and lower airway, and/or systemic allergic symptoms are observed with rapid onset (minutes) following a definable latex exposure, Type I hypersensitivity should be suspected. One or several confirmatory tests for latex-specific IgE antibody in the skin or blood may next be performed to verify a sensitized (IgE antibody positive) state. If the clinical history remains discordant with a skin test or blood test result, in vivo provocation tests may be cautiously considered for adjudication. Diagnostic methods for latex-specific IgE antibody detection in skin and blood are overviewed, with a focus on their performance, advantages, and limitations.

Repeated latex aeroallergen challenges employing a hooded exposure chamber: safety and reproducibility

BACKGROUND

Bronchial, nasal, and conjunctival challenges are useful for clarifying discordant clinical history (Hx) and skin and/or serologic tests and in assessing semiquantitative changes in biologic sensitivity over time. The objective of this study was to determine the safety and reproducibility of repeated latex-allergen challenges with a hooded exposure chamber (HEC).

METHODS

The HEC system comprises a powered forced-air respirator with a fitted face shield and hood that uses glove-derived latex-allergen associated cornstarch particles (LAC) to expose simultaneously the conjunctiva, nose, and lungs. Serial control and incremental LAC challenges are conducted until an endpoint based on upper and/or lower respiratory tract symptoms and peak expiratory flow rates is reached. Six latex-allergic (Hx and puncture skin test [PST]- and 5/6 radioallergosorbent test [RAST]-positive) subjects were challenged on three separate occasions at least 2 weeks apart. Serial latex PST midpoints and serum anti-latex IgE by RAST were monitored at each visit and at a fourth follow-up visit.

RESULTS

All subjects responded to LAC, but not to air or control cornstarch administered as controls. All responses were confined to mild symptoms of allergic rhinoconjunctivitis and/or asthma that either resolved spontaneously or were reversed with inhaled albuterol. No subject experienced a systemic or delayed reaction. There were no significant changes in the endpoint LAC doses over the three challenge visits (P>0.2). The mean coefficient of variation for log2 endpoints within-subjects was 17.3+/-17.2% (SD). The serum latex-specific IgE was not significantly boosted by the three challenges (P>0.2). The concentration of latex extract necessary to produce an 8-mm wheal by PST was not significantly changed during the study (P>0.1), indicating that latex sensitivity was not affected by the repeated LAC exposures.

CONCLUSIONS

The results of this study indicate that repeated HEC latex-allergen challenges are both reproducible and safe, and do not increase latex sensitivity.

Conjunctival provocation test: high clinical reproducibility but little local temperature change

Ten atopic and five healthy individuals participated in eight conjunctival provocation tests (CPT) in an effort to improve the CPT procedure. Results were evaluated by thermography and the use of conventional criteria under various conditions. Due to considerable spontaneous variability and change in temperature already after instillation of diluent, thermography was not sensitive enough to identify positive CPT results. The precision of the CPT was within one 10-log step in all tests and in all patients. Itching appeared before erythema in 83% of subjects and within 5-8 min after instillation of the allergen. This was true also when only one eye was used for the CPT. We therefore conclude that the CPT procedure can be used in one eye every 5-8 min when indicated in clinical routine and that it is a safe, precise method.

Physiologic responses to intranasal dose-response challenges with histamine, methacholine, bradykinin, and prostaglandin in adult volunteers with and without nasal allergy

The dose-response (dose, 0.01, 0.05, 0.1, 0.5, 1, and 5 mg) profiles of 10 atopic and 10 nonatopic subjects were determined for nasal patency, secretion weight, pulmonary function, eustachian tube function, middle-ear function, and symptoms after intranasal inhalation challenges with histamine, bradykinin, methacholine, prostaglandin D2, and prostaglandin F2 alpha (PGF2 alpha). Results demonstrated that challenge with PGF2 alpha increased nasal patency, whereas challenge with all other substances decreased patency. The relationship between substances in eliciting a nasal congestive response was prostaglandin D2 greater than histamine greater than bradykinin greater than methacholine. A similar effect ordering was noted for the postchallenge development of eustachian tube dysfunction. Secretion weights were significantly greater after challenge with histamine compared to all other substances. A decrease in pulmonary function was observed only after challenge with PGF2 alpha, although the effect was not statistically significant. No changes in middle-ear pressure were observed for challenges with any of the substances. Only histamine challenge provoked sneezing, whereas challenge with either of the prostaglandins provoked cough. With the exception of methacholine, all substances caused symptoms of rhinorrhea, congestion, and sore throat. Bradykinin was particularly effective in provoking "pain/pressure"-related symptoms. With the exception of secretion weight, the differences between responses of atopic and nonatopic subjects were not statistically significant. These results document mediator specificity in the physiologic and symptomatic responses to intranasal challenge.

Allergen-induced nasal hyperreactivity appears unrelated to the size of the nasal and dermal immediate allergic reaction

It has been previously demonstrated in nasal challenge studies that there is an increased sensitivity to allergen following an initial allergen challenge. A similar feature has been demonstrated following natural allergen exposure in patients with seasonal allergic rhinitis. To further explore the characteristics of this "priming" phenomenon and its relationship to other expressions of their allergic airway disease, 28 hay fever patients with strictly seasonal disease were studied. Skin tests with the relevant pollen allergen and histamine were performed and the size of the immediate and late phase allergic reaction was determined. An initial nasal allergen challenge was followed by a rechallenge of the nose with allergen 24 h later using a lavage technique. Determinations of TAME-esterase activity, as a biochemical marker of the allergic reaction, were made in the returned lavage fluid. The number of sneezes was counted and nasal symptoms were also assessed using a scoring technique. 19 of 28 patients (67%), displayed an increased responsiveness at rechallenge with similar findings in terms of symptom scores and TAME-esterase measurements. The increase was statistically significant for the symptoms of nasal blockage, which increased from 0.7 +/- 0.1 (mean +/- SEM) to 1.1 +/- 0.2 (P less than 0.05), and nasal secretion which rose from 1.1 +/- 0.2 to 1.7 +/- 0.2 (P less than 0.01). A composite nasal symptom score which also took account of the number of sneezes, increased from 2.9 +/- 0.4 to 4.0 +/- 0.3 (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)