Analysis of cytokine production by peanut-reactive T cells identifies residual Th2 effectors in highly allergic children who received peanut oral immunotherapy

BACKGROUND

Only limited evidence is available regarding the cytokine repertoire of effector T cells associated with peanut allergy, and how these responses relate to IgE antibodies to peanut components.

OBJECTIVE

To interrogate T cell effector cytokine populations induced by Ara h 1 and Ara h 2 among peanut allergic (PA) children in the context of IgE and to evaluate their modulation during oral immunotherapy (OIT).

METHODS

Peanut-reactive effector T cells were analysed in conjunction with specific IgE profiles in PA children using intracellular staining and multiplex assay. Cytokine-expressing T cell subpopulations were visualized using SPICE.

RESULTS

Ara h 2 dominated the antibody response to peanut as judged by prevalence and quantity among a cohort of children with IgE to peanut. High IgE (> 15 kU(A)/L) was almost exclusively associated with dual sensitization to Ara h 1 and Ara h 2 and was age independent. Among PA children, IL-4-biased responses to both major allergens were induced, regardless of whether IgE antibodies to Ara h 1 were present. Among subjects receiving OIT in whom high IgE was maintained, Th2 reactivity to peanut components persisted despite clinical desensitization and modulation of allergen-specific immune parameters including augmented specific IgG4 antibodies, Th1 skewing and enhanced IL-10. The complexity of cytokine-positive subpopulations within peanut-reactive IL-4(+) and IFN-γ(+) T cells was similar to that observed in those who received no OIT, but was modified with extended therapy. Nonetheless, high Foxp3 expression was a distinguishing feature of peanut-reactive IL-4(+) T cells irrespective of OIT, and a correlate of their ability to secrete type 2 cytokines.

CONCLUSION

Although total numbers of peanut-reactive IL-4(+) and IFN-γ(+) T cells are modulated by OIT in highly allergic children, complex T cell populations with pathogenic potential persist in the presence of recognized immune markers of successful immunotherapy.

Infection with human rhinovirus 16 promotes enhanced IgE responsiveness in basophils of atopic asthmatics

BACKGROUND

Rhinovirus and IgE act in concert to promote asthma exacerbations. While basophils are the principal cell type in the blood that is activated by IgE, their role in virus-induced asthma episodes remains elusive.

OBJECTIVE

To monitor IgE responsiveness in circulating basophils of rhinovirus-infected atopic asthmatics during acute infection and convalescence.

METHODS

The capacity for basophils to respond to IgE was assessed by testing the effects of allergen, or cross-linking anti-FcεRI and anti-IgE antibodies, on surface TSLP receptor in 24-hour PBMC cultures. Activation profiles of basophils from atopic asthmatics challenged intranasally with human rhinovirus 16 were monitored directly ex vivo or else in 24-hour cultures, at baseline (day 0), and then at days 4 and 21 post-challenge.

RESULTS

Basophils in atopic asthmatics, but not in non-atopic controls, upregulated TSLP receptor upon IgE receptor ligation. The magnitude of this response was correlated with the proportion of serum total IgE that was allergen-specific (r = 0.615, P < 0.05). Following rhinovirus infection, all subjects developed nasal symptoms that peaked 3-5 days after viral challenge. Basophils displayed maximal IgE responsiveness 3 weeks post-challenge as judged by TSLP receptor levels in 24-hour cultures. No significant change in total IgE or specific IgE antibodies was detected during rhinovirus infection. By contrast, levels of IgE receptor-associated spleen tyrosine kinase, Syk, were increased on day 4 (P < 0.05), and elevated levels were also detected three weeks post-challenge.

CONCLUSIONS AND CLINICAL RELEVANCE

Circulating basophils display increased IgE responsiveness 3 weeks after rhinovirus infection in atopic asthmatics. This observation, coupled with increased expression of Syk, implicates basophils in promoting, or else prolonging, rhinovirus-induced inflammation in atopic asthmatics.

Sensitization to food and inhalant allergens in relation to age and wheeze among children with atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is common in children; however, persistence of AD with or without asthma is less common. Longitudinal studies remain limited in their ability to characterize how IgE antibody responses evolve in AD, and their relationship with asthma.

OBJECTIVE

To use a cross-sectional study design of children with active AD to analyse age-related differences in IgE antibodies and relation to wheeze.

METHODS

IgE antibodies to food and inhalant allergens were measured in children with active AD (5 months to 15 years of age, n = 66), with and without history of wheeze.

RESULTS

Whereas IgE antibodies to foods persisted at a similar prevalence and titre throughout childhood, IgE antibodies to all aeroallergens rose sharply into adolescence. From birth, the chance of sensitization for any aeroallergen increased for each 12-month increment in age (OR ≥ 1.21, P < 0.01), with the largest effect observed for dust mite (OR = 1.56, P < 0.001). A steeper age-related rise in IgE antibody titre to dust mite, but no other allergen was associated with more severe disease. Despite this, sensitization to cat was more strongly associated with wheeze (OR = 4.5, P < 0.01), and linked to Fel d 1 and Fel d 4, but not Fel d 2. Comparison of cat allergic children with AD to those without, revealed higher IgE levels to Fel d 2 and Fel d 4 (P < 0.05), but not Fel d 1.

CONCLUSIONS AND CLINICAL RELEVANCE

Differences in sensitization to cat and dust mite among young children with AD may aid in identifying those at increased risk for disease progression and development of asthma. Early sensitization to cat and risk for wheeze among children with AD may be linked to an increased risk for sensitization to a broader spectrum of allergen components from early life. Collectively, our findings argue for early intervention strategies designed to mitigate skin inflammation in children with AD.

The role of allergy in severe asthma

The classification of asthma to identify forms which have different contributing causes is useful for all cases in which the disease requires regular treatment, but it is essential for the management of severe asthma. Many forms of the disease can occur, and complex mixtures are not uncommon; here we artificially separated the cases into four groups: (i) inhalant allergy, (ii) fungal sensitization with or without colonization (including ABPA); (iii) severe sinusitis with or without aspirin-exacerbated respiratory disease (AERD), and (iv) non-inflammatory cases, including those associated with severe obesity and vocal cord dysfunction (VCD). The reason for focusing on these groups is because they illustrate how much the specific management depends upon correct classification. Inhalant allergy can present as chronically severe asthma. However, severe attacks of asthma requiring hospital admission can occur in cases which are generally only mild or moderate. The best recognized and probably the most common cause of these acute episodes is acute infection with a rhinovirus. Recent evidence suggests that high titre IgE, particularly to dust mite, correlates to exacerbations of asthma related to rhinovirus infection. Although it is well recognized that the fungus Aspergillus can colonize the lungs and cause severe disease, it is less well recognized that those cases may not have full criteria for diagnosis of ABPA or may involve other fungi. Identifying fungal cases is important, because treatment with imidazole antifungals can provide significant benefit. Taken together, specific treatment using allergen avoidance, immunotherapy, anti-IgE, or antifungal treatment is an important part of the successful management of severe asthma, and each of these requires correctly identifying specific sensitization.

