The association of individual allergen reactivity with respiratory disease in a national sample: data from the second National Health and Nutrition Examination Survey, 1976-80 (NHANES II)

Comparative prevalence of sensitization to common animal, plant and mould allergens in subjects with asthma, or atopic dermatitis and/or allergic rhinitis living in a tropical environment

BACKGROUND AND OBJECTIVES

Current information suggests that the expression of allergic diseases is determined by the exposure and nature of the allergen. The objectives of the present study were to determine if the nature of allergenic exposition to animal, plant or fungal allergens influenced the clinical manifestations of atopic dermatitis (AD), allergic rhinitis (AR) or asthma (AS) in patients living in a tropical environment. The prevalence and degree of sensitization to these allergens were analysed by age and gender.

SUBJECTS AND METHODS

A total of 1496 atopic cases, grouped according to the primary diagnosis of AD or AR or AS, were skin tested using a standardized allergen panel. Participants were categorized by age groups. The atopic index (AI) and mean weal diameter (MWD) as well as the prevalence of positive skin tests were determined for each of the patient groups and compared by age groups.

RESULTS

The prevalence of atopy as well as the AI and the MWD peaked at 6-15 years of age and declined thereafter. In all the patients tested, the prevalence of sensitization was, in decreasing order; dust mites 94.3%, cockroach 41.5%, pets 31.5%, plant allergens 31.1% and fungal 19.4%. Eight hundred and ninety-three atopic patients were exclusively sensitized only to animal allergens. Of these, 38.4% had AD, 31.3% had AR and 30.5% with AS.

CONCLUSION

These data demonstrate that for patients with AD, AR and AS living in a tropical environment, the prevalence of positive skin reactions to animal allergens is highest followed by plant and fungal allergens. We did not observe any association between the type of allergen and clinical manifestations. The index of atopy was similar for both sexes. The prevalence and degree of sensitization were shown to peak in young adults independent of the allergen in AD and AR patients.

Nasal involvement in allergic asthma

Even since the late 19th century, a relationship has been suspected between upper airway disease and the subsequent development or aggravation of asthma symptoms. To date, it has been generally accepted that pathologic conditions of the upper airways, e.g. allergic rhinitis, chronic sinusitis and nasal polyposis, may influence the lower airways. However, the mechanisms underlying this relationship were, for a long time, poorly understood. Recently, evidence has been accumulating which indicates a systemic connection as one of the responsible mechanisms in nasobronchial crosstalk. In this review, the pathophysiologic and immunologic aspects of the interaction between upper and lower airways will be discussed.

Effect of ultraviolet germicidal lights installed in office ventilation systems on workers' health and wellbeing: double-blind multiple crossover trial

BACKGROUND

Workers in modern office buildings frequently have unexplained work-related symptoms or combinations of symptoms. We assessed whether ultraviolet germicidal irradiation (UVGI) of drip pans and cooling coils within ventilation systems of office buildings would reduce microbial contamination, and thus occupants' work-related symptoms.

METHODS

We undertook a double blind, multiple crossover trial of 771 participants. In office buildings in Montreal, Canada, UVGI was alternately off for 12 weeks, then turned on for 4 weeks. We did this three times with UVGI on and three times with it off, for 48 consecutive weeks. Primary outcomes of self-reported work-related symptoms, and secondary outcomes of endotoxin and viable microbial concentrations in air and on surfaces, and other environmental covariates were measured six times.

FINDINGS

Operation of UVGI resulted in 99% (95% CI 67-100) reduction of microbial and endotoxin concentrations on irradiated surfaces within the ventilation systems. 771 participants appeared to remain masked, and reported no adverse effects. On the basis of within-person estimates, use of UVGI was associated with significantly fewer work-related symptoms overall (adjusted odds ratio 0.8 [95% CI 0.7-0.99]), as well as respiratory (0.6 [0.4-0.9]) and mucosal (0.7 [0.6-0.9]) symptoms than was non-use. Reduction of work-related mucosal symptoms was greatest among atopic workers (0.6 [0.5-0.8]), and never-smokers (0.7 [0.5-0.9]). With UVGI on, never-smokers also had large reduction of work-related respiratory (0.4 [0.2-0.9]), and musculoskeletal symptoms (0.5 [0.3-0.9]).

INTERPRETATION

Installation of UGVI in most North American offices could resolve work-related symptoms in about 4 million employees, caused by microbial contamination of heating, ventilation, and air-conditioning systems. The cost of UVGI installation could in the long run prove cost-effective compared with the yearly losses from absence because of building-related illness.

IgE-mediated allergy to fungal allergens in Finland with special reference to Alternaria alternata and Cladosporium herbarum

BACKGROUND

Alternaria alternata and Cladosporium herbarum are common fungi in outdoor environments, but their clinical significance has not been elucidated in Finland.

OBJECTIVE

To evaluate the prevalence of IgE-mediated allergy and clinical outcomes caused by sensitization to fungal allergens in patients with suspected allergy.

METHODS

Skin prick tests (SPTs) were performed with C. herbarum in 6,376 patients and also with A. alternata in 1,504 of these patients. SPTs were repeated in 40 patients who showed a positive reaction to either allergen using commercial and in-house extracts. The association of SPT with allergen-specific IgE antibodies in serum was evaluated. Seven patients also underwent a conjunctival challenge test with these fungal allergens.

RESULTS

The prevalence of positive SPT results to A. alternata and C. herbarum was low (2.8% and 2.7%, respectively). Among the 40 patients, atopic eczema/dermatitis syndrome was found in 58%, asthma in 44%, and rhinitis in 31%. Most of the patients displayed SPT reactions also to several other fungal allergens, and 75% to 80% showed a positive SPT reaction to allergens of pet animals or pollens. Four patients had a positive reaction to A. alternata and 6 to C. herbarum in the conjunctival challenge test.

CONCLUSION

In the Finnish population with allergic symptoms, IgE-mediated sensitization to 2 common fungal allergens was rare and of minor clinical importance. SPT reactions to fungi are mostly observed in patients with multiple sensitivity to various allergens.

Links between rhinitis and asthma

There is compelling evidence of a close relationship between the upper and lower airways in asthma and rhinitis. Rhinitis is present in the majority of patients with asthma, and a significant minority of patients with rhinitis have concomitant asthma. Similarities between the two conditions occur in the nature of the inflammation present in the target tissues. A common initiating step in the inflammatory process of allergic airways disease is the presence of immunoglobulin E providing an adaptor molecule between the offending allergen and inflammatory cell activation and mediator release. Differences in the two conditions arise largely from the structural differences between the nose and the lungs. In an asthmatic, concomitant allergic rhinitis increases healthcare costs and further impairs quality of life. The presence of rhinitis should always be investigated in children and young adults with asthma. Subjects with allergic rhinitis have an increased risk of developing asthma and may form a suitable population for secondary intervention to interrupt the 'allergic march'.

