Relative risks of bronchial hyper-responsiveness associated with skin-prick test responses to common antigens in young adults

[Skin sensitisation profiles of outpatients with symptoms of respiratory allergies]

AIM

The main objective of the survey was to determine the frequency of the mono and polysensitizations in patients consulting for respiratory allergy, rhinitis or/and asthma. The secondary objectives were to evaluate the severity, the number and the type of the sensitizations, the frequency of the asthma or rhinitis as a function of the sensitizations, the evolution of the sensitizations with age, and identify the principal responsible pneumallergens.

PATIENTS AND METHODS

The multicentric survey included a patient questionnaire allowing the collection and anonymous treatment of data on socio-demographic characteristics, clinical symptoms, cutaneous tests and sensitizations.

RESULTS

A sample of 505 patients, mean age 24 years, consulting for rhinitis or asthma, monosensitized (36%) or polysensitized (64%), was evaluated. The percentage of polysensitized patients was similar in asthmatics, patients with rhinitis, and patients with both asthma and rhinitis (60%, 65%, and 63%, respectively). The mean number of the sensitizations was 2.4 for patients with asthma, 2.6 for those with rhinitis, and 2.6 for patients with both asthma and rhinitis. The greater the severity of the rhinitis or asthma, the higher the number of the sensitizations. Sensitizations to acarids, gramineae and cat were the most frequent. When practioners were asked about their intention to undertake desensitization in polysensitized patients, 52% of them replied positively.

CONCLUSION

Data collected during this survey showed that a large proportion of the patients who consulted for rhinitis or asthma were monosensitized (36%). Sensitization to acarids was the most frequent. Even in polysensitized patients, more than half the practioners said they would use desensitization.

Efficacy and safety of allergen immunotherapy in children

OBJECTIVE

To determine the efficacy and safety of immunotherapy in children with allergic rhinitis and allergic asthma.

DATA SOURCES

Current Contents database for 1967 to 2005.

STUDY SELECTION

The expert opinion of the author was used to select studies for inclusion in this review.

RESULTS

Meta-analyses have confirmed the clinical effectiveness of allergen immunotherapy in patients with allergic rhinitis and asthma; however, most studies involved immunotherapy with a single allergen. Special considerations of safety regarding immunotherapy in children are also necessary, since fatalities have been reported. Fatal reactions occur primarily in patients with asthma and particularly those whose asthma is not well controlled. There is probably increased risk during the build-up phase and with the first injection from a new vial. Injections at home or in clinics without adequate supervision also constitute an increased risk of a fatal outcome.

CONCLUSIONS

Specific immunotherapy has been demonstrated to have some protective effect against the development of additional sensitivities in the monosensitized child and to reduce the risk of developing asthma in children with allergic rhinitis. Because of the modification of the underlying immune process, the beneficial effects of immunotherapy persist for a long but not yet fully determined period after the cessation of treatment. This persisting effect makes immunotherapy an attractive supplement to symptomatic treatment of children with allergic asthma and allergic rhinitis. The treatment is not without risk, however, especially in the child with asthma, so it should be administered with caution.

PDCD1: a tissue-specific susceptibility locus for inherited inflammatory disorders

Variation in genes encoding costimulatory molecules expressed on lymphocytes has been expected to contribute to the genetic component of inflammatory disease, but only the gene encoding the inhibitory protein, CTLA-4, seems consistently to confer disease susceptibility. Studies in murine models implicate the inhibitory product of the pd1 gene, programmed death-1, in the maintenance of peripheral tolerance to self-antigens. We identify 22 single-nucleotide polymorphisms (SNPs) in the equivalent human gene, PDCD1, a number of which show significant associations with the specific immunoglobulin E response to grass allergens in atopic individuals. Stepwise analyses indicate that four of the disease-associated SNPs have independent effects. The two most common haplotypes show positive and negative associations but rarer haplotypes are also likely to be of influence. In a case-control study, multiple regression analysis of genotypic data implies that PDCD1 also confers susceptibility to rheumatoid arthritis. Along with work linking PDCD1 with susceptibility to another autoimmune condition, systemic lupus erythematosus, our data identify PDCD1 as a second immunomodulatory gene with pleiotropic effects in human disease. Genes encoding negative regulators may generally confer a significant fraction of the genetic risk associated with inherited inflammatory disorders.