International consensus on (ICON) pediatric asthma

Asthma is the most common chronic lower respiratory disease in childhood throughout the world. Several guidelines and/or consensus documents are available to support medical decisions on pediatric asthma. Although there is no doubt that the use of common systematic approaches for management can considerably improve outcomes, dissemination and implementation of these are still major challenges. Consequently, the International Collaboration in Asthma, Allergy and Immunology (iCAALL), recently formed by the EAACI, AAAAI, ACAAI, and WAO, has decided to propose an International Consensus on (ICON) Pediatric Asthma. The purpose of this document is to highlight the key messages that are common to many of the existing guidelines, while critically reviewing and commenting on any differences, thus providing a concise reference. The principles of pediatric asthma management are generally accepted. Overall, the treatment goal is disease control. To achieve this, patients and their parents should be educated to optimally manage the disease, in collaboration with healthcare professionals. Identification and avoidance of triggers is also of significant importance. Assessment and monitoring should be performed regularly to re-evaluate and fine-tune treatment. Pharmacotherapy is the cornerstone of treatment. The optimal use of medication can, in most cases, help patients control symptoms and reduce the risk for future morbidity. The management of exacerbations is a major consideration, independent of chronic treatment. There is a trend toward considering phenotype-specific treatment choices; however, this goal has not yet been achieved.

Detection of IgA and IgG but not IgE antibody to respiratory syncytial virus in nasal washes and sera from infants with wheezing

BACKGROUND AND OBJECTIVE

The capacity of respiratory syncytial virus (RSV) to stimulate an IgE antibody response and enhance the development of atopy and asthma remains controversial. Nasal washes and sera from 40 infants (20 with wheezing, 9 with rhinitis, and 11 without respiratory tract symptoms) were obtained to measure IgE, IgA, and IgG antibody to the immunodominant, F and G, virion proteins from RSV.

STUDY DESIGN

Children (aged 6 weeks to 2 years) were enrolled in the emergency department during the mid-winter months and seen at follow-up when they were asymptomatic. All nasal washes were tested for RSV antigen. Determinations of antibody isotypes (IgE, IgA, and IgG) to RSV antigens were done in nasal washes and sera by using an enzyme-linked immunosorbent assay. In a subset of nasal washes, IgE to RSV was also evaluated by using a monoclonal anti-F(c)E antibody-based assay.

RESULTS

Fifteen patients with wheezing, two with rhinitis, and one control subject tested positive for RSV antigen at enrollment. Thirteen patients with wheezing were <6 months old, and most (77%) were experiencing their first attack. Among the children with positive test results for RSV antigen, an increase in both nasal wash and serum IgA antibody to RSV-F(a) and G(a) was observed at the follow-up visit. However, there was no evidence for an IgE antibody response to either antigen.

CONCLUSION

Both IgA and IgG antibodies to the immunodominant RSV-F(a) and G(a) antigens were readily detected in the nasal washes and sera from patients in this study. We were unable to demonstrate specific IgE antibody to these antigens and conclude that the production of IgE as a manifestation of a T(H)2 lymphocyte response to RSV is unlikely.

Lactoferrin and eosinophilic cationic protein in nasal secretions of patients with experimental rhinovirus colds, natural colds, and presumed acute community-acquired bacterial sinusitis

To distinguish sinusitis from uncomplicated "colds," we examined lactoferrin and eosinophilic cationic protein (ECP) in nasal secretions. Lactoferrin titers were >/=1:400 in 4% of persons with uncomplicated colds and controls but in 79% of persons with sinusitis or purulent sputa. ECP levels were >200 ng/ml in 61% of persons with colds and >3,000 ng/ml in 62% of persons with sinusitis. Nasal lactoferrin helps distinguish sinusitis from colds.

Specific and nonspecific obstructive lung disease in childhood: causes of changes in the prevalence of asthma

Reversible airway obstruction in childhood includes two major groups of patients: those with recurrent wheezing following bronchiolitis in early childhood, and those with allergic asthma, which represents an increasingly large proportion of cases through the school years. Over the last 40 years of the 20th century, allergic asthma has increased in many countries and in relation to several different allergens. Although this increase has differed in magnitude in different countries and also in the social groups most affected, it has had several features in common. The increase generally started between 1960 and 1970, has been progressive since then, and has continued into the 1990s without a defined peak. Among children 5-18 years of age, the increase has predominantly been among allergic individuals. Theories about the causes of the increase in asthma have focused on two scenarios: a) that changes in houses combined with increased time spent indoors have increased exposure to relevant allergens, or b) that changes in diet, antibiotic use, immunizations, and the pattern of infections in childhood have led to a change in immune responsiveness such that a larger section of the population makes T(H)2, rather than T(H)1 responses including IgE antibodies to inhalant allergens. There are, however, problems with each of these theories and, in particular, none of the proposed changes can explain the progressive nature of the increase over 40 years. The fact that the change in asthma has much in common with epidemic increase in diseases such as Type II diabetes or obesity suggests that similar factors could be involved. Several lines of evidence are reviewed that suggest that the decline in physical activity of children, particularly those living in poverty in the United States, could have contributed to the rise in asthma. The hypothesis would be that the progressive loss of a lung-specific protective effect against wheezing has allowed allergic children to develop symptomatic asthma. What is clear is that current theories do not provide either an adequate explanation of the increase or a practical approach to reversing the current trend.

Salivary cotinine levels in children presenting with wheezing to an emergency department

We set out to evaluate salivary cotinine concentrations to judge tobacco smoke exposure among infants and children, and to examine the results in relation to age and wheezing. This was a case-control study of wheezing children (n = 165) and children without respiratory tract symptoms (n = 106) who were enrolled in the Pediatric Emergency Department at the University of Virginia. The age range of both wheezing and control patients was 2 months to 16 years. Questionnaires were combined with cotinine assays in saliva to evaluate exposure to environmental tobacco smoke (ETS) for each child. The prevalence of exposure to one or more smokers at home was high (68%); and 43% of the children enrolled were exposed to ETS from their mothers. According to the questionnaires, and after adjusting for age and race, a wheezing child in this study was more likely than a control to be exposed to at least one smoker at home (odds ratio = 1.9; 95% CI = 1.1-3.4). However, the odds of exposure to ETS from smoking mothers did not differ significantly between wheezing and control patients, and no significant association was found between the presence of wheezing and salivary cotinine levels. Among children exposed to ETS at home, cotinine levels were significantly higher in saliva from those under the age of two years, and from toddlers aged 2 and 3 years, compared to values from children over age 4 years. Moreover, the number of smokers in the home strongly influenced cotinine levels from children under age 4 years. In addition, higher cotinine levels were observed in saliva from children under age 2 years who were exposed to ETS from their mothers. Cotinine levels were similar and significantly correlated in paired samples of saliva and serum from children under 4 years of age (n = 54), (r = 0.92, P < 0.001). Based on information gathered from questionnaires, the results indicate that wheezing children were more likely than controls to be exposed to ETS at home. However, significant differences in ETS exposure between wheezing and control groups with respect to maternal smoke exposure or comparisons of salivary cotinine levels were not apparent. It was clear that determinations of salivary cotinine for monitoring the prevalence and intensity of household smoke exposure in this study were most valuable during the first 4 years of life.