Mucosal and systemic inflammatory changes in allergic rhinitis and asthma: a comparison between upper and lower airways

BACKGROUND

Local airway inflammation and airway remodelling are considered important in the clinical expression of allergic asthma.

OBJECTIVE

The aim of this study was to compare airway inflammation and remodelling in nasal and bronchial mucosa of subjects with allergic rhinitis with or without asthma.

METHODS

Four experimental groups were formed: allergic asthma and rhinitis (n = 19); allergic rhinitis, no asthma (n = 18); atopic subjects, no asthma, no rhinitis (n = 8) and non-allergic healthy control subjects (n = 16). Blood samples, nasal and bronchial biopsy specimens were collected during stable disease. Immunohistochemistry was performed for eosinophils (MBP), mast cells (CD117) and vascular endothelium (CD31). Epithelial loss, reticular basement membrane (RBM) thickness and subepithelial vascularity was assessed with a computer-assisted image analysis system.

RESULTS

In nasal and bronchial mucosa, numbers of eosinophils were significantly higher in rhinitis patients with and without asthma than in asymptomatic atopics (P < 0.05) and controls (P < or = 0.01). In bronchial mucosa, the RBM was significantly thickened in rhinitis patients with and without asthma compared to asymptomatic atopics (P < 0.05) and controls (P < 0.01), while in nasal mucosa no differences were seen. Patients with asthma and rhinitis had increased numbers of blood eosinophils (P = 0.05) and skin test reactivity (P = 0.01) compared to patients with rhinitis only. No significant differences could be found between the investigated groups with respect to serum IL-5 and eotaxin levels, the number of mucosal mast cells and the degree of epithelial loss and subepithelial vascularity. Epithelial desquamation was significantly increased in the bronchial mucosa compared to nasal mucosa, not only in asthmatics (P < 0.001), but also in atopics without asthma and rhinitis (P = 0.02).

CONCLUSIONS

This study shows that allergic inflammation, increased basement membrane thickness and epithelial desquamation are present in the lower airways of atopic subjects, even before the onset of clinical symptoms. Despite the presence of inflammatory cells, no structural changes could be assessed in nasal mucosa of allergic patients.

Natural exposure to Alternaria spores induces allergic rhinitis symptoms in sensitized children

Allergic rhinitis is associated with exposure to inhaled allergens. Allergic sensitization to the fungus Alternaria is common, especially in warm climates, but the relevance of sensitization to Alternaria in the generation of rhinitis has not been elucidated. The aim of this study was to determine whether natural exposure to Alternaria induces rhinoconjuctivitis symptoms in Alternaria-sensitized children. Symptoms of rhinoconjuctivitis in 132 atopic (measured by skin prick tests) children (aged 7-12 years) in inland New South Wales Australia were measured using parent-completed questionnaires in summer and winter 1998. Airborne concentrations of Alternaria spores and grass pollen were measured throughout the study period using a Burkard volumetric trap. The relation between airborne concentrations of Alternaria spores and symptoms of rhinoconjunctivitis was examined using Wilcoxon's matched pairs signed ranked test and generalized estimating equations. The proportion of children atopic to Alternaria reporting symptoms of rhinitis was significantly higher in the summer, when airborne concentrations of Alternaria were high, than in the winter, when airborne concentrations were low (66.2% vs. 38.2% for nasal symptoms at night, p = 0.0001, 70.6% vs. 51.52% for nasal symptoms during the day, p = 0.02). The proportion of children using anti-allergic treatment was also higher in summer than in winter (anti-allergic medication for the nose 39.7% vs. 17.7%, p = 0.0003). A strong correlation between airborne concentrations of grass pollen and Alternaria was found (R = 0.94, p < 0.001). However, when all children atopic to ryegrass were excluded from the analyses, significant associations between symptoms and season remained. We conclude that exposure to Alternaria spores may be an important cause of allergic rhinoconjunctivitis.

Hay fever and predictive value of prick test and specific IgE antibodies: a prospective study in children

Little is known from population-based studies in children about the diagnostic values of allergen-specific IgE antibodies (RAST) and skin prick test (SPT) with respect to hay fever. We aimed to determine and compare the diagnostic values of SPT and RAST to aeroallergens with respect to the incidence of hay fever cases in schoolchildren at different cut-off points. A prospective cohort study was performed on 1100 school children (5-7 and 8-10 years). Information on a doctor's diagnosis of hay fever was obtained by questionnaire and allergic sensitization to grass and birch pollen, cat, and Dermatophagoides pteronyssinus were measured using SPT and RAST between September 1992 and July 1993. Thirty-eight children give a history of hay fever (3.5%) in 1992/93 and additionally 37 cases occurred until 1996. Allergic sensitization was present in 17.9% (SPT), 30.2% (RAST) and more frequent in children with a history of hay fever (SPT: OR 11.7, 5.5-24.7; RAST: OR 10.6, 4.3-26.4). This difference was most pronounced for sensitization to pollen allergens. The sensitivity, specificity, positive and negative predictive values (PPV, NPV) for SPT and RAST were 65.6, 83.7, 11.9, 98.6 and 79.3, 71.6, 9.3, 99.0, respectively, with differences for specificity being significant (p < 0.001). Whereas NPV were equally high for SPT (99.2) and RAST (99.3), the incidence of hay fever cases were predicted rather poorly though somewhat better by SPT than by RAST (PPV 16.7 vs. 9.8; p < 0.001) initially. With increasing cut-off point for RAST reactivity, the PPV increased and reached 25.0 at 17.5 kU/l, whereas the NPV decreased to 97.9, which was lower than that of SPT reactivity (p < 0.01). At the cut-off point of 1.5 kU/l almost identical predictive values for SPT and RAST were obtained. SPT and RAST perform better in the negative than positive prediction of hay fever cases in epidemiological studies. Differences in the predictive capabilities depend on the chosen cut-off point for RAST reactivity.

Methodologic aspects of the quantification of skin prick test responses: the EGEA study

BACKGROUND

The expression of responses of allergy skin prick tests is not standardized. Usual definitions of atopy are not quantitative.

OBJECTIVE

We sought to perform a biometric analysis of responses to various allergens to propose synthetic, quantitative indices independent of the heterogeneity of responses to various allergens.

METHODS

Adults (N = 1286) from the Epidemiological Study on the Genetics and Environment of Asthma, Bronchial Hyperresponsiveness, and Atopy (EGEA) were included in the analysis. The first step, conducted for 678 subjects with at least 1 wheal >0, was to perform a standardization of wheal diameters to obtain comparable figures for 10 allergens through use of the means of the squares of wheal size as a scaling factor. The second step was a factor analysis of the standardized responses conducted not only for all subjects but also separately for asthmatic case and nonasthmatic control subjects. Finally, the strength of the link between various dichotomous and quantitative scores was assessed with multiRAST, total IgE, and asthma. Analyzed quantitative scores were based on the number of positive responses and on the nonstandardized and standardized sizes of the wheals.