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.

Age-specific relationship between CD14 and atopy in a cohort assessed from age 8 to 25 years

CD14 influences postnatal switching of T helper cell responses. CD14 C-159T has been associated with altered CD14 and IgE levels in cross-sectional studies. Identifying whether associations vary with age requires data from children of the same age followed longitudinally over many years. In this study, an unselected population with extensive longitudinal data was used to test the hypothesis that CD14 C-159T was associated with early-onset atopy. A total of 305 subjects were assessed on up to seven occasions between ages 8 and 25 years by questionnaire, histamine challenge, and skin prick test. For atopy, airway hyperresponsiveness (AHR), and wheeze, each subject was classified as having early onset, late onset, or no disease onset during follow-up. Compared with subjects with -159CT and -159TT, subjects with -159CC had an odds ratio of 2.2 (p = 0.018) for early-onset atopy and an odds ratio of 2.6 (p = 0.019) for early-onset AHR. Cross-sectional analysis showed increased prevalence of -159CC in subjects with atopy and AHR in childhood but not adulthood. These data suggest that the influence of CD14 -159C on the atopic phenotype may be age specific, exerting an effect during midchildhood, which is no longer apparent by early adulthood.

Genetic analyses in asthma: current concepts and future directions

Asthma is a complex genetic disorder with a heterogeneous phenotype, largely attributed to the interactions among many genes and between these genes and the environment. Numerous loci and candidate genes have been reported to show linkage and association of asthma and the asthma-associated phenotypes, atopy, elevated immunoglobulin E (IgE) levels, and bronchial hyper-responsiveness to alleles of microsatellite markers and single nucleotide polymorphisms (SNPs) within specific cytokine/chemokine, and IgE regulating genes. While many studies reporting these observations are compelling, only one asthma gene conferring high risk has been mapped. In this review, we present studies that support linkage and/or associations to the various genetic loci and genes in asthma. The first genome-wide scan for linkage to quantitative traits underlying asthma identified linkage on chromosome 4q, 6, 7, 11q, 13q and 16. A genome scan in American families from three racial groups revealed linkage to chromosome 2q, 5q, 6p, 12q, 13q and 14q. A two-stage scan in Hutterite families from the US found linkage on chromosome 5q, 12q, 19q and 21q. A screen in German families identified linkage to asthma on chromosome 2q, 6p, 9 and 12q and a two-stage genome scan in French families found replicated linkage on chromosomes 1p, 12q and 17q. A study of asthma in Finland showed linkage to high IgE on 7q14. Apart from a European linkage study of 199 families with atopic dermatitis, which demonstrated significant linkage to chromosome 3q21, three other studies have reported linkage results of genome-wide significance, including a linkage study in 175 Icelandic asthma families (14q24), a study in 533 Chinese families with bronchial hyper-responsiveness (chromosome 2) and a study in 47 Japanese families with mite-sensitive atopic asthma (5q31), suggesting that these regions may harbor genes contributing to the development of asthma and allergies. While significant progress has been made in the field of asthma genetics in the past decade, the clinical implications of the genes and genetic variations within the numerous candidate asthma genes that have been found to associate with the expression of the asthmatic phenotype, remain undetermined.

Asthma genetics

Asthma is the most common chronic childhood disease in developed nations and is a complex disease that has high social and economic costs. Asthma and its associated intermediate phenotypes are under a substantial degree of genetic control. Identifying the genes underlying asthma offers a means of better understanding its pathogenesis, with the promise of improving preventive strategies, diagnostic tools, and therapies. A number of chromosomal regions containing genes influencing asthma and atopy have been identified consistently by different groups, and a role for several candidate genes has been established.