The relevance of allergen exposure to the development of asthma in childhood

Sensitization to 1 or more of the common indoor allergens has been consistently associated with asthma among children and young adults (odds ratios for asthma, 3-18). For dust mite and cockroach allergens, there is a dose response relationship between domestic exposure and sensitization. Given that allergen provocation can induce many of the features of asthma, the findings strongly suggest that there is a causal relationship between allergen exposure in the home and asthma. However, it remains unclear at what time the critical exposure occurs (ie, in infancy or later) and what role allergen exposure has played in the increasing prevalence and severity of asthma. Objective evidence of an immune response to allergens is generally not present until after 2 years of age. Viral infections play several different roles in asthma in childhood. In infancy, respiratory syncytial virus infection can induce bronchiolitis and set up recurrent wheezing over the next few years. However, the risk factors for this are maternal smoking and small lungs at birth, rather than allergy. By contrast, the role of rhinovirus in precipitating attacks in children and young adults is strongly associated with allergy. Thus the likely scenario is that allergen exposure over the first few years of life induces sensitization (ie, T(H2) cells and IgE antibodies). Continuing exposure can maintain inflammation in the nose and lungs. However, many other factors contribute to wheezing such that there is no simple relationship between allergen exposure and asthma. Nonetheless, it is clear that the changes that have increased asthma have acted on allergic children.

Rhinovirus and respiratory syncytial virus in wheezing children requiring emergency care. IgE and eosinophil analyses

This cross-sectional emergency department study of 70 wheezing children and 59 control subjects (2 mo to 16 yr of age) examined the prevalence of respiratory viruses and their relationship to age, atopic status, and eosinophil markers. Nasal washes were cultured for respiratory viruses, assayed for respiratory syncytial virus (RSV) antigen, and tested for coronavirus and rhinovirus RNA using reverse transcription-PCR (RT-PCR). Also evaluated were eosinophil numbers and eosinophil cationic protein (ECP) in both nasal washes and serum, along with total IgE and specific IgE antibody in serum. Respiratory viruses were detected in 82% (18 of 22) of wheezing infants younger than 2 yr of age and in 83% (40 of 48) of older wheezing children. The predominant pathogens were RSV in infants (detected in 68% of wheezing subjects) and rhinovirus in older wheezing children (71%), and both were strongly associated with wheezing (p < 0.005). RSV was largely limited to wheezing children younger than 24 mo of age, but rhinovirus was detected by RT-PCR in 41% of all infants and in 35% of nonwheezing control subjects older than 2 yr of age. After 2 yr of age the strongest odds for wheezing were observed among those who had a positive RT-PCR test for rhinovirus together with a positive serum radioallergosorbent testing (RAST), nasal eosinophilia, or elevated nasal ECP (odds ratios = 17, 21, and 25, respectively). Results from this study demonstrate that a large majority of emergent wheezing illnesses during childhood (2 to 16 yr of age) can be linked to infection with rhinovirus, and that these wheezing attacks are most likely in those who have rhinovirus together with evidence of atopy or eosinophilic airway inflammation.

The role of domestic allergens

The documented increase in asthma has been almost entirely in perennial asthma and a large proportion of the cases are allergic to one of the common allergens found all year round in houses, i.e. house dust mites, cats, dogs or cockroaches. In population and case-control studies sensitization to one of these allergens is the strongest risk factor for asthma (adjusted odds ratios > or = 4). Using monoclonal antibody-based assays for the major indoor allergens it has been shown that sensitization to house dust mites is directly related to the concentration of Group 1 mite allergen in dust. This led to the hypothesis that increases in mite allergen secondary to changes in houses were responsible for increases in asthma. However, asthma has also increased in areas of the world where mites do not flourish. In these dry areas sensitization to one of the other indoor allergens is the major risk factor for asthma. Although sensitization of asthmatics reflects the concentration of allergens in their houses, these measurements of exposure do not accurately predict severity of symptoms. Other factors that can contribute to the symptoms of asthma may also have increased. In particular, diesel particulates, ozone, beta 2-agonists, endotoxin and rhinovirus infection have each been shown to enhance the inflammatory response to inhaled allergens. Increases in asthma must relate to some aspect of our predominantly sedentary indoor lifestyle; this could be either increased exposure to allergens or an increase in factors that enhance the response of the lungs to foreign proteins.

Changing concepts of allergic disease: the attempt to keep up with real changes in lifestyles

In the past 100 years, changes have occurred in the outdoor environment and in houses that have contributed to the increased prevalence of hay fever and asthma. Much evidence indicates that exposure to indoor allergens is an important cause of asthma. Changes in housing that have contributed to the increased prevalence and severity of asthma include increased temperature, decreased ventilation, and permanent carpeting. In addition to these changes, geographic differences in allergens, deficiencies in cleanliness, poor health care, passive smoke, and lack of exercise also contribute to the increase in severity of asthma that has occurred. The management of asthma includes controlling exposure to indoor allergens and seeking additional treatable causes of asthma (e.g., fungal allergens). Changes will continue to occur, and physicians who treat allergic diseases should become involved in the design of houses to limit exposure. Many questions regarding allergen measurement and control remain.

Eosinophil cationic protein in serum and nasal washes from wheezing infants and children

OBJECTIVE

To compare eosinophil counts and concentrations of eosinophil cationic protein (ECP) in serum and nasal wash fluid from wheezing infants and children with those from age-matched children without respiratory tract symptoms.

DESIGN

A case-control study of 71 children treated for wheezing and 59 control subjects in the University of Virginia Pediatric Emergency Department. The patients ranged from 2 months to 16 years of age. Eosinophil numbers and ECP concentrations were assessed in serum and nasal washes. Total serum IgE was measured and the radioallergosorbent test was used to measure IgE antibody to common inhalant allergens.

RESULTS

Among children less than the age of 2 years, markedly elevated levels of ECP (> 200 ng/ml) were measured in nasal washes from 9 (41%) of 22 wheezing patients and 1 (6%) of 17 control subjects (p < 0.03). None of these children had a positive radioallergosorbent test result for IgE antibody to common aeroallergens or a nasal smear containing 10% eosinophils. Few of the wheezing children under 2 years of age had either increased concentrations of total IgE or ECP in their serum or an elevated total blood eosinophil count. After the age of 2 years, the percentage of patients with nasal ECP levels greater than 200 ng/ml was also significantly higher in wheezing children than in control subjects (p < 0.001), and a positive correlation was observed between ECP concentrations in their nasal washes and other eosinophil responses (total blood eosinophil counts, serum ECP levels, and nasal eosinophil counts).

CONCLUSION

Increased concentrations of ECP were detected in nasal washes from wheezing infants and children, indicating that eosinophils may contribute to the pathogenesis of airway inflammation in some children who wheeze early in life.