RESULTS

The standardization was efficient. Among asthmatic subjects but not other subjects, factor analysis evidenced a pattern with 3 factors, corresponding to outdoor, indoor, and mold allergens. The link study showed that all scores performed very similarly.

CONCLUSION

The number of positive tests is a quantitative score with valid biometric properties. It should be used more widely in clinical settings and in epidemiology to assess the severity of atopy.

Omalizumab improves asthma-related quality of life in children with allergic asthma

BACKGROUND AND OBJECTIVE

Omalizumab is a recombinant, humanized, monoclonal anti-immunoglobulin E (IgE) antibody, developed for the treatment of IgE-mediated diseases. In children with allergic asthma, it was shown to reduce the requirement for inhaled corticosteroids while protecting against disease exacerbation. Here we report the effects of treatment with omalizumab on asthma-related quality of life (AQoL) in children with allergic asthma.

METHODS

This evaluation was part of a previously reported 28-week, randomized, double-blind, placebo-controlled study to assess the efficacy, safety, and tolerability of omalizumab (at least 0.016 mg/kg/IgE [IU/mL] per 4 weeks) in children with allergic asthma who were well controlled on daily treatment with inhaled corticosteroids. Dosage of beclomethasone dipropionate was kept constant for 16 weeks (steroid-stable phase), then reduced over 8 weeks to the minimum effective dose (steroid-reduction phase). This dose was then maintained for the final 4 weeks. The Pediatric Asthma Quality of Life Questionnaire (PAQLQ) was administered at baseline, week 16, and week 28.

RESULTS

Baseline demographics, PAQLQ scores, and other data were comparable for the 2 treatment groups. At the end of the steroid-reduction phase, patients in the omalizumab-treated group reported significant improvements in the "activities" and "symptoms" domain scores as well as overall AQoL compared with placebo. More patients in the omalizumab group achieved clinically relevant (> or =0.5) changes in PAQLQ scores during the course of the study, and this difference was significant for activities and overall AQoL.

CONCLUSION

Omalizumab improves AQoL in children with allergic asthma.

Evidence for the genetic control of immunoglobulin E reactivity to the allergens of Alternaria alternata

BACKGROUND

The fungus Alternaria alternata contains potent allergens, and sensitization to these allergens is associated with a high risk of respiratory disease. The influence of genetic regulation on sensitization to Alternaria is unknown.

OBJECTIVE

To determine the influence of genetic factors on IgE responses to specific allergens of Alternaria.

METHODS

The concordance of skin prick test (SPT), radioallergosorbent test (RAST) and IgE-binding profiles of sera were examined from a large cohort of monozygotic and dizygotic twins.

RESULTS

Casewise concordance for a positive SPT response was monozygous (MZ) 66%: dizygous (DZ) 40% (P = 0.002). Logistic regression confirmed that casewise concordance was significantly stronger between MZ than DZ pairs. Immunoblotting against an Alternaria extract revealed 19 allergenic bands. The differences in concordance between the different bands were not significant for either the MZ (P = 0.97) or DZ (P = 0.84) groups. The pooled MZ : DZ difference in concordance was just significant (P = 0.049), suggesting an overall genetic effect on the response to Alternaria. This was reinforced by the comparison of the MZ and DZ correlations for total number of bands recognized (MZ r = 0.65; DZ r = 0.37, P = 0.015). Overall, there was a moderate correlation between the individual SPT weal size and RAST score (r(2) = 0.41) and a substantial correlation between the number of immunoblotted bands and RAST scores (r(2) = 0.79).

CONCLUSION

There is a strong genetic influence on IgE response to the mixture of Alternaria allergens and a lesser effect on IgE response to individual allergens.

Environmental controls in the management of allergic asthma

Environmental allergen control is one of the four primary goals of good asthma management. The American Academy of Allergy, Asthma, and Immunology has published a position statement [78] that endorses the National Asthma Education and Prevention Program management guidelines [23] and recommends that every patient with persistent asthma be evaluated for environmental allergen sensitivity. Patients who have sensitivities should receive practical advice on allergen avoidance. An accumulating body of knowledge indicates that such measures, when strictly applied for a sufficient period of time, can indeed reduce asthma symptoms, need for medication, and airway hyperresponsiveness. Ongoing prospective trials in large numbers of patients are being conducted and should enhance the ability to make proper recommendations to patients.

The effect of allergen exposure in early childhood on the development of atopy

While there is good evidence for the association between allergen exposure and disease severity in sensitized individuals, and allergen exposure and development of sensitization, the relationship between allergen exposure and development of allergic disease is as yet unresolved. A protective effect of cat ownership on sensitization and allergic disease has been reported. The dose-response relationship between allergen exposure and sensitization may be different for different allergens (eg, linear for mite, bell-shaped for cat). Exposure to a high level of cat allergen may result in a modified Th2 response characterized by the presence of IgG4 antibody to cat proteins without IgE response, which could be regarded as a form of tolerance. The long-term prospective follow-up of well-defined cohorts with objective exposure and outcome measures will elucidate the complex relationship between environmental allergen exposures, sensitization, and asthma.

IgE-reactive proteins from Stachybotrys chartarum

BACKGROUND

Stachybotrys chartarum has been associated with idiopathic pulmonary hemorrhage in infants. This is thought to be mycotoxin-related. There are increasing numbers of reports linking this fungus to the indoor environment of patients with other pulmonary problems, including allergies and asthma.

OBJECTIVE

Given the potential significance of this fungus as a pulmonary pathogen, this work evaluates the antigenic proteins of S. chartarum as to their molecular size and the prevalence of immunoglobulin (Ig)E and IgG directed against them in the general population.

METHODS

S. chartarum was isolated from a local home. S. chartarum for extract production was grown on minimum salts and glucose. Plasma from 132 healthy individuals was evaluated for IgE and IgG directed against S. chartarum using direct and inhibition enzyme immunoassay. The number and molecular size of those proteins that were bound by IgE from pooled sera known to contain IgE to S. chartarum were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis immunoblotting.

RESULTS

Enzyme immunoassay indicated 65 of 132 (49.2%) sera tested contained IgG against S. chartarum and 13 of 139 (9.4%) sera tested contained IgE against S. chartarum. Pooled sera identified two IgE-binding proteins from extracts of S. chartarum spores and mycelia. These proteins are 34 and 52 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis immunoblot.

CONCLUSIONS

We conclude sensitivity to S. chartarum is potentially much more widespread than previously appreciated. This fungus may impact the asthmatic and allergic population through both immunologic and toxic mechanisms. Its significance in the milieu of allergenic fungi may need to be re-evaluated.