A detailed genetic map of the chromosome 7 bronchial hyper-responsiveness locus

Non-specific bronchial hyper-responsiveness to various inhaled stimuli is a characteristic of asthma. We have previously shown linkage of bronchial responsiveness to methacholine (measured as dose-response slope (DRS)) and the peripheral blood eosinophil count (EOS) to chromosome 7. We have now further investigated these linkages by genotyping 49 microsatellite markers across the DRS locus on chromosome 7. The markers were spaced on average 2.6 cM apart and spanned a sex averaged cumulative genetic distance of 129 cM. Multipoint linkage to DRS was bimodal and dipped at the centromere. The two peaks of linkage were close to markers D7S484 (P=0.0003) and D7S669 (P=0.006) respectively. Separate testing for linkage to paternally and maternally derived alleles showed that the linkage near D7S484 was paternally derived (P<0.00001): maternally derived alleles did not exhibit significant linkage. The results indicate that two disparate loci may be influencing asthma from chromosome 7.

Current concepts on the genetics of asthma

Asthma is a complex genetic disorder with variable phenotype, largely attributed to the interactions of the environment and multiple genes, each potentially having small effects. Numerous asthma and atopy loci have been reported in studies demonstrating associations and/or linkage of the asthma-associated phenotypes, atopy, elevated IgE levels, and bronchial hyperresponsiveness to alleles of microsatellite markers and single nucleotide polymorphisms within specific cytokine/chemokine and IgE regulating genes. Although the studies reporting these observations are compelling, most of them lack statistical power. This review compiles the evidence that supports linkage and associations to the various genetic loci and candidate genes. Whereas significant progress has been made in the field of asthma genetics in the past decade, the roles of the genes and genetic variations within the numerous candidate asthma genes that have been found to associate with the expression of the asthmatic phenotype remain to be determined.

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.)

Contributing factors to the pathobiology. The genetics of asthma

Markers in 19 chromosomal regions have shown some evidence of linkage to asthma, atopy, or related phenotypes in multiple independent genome-wide searches. Linkages to five of these regions (5q, 6p, 11q, 12q, and 13q) have also been reported in non-genome-wide screens. In addition, at least two independent studies have reported linkages to markers on 16p. Numerous candidate genes in these regions have shown varying levels of association to asthma or atopic phenotypes, potentially implicating them as disease susceptibility loci. These include the IL4, CD14, and B2ADR genes on 5q, the HLA-DRB1 and TNF genes on 6p, the FCERB1 and CC16 genes on 11q, and the IL4RA gene on 16p. It still remains to be determined whether polymorphisms in these genes account for the reported linkages in these regions. Studies are underway in laboratories around the world to identify the disease-causing variations in these genes that account for the linkages just discussed. Identifying specific genetic polymorphisms that influence asthma and atopic phenotypes will shed light on the molecular pathways involved in these complex disorders and provide a better understanding of the pathophysiology of asthma and atopy.

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.

Significant evidence for linkage of mite-sensitive childhood asthma to chromosome 5q31-q33 near the interleukin 12 B locus by a genome-wide search in Japanese families