Monitoring allergen exposure in asthma: new treatment strategies

The development of monoclonal antibody-based enzyme-linked immunosorbent assay technology for measuring environmental allergen exposure has provided a benchmark for assessing the role of indoor allergens in causing asthma and other allergic diseases. Epidemiological studies from several parts of the world have shown that immunoglobulin E (IgE)-mediated sensitization to indoor allergens (mite, cat, dog and cockroach) is a risk factor for asthma attacks. A dose-response relationship between allergen exposure and sensitization has been demonstrated for mite allergens, and threshold values for exposure levels leading to sensitization or to exacerbations of symptoms have been defined. Comparative studies on airborne allergen levels have made it possible to determine the properties of aeroallergen particles, their concentration in indoor air, and the relationship to clinical symptoms. Together, these studies provide strong evidence that allergen exposure plays a causal role in the development of bronchial hyperreactivity and of the chronic inflammatory responses seen in patients with asthma. Logically, the primary preventive treatment should be allergen avoidance. Through knowledge of indoor allergen levels, both in dust and in the air, different avoidance strategies have been applied to the various indoor allergens, and there is increasing evidence of their clinical efficacy. Monitoring allergen levels in patients' houses should improve their understanding of the role of allergens in asthma and improve compliance with avoidance measures.

Development of immune responses to Aspergillus at an early age in children with cystic fibrosis

Although the ability of Aspergillus organisms to colonize the respiratory tract in patients with cystic fibrosis (CF) is well recognized, the contribution of Aspergillus to the disease process is poorly understood. Using sera from 147 CF patients (age 5 to 43 yr), we measured IgE antibody (ab) to Aspergillus fumigatus and five common inhalant allergens with a radioallergosorbent test (RAST). Total IgE levels and IgG ab to radio-labeled Asp f I, an allergen purified from A. fumigatus and a potent inhibitor of protein synthesis, were also measured. Thirty (20%) of the patients had IgE ab to A. fumigatus, and 22 (15%) of these patients had developed total IgE levels > or = 400 IU/ml, raising the consideration of a diagnosis of allergic bronchopulmonary aspergillosis (ABPA). Five of the 22 patients developed these IgE responses by age 5 yr and 14 by age 10 yr. The proportion of patients with IgE ab to one or more of the other allergens tested was not significantly different from that of control subjects without respiratory symptoms. A striking proportion (84%) of CF sera contained IgG ab to Asp f I, compared with 6% of sera from control patients and 20% of sera from allergic children with asthma (n = 25), only one of whom had IgE ab to A. fumigatus. In an examination of additional sera from young CF patients, IgG anti-Asp f I ab was detected in 41% of these sera from patients 5 yr of age or older, increasing to 98% of 89 sera from patients older than age 10.(ABSTRACT TRUNCATED AT 250 WORDS)

Monoclonal antibodies to group II Dermatophagoides spp. allergens: murine immune response, epitope analysis, and development of a two-site ELISA

BACKGROUND

Group II allergens are a major cause of sensitization in patients allergic to mites. To facilitate the antigenic analysis of group II allergens and to develop improved methods of allergen detection, we compared IgG anti-group II antibody responses in inbred mouse strains and raised a panel of monoclonal antibodies (mAbs).

METHODS

IgE antibody responses were compared by antigen-binding radioimmunoassay. Epitope specificity of the mAbs was analyzed by two-site binding assays and by cross-inhibition radioimmunoassays.

RESULTS

Comparison of polyclonal IgG antibody responses in five BALB congenic strains showed that H-2d mice had poor responses, whereas H-2b and H-2k mice had strong, cross-reactive, IgG anti-group II responses. The specificities of nine anti-Der p II IgE mAbs raised in A/J mice were compared with specificities of seven mAbs produced previously. Most mAbs (11 of 16) recognized common epitopes on Der p II and Der f II: three were specific to Der p II, and two showed high binding to Der f II. Epitope analysis showed that the mAbs defined four cross-reactive, nonoverlapping sites on the group II allergens. Binding of several combinations of mAbs was compared, and a two-site ELISA for group II antigens was developed. Linear regression analysis showed an excellent correlation between results of this assay and group II radioimmunoassay of house dust samples (n = 40, r = 0.85, p < 0.001).

CONCLUSIONS

There are multiple cross-reactive B-cell epitopes on group II allergens. The group II ELISA has several important applications, including assessment of environmental allergen exposure, monitoring of the efficacy of avoidance procedures, and standardization of commercial mite allergen extracts.

Risk factors for acute wheezing in infants and children: viruses, passive smoke, and IgE antibodies to inhalant allergens

OBJECTIVE

To examine the prevalence of viral infection, passive smoke exposure, and IgE antibody to inhaled allergens in infants and children treated for acute wheezing.

DESIGN

Case-control study of actively wheezing children who were compared with children without respiratory tract symptoms.

SETTING

University of Virginia Pediatric Emergency Room.

PATIENTS

Convenience sample of 99 wheezing patients (2 months to 16 years of age) and 57 control patients (6 months to 16 years of age).

MEASUREMENTS AND RESULTS

Serum IgE antibody to inhalant allergens, measured by radioallergosorbent test (RAST), was uncommon in wheezing and control patients under age 2. After 2 years of age, the percentage of RAST-positive patients increased markedly and was significantly higher in wheezing patients than controls after age 4 (72%, n = 54, and 30%, n = 40, respectively, P < .001). Total IgE levels and nasal eosinophilia were strongly correlated with a positive RAST after age 2. Viral pathogens, predominantly respiratory syncytial virus, were identified in nasal washes from 70% (n = 20) of wheezing patients younger than 2 years of age compared with 20% of controls (n = 10), P < .05. After age 2, viruses, particularly rhinovirus, were isolated in washes from 31% (n = 70) of wheezing patients, 64% of whom were also RAST-positive. Levels of cotinine, a nicotine metabolite, were elevated (> or = 10 ng/mL) in saliva from a large percentage of smoke-exposed, wheezing patients under 2 (74%, n = 19) compared with those over 2 (14%, n = 51), P < .001. Odds ratios for wheezing were significant for virus (8.2, confidence interval [CI] = 1.3 to 5.0), and cotinine (4.7, CI = 1.0 to 21.3) in children under 2, and IgE antibody by RAST (4.5, CI = 2.0 to 10.2), virus (3.7, CI = 1.3 to 10.6), and the combination of IgE antibody and virus (10.8, CI = 1.9 to 59.0) were significant risk factors after age 2.

CONCLUSION

Wheezing children younger than 2 years of age had a high rate of viral infection and a low rate of IgE antibody to inhalant allergens. When these children were exposed to passive smoke, salivary cotinine levels were elevated suggesting heavy exposure. After 2 years of age, sensitization to inhaled allergens became increasingly important and viruses remained a significant risk factor for wheezing. These data support recommendations to reduce tobacco smoke exposure at home, especially for young patients, and to consider sensitization to inhaled allergens and allergen avoidance in wheezing children at an early age, particularly after age 2 years.