Effect of 2-year placebo-controlled immunotherapy on airway symptoms and medication in patients with birch pollen allergy

BACKGROUND

Birch pollen is a common allergen in northern, central, and eastern Europe. Earlier studies of specific immunotherapy using birch pollen extract were not placebo-controlled or were only preseasonal. Long-term, placebo-controlled studies with subcutaneously administered standardized birch pollen extract are lacking.

OBJECTIVE

The aim of this study was to evaluate the effect of immunotherapy with birch pollen extract on airway symptoms and use of medication in adult birch pollen-allergic patients in a double-blind, placebo-controlled trial.

METHODS

Forty-nine patients with histories of birch pollen allergy from the upper and lower airways, positive skin prick test and conjunctival provocation test results, and in vitro specific IgE to birch pollen (Betula verrucosa ) extract were included. Immunotherapy with birch pollen extract was given during 2 consecutive years in a double-blind, randomized, placebo-controlled study. Clinical symptom scores from the upper and lower airways and use of rescue medication were registered throughout the pollen season.

RESULTS

Forty-six patients reached the maintenance dose and were maintained on that dose during the 2-year study. The median symptom scores during the 1997 and 1998 seasons were 1.3 and 2.6, respectively, in the specific immunotherapy group and 2.1 and 4.3, respectively, in the placebo group. The differences between the groups were significant (P =.05 in 1997 and P =.005 in 1998). The placebo group used significantly more rescue medication during both seasons than the specific immunotherapy group (P =.004 for 1997 and P =.004 for 1998).

CONCLUSION

Specific immunotherapy with birch pollen extract is an effective and safe treatment for reducing clinical allergy symptoms and medication use in birch pollen-allergic patients during the pollen season.

Assessment and control of fungal allergens

Fungal sensitivity is a significant cause of allergic disease. Understanding the role fungi play in allergic disease, and how to best control exposure among those with allergy, can have important clinical ramifications.

Effects of zafirlukast upon clinical, physiologic, and inflammatory responses to natural cat allergen exposure

BACKGROUND

Leukotriene receptor antagonists have been shown to attenuate physiologic changes in the upper and lower airways induced by allergen challenge. However, it is unknown whether these drugs modulate airway inflammation after exposure to allergen in a natural setting.

OBJECTIVE

To determine the effects of the oral leukotriene receptor antagonist zafirlukast upon symptoms, changes in pulmonary function, and indices of inflammation in the upper and lower airways induced by natural exposure to cats.

METHODS

Zafirlukast, 20 mg twice daily, or placebo was administered to 18 cat-allergic asthmatic patients in this randomized, double-blind, crossover study. Cat room challenges were performed after a 1-week period of each treatment. Upper and lower airway symptoms were measured and spirometry performed before and at regular intervals during each challenge. Nasal lavage and sputum induction were performed 24 hours before and after each challenge.

RESULTS

Zafirlukast significantly improved the prechallenge baseline FEV1 (P = 0.001) and attenuated the decrease in FEV1 induced by cat challenge (P = 0.019). Zafirlukast also significantly reduced lower airway symptoms associated with cat challenge (P = 0.005) but had no effects on nasal symptoms. Although zafirlukast did not significantly differ from placebo in its effects on sputum inflammatory cells or eosinophil cationic protein, it significantly reduced the absolute counts of total white cells, lymphocytes, neutrophils, and basophils in nasal lavage fluid.

CONCLUSIONS

Zafirlukast, 20 mg twice daily for 1 week, demonstrated a significant protective effect on symptoms of asthma and alterations in pulmonary function induced by natural cat exposure, whereas nasal symptoms and markers of sputum inflammation were not affected by the medication.

Treatment of childhood asthma with anti-immunoglobulin E antibody (omalizumab)

BACKGROUND AND OBJECTIVE

There seems to be a strong causal relationship between allergy and the origins of asthma. Susceptibility to both is determined by a combination of genetics and environment acting through a complex network of cytokines. Nearly 90% of affected children have positive skin tests indicating the presence of specific immunoglobulin E (IgE), with sensitivity to house dust mite, Alternaria, cockroach, cat, and dog most closely linked to the disease. Greater exposure to house dust mite during infancy leads to earlier onset of wheezing, and elevated serum IgE levels correlate with the appearance of asthma symptoms. Specific IgE binds to high-affinity (FcepsilonRI) receptors on mast cells and basophils. The IgE-mediated reactions that follow exposure of sensitized mast cells to an allergen are designated early- and late-phase asthmatic responses (EAR and LAR). EAR is characterized by release of histamine and other preformed mediators within 1 hour of allergen exposure. It is often followed by LAR, an infiltration of the airways by inflammatory cells associated with an episode of more prolonged, and usually more severe airflow obstruction, 4 to 8 hours after antigen exposure. Chronic airway symptoms result from persistent LAR caused by continuous allergen exposure. IgE antibodies are capable of passive transfer of both EAR and LAR sensitivity. IgE-mediated mast cell activation contributes to chronic tissue eosinophilia and airway remodeling, with permanent loss in pulmonary function. Omalizumab (rhuMAb-E25) is a recombinant, humanized, monoclonal anti-IgE antibody of mouse origin developed for the treatment of IgE-mediated diseases. Omalizumab binds to free IgE at the same site as the high-affinity receptor. Although it attaches to free IgE, it does not bind to IgA, IgG, or cell-bound IgE. It therefore does not induce cross-linking of cell-bound IgE, which would lead to the release of allergic mediators. It has been reported to decrease serum IgE levels in a dose-dependent manner, inhibit EAR and LAR, and cause a down-regulation of FcepsilonRI receptors on basophils. Omalizumab has been reported to be safe and effective in improving asthma control and reducing the requirement for oral and inhaled corticosteroids. This double-blind, randomized, placebo-controlled study evaluated the safety, steroid-sparing effects, and impact on disease exacerbations of omalizumab in the treatment of childhood asthma. Methods. Participants were 334 males and premenarchal females aged 6 to 12 years, with moderate to severe allergic asthma requiring treatment with inhaled corticosteroids. During a run-in phase, all children were switched to equivalent doses of beclomethasone dipropionate (BDP), and the dose was adjusted to assure maintenance of asthma control achieved with previous corticosteroid treatment. Children were randomized to subcutaneously administered placebo (N = 109) or omalizumab (N = 225) at a dose based on body weight and initial serum IgE (0.016 mg/kg/IgE [IU/mL] per 4 weeks). BDP dose (initial range 168-420 microg/d) was kept stable for 16 weeks (stable-steroid phase), reduced over 8 weeks to the minimum effective dose (steroid-reduction phase), and maintained constant for the final 4 weeks.