Childhood-onset asthma is frequently found in association with atopy. Although asthmatic children may develop IgE antibodies against variety of allergens, asthma is associated primarily with allergy to house-dust mites, molds, or other allergens. In this study, we conducted a genome-wide linkage search in 47 Japanese families (197 members) with more than two mite-sensitive atopic asthmatics (65 affected sib-pairs) using 398 markers. Multipoint linkage analysis was carried out for atopic asthma as a qualitative trait using the MAPMAKER/SIB program. We observed significant evidence for linkage with maximum lod scores (MLS) of 4.8 near the interleukin 12 B gene locus on chromosome 5q31-q33. In addition, suggestive evidence on 4q35 with MLS = 2.7 and on 13q11 with MLS = 2.4 was obtained. The other possible linkage regions included 6p22-p21.3 (MLS = 2.1), 12q21-q23 (MLS = 1.9), and 13q14.1-q14.3 (MLS = 2.0). Many of the linkage loci suggested in this study were at or close to those suggested by genome-wide studies for asthma in Caucasian populations. The present study suggests the contribution of the interleukin 12 B gene or nearby gene(s) to mite-sensitive atopic asthma and a considerable number of genetic variants common across Caucasians and Japanese populations contributing to asthma, although the relative importance of various variants may differ between the groups.

Family patterns of asthma, atopy and airway hyperresponsiveness: an epidemiological study

BACKGROUND

The patterns of inheritance of asthma have largely been explored using data of symptom history collected by questionnaires which are subject to bias and which may therefore distort the measured relationship.

OBJECTIVE

The purpose of this study was to examine family patterns of allergic disease using objective measurements of atopy and of airway hyperresponsiveness (AHR).

METHODS

A large random sample of children aged 8-11 years was studied and 3 months later, their parents were also invited for study. Of the sample of 1655 children, both parents of 661 children were studied. In all subjects, respiratory illness history was measured by questionnaire, atopy by skin tests and AHR by responsiveness to histamine.

RESULTS

The odds ratio for a child to have AHR if either parent had the same condition was approximately 2. 0, which was the same as the odds ratio for wheeze or diagnosed asthma in the presence of the same condition in either parent. The odds ratio for atopy was smaller (approximately 1.4, NS) but the risk of a nonatopic child having AHR if the parent had AHR was 3.0 (P = 0.01). The correlation between weal size in the child and parent was poor and the severity of AHR in the child was only modestly correlated with the severity of AHR in the parent (R = 0.51, P = 0.04).

CONCLUSION

The use of objective measurements did not strengthen the association between atopic or asthmatic conditions in the parent and child, but did suggest that atopy and AHR are inherited independently.

Recent advances in the genetics of allergy and asthma

Asthma is a common condition that results from the interaction of an unknown number of genes with environmental factors. About 10% of children have asthma, usually as part of a syndrome of atopy, which is characterized by the presence of allergy, asthma, seasonal rhinitis and eczema, and tends to occur in familial clusters. The incidence of asthma is lower in adults (5%) and a significant proportion is seen without an atopic background. The prevalence of asthma has increased substantially over the past decades, particularly in the western world. Allergy and asthma are not inherited as single-gene disorders and do not show a simple pattern of inheritance. Environmental and genetic factors interact in a complex fashion to produce disease susceptibility and expression. Here, we describe the recent advances in the understanding of the inherited susceptibility to asthma and atopy and discuss their potential implications.

Relationships between duration of asthma and asthma severity among children in the Childhood Asthma Management Program (CAMP)

BACKGROUND

Many factors, including heredity, atopic status, and environment, have been implicated in the determination of asthma severity. Relatively little is known about the degree to which asthma duration influences asthma severity.

OBJECTIVE

The Childhood Asthma Management Program (CAMP), consisting of 1041 children (age 8. 9 +/- 2.1 years at enrollment) with mild-to-moderate asthma, offers an opportunity to examine the relationship between asthma duration and asthma severity.

METHODS

By using the extensive CAMP baseline cross-sectional data on asthma duration, spirometry, bronchial responsiveness, symptomatology, and markers of atopy, univariate and multivariate regression models were used to evaluate whether asthma duration is associated with asthma severity.