Benzyl benzoate moist powder: investigation of acaricidal [correction of acarical] activity in cultures and reduction of dust mite allergens in carpets

Despite advances in the understanding of dust mites, it remains difficult to control exposure to mite allergens, and it is particularly difficult to reduce mites in fitted carpets or sofas. Several chemicals have been demonstrated to kill mites or denature mite allergens, and some of these chemicals have been investigated in carpets. Benzyl benzoate (BB), which has been widely used to kill scabies mites and is known to kill mites of the genus Dermatophagoides, has been used as a method of treating carpets. The present article describes experiments in the laboratory and in houses in testing two preparations of BB, a moist powder and a foam. The moist powder is composed of two ingredients, a wetted "inert" cellulose, which is designed to act as a cleaning agent, and the active BB adsorbed onto silicates. The active powder kills 90% of mites in culture within 12 hours and 100% in 24 hours, whereas the cellulose is not acaricidal. The moist-powder preparation was highly effective at killing D. farinae and D. pteronyssinus mites in the laboratory. In carpets the moist powder, applied for 12 hours with repeated brushing, was demonstrated to reduce the concentrations of group I and group II dust mite allergens in dust recovered at 1 month. This decrease in concentration could, in part, be explained by a persistent increased recovery of dust caused by residual white powder. However, when the recovery of group II allergens was calculated as the total allergen recovered, the decrease was highly significant at 2 weeks and 4 weeks after treatment (p less than 0.001). Application of the powder to carpets for 4 hours or of the foam to sofas was less effective. After 2 months the effect on mite antigen in carpets was still present, but some increase was apparent, suggesting that repeat application after 2 or 3 months would be necessary to control mite-allergen levels.

Airborne dust mite allergens: comparison of group II allergens with group I mite allergen and cat-allergen Fel d I

The form in which allergens become airborne is important because it may influence both symptoms caused by allergen exposure and methods used to reduce exposure. The group I allergens from dust mites only become airborne during disturbance and fall rapidly, which is in keeping with their being carried on fecal pellets. Their mean size is approximately 20 microns in diameter. By contrast, the cat-allergen Fel d I is airborne on particles varying from greater than 10 to less than 2 microns in diameter, some of which remain airborne even without disturbance. A second group of mite allergens, molecular weight 14,000, are equally important and are associated predominantly with mite bodies. With a monoclonal antibody-based assay and a cascade impactor, we have investigated the form in which group II mite allergens become airborne. The results reveal that these allergens only become airborne during disturbance and that they fall within 15 minutes. However, the mean size of particles carrying group II allergens appears to be slightly smaller than the mean size of particles carrying group I allergens. In addition, the quantities of group II allergen becoming airborne during disturbance (mean, 26 ng/m3) could not be explained by the quantity found in fecal particles. Thus, group II mite allergens become airborne in a form quite distinct from cat allergens and very similar to group I mite allergens; however, it appears unlikely that fecal particles are the main form in which group II allergens become airborne.

Epidemiology of the relationship between exposure to indoor allergens and asthma

A very high prevalence of immediate hypersensitivity to common indoor allergens can be demonstrated among children and young adults, with asthma. Recent progress in the immunochemistry of cat, dust mite and cockroach allergens has made it possible to measure exposure to these allergens and to start to define threshold levels of exposure which increase the risk of sensitization and symptomatic asthma. Indeed, it is already clear that exposure to greater than 2 micrograms group I dust mite allergen (or 100 mites) per gram of dust increases the risk of children developing sensitization and asthma. Furthermore, from studies on patients presenting to emergency rooms with asthma, it is clear that the risk of sensitization to allergens derived from cats or cockroaches or grass pollen is restricted to patients who are exposed to high levels of these allergens. Given the increasing morbidity and mortality of asthma it is clear that therapeutic efforts should be focused on identifying relevant allergens and advising patients about techniques for reducing exposure.

Recent progress in mite allergen immunochemistry

The successful purification of several mite allergens within the last few years has considerably enhanced our understanding of mite allergen immunochemistry. The role of these glycoproteins in stimulating human IgE ab and their role as immunogens in mice and rabbits has been studied extensively in a number of laboratories worldwide. In particular, purified allergens have facilitated the production of murine IgG Mabs that have been used to purify mite allergens by affinity chromatography; to investigate the diversity of antigenic sites on purified allergens; and to develop Mab based immunoassays for measuring allergen concentrations in dust samples and extracts. Full amino acid sequencing of several mite allergens is now in progress together with efforts to identify antigenically important peptide fragments. Such investigations are aimed to further increase our knowledge of humoral and cellular immune responses at the molecular level. For years, pollen counts have been used to judge airborne pollen allergen levels and to predict, in turn, the severity of symptom days for patients with hay fever. In contrast, simple methods for measuring dust allergens (e.g., mite allergen) have not been available. The development of Mab immunoassays, which can be converted from radiolabeled to enzyme labeled or fluorescence labeled assays, should provide rapid and quantitative measurements of specific mite allergen levels in house dust. Not only can such measurements provide useful clinical information in judging the exposure of patients to mite allergen, but the effectiveness of allergen avoidance regimes can be monitored objectively. By measuring the concentration of specific allergens in extracts, these assays could significantly improve efforts to standardize extracts used for diagnosis and treatment.

Conformational stability of B cell epitopes on group I and group II Dermatophagoides spp. allergens. Effect of thermal and chemical denaturation on the binding of murine IgG and human IgE antibodies

The conformational stability of B cell epitopes on the 25-kDa group I and 14-kDa group II mite allergens was compared by using heat-treated or chemically denatured allergens to inhibit the binding of native 125I allergens to murine mAb or to human IgE antibodies. Structural changes after treatment were assessed by SDS-PAGE and circular dichroism spectroscopy. Heating for 1 h at greater than 75 degrees C, treatment at pH 2.0 or pH 12.0, or with 6M guanidine or 6M urea, reduced the binding of the group I allergens to mAb or IgE antibodies by 10- to 1000-fold. The group II allergens were heat stable and even after prolonged heat treatment (5 h at 75 degrees C or 30 min at 100 degrees C) their antibody binding activity was reduced by less than twofold. The group II allergens were also resistant to pH and to denaturation with 6M guanidine. However, after reduction and alkylation, antibody binding sites on both the group I and group II allergens were destroyed. Reduction of disulfide bonds with 2-ME caused a marked shift in the molecular mass of group I allergens on SDS-PAGE, from 25 kDa to 28-31 kDa. Reduction and alkylation also generated two high m.w. forms of Der p I and Der f I. After heating (100 degrees for 30 min), both Der f I and Der f II retained significant secondary structure, as judged by circular dichroism spectroscopy, but on reduction they showed the typical spectra of fully denatured proteins (greater than 85% random structure). The results show clear differences between the susceptibility of B cell epitopes on the group I and group II allergens to denaturation. Despite these differences in stability, both allergens are equally potent immunogens for IgE antibody responses in man. The results support the view that the physical properties of allergens (low m.w. and solubility), limiting low dose exposure (1 to 10 ng/day), and host genetic and immunoregulatory processes, are more important than gross structural features in the induction and maintenance of IgE antibody responses.