RESULTS

More participants in the omalizumab group decreased their BDP dose, and their reduction was greater than that of the placebo group (median reduction 100% vs 66.7%). BDP was withdrawn completely in 55% of the omalizumab group versus 39% of the placebo group. The incidence and the frequency of asthma exacerbations requiring treatment with doubling of BDP dose or systemic corticosteroids were lower in the omalizumab group. The treatment differences were statistically significant during the steroid-reduction phase, during which fewer participants in the omalizumab group had asthma exacerbation episodes (18.2% vs 38.5%), and the mean number of episodes per patient was smaller than with placebo (0.42 vs 2.72). Five asthma exacerbations requiring hospitalization all occurred in the placebo group. Participants' and investigators' global evaluations of treatment effectiveness were more favorable for omalizumab than placebo. Investigators rated effectiveness excellent for 31.5% of the omalizumab group versus 16.3% of the placebo group and good for 44.7% of the omalizumab group versus 32.7% of the placebo group. There was little change in asthma symptom scores or spirometry measurements during either the stable-steroid or steroid dose-reduction phase, with minimal differences between the treatment groups. The requirement for rescue medication in the omalizumab group during both the stable-steroid and steroid dose-reduction phases was consistently lower than at baseline. At week 28, the median number of puffs of rescue medication taken daily was 0 in the omalizumab group and 0.46 in the placebo group. The change from baseline was significant in favor of omalizumab. (ABSTRACT TRUNCATED)

Clinical importance of Alternaria exposure in children

The fungus Alternaria is known to be allergenic and is one of the most common fungi worldwide. We investigated the extent to which exposure to Alternaria increases the severity of asthma. We undertook a prospective cohort study in Australia of 399 school children who had positive skin tests to one or more aeroallergens. Airway responsiveness to histamine, wheeze, and bronchodilator use in 1 mo was measured five times between 1997 and 1999. Airway hyperresponsiveness was defined as PD(20)FEV(1) = 3.9 micromol histamine. Airborne concentrations of Alternaria spores were measured throughout the study, and mean daily concentrations over 1 mo ranged from 2.2 to 307.7 spores/m(3) of ambient air. Using generalized estimating equations, we found that airway responsiveness, wheeze, and bronchodilator use increased significantly in association with increased spore concentrations and that the increase in airway responsiveness was greater in children sensitized to Alternaria than in other children (p = 0.01). The odds ratio for airway hyperresponsiveness in children sensitized to Alternaria was 1.26 (95% CI, 1.14 to 1.39) after an increase in mean exposure of 100 spore/m(3)/d over 1 mo. These results suggest that Alternaria allergens contribute to severe asthma in regions where exposure to the fungus is high.

Allergenic materials in the house dust of allergy clinic patients

INTRODUCTION

Environmental agents including animal, fungal, tree, and weed antigens are known to cause allergic rhinitis and asthma. The following study was performed to measure the antigen concentration of several of these in house dust of children seen in an allergy clinic. Comparisons are made between household allergen levels of children seen for asthma and children seen for other reasons.

METHODS

Dust samples were solicited from patients in a pediatric allergy specialty clinic and other individuals associated with the clinic. Persons submitting dust were asked to complete a questionnaire describing their house. Samples were extracted, centrifuged, and filtered for sterility. Samples were stored in 50% glycerol at -20 degrees C. Specific antigens for Alternaria, Cladosporium, Aspergillus, Candida, Dermatophagoides farinae, cat, dog, oak, fescue, ragweed, plantain, and cockroach were measured using inhibition assays developed with whole antigen extract. Allergens Der p1, Der f 1, Alt a 1, and Alt a 70 kD were measured using double monoclonal antibody assays.

RESULTS

Significant concentrations of whole antigen from cat, dog, oak, Alternaria, and Cladosporium were detected. Between 0.1 and 18 microg of Der f1 and Der p1 per gram of dust were also measured. Alt a 1 and Alt a 70 kD levels varied between 3.0 and 1000 U/g of dust. Significant positive correlations were observed in levels of dust mite and Alternaria allergen for patients with an evaluation of asthma.

CONCLUSIONS

We found measurable levels of fungal antigens (Alternaria, Cladosporium), mite antigens, and animal antigens (dog and cat) in the majority of dust samples in this self-selected set of allergy clinic patients. Specific allergens Alt a 1, Alt a 70kD, and Der p 1 were significantly higher in the homes of asthmatic patients when compared with patients seen for reasons other than asthma. These studies support the hypothesis that fungal allergen exposure is an important component in the pathogenesis of the clinical condition known as asthma.

Sensitization to silk and childhood asthma in rural China

OBJECTIVE

Sensitization to perennial aeroallergens is associated with asthma in industrialized countries with a Western lifestyle. Because silk products are commonly used in Chinese society, we were interested in examining the relation between sensitization to silk and asthma.

DESIGN

Cross-sectional study of 871 children in 503 families living in Anqing, a predominantly rural province of China.

RESULTS

After adjustment for age, gender, familial correlations, and sensitization to other aeroallergens, skin test reactivity to silk was an independent predictor of asthma (odds ratio = 2.6; 95% confidence interval = 1.2-5.7). This association became stronger after inclusion of the eosinophil count and history of parasitic diseases of the participants in the multivariate model (odds ratio = 3.6; 95% confidence interval = 1.4-8.9).

CONCLUSION

Because sericulture is an important activity in China and other countries throughout the world, sensitization to silk may influence the pathogenesis and severity of asthma in people living in these nations.

Asthma, rhinitis, and skin test reactivity to aeroallergens in families of asthmatic subjects in Anqing, China

In industrialized countries with a Western lifestyle, sensitization to perennial aeroallergens is strongly associated with asthma, whereas sensitization to seasonal aeroallergens is closely related to allergic rhinitis. Little is known, however, about the relation between skin test reactivity to aeroallergens and either asthma or rhinitis in mainland China. We studied 10,009 members of 2,544 families in Anqing (China) that were selected on the basis of physician-diagnosed asthma in at least two siblings. Generalized estimating equations were employed to study the association between skin test reactivity to aeroallergens and either asthma or rhinitis. After adjustment for age, sex, intensity of smoking, skin test reactivity to other aeroallergens, and household correlations, sensitization to dust mite was an independent predictor of both asthma (OR = 1.3, 95% CI = 1.1 to 1.5, p = 0.008) and rhinitis (OR = 1.3, 95% CI = 1.0 to 1.8, p = 0.04). Sensitization to mold was significantly associated with asthma (OR = 1.6, 95% CI = 1.1 to 2.3, p = 0.008), and sensitization to silk was an independent predictor of rhinitis (OR = 1.5, 95% CI = 1.1 to 2.2, p = 0.02). Although 46.9% of the study participants were sensitized to at least one allergen, only 3.5% of study subjects reported nasal symptoms consistent with rhinitis. Among asthmatic subjects, 6.2% reported nasal symptoms. Whereas sensitization to perennial aeroallergens was associated with asthma among families of asthmatic subjects in rural China, sensitization to silk was the strongest predictor of rhinitis in this population. Our findings also suggest that allergic rhinitis is far less common among asthmatic subjects in rural China than in asthmatic subjects in industrialized countries with a Western lifestyle.