RESULTS

Duration of asthma in the study cohort from time of diagnosis until randomization into CAMP ranged from 0.3 to 12.1 years (mean, 5.0; SD, 2.7; median, 4.8). Asthma duration is associated in univariate analyses both with lower levels of several lung functions (P <.001), including methacholine bronchial reactivity (natural log [ln] FEV1 PC20, mg/mL; r = -0.112), prebronchodilator and postbronchodilator percent predicted FEV1 (r = -0.176 and r = -0.130, respectively), and prebronchodilator and postbronchodilator FEV1 /forced vital capacity (FVC) (%) (r = -0.237 and r = -0.211, respectively), as well as higher levels of symptoms (symptom score: r = 0.147, P <. 001) and borderline greater use of albuterol for symptoms (r = 0.058, P =.064) during a 28-day screening period before randomization. Simple linear regression detected the following differences in lung functions per year of asthma duration: ln FEV1 PC20, -0.050 mg/mL/y; prebronchodilator FEV1, -0.907 percent predicted/y; and prebronchodilator FEV1 /FVC, -0.729 percent predicted/y. After controlling for potential explanatory variables (atopy, inflammatory markers, household Der p 1 levels, anti-inflammatory medication use, and clinical center), regression models revealed that the duration of asthma remained significantly and independently associated with ln FEV1 PC20 (P =.004), prebronchodilator percent predicted FEV1 (P =.043), and prebronchodilator and postbronchodilator FEV1 /FVC (%) (P <.001), as well as being positively associated with mean daily symptom score (P <.001) and albuterol use for symptoms (P =.003) during a 28-day screening period. Duration was also found to be significantly associated with physician/nurse assessment of asthma severity and other historical measures of medication use.

CONCLUSIONS

These data demonstrate that asthma duration is associated with lower lung function, greater methacholine responsiveness, more asthma symptomatology, and greater use of as-needed albuterol, which are all measures of asthma severity. As such, early diagnosis and intervention may be necessary to ameliorate these adverse effects of persistent asthma.

Linkage of house dust mite allergy with the HLA region

BACKGROUND

Atopy is a multifactorial disease, the pathogenesis of which is influenced by both genetic and environmental conditions. Genes in the HLA region have been involved in the control of the IgE response.

OBJECTIVE

In order to investigate whether allergy to house dust mite is associated with HLA in our population, we performed sib-pair analysis in 18 families and a case/control study of 161 non-related individuals.

METHODS

Levels of total and specific IgE were determined, skin-prick tests were carried out and clinical history was reviewed for every subject in the study. HLA class II typing was performed by the polymerase chain reaction with sequence specific primers.

RESULTS

We observed a significant difference from expected values in haplotypes shared by affected sibs; however, the case/control study did not reveal any association with any particular allele.

CONCLUSION

These results suggest that any particular HLA-DRB1/DQA1/DQB1 allele is responsible for the development of allergy to house dust mite in the Spanish population. Some other locus in or close to the HLA region might be involved, e.g., the tumour necrosis factor gene, a possibility that would explain the significant difference from expected values in the segregation of HLA haplotypes.

Effect of anti-IL-4 and anti-IL-5 antibodies on allergic airway hyperresponsiveness in mice

In order to study the role of IL-4 and IL-5 in allergen-induced airway hyperresponsiveness in mice, the effect of the combined administration of anti-IL-4 and anti-IL-5 monoclonal antibodies (mAbs) on IgE response, airway inflammation and airway hyperresponsiveness was studied in sensitized Balb/c mice. Three inhalations of antigen caused an increase in the number of eosinophils in bronchoalveolar lavage fluid and in airway responsiveness to acetylcholine, with a significant elevation in the serum antigen-specific IgE level. Anti-IL-4 mAb inhibited IgE production but did not affect airway eosinophilia or hyperresponsiveness. Moreover, anti-IL-5 mAb inhibited airway eosinophilia but did not affect IgE production or airway hyperresponsiveness. The combined administration of anti-IL4 and anti-IL-5 mAbs, however, inhibited IgE antibody production, airway eosinophilia and hyperresponsiveness. These results suggest that inhibitory action of IL-4 and IL-5 in combination can effectively suppress the onset of antigen-induced airway hyperresponsiveness in mice.