Conformational stability of B cell epitopes on group I and group II Dermatophagoides spp. allergens. Effect of thermal and chemical denaturation on the binding of murine IgG and human IgE antibodies

The conformational stability of B cell epitopes on the 25-kDa group I and 14-kDa group II mite allergens was compared by using heat-treated or chemically denatured allergens to inhibit the binding of native 125I allergens to murine mAb or to human IgE antibodies. Structural changes after treatment were assessed by SDS-PAGE and circular dichroism spectroscopy. Heating for 1 h at greater than 75 degrees C, treatment at pH 2.0 or pH 12.0, or with 6M guanidine or 6M urea, reduced the binding of the group I allergens to mAb or IgE antibodies by 10- to 1000-fold. The group II allergens were heat stable and even after prolonged heat treatment (5 h at 75 degrees C or 30 min at 100 degrees C) their antibody binding activity was reduced by less than twofold. The group II allergens were also resistant to pH and to denaturation with 6M guanidine. However, after reduction and alkylation, antibody binding sites on both the group I and group II allergens were destroyed. Reduction of disulfide bonds with 2-ME caused a marked shift in the molecular mass of group I allergens on SDS-PAGE, from 25 kDa to 28-31 kDa. Reduction and alkylation also generated two high m.w. forms of Der p I and Der f I. After heating (100 degrees for 30 min), both Der f I and Der f II retained significant secondary structure, as judged by circular dichroism spectroscopy, but on reduction they showed the typical spectra of fully denatured proteins (greater than 85% random structure). The results show clear differences between the susceptibility of B cell epitopes on the group I and group II allergens to denaturation. Despite these differences in stability, both allergens are equally potent immunogens for IgE antibody responses in man. The results support the view that the physical properties of allergens (low m.w. and solubility), limiting low dose exposure (1 to 10 ng/day), and host genetic and immunoregulatory processes, are more important than gross structural features in the induction and maintenance of IgE antibody responses.

Antigenic and structural analysis of group II allergens (Der f II and Der p II) from house dust mites (Dermatophagoides spp)

Monoclonal antibody affinity chromatography was used to purify two homologous mite allergens, Der f II from Dermatophagoides farinae and Der p II from D. pteronyssinus. They have the same molecular weight (MW) (15 kd) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, they have similar amino acid compositions, and their N-terminal amino acid sequences differ in only four of the first 35 residues. An excellent correlation was observed between IgE antibody to Der f II and Der p II measured in sera from 65 mite-allergic patients (r = 0.94; p less than 0.001) and between quantitative intradermal skin tests to both allergens. A third allergen (Der f III, MW 29 kd) was purified from D. farinae by repeated gel filtration. In sera from 51 mite-allergic patients, IgE antibody to Der f II, Der f III, and previously purified Der f I (MW 24 kd) was detected in 92%, 16%, and 78% of the sera by radioimmunoassay, respectively. Most patients, 41/51 (80%), demonstrated IgE antibody to more than one allergen. With monoclonal antibodies fully cross-reactive with Der f II and Der p II, a two-site immunoassay was developed for measuring absolute quantities (nanograms or micrograms) of these allergens. In extracts rich in mite-fecal material (n = 5), Der f I and Der p I (group I allergens) and Der f II and Der p II (group II allergens) were measured in ratios of 11:1 to 35:1. Lower ratios (1.1:1 to 7:1) were observed in mite body extracts (n = 6). These experiments clearly define a second group of major dust mite allergens that demonstrate extensive structural and antigenic homology.

Epitope mapping of two major inhalant allergens, Der p I and Der f I, from mites of the genus Dermatophagoides

The repertoire of antigenic sites on two major dust mite allergens, Der p I of Dermatophagoides pteronyssinus and Der f I of D. farinae, was studied using murine (BALB/c) monoclonal antibodies (Mab), polyclonal rabbit IgG antibodies, and human IgE antibodies. Fifty-three IgG Mab were analyzed from six different fusions (five vs Der p I, one vs Der f I). By antigen binding radioimmunoassay (RIA), most Mab were either Der p I or Der f I specific, and only 2/53 bound to both allergens. Epitope mapping studies using cold Mab to inhibit the binding of six 125I labeled Mab to solid phase allergen defined four nonrepeated, nonoverlapping epitopes on Der p I, a single species-specific epitope on Der f I and a cross-reacting epitope present on each allergen. All but one of the 53 Mab bound to one of these six epitopes. Seventy percent (25/35) of anti-Der p I Mab were directed to the same epitope, suggesting that this epitope is immunodominant for BALB/c mice. Similarly, 88% (16/18) of anti-Der f I Mab bound to the same epitope on Der f I. Parallel cross-inhibition curves were obtained using the species-specific Mab, 10B9, and the cross-reacting Mab, 4C1, to compete for binding to Der p I, suggesting that the epitopes defined by these two Mab on Der p I are adjacent to one another. Both murine Mab and polyclonal rabbit IgG antibodies to cross-reacting sites on both allergens were used to inhibit binding of human IgE antibodies to Der p I by using 19 sera from mite allergic patients. Cross-reacting rabbit IgG antibodies strongly inhibited all sera tested (mean 79.5% +/- 7.7) and two Mab, 10B9 and 4C1, partially inhibited (38% +/- 12). However, the four Mab directed against separate species-specific epitopes (including murine immunodominant sites) showed little or no inhibition (less than or equal to 20%). Our results suggest that most of the epitopes defined by Mab are not the same as, or close to, those defined by human IgE antibody. The striking differences in the repertoires of murine IgG and human IgE antibody responses to Der p I and Der f I could be explained by genetic differences or by altered antigen processing and presentation occurring as a result of different modes of immunization in mice and in mite allergic humans.

Epitope mapping of two major inhalant allergens, Der p I and Der f I, from mites of the genus Dermatophagoides

The repertoire of antigenic sites on two major dust mite allergens, Der p I of Dermatophagoides pteronyssinus and Der f I of D. farinae, was studied using murine (BALB/c) monoclonal antibodies (Mab), polyclonal rabbit IgG antibodies, and human IgE antibodies. Fifty-three IgG Mab were analyzed from six different fusions (five vs Der p I, one vs Der f I). By antigen binding radioimmunoassay (RIA), most Mab were either Der p I or Der f I specific, and only 2/53 bound to both allergens. Epitope mapping studies using cold Mab to inhibit the binding of six 125I labeled Mab to solid phase allergen defined four nonrepeated, nonoverlapping epitopes on Der p I, a single species-specific epitope on Der f I and a cross-reacting epitope present on each allergen. All but one of the 53 Mab bound to one of these six epitopes. Seventy percent (25/35) of anti-Der p I Mab were directed to the same epitope, suggesting that this epitope is immunodominant for BALB/c mice. Similarly, 88% (16/18) of anti-Der f I Mab bound to the same epitope on Der f I. Parallel cross-inhibition curves were obtained using the species-specific Mab, 10B9, and the cross-reacting Mab, 4C1, to compete for binding to Der p I, suggesting that the epitopes defined by these two Mab on Der p I are adjacent to one another. Both murine Mab and polyclonal rabbit IgG antibodies to cross-reacting sites on both allergens were used to inhibit binding of human IgE antibodies to Der p I by using 19 sera from mite allergic patients. Cross-reacting rabbit IgG antibodies strongly inhibited all sera tested (mean 79.5% +/- 7.7) and two Mab, 10B9 and 4C1, partially inhibited (38% +/- 12). However, the four Mab directed against separate species-specific epitopes (including murine immunodominant sites) showed little or no inhibition (less than or equal to 20%). Our results suggest that most of the epitopes defined by Mab are not the same as, or close to, those defined by human IgE antibody. The striking differences in the repertoires of murine IgG and human IgE antibody responses to Der p I and Der f I could be explained by genetic differences or by altered antigen processing and presentation occurring as a result of different modes of immunization in mice and in mite allergic humans.