Quantitation of the major fungal allergens, Alt a 1 and Asp f 1, in commercial allergenic products

BACKGROUND

Alternaria is one of the most important fungi associated with allergic disease, whereas Aspergillus fumigatus is involved in a broad spectrum of pulmonary diseases. Currently, fungal extracts used for diagnosis in the United States are unstandardized, and their allergenic content cannot be compared directly.

OBJECTIVE

The goal of this study was to compare the variability of major allergen levels among US allergenic products derived from fungi: specifically, Alt a 1 levels in Alternaria alternata extracts, and Asp f 1 levels in A fumigatus extracts.

METHODS

A novel 2-site monoclonal antibody ELISA was used for measuring Alt a 1 using recombinant Alt a 1 as a standard. Asp f 1 was also measured by ELISA. Allergenic products produced by 8 US manufacturers over a 2-year period were compared, as were multiple lots produced by a single company.

RESULTS

Alt a 1 levels in Alternaria extracts from 8 companies produced in 1998 and 1999 ranged from less than 0.01 to 6.09 microg/mL (mean 1.4 +/- 1.6 microg/mL, n = 15). In general, Alt a 1 levels were consistent within and between companies (1.4 +/- 1.1 microg/mL, n = 27), with 21 of 32 (66%) of all extracts tested containing 0.7 to 2 microg/mL Alt a 1. Aspergillus extracts showed much greater variability in Asp f 1 levels, with extracts from 8 companies containing from less than 0.1 to 64 microg/mL Asp f 1 (mean 16.3 +/- 23.9 microg/mL, n = 15). Overall variability was greater for Aspergillus products within and between manufacturers (22 +/- 22 microg/mL Asp f 1, n = 20).

CONCLUSIONS

ELISA-based assays for specific allergens showed greater consistency among allergenic products derived from Alternaria than from Aspergillus. These assays should facilitate improved quality control and standardization of fungal allergen extracts and lead to the development of more consistent products for clinical use.

Receiver operating characteristics curve analysis of cutaneous skin test reactions to predict hay fever and asthma symptoms in the Normative Aging Study

BACKGROUND

We used receiver operating characteristic (ROC) curves to determine optimal cutoff values and to evaluate the ability of ragweed, mixed grasses, mixed trees, and house-dust antigens to predict symptoms of hay fever and asthma.

METHODS

Between 1984 and 1993, 1386 members of the Normative Aging Study cohort had at least one examination that included evaluation of cutaneous hypersensitivity to common aeroallergens by skin prick testing. Standard questionnaires based on the American Thoracic Society DLD-78 questionnaire obtained information on respiratory symptoms, illness, and smoking habits.

RESULTS

Ragweed was the best univariate predictor for both hay fever and asthma symptoms: the area under the ROC curve for hay fever was 0.71 (95%) CI 0.67-0.74); for asthma, it was 0.65 (95% CI 0.55-0.75). For hay fever, dichotomizing the average reaction to four antigens at 2 mm gave a sensitivity of 56% and a specificity of 83%; at 3 mm, the sensitivity was 38% and specificity 92%. For asthma, dichotomizing the skin test reaction at 2 mm gave a sensitivity ranging from 30% for reaction to mixed grasses to 56% for the ragweed antigen reaction.

CONCLUSIONS

Although in this older population skin test reactivities did not predict current asthma symptoms with high sensitivity, our results support the use of cutoff values of 2 or 3 mm as commonly used in studies of hay fever symptoms.

The role and abatement of fungal allergens in allergic diseases

Sensitivity to a variety of fungi is known to be a factor in allergic rhinitis and asthma. In this review methods for measuring exposure to fungi in the indoor environment are evaluated. A variety of markers for the presence of fungi are also described in addition to their known relationship to either toxic or adverse immunologic effects. Key studies documenting the clinical effects of different types of fungi are also reviewed, as well as a description of abatement methods that either have been successful or need further investigation. Although many studies have shown an association between exposure to fungi and allergic disease, in many cases a direct cause-and-effect relationship has not been established. Improved knowledge of the epidemiology and mechanisms behind fungal-induced human disease will hopefully establish this causal link and suggest methods for reducing morbidity.

The nose-lung interaction in allergic rhinitis and asthma: united airways disease

The link between upper and lower respiratory tracts has been repeatedly observed in the past 50 years but only carefully investigated during the past decade. Several clinical and experimental observations suggested the hypothesis of the unity of upper and lower airways (allergic rhinobronchitis or united airways disease). The relationships between rhinitis (and sinusitis) and asthma also include non-epidemiological aspects such as viral infections and bronchial hyperreactivity. The hypotheses have been confirmed by means of epidemiological observations, functional and immunological evidence and, indirectly, by observing the effects of drugs used mainly for rhinitis on asthma symptoms. In this article, therefore, we collected and reviewed the most relevant experimental results available to support the hypothesis for united airways disease and the studies conducted on the possible mechanisms of nose-lung interaction.

The natural history of respiratory allergy: a follow-up study of 99 patients up to 10 years

A strict relationship between allergic rhinitis and allergic asthma has been seen recently, and in many ways respiratory allergy could be seen as a single disorder of the airways. The link between rhinitis and asthma can be elucidated only by studying the natural history of the disease over long periods. We describe the follow-up of 99 allergic patients up to 10 years and the evolution of their disease. Ninety-nine patients (50 male, 49 female, mean age 31 years) out of 142, suffering from allergic rhinitis or allergic asthma, could be monitored up to 10 years after the initial diagnosis. Demographics, sensitizations and smoke habit were assumed as evaluation parameters. At baseline, 44 patients suffered from AR alone, 12 from AA alone and 43 from AR+AA. After 10 years, 31.8% of the AR patients developed developed AA and 50% of the patients with AA developed AR. Only the familial history for atopy significantly influenced the disease's evolution, whereas gender, age, smoking habit and skin sensitization did not. Sixty-five percent of patients with a single sensitization at the beginning developed new sensitizations. In conclusion, this long-term survey confirms that a relevant percentage of patients with AR alone or AA alone have a progression of the disease.

The importance of allergens in the development of asthma and the persistence of symptoms

The importance of allergies and allergens in the development and persistence of asthma is suggested by 3 lines of evidence. First, a number of epidemiologic studies demonstrate that sensitization to indoor allergens and the spores of the outdoor seasonal fungus Alternaria is a risk factor for the development of asthma in both children and adults. Sensitivity to pollens, on the other hand, rarely constitutes a risk for asthma but does constitute a risk for seasonal allergic rhinitis. Second, several studies, again in both children and adults, have demonstrated that, in persons sensitive to indoor allergens, the severity of asthma symptoms will vary with the level of exposure. Third, the elimination of exposure to house-dust mites has produced a remarkable reversal of asthma in sensitive children and adults. Not only have symptoms and pulmonary function improved, but there has also been evidence of a reduction in airway inflammation and hyperresponsiveness. Taken together, these studies make a strong argument for the importance of allergy and allergen exposure as aggravating factors in asthma in both children and adults and reinforce the importance of the identification and treatment of these allergen sensitivities. (J Allergy Clin Immunol 2000;105:S628-32.)