Genetic and environmental risk factors for asthma: a cotwin-control study

In complex diseases of genetic etiology such as asthma and atopy, it is difficult to differentiate causes of disease from consequences, and quantitate the importance of such causative factors. We examined possible risk factors for the development of wheezing and bronchial hyperresponsiveness in a cotwin-control study nested within a larger community-based twin-family study. In 62 monozygotic (MZ) twin pairs discordant for a history of wheezing, skin prick test to house dust extract was the most important discriminator, followed by sensitization to cat and cockroach allergens. In contrast, 62 dizygotic (DZ) discordant twin pairs differed additionally in sensitization to grass pollens and fungi. Markers such as serum haptoglobin, serum magnesium, and alpha-1-antitrypsin levels did not differ significantly between discordant twins. This MZ/DZ difference suggests that pollen allergy in asthmatics is more an epiphenomenon due to a genetic correlation between asthma and the allergic diathesis, whereas indoor allergens are likely to be direct environmental causes of asthma.

Skin prick test reactivity to common aeroallergens in relation to total IgE, respiratory symptoms, and smoking in a general population sample of northern Italy

Skin prick test (SPT) reactivity to common airborne allergens and its relationships to sex, age, smoking habits, and respiratory symptoms/diseases were evaluated in a general population sample (n = 2841, 8-75 years of age) living in the Po delta area (northern Italy). Subjects completed a standardized questionnaire and underwent prick tests (12 local allergens, a negative and a positive control) and determination of total serum IgE. Atopy was evaluated by measuring the maximal diameter for each allergen, after subtracting that of the negative control. Thirty-one percent of subjects showed a positive skin response at a 3-mm threshold. Pollens, Dermatophagoides pteronyssinus, and D. farinae caused the highest frequencies of reactions. Young people and those who had never smoked had higher prevalence rates of SPT reactivity. Asthma, asthma symptoms, and rhinitis were significantly associated with SPT reactivity in both sexes (cough only in females) and with the number of positive reactions. IgE values were also significantly associated with SPT reactivity. In conclusion, our findings indicate that almost one-third of the general population of an Italian rural area is skin test positive, emphasizing the importance of assessing atopy in respiratory epidemiologic surveys.

Sensitivity and maximal response to methacholine in perennial and seasonal allergic rhinitis

BACKGROUND

Airway hyperresponsiveness to pharmacological agonists is a common feature in subjects with allergic rhinitis.

OBJECTIVE

The aim of this study was to investigate differences in threshold value and shape of the concentration-response curves to methacholine between subjects with perennial allergic rhinitis and subjects with seasonal rhinitis.

METHODS

We studied a sample of 72 non-asthmatic patients with allergic rhinitis. They were subdivided into two groups: subjects with only seasonal symptoms and skin sensitization to grass and/or Parietaria pollen allergens (seasonal group, n = 38), and subjects with perennial symptoms and skin sensitization to house dust mite, alone or with other allergens (perennial group, n = 34). They were challenged with methacholine (up to 200 mg/mliter), and concentration-response curves were characterized by the threshold value (PC20 = provocative concentration of methacholine required to produce a 20% fall in FEV1) and maximal response plateau, if possible. The measurements in the seasonal group were done within the pollen season.

RESULTS

The geometric mean methacholine PC20 for subjects of the perennial group was 6.9 mg/mliter, compared with 23.4 mg/mliter in subjects of the seasonal group (P < 0.01). A plateau response was detected in 16 subjects of the perennial group and in 28 subjects of the seasonal group (P < 0.05). Moreover, the level of plateau was higher in subjects of the perennial group when compared with subjects of the seasonal group (23.8 +/- 2.0% vs 19.2 +/- 1.6%, P < 0.05).