Monoclonal immunoassays for major dust mite (Dermatophagoides) allergens, Der p I and Der f I, and quantitative analysis of the allergen content of mite and house dust extracts

Monoclonal, two-site radioimmunoassays (RIAs) were developed to measure allergen Der p I of Dermatophagoides pteronyssinus or Der f I of D. farinae. Microtiter plates coated with monoclonal antibody (Mab) were incubated with mite extract, and bound allergen was detected with a second 125I-labeled Mab of different epitope specificity. The Mab RIAs were very sensitive (nanogram range) and highly specific. D. pteronyssinus extracts with different concentrations of Der p I demonstrated parallel binding curves, whereas a potent D. farinae extract demonstrated less than 5% of the Der p I binding in the same assay. Similar parallel curves were obtained with several D. farinae extracts in the Der f I assay, whereas D. pteronyssinus extract demonstrated little or no binding. The Mab RIAs were compared with an inhibition RIA that measured cross-reacting determinants on both Der p I and Der f I (antigen P1 equivalent [AgP1Eq]). The results demonstrated good quantitative agreement between these assays in commercial mite and house dust extracts (mean difference 1.57 +/- 0.5-fold). Thirty house dust samples with known mite counts, Der p I, and AgP1Eq content were also compared. The summed Mab RIA values for Der p I and Der f I demonstrated a very good correlation with AgP1Eq values (r = 0.86; p less than 0.001) and with assessments of total mite-allergen content by RAST inhibition (n = 21, r = 0.77; p less than 0.001). Furthermore, in samples with more than 10 mites per 100 mg of dust, the Der p I: Der f I ratio closely correlated with the ratio of the two mites counted by microscopy (n = 15, r = 0.89; p less than 0.001). The Mab RIAs can measure allergen levels in mite or dust extracts without the need for purified allergen or affinity-purified antibodies and can readily be standardized. These assays will be useful in epidemiologic studies of allergic asthma, to assess patients' exposure to mite allergens, and the effects of avoidance regimens. Because of the long-term stability and reproducibility of the reagents, Mab-based assays for specific allergens will also play an important role in the standardization of mite and other allergen extracts.

Asthma and rhinitis related to laboratory rats: use of a purified rat urinary allergen to study exposure in laboratories and the human immune response

Using the major rat allergen as a model has made it possible to study both natural exposure and the human immune response to an important laboratory animal. The close correlation between positive skin tests to whole rat urine and IgE antibody to the major urinary allergen in this and previous studies supports the use of this protein as a model rat allergen. Measurements of airborne rat allergen confirm that the maximum levels are higher than those reported with pollen or mite allergens. However, it is possible that exposure to rat allergens is comparable to levels of exposure to cat salivary allergens in houses with cats. The clear implication is that the high levels of exposure are responsible for the fact that a large proportion of exposed individuals develop IgG antibodies. Our results suggest that the prevalence of IgG antibodies (not individual levels) in a group of workers would be a good guide to exposure. This leaves unresolved why some of the individuals who develop IgG ab also develop IgE ab and become at risk for developing asthmatic responses. Only part of this risk is related to atopy. A striking feature of all the studies on animal allergy is the close association between IgE ab and asthma. It appears clear that it is those immune responses that include IgE ab that are a risk factor for asthma. It is not sensible for anyone to remain consistently sick with asthma and continue working with laboratory animals because there are well documented examples of occupational asthma that has not resolved after ceasing exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigen Der f I from the dust mite Dermatophagoides farinae: structural comparison with Der p I from Dermatophagoides pteronyssinus and epitope specificity of murine IgG and human IgE antibodies

The physicochemical and antigenic properties of an allergen purified from Dermatophagoides farinae, Der f I, were compared with Der p I from Dermatophagoides pteronyssinus. On SDS-PAGE, Der f I migrated as a single polypeptide chain with the same m.w. as Der p I (24,000). Two isoallergenic peaks of Der f I were identified on preparative isoelectric focusing (pI 5.7 to 6.3 and pI 6.6 to 6.95). Fractions from each peak were shown to have an identical amino acid composition (which was similar but not identical to Der p I) and the same N-terminal amino acid sequence. There was a good correlation between quantitative intradermal skin tests to both purified allergens and to D. farinae extract in mite-allergic patients, with positive results when using as little as 10(-5) micrograms/ml of Der f I. The majority of sera with detectable IgE antibody to D. farinae also had IgE antibody to Der f I both among children (29/42 = 69%) and adults (55/63 = 87%). By RAST, there was an excellent correlation between IgE antibody to Der f I and Der p I in sera from 42 mite-allergic children (n = 0.94, p less than 0.001). Polyclonal IgG antibodies from six mice immunized with Der f I showed preferential binding to that allergen, and most monoclonal antibodies (16 of 18) raised against Der f I did not bind Der p I. However, two monoclonal antibodies from this fusion showed cross-reactive binding to both allergens. Immunoabsorption experiments, using D. pteronyssinus and D. farinae extracts coupled to Sepharose, showed that a large proportion of murine antibodies (74% to Der p I and 60 to 93% to Der f I) could not be absorbed by the heterologous extract on the immunosorbent. In contrast, in sera from seven mite-allergic patients, most of the specific IgE and IgG antibody (i.e., greater than or equal to 82%) was removed by either immunosorbent. Thus, Der f I and Der p I represent a homologous pair of major allergens which possess both cross-reacting and species-specific epitopes. The antibody response in mice immunized with either allergen in complete Freund's adjuvant was largely directed against species-specific epitopes, whereas in allergic humans, IgE- and IgG-specific antibodies bound predominately to cross-reacting epitopes.