Prevalence and predictors of rhinitis in Danish children and adolescents

BACKGROUND

The prevalence of self-reported symptoms of allergic rhinitis is increasing in many countries, but the reasons for this trend are not well understood. Data from a 6-year follow-up study of a population sample of children and adolescents (n=408), aged 7-17 years at enrolment in 1986, were analyzed to investigate the prevalence and predictors of self-reported rhinitis.

METHODS

Case history was used to assess the presence or absence of rhinitis (sneezing and running or blocked nose not associated with a cold), asthma, and eczema. Pulmonary function, skin prick test reactivity, and airway responsiveness to histamine were measured in all participants; a screening test for IgE antibodies to common allergens (Magic Lite SQ, Allergy Screen, ALK, Denmark) was performed in 237 (58%) of the participants.

RESULTS

The point prevalence of rhinitis increased from the first to the second survey, 14% and 22%, respectively; 54 (13%) of the subjects reported rhinitis only at the second survey (new rhinitis). Confining the analysis to participants without symptoms of rhinitis at the first survey showed that self-reported eczema (relative risk [RR] 2.3, 95% confidence interval [CI] 1.2-4.7), airway hyperresponsiveness (RR 2.5, CI 1.8-3.0), atopy to grass pollen (RR 2.6, CI 1.7-3.3), atopy to dog dander (RR 2.4, CI 1.6-3.3), and atopy to house-dust mite (RR 2.7, CI 1.4-5.2) at the first survey predicted an increased risk of the presence of rhinitis at the second survey. A positive Allergy Screen test at enrollment was associated with an increased risk of self-reported rhinitis at follow-up (RR 2.4, CI 1.4-3.4).

CONCLUSIONS

This longitudinal population study of children and adolescents showed an age-related increase in the point prevalence of self-reported rhinitis; furthermore, sensitization to common aeroallergens, airway hyperresponsiveness, and the presence of self-reported eczema were significantly associated with an increased risk of subsequent development of rhinitis.

The association of sensitization to inhalant allergens with allergy symptoms: the influence of bronchial hyperresponsiveness and blood eosinophil count

BACKGROUND

We investigated whether the association of allergy symptoms with sensitization to inhalant allergens depends on bronchial hyperresponsiveness, blood eosinophil count, or the degree and nature of sensitization.

METHODS

Data on asthma and rhino-conjunctivitis symptoms were obtained from 1904 subjects from a random sample of the Dutch population, aged 20-70 years by the ECRHS questionnaire. Total IgE and specific IgE to four inhalant allergens were measured using CAP System. Bronchial hyperresponsiveness (BHR) was defined as PD20 </= 2 mg methacholine and 'high eosinophil count' as an eosinophil count in the highest quartile.

RESULTS

Forty-three percent of the subjects with specific IgE to inhalant allergens was asymptomatic. These subjects had a lower degree of sensitization than symptomatic sensitized subjects and had 'normal' prevalences of BHR and 'high eosinophil count'. Logistic regression showed that the presence of BHR increased the risk of having symptoms for subjects who were sensitized to indoor allergens. Low levels of specific IgE to indoor allergens were only associated with symptoms when BHR was present. Sensitization to outdoor allergens was associated with symptoms at all levels of specific IgE, independently of BHR or eosinophils.

CONCLUSION

Our epidemiological data suggest that whether low levels of specific IgE to indoor allergens lead to allergic symptoms is probably determined by the concurrent existence of inflammation of the airways.

The importance of allergens in the development of asthma and the persistence of symptoms

The importance of allergies and allergens in the development and persistence of asthma is suggested by 3 lines of evidence. First, a number of epidemiologic studies demonstrate that sensitization to indoor allergens and the spores of the outdoor seasonal fungus Alternaria is a risk factor for the development of asthma in both children and adults. Sensitivity to pollens, on the other hand, rarely constitutes a risk for asthma but does constitute a risk for seasonal allergic rhinitis. Second, several studies, again in both children and adults, have demonstrated that, in persons sensitive to indoor allergens, the severity of asthma symptoms will vary with the level of exposure. Third, the elimination of exposure to house-dust mites has produced a remarkable reversal of asthma in sensitive children and adults. Not only have symptoms and pulmonary function improved, but there has also been evidence of a reduction in airway inflammation and hyperresponsiveness. Taken together, these studies make a strong argument for the importance of allergy and allergen exposure as aggravating factors in asthma in both children and adults and reinforce the importance of the identification and treatment of these allergen sensitivities.

Watch, Discover, Think, and Act: a model for patient education program development

In this report we describe the development of the Watch, Discover, Think and Act asthma self-management computer program for inner-city children with asthma. The intervention focused on teaching two categories of behaviors--asthma specific behaviors such as taking preventive medication and self-regulatory processes such as monitoring symptoms and solving asthma problems. These asthma self-management behaviors were then linked with empirical and theoretical determinants such as skills and self-efficacy. We then further used behavioral science theory to develop methods such as role modeling and skill training linked to the determinants. We matched these theoretical methods to practical strategies within the computer simulation and created a culturally competent program for inner-city minority youth. Finally, we planned a program evaluation that linked program impact and outcomes to the theoretical assumptions on which the intervention was based.

Asthma triggers in the elementary school environment: a pilot study

Asthma, a major cause of school absenteeism, can be triggered by allergens and irritants in the child's environment. A new measurement tool, the Environmental Observation Checklist (EOC), was developed and piloted for qualitative assessment of indoor asthma triggers (allergens and irritants), adequacy of ventilation, and existing environmental control practices. Seventy-five classrooms in 20 schools from two large urban school districts in Texas were surveyed using the EOC. A Q-TRAK Air Quality Monitor was used to assess indoor carbon dioxide, temperature, and relative humidity, concurrently. The EOC appears to be a useful screening tool for identifying schools in need of intervention.

The relationships among environmental allergen sensitization, allergen exposure, pulmonary function, and bronchial hyperresponsiveness in the Childhood Asthma Management Program

BACKGROUND

Sensitivity and exposure to indoor allergens constitutes a risk factor for the development and persistence of asthma in children.

OBJECTIVE

Our purpose was to evaluate the relationship between sensitivity and exposure to inhalant allergens and lung function and bronchial responsiveness in a group of children (n = 1041) aged 8.9 +/- 2.1 years with mild to moderate asthma enrolled in the Childhood Asthma Management Program (CAMP).

