Childhood Asthma and Indoor Aeroallergens and Endotoxin in Palestine: A Case-Control Study

Sharif, Nuha El; Douwes, Jeroen; Hoet, Peter; Nemery, Benoît

doi:10.1080/02770900600567122

Cited by 15 publications

(9 citation statements)

References 28 publications

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“…Despite showing a protective effect of endotoxin on atopic asthma or wheeze, the study from Germany, Switzerland and Austria also found an increased risk of non-atopic wheeze with higher endotoxin levels among children from non-farming households [7] showing some disagreement with ours. A separate case–control study in Palestine that included 6 to 12 year old children [25] showed inverse associations between medium endotoxin levels from the mattress and being a non-sensitized case (report of wheeze in the past 12 months) compared to a non-sensitized control [25], in agreement with the results of our study. We found stronger protective effects of endotoxin among those without a history of allergic disease.…”

Section: Discussionsupporting

confidence: 91%

“…We found stronger protective effects of endotoxin among those without a history of allergic disease. However, our observations regarding the personal history of allergy should be interpreted with some caution because of the lack of an objective measure of allergy and may account for the differences between our study and the study by Braun-Fahrländer et al [7,25] One explanation for our results could be the timing and duration of endotoxin exposure, both factors which could affect allergy and asthma onset. It may be that among those who did not have a history of allergy there was more early exposure to endotoxin prior to allergen exposure while those with a history of allergy had earlier exposure to allergens leading to sensitization.…”

Section: Discussioncontrasting

confidence: 74%

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Endotoxin as a determinant of asthma and wheeze among rural dwelling children and adolescents: A case–control study

et al. 2012

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BackgroundThe association between endotoxin exposure and asthma is complex and has been associated with rural living. We examined the relationship between domestic endotoxin and asthma or wheeze among rural school-aged children (6–18 years) and assessed the interaction between endotoxin and other characteristics with these outcomes.MethodsBetween 2005 and 2007 we conducted a case–control study of children 6–18 years in the rural region of Humboldt, Canada. Cases (n = 102) reported doctor-diagnosed asthma or wheeze in the past year. Controls (n = 208) were randomly selected from children without asthma or wheeze. Data were collected to ascertain symptoms, asthma history and indoor environmental exposures (questionnaire), endotoxin (dust collection from the play area floor and child’s mattress), and tobacco smoke exposure (saliva collection). Statistical testing was completed using multiple logistic regression to account for potential confounders and to assess interaction between risk factors. A stratified analysis was also completed to examine the effect of personal history of allergy.ResultsAmong children aged 6–12 years, mattress endotoxin concentration (EU/mg) and load (EU/m2) were inversely associated with being a case [odds ratio (OR) = 0.44, 95% confidence interval (CI) = 0.20-0.98; and OR = 0.38, 95% CI = 0.20-0.75, respectively]. These associations were not observed in older children or with play area endotoxin.ConclusionsOur results suggest that endotoxin exposure might be protective for asthma or wheeze. The protective effect is found in younger school-aged, non-allergic children. These results may help explain the inconsistencies in previous studies and suggest that the protective effects of endotoxin in the prevention of atopy and asthma or wheeze are most effective earlier in life.

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Section: Discussionsupporting

confidence: 91%

Section: Discussioncontrasting

confidence: 74%

Endotoxin as a determinant of asthma and wheeze among rural dwelling children and adolescents: A case–control study

et al. 2012

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“…However, whereas some studies have shown a positive association between endotoxin and asthma (Ross et al 2000; Thorne et al 2005), others have suggested that LPS protects against development of this disease (Braun-Fahrländer et al 2002; El-Sharif et al 2006; Gehring et al 2004). In mice, very high doses of inhaled LPS have been previously reported to promote Th1 responses, with lower doses promoting Th2 responses (Eisenbarth et al 2002).…”

Section: Discussionmentioning

confidence: 99%

“…Lipopolysaccharide (LPS), a major component of the outer cell wall of gram-negative bacteria, is ubiquitous in the environment, and some studies have indicated that exposure to relatively high levels of LPS during childhood protect against developing asthma later in life (Braun-Fahrländer et al 2002; El-Sharif et al 2006; Gehring et al 2004). Conversely, other studies have demonstrated a positive association between asthma and household levels of bacteria and LPS (Ross et al 2000; Thorne et al 2005).…”

Section: Introductionmentioning

confidence: 99%

Modulation of Distinct Asthmatic Phenotypes in Mice by Dose-Dependent Inhalation of Microbial Products