Antigen Der f I from the dust mite Dermatophagoides farinae: structural comparison with Der p I from Dermatophagoides pteronyssinus and epitope specificity of murine IgG and human IgE antibodies

The physicochemical and antigenic properties of an allergen purified from Dermatophagoides farinae, Der f I, were compared with Der p I from Dermatophagoides pteronyssinus. On SDS-PAGE, Der f I migrated as a single polypeptide chain with the same m.w. as Der p I (24,000). Two isoallergenic peaks of Der f I were identified on preparative isoelectric focusing (pI 5.7 to 6.3 and pI 6.6 to 6.95). Fractions from each peak were shown to have an identical amino acid composition (which was similar but not identical to Der p I) and the same N-terminal amino acid sequence. There was a good correlation between quantitative intradermal skin tests to both purified allergens and to D. farinae extract in mite-allergic patients, with positive results when using as little as 10(-5) micrograms/ml of Der f I. The majority of sera with detectable IgE antibody to D. farinae also had IgE antibody to Der f I both among children (29/42 = 69%) and adults (55/63 = 87%). By RAST, there was an excellent correlation between IgE antibody to Der f I and Der p I in sera from 42 mite-allergic children (n = 0.94, p less than 0.001). Polyclonal IgG antibodies from six mice immunized with Der f I showed preferential binding to that allergen, and most monoclonal antibodies (16 of 18) raised against Der f I did not bind Der p I. However, two monoclonal antibodies from this fusion showed cross-reactive binding to both allergens. Immunoabsorption experiments, using D. pteronyssinus and D. farinae extracts coupled to Sepharose, showed that a large proportion of murine antibodies (74% to Der p I and 60 to 93% to Der f I) could not be absorbed by the heterologous extract on the immunosorbent. In contrast, in sera from seven mite-allergic patients, most of the specific IgE and IgG antibody (i.e., greater than or equal to 82%) was removed by either immunosorbent. Thus, Der f I and Der p I represent a homologous pair of major allergens which possess both cross-reacting and species-specific epitopes. The antibody response in mice immunized with either allergen in complete Freund's adjuvant was largely directed against species-specific epitopes, whereas in allergic humans, IgE- and IgG-specific antibodies bound predominately to cross-reacting epitopes.

Cross-reacting and species-specific determinants on a major allergen from Dermatophagoides pteronyssinus and D. farinae: development of a radioimmunoassay for antigen P1 equivalent in house dust and dust mite extracts

Two species of mites of the genus Dermatophagoides are common in house dust and make a major contribution to the allergen content of house dust. As judged by skin tests and the radioallergosorbent test, these mites, D. pteronyssinus and D. farinae, demonstrate extensive cross-reactivity. When the major allergen from D. pteronyssinus, antigen P1, was compared with the equivalent allergen from D. farinae, these two proteins were found to have both species-specific and common antigenic determinants. With specifically purified antibodies directed against the common determinants, we developed a radioimmunoassay for these antigen P1 equivalent proteins in mite extracts as well as house dust extracts. The quantity of allergen in dust from 63 houses (255 samples) was measured, and values ranged from less than 100 to greater than 100,000 ng/gm of fine dust. The correlation between antigen P1 equivalent (ng/gm) and the number of mites per gram of dust (identified by microscopy) was very good (r = 0.74; p less than 0.001). Furthermore, this correlation was not affected by the species of mite in the dust sample. Of 9243 mites identified, 95% were of the genus Dermatophagoides, and of these, 16.4% and 18% could be positively identified as D. farinae and D. pteronyssinus, respectively. When the assay for antigen P1 equivalent was applied to isolated components of mite cultures of both species, significant allergen was found in the mite bodies, cuticles, and their excreta (fecal particles). For the house-dust samples, less than 10% of the allergen measured could be explained by the allergen content of mite bodies. Our results demonstrate that a radioimmunoassay for antigen P1 equivalent can provide an accurate and simple means of assessing the quantity of mite-derived allergen in dust-mite extracts, house-dust extracts, or house dust.

Airborne allergens associated with asthma: particle sizes carrying dust mite and rat allergens measured with a cascade impactor

Patients with asthma may develop acute symptoms after exposure to domestic or laboratory animal allergens; however, they are usually not aware of a direct relationship between their acute attacks and exposure to pollen or dust mite allergens. The present experiments were designed to study whether the differences in symptoms could be explained by differences in the number or size of particles carrying airborne allergens. Airborne particles were collected with a filter or on the stages of a cascade impactor, and allergens were measured by use of inhibition radioimmunoassays. In rat rooms and during disturbance of rat litter, a large proportion of rat urinary allergen (45.9%) was collected on the second stage of the impactor (mean size approximately 7 microns diameter). When sampled 15 to 35 minutes after disturbance, 16% of these medium-sized particles were still airborne. By contrast, during disturbance of house dust, a significantly larger proportion of dust mite, antigen P1 (80.6 +/- 11.8%; p less than 0.001) was collected on the first stage of the impactor, and in keeping with the apparent size of these particles (diameter greater than 10 microns), very little of this allergen (less than 4%) was still airborne when sampled 15 to 35 minutes after disturbance. With nebulized diluted rat urine, approximately 75% of the allergen was collected on the fourth and final stages of the cascade impactor in keeping with the expected size, 0.5 to 3 microns in diameter. These results demonstrate that natural exposure to both allergens is strikingly different from the conditions used for bronchial provocation.(ABSTRACT TRUNCATED AT 250 WORDS)

Natural exposure and serum antibodies to house dust mite of mite-allergic children with asthma in Atlanta

Pyroglyphid mites in house dust are important allergens associated with asthma in Europe, but comparable studies of house dust mites in the homes of patients with asthma have not been done in the United States. We examined the distribution of mites and mite allergen in the houses of 20 mite-sensitive children with asthma in Atlanta and measured IgE antibodies to mite allergens in their sera. One or more dust samples from bedding, bedroom floor, television room floor, or television room furniture from 17/20 houses contained greater than 10,000 ng of antigen P1 equivalent per gram of fine dust; amounts ranged from 280 to 230,400 ng/gm. Allergen levels were higher in dust samples from furniture and bedding than from floors. Dust samples obtained from houses in June to September had more mites and mite allergen than those houses sampled in March to April; relative humidity in the room also was higher in June to September. Mite numbers and allergen in floor and furniture samples were correlated with relative humidity in the room and were high when relative humidity was greater than 50%; antigen P1 equivalent was greater than 10,000 ng/gm in 21/39 such samples. Dermatophagoides pteronyssinus was present in all houses and dominant in 11/20. D. farinae was found in 17 houses and was dominant in six. All children studied had high IgE antibody with either D. farinae or D. pteronyssinus RAST; 16 of the 20 children also had IgE to antigen P1. It is likely that the IgE antibody responses in these 20 children with asthma were a direct result of exposure to high levels of mite allergen.(ABSTRACT TRUNCATED AT 250 WORDS)

The relevance of inhalant and food allergens to the etiology and management of patients with atopic dermatitis

Patients with atopic dermatitis have IgE antibodies to common environmental antigens, both foods and inhalants. Such antibodies are probably relevant and exposure to the corresponding antigens can give rise to eczema. Nevertheless, the mechanisms involved and the role of other etiologies, e.g. contact reactions, remain to be elucidated. Patients with atopic dermatitis should have comprehensive evaluations to determine the role of environmental antigens.

Medical examination of children referred for special education

The results of medical examinations of 184 children referred for special educational services were reviewed, with particular attention paid to the value of the examination in the detection of abnormalities that would have an adverse educational impact and of previously undiagnosed abnormalities. Seventeen students (9%) were found to have educationally important abnormalities previously unknown to the school. Fifteen students had abnormalities detected through screening tests. The two remaining students had abnormalities apparent on physical examination that conceivably could interfere with physical education but should not hinder academic achievement. Thus, a separate physical examination, apart from those recommended for all children by the American Academy of Pediatrics, may not be productive for children referred for special educational services, but screening tests currently available in many schools are more likely to be beneficial.