METHODS

With use of the extensive CAMP baseline cross-sectional data on spirometry, bronchial responsiveness, allergen sensitivities, and household allergen levels, the relationship of sensitization and exposure to allergens to lung function and methacholine sensitivity was evaluated. Children who enrolled in CAMP stopped all antiasthma medication except rescue use of albuterol and prednisone for exacerbations during the 5- to 16-week screening period. During the last 2 of these weeks they underwent spirometry and methacholine challenge. Indoor allergen exposures were determined from questionnaires completed by the parent. Household levels of indoor allergens (mite, cat, dog, cockroach, mold) were determined on house dust samples. Allergen sensitivity was determined by percutaneous skin testing with a standard battery of allergens plus locally important pollen and fungal spores. Lung function and bronchial hyperresponsiveness were compared for children sensitive and not sensitive to both indoor and outdoor allergens on skin testing and, if sensitive, for exposed and not exposed to the allergens to which they were positive on skin testing.

RESULTS

There was a strong direct correlation between increased sensitivity to inhaled methacholine and skin test sensitivity to tree, weed, Alternaria, cat, dog, and indoor molds. When the relationship was examined by stepwise regression, the skin test sensitivities showing the strongest associations with the concentration of methacholine that caused a 20% fall in FEV(1) were dog (P =.003), Alternaria (P =.01), and cat (P =.05). Children sensitive to any one of the aeroallergens tested were compared for the presence or absence of exposure to that allergen at the time that the methacholine challenge was performed. Those who were sensitive and exposed to weed and cat had greater methacholine sensitivity than those similarly sensitive but not exposed (P =.003 and P =.02, respectively).

CONCLUSIONS

Sensitivity to dog or cat dander or Alternaria by skin testing was associated with increased bronchial responsiveness but not decreased lung function in children with mild to moderate asthma. These findings support the important role that sensitization to certain allergens plays in modulating bronchial responsiveness.

Chicago community-based asthma intervention trial: feasibility of delivering peer education in an inner-city population

The most effective means of educating children with asthma and their families has not been clearly demonstrated in previous studies. Peer education is uniquely suited to the complex problems encountered in underserved populations. The purpose of this study was to show the feasibility of delivering a peer education program for children with asthma and the effect of the program on indoor allergen levels in an inner-city population in Chicago. Overall, the program was well received. Baseline allergen levels were consistent with some previous studies in showing low levels of mite allergens and high levels of cockroach allergens, with 79.6% of samples having levels > 8 U/g. A total of 28.2% of samples had cat allergen levels > 2 microg/g, although only 9.7% of homes had cats, confirming previous reports that cat allergen is ubiquitous. Mold levels were seasonal, with the highest levels in the summer. Results from this study suggest that intervention programs should focus more on elimination of cockroaches than was previously appreciated, while minimizing the use of pesticides, and on identification of the sources of cat allergen. Structural and psychosocial issues in homes need to be addressed in future studies. This study has demonstrated the feasibility of delivering peer education in a inner-city population and highlighted the need for comprehensive intervention strategies addressing complex issues facing underserved neighborhoods.

Molecular cloning of a major Alternaria alternata allergen, rAlt a 2

BACKGROUND

Sensitivity to the fungus Alternaria alternata is a common cause of asthma. Epidemiologic studies from a variety of locations worldwide indicate that A alternata sensitivity is closely linked with the development of asthma. Furthermore, A alternata sensitivity has been associated with severe and potentially fatal attacks of asthma.

OBJECTIVE

The diagnosis of A alternata sensitivity is hampered by the lack of standardized and well-characterized allergenic extracts. Molecular cloning of allergens offers the possibility of providing large quantities of purified, well-characterized allergens not only for diagnostic purposes but also for studying the pathogenesis of A alternata sensitivity. We used molecular cloning to identify, purify, and produce a major A alternata allergen in quantity.

METHODS

We prepared messenger (m)RNA from A alternata to produce a complementary (c)DNA library. The library was screened for A alternata allergens by using sera from A alternata-sensitive individuals. A recombinant allergen was isolated, the cDNA sequence was determined, and the protein was expressed in Pichia pastoris.

RESULTS

A unique A alternata allergen, rAlt a 2, was identified. A 2.2-kb cDNA sequence was obtained that has homology with a common transposable region and mouse RNA-dependent eukaryote initiation factor-2 alpha-kinase but no homology to any known allergen. No N-glycosylation sites were found in the cDNA sequence. The recombinant allergen was recognized by IgE antibodies in the sera of 16 of 26 (61%) individuals allergic to A alternata, which defines Alt a 2 as a major allergen.

CONCLUSIONS

We have molecularly cloned a unique major A alternata allergen, rAlt a 2. Identification and expression of the recombinant allergen should enhance the development of standardized A alternata allergenic extracts and provide stable reagents for investigating the pathogenesis of A alternata sensitivity.

Two subphenotypes of childhood asthma that differ in maternal and paternal influences on asthma risk

Asthma is a phenotypically heterogeneous disease. Two subgroups are defined here based initially on skin test reactivity to the allergen Alternaria at age 6 from among a large population of children born and raised in the Southwestern desert environment of Tucson, Arizona. When compared with asthma among Alternaria-positive subjects, asthma among Alternaria-negative subjects was associated with lower levels of total serum IgE, no relation to local aeroallergen skin tests, a younger age at diagnosis, greater remittance by age 11, and more frequent wheezing lower respiratory illnesses (LRIs) in the first year of life. Despite the difference in total serum IgE, however, IgE concentrations were significantly higher in each asthma group compared with its respective control group. Asthma in each parent contributed approximately equivalent risk for Alternaria-positive asthma in the child. However, neither parental skin test sensitization nor total serum IgE levels provided risk for asthma in the child. Inheritance patterns for Alternaria-negative asthma revealed a contribution from maternal but not paternal asthma. Thus, dividing asthma in children at age 6 into Alternaria-positive and Alternaria-negative groups identifies subphenotypes that are further distinguished by differences in phenotypic markers and parental influences.

PEDIATRIC ALLERGY

The current paradigm of allergy pathogenesis is that allergy develops in individuals with a genetic predisposition only after they are exposed to allergens (Fig. 1). This hypothesis implies that factors in the environment can determine the initiation of allergic sensitization and can potentially influence the clinical manifestations and severity of disease. Because the prevalence of atopic diseases such as allergic rhinitis, asthma, atopic dermatitis, and food allergy have increased worldwide in the past several decades, and there is no mechanism for changes in population genetics over this short period of time, changes in the human environment are most likely responsible for these trends. From this line of reasoning, it follows that if the factors responsible for the increasing prevalence can be identified, then there would be an opportunity to develop strategies to reverse these trends. It also would be helpful to identify infants who are at risk for developing allergy, so that preventive strategies could be used most effectively.

In this article, studies to determine the contributions of genetics and the environment to the development of allergic diseases in childhood are explored. In addition, progress in identifying risk factors for allergy and preventive therapies for those children at risk are also addressed.