Whitehead

Thomas

Cook

2014

Environ Health Perspect

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Background: Humans with asthma display considerable heterogeneity with regard to T helper (Th) 2–associated eosinophilic and Th17-associated neutrophilic inflammation, but the impact of the environment on these different forms of asthma is poorly understood.Objective: We studied the nature and longevity of asthma-like responses triggered by inhalation of allergen together with environmentally relevant doses of inhaled lipopolysaccharide (LPS).Methods: Ovalbumin (OVA) was instilled into the airways of mice together with a wide range of LPS doses. Following a single OVA challenge, or multiple challenges, animals were assessed for pulmonary cytokine production, airway inflammation, and airway hyperresponsiveness (AHR).Results: Mice instilled with OVA together with very low doses (≤ 10–3 μg) of LPS displayed modest amounts of Th2 cytokines, with associated airway eosinophilia and AHR after a single challenge, and these responses were sustained after multiple OVA challenges. When the higher but still environmentally relevant dose of 10–1 μg LPS was used, mice initially displayed similar Th2 responses, as well as Th17-associated neutrophilia. After multiple OVA challenges, however, the 10–1 μg LPS animals also accumulated large numbers of allergen-specific T regulatory (Treg) cells with high levels of inducible co-stimulatory molecule (ICOS). As a result, asthma-like features in these mice were shorter-lived than in mice sensitized using lower doses of LPS.Conclusions: The nature and longevity of Th2, Th17, and Treg immune responses to inhaled allergen are dependent on the quantity of LPS inhaled at the time of allergic sensitization. These findings might account in part for the heterogeneity of inflammatory infiltrates seen in lungs of asthmatics.Citation: Whitehead GS, Thomas SY, Cook DN. 2014. Modulation of distinct asthmatic phenotypes in mice by dose-dependent inhalation of microbial products. Environ Health Perspect 122:34–42; http://dx.doi.org/10.1289/ehp.1307280

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“…In our earlier study of children with asthma, we found that measured exposure (to levels above detection) and sensitization to Can f 1, but not to Fel d 1 were significantly associated with asthma morbidity (as measured by use of controller medication for ≥9 months during the year of follow-up) (Gent et al, 2009). Another study of asthmatic children where levels of pet allergen were measured found no associations between level of exposure and wheezing in analyses controlling for any atopic sensitization (El-Sharif et al, 2006). In contrast, two studies of adult asthmatics did find associations between risk of wheezing and specific sensitization/exposure status for measured levels of Fel d 1 (Gehring et al, 2001; Lewis et al, 2002).…”

Section: Discussionmentioning

confidence: 99%

Household mold and dust allergens: Exposure, sensitization and childhood asthma morbidity

Gent¹,

Kezik²,

Hill³

et al. 2012

Environmental Research

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Background Few studies address concurrent exposures to common household allergens, specific allergen sensitization and childhood asthma morbidity. Objective To identify levels of allergen exposures that trigger asthma exacerbations in sensitized individuals. Methods We sampled homes for common indoor allergens (fungi, dust mites (Der p 1, Der f 1), cat (Fel d 1), dog (Can f 1) and cockroach (Bla g 1)) for levels associated with respiratory responses among school-aged children with asthma (N=1233) in a month-long study. Blood samples for allergy testing and samples of airborne fungi and settled dust were collected at enrollment. Symptoms and medication use were recorded on calendars. Combined effects of specific allergen sensitization and level of exposure on wheeze, persistent cough, rescue medication use and a 5-level asthma severity score were examined using ordered logistic regression. Results Children sensitized and exposed to any Penicillium experienced increased risk of wheeze (odds ratio [OR] 2.12 95% confidence interval [CI] 1.12, 4.04), persistent cough (OR 2.01 95% CI 1.05, 3.85) and higher asthma severity score (OR 1.99 95% CI 1.06, 3.72) compared to those not sensitized or sensitized but unexposed. Children sensitized and exposed to pet allergen were at significantly increased risk of wheeze (by 39% and 53% for Fel d 1 > 0.12 µg/g and Can f 1>1.2 µg/g, respectively). Increased rescue medication use was significantly associated with sensitization and exposure to Der p 1 > 0.10 µg/g (by 47%) and Fel d 1>0.12 µg/g (by 32%). Conclusion Asthmatic children sensitized and exposed to low levels of common household allergens Penicillium, Der p 1, Fel d 1 and Can f 1 are at significant risk for increased morbidity.

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Childhood Asthma and Indoor Aeroallergens and Endotoxin in Palestine: A Case-Control Study

Cited by 15 publications

References 28 publications

Endotoxin as a determinant of asthma and wheeze among rural dwelling children and adolescents: A case–control study

Endotoxin as a determinant of asthma and wheeze among rural dwelling children and adolescents: A case–control study

Modulation of Distinct Asthmatic Phenotypes in Mice by Dose-Dependent Inhalation of Microbial Products

Household mold and dust allergens: Exposure, sensitization and childhood asthma morbidity

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