CONCLUSION

In subjects with allergic rhinitis, sensitization to perennial allergens is associated not only with lower methacholine threshold values, but also with lower prevalence and higher level of plateau than sensitization to pollen allergens.

Influence of skin prick test criteria on estimation of prevalence and incidence of allergic sensitization in children

In a prospective cohort study on atopy in childhood, three skin prick tests (SPT) were performed in 1135 primary schoolchildren over a 2-year period. We studied the development of average sizes of allergen wheals in reactive children and of average sizes of histamine wheals in all children, and we investigated the influence of choice of SPT criterion on the prevalence and incidence of sensitization. A year-to-year increase of average allergen wheal sizes as well as of average histamine wheal sizes was observed. These increases seemed to be related to the natural growth of the children. Furthermore, an observer bias effect of the person who did the pricking on average wheal sizes was found. There were considerable differences in estimations of prevalences and incidences depending on the definition of SPT criterion. Estimations using a criterion based solely on the allergen wheal size were affected by variation of allergen wheal sizes caused by growth and observer effects. The ratio criterion was not influenced by observer effects, nor did it seem to be affected by aging effects. In conclusion, our data suggest that the ratio criterion, which relates the size of the allergen wheal to the size of the histamine wheal, is the most appropriate SPT criterion because it is not affected by growth of allergen wheals in childhood and it appears to compensate for possible observer bias.

Role of atopy in the natural history of wheeze and bronchial hyper-responsiveness in childhood

The role of atopy in the development of asthma has become increasingly recognised. We have been prospectively following a birth cohort of children of atopic parents to document the development of atopic disease. Our aim in this study was to document the natural history of BHR and wheeze at 10 years of age and to relate this to atopy. We reviewed 47 of our original cohort of 79 infants at 10 years of age and documented their clinical history of atopic disease and performed allergen skin prick tests and BHR to histamine. Thirty-three (70%) children wheezed at some time during their 10 years of life, with 13 commencing in infancy. Twenty-two children (47%) had current wheeze at 10 years of age. Wheeze in infancy was a poor predictor (RR 1.23, CI95 0.66-2.23) of current wheeze while wheeze commencing after infancy was a good predictor (RR 2.89, CI95 1.45-5.2). In contrast both atopy in infancy (RR 2.94, CI95 1.92-4.53) and current atopy (RR 3.58, CI95 1.43-9.03) were strong predictors of current wheeze. Analysis of BHR confirmed the importance of atopy in predicting its occurrence and severity. Sensitisation to D. pteronyssinus appeared to be the strongest predictor of both current wheeze and BHR. These observations confirm the importance of atopy in predicting outcome in children with asthma and suggest that wheezing in infancy and wheezing in later childhood may have different pathogenetic mechanisms.

HLA-DR and HLA-DP genotypes and immunoglobulin E responses to common major allergens

In order to test for human histocompatibility leucocyte antigens (HLA) class II restriction of IgE responses, 431 subjects from 83 families were genotyped at the HLA-DR and HLA-DP loci and serotyped for IgE responses to six major allergens from common aero-allergen sources. A possible excess of HLA-DR1 was found in subjects who were responsive to Fel d I compared with those who were not (Odds Ratio (OR) = 2, P = 0.002), and a possible excess of HLA-DR4 was found in subjects responsive to Alt a I (OR = 1.9, P = 0.006). Increased sharing of HLA-DR/DP haplotypes was seen in sibling pairs responding to both allergens. Der p I, Der p II, Phl p V and Can f I were not associated with any definite excess of HLA-DR alleles. No significant correlations were seen with HLA-DP genotype and reactivity to any of the allergens. The results suggest class II HLA restriction is insufficient to account for individual differences in reactivity to common allergens.

Seasonal allergic symptoms and their relation to pollen exposure in south-east France

In order to evaluate the relationship between pollen exposure and prevalence of allergic respiratory symptoms, we performed a cross-sectional epidemiological study in 2 areas with contrasted exposure to cypress and grass pollens. The study population consisted of 5427 subjects 18 to 65-years-old representative of the general population. All answered an abridged version of the 1978 ATS questionnaire and a sample had a skin test evaluation including grass and cypress pollens. Prevalence of hay fever symptoms was equal to 31.5% and 14.1%, respectively, in exposed and less exposed community (P < 0.001). Prevalence of hay fever symptoms together with a positive skin test to pollen was also significantly higher in the exposed (13.6%) vs less exposed community (5.5%, P < 0.001). In contrast, overall prevalence of asthma was equal to 4.5% and 3.4%, respectively. Prevalence of asthma with positive skin tests was also not statistically significant, equal to 2.5% and 1.9%, respectively. Thus, high exposure to pollen is a risk factor for developing hay fever but not asthma.

Development and transfer of immediate cutaneous hypersensitivity in mice exposed to aerosolized antigen

We previously showed that BALB/c mice sensitized to ovalbumin (OVA) by brief daily inhalations of antigen over 10 consecutive days exhibit elevated antigen-specific serum IgE antibody levels and increased airways responsiveness. For the first time, we now show that animals sensitized in this fashion to either OVA or ragweed (RGW) develop immediate hypersensitivity skin test reactions when challenged 2 d after completion of the sensitization protocol. Skin testing, performed by direct assessment of wheal formation after intradermal injection of allergen, was sensitive and specific, since animals exposed to RGW by inhalation only responded to RGW, and OVA-sensitized animals responded only to OVA. Positive reactions were associated with mast cell degranulation, whereas control injections were not. Since only sensitized IgE high responder BALB/c mice but neither nonsensitized BALB/c mice nor OVA-sensitized IgE low responder SJL/J mice exhibited wheal responses, induction of OVA-specific IgE appeared to be essential for the mediation of OVA-specific immediate hypersensitivity reactions of the skin in this model. Passive cutaneous anaphylaxis (PCA) testing confirmed the presence of antigen-specific IgE in the serum. Mice that developed IgG (predominantly IgG2b) anti-OVA antibodies did not respond to OVA injection, indicating that OVA-specific IgG was not involved in this system. Further support for the role of IgE in the immediate hypersensitivity response included the wheal response to intradermal injection of anti-IgE antibody that occurred in OVA- and RGW-sensitized mice at 10-fold lower concentrations than in nonsensitized BALB/c mice and not in sensitized SJL/J mice. After transfer of mononuclear cells from peribronchial lymph nodes of OVA- or RGW-sensitized BALB/c mice, naive, syngeneic recipients developed antigen-specific IgE and specific immediate hypersensitivity responses, indicating that the local lymphoid tissue at the site of sensitization can transfer responsiveness to these allergens. These results demonstrate for the first time the ability to elicit and study IgE-mediated immediate skin hypersensitivity responses in the mouse and illustrate the association of increased antigen-specific and total serum IgE levels, airways hyperresponsiveness, and antigen-specific immediate cutaneous reactivity after sensitization to allergen via the airways.

Risk factors for developing wheezing and asthma in childhood

Wheezing lower respiratory tract illness in infancy and asthma share the clinical findings of wheezing and respiratory distress. Although the link between wheezing lower respiratory tract illness in infancy and the subsequent development of asthma is a limited one, both conditions do share some common risk factors, including exposure to environmental tobacco smoke, difficult living conditions (low socioeconomic class, crowding, allergen exposure), and increased risk in males. The impact of baseline lung function on wheezing lower respiratory tract illness risk is substantial and may be independent of airway reactivity. In contrast, the development of chronic airway inflammation mediated by allergic sensitization plays a central role in the development of persistent asthma. Although the endogenous risks for these two outcomes may be fixed, it is clear that caregivers may help to reduce or eliminate the exogenous risks listed earlier by parental education and improvement of the living conditions of young children.