Multiple microbial exposures in the home may protect against asthma or allergy in childhood.
BACKGROUND
Experimental animal data on the gram-negative bacterial (GNB) biomarker endotoxin suggest that persistence, dose, and timing of exposure are likely to influence its effects on allergy and wheeze. In epidemiologic studies, endotoxin may be a sentinel marker for a microbial milieu, including gram-positive bacteria (GPB) as well as GNB, that may influence allergy and asthma through components (pathogen-associated molecular patterns) that signal through innate Toll-like receptor pathways.


OBJECTIVE
To determine the influence of current GNB and GPB exposures on asthma and allergic sensitization in school-aged children.


METHODS
We examined the relationship between bacterial biomarkers and current asthma and allergic sensitization in 377 school-aged children in a birth cohort study. We then evaluated the effects of school-aged endotoxin, after controlling for exposure in early life.


RESULTS
Exposure to GNB was inversely associated with asthma and allergic sensitization at school age [for >median endotoxin: prevalence odds ratio (POR)=0.34, 95% CI=0.2-0.7, for current asthma and prevalence ratio=0.77, 95% CI=0.6-0.97, for allergic sensitization]. In contrast, elevated GPB in the bed was inversely associated with current asthma (POR=0.41, 95% CI=0.2-0.9) but not with allergic sensitization (POR=1.07, 95% CI=0.8-1.4). School-aged endotoxin exposure remained protective in models for allergic disease adjusted for early-life endotoxin.


CONCLUSIONS
Both GNB and GPB exposures are associated with decreased asthma symptoms, but may act through different mechanisms to confer protection. Endotoxin exposure in later childhood is not simply a surrogate of early-life exposure; it has independent protective effects on allergic disease.
Sordillo
J E
JE
Channing Laboratory, Boston, MA, USA. rejoa@channing.harvard.edu
Hoffman
E B
EB
Celedón
J C
JC
Litonjua
A A
AA
Milton
D K
DK
Gold
D R
DR
D000485:Allergens / Q000276:immunology; D001249:Asthma / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D004391:Dust / Q000276:immunology; D004731:Endotoxins / Q000276:immunology*; D004781:Environmental Exposure; D005260:Female; D006090:Gram-Negative Bacteria / Q000276:immunology; D006094:Gram-Positive Bacteria / Q000276:immunology; D006798:Housing; D006801:Humans; D006967:Hypersensitivity / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control; D008297:Male; D009112:Muramic Acids / Q000276:immunology
D000485:Allergens; D004391:Dust; D004731:Endotoxins; D009112:Muramic Acids
J Allergy Clin Immunol. 2005 Aug;116(2):431-7
16083802
Am J Ind Med. 2006 Apr;49(4):286-95
16550567
Am Ind Hyg Assoc J. 1997 Dec;58(12):861-7
9425646
Int Arch Allergy Immunol. 2003 Mar;130(3):180-92
12660422
Clin Exp Allergy. 2004 Mar;34(3):389-97
15005732
J Intern Med. 2007 May;261(5):412-7
17444880
Clin Exp Allergy. 2000 Feb;30(2):187-93
10651770
J Exp Med. 1955 Apr 1;101(4):421-36
14354110
J Allergy Clin Immunol. 2004 May;113(5):916-24
15131575
Am J Respir Crit Care Med. 1999 Jul;160(1):227-36
10390405
N Engl J Med. 2002 Sep 19;347(12):869-77
12239255
Am J Ind Med. 2006 Apr;49(4):296-300
16550568
J Environ Monit. 2004 Apr;6(4):300-4
15054538
J Exp Med. 2006 Dec 25;203(13):2853-63
17178920
Clin Exp Allergy. 2005 Mar;35(3):397-402
15784121
Clin Exp Allergy. 2000 Feb;30(2):201-8
10651772
Am J Respir Crit Care Med. 2001 Feb;163(2):322-8
11179100
J Allergy Clin Immunol. 2006 May;117(5):1082-9
16675336
Pathobiology. 2002-2003;70(5):255-9
12771505
J Exp Med. 2002 Dec 16;196(12):1645-51
12486107
Toxicology. 2000 Nov 2;152(1-3):25-30
11090936
J Allergy Clin Immunol. 2007 Jul;120(1):144-9
17507083
Pediatrics. 2004 Jul;114(1):13-8
15231902
Curr Opin Allergy Clin Immunol. 2004 Apr;4(2):113-7
15021064
J Allergy Clin Immunol. 2004 May;113(5):860-7
15131567
Environ Res. 1992 Apr;57(2):212-30
1568442
J Biol Chem. 1999 Jun 18;274(25):17406-9
10364168
J Exp Med. 2003 Feb 17;197(4):403-11
12591899
Environ Health Perspect. 2001 Aug;109(8):859-64
11564624
Int J Epidemiol. 1997 Feb;26(1):220-3
9126523
Am J Ind Med. 2006 Apr;49(4):301-6
16526062
J Allergy Clin Immunol. 2002 Nov;110(5):736-42
12417882
J Immunol. 1999 Jul 1;163(1):1-5
10384090
Int Arch Allergy Immunol. 2002 Oct;129(2):119-28
12403929
Am J Respir Crit Care Med. 2006 Aug 15;174(4):386-92
16614348
J Interferon Cytokine Res. 2004 Sep;24(9):543-52
15450130
J Allergy Clin Immunol. 2006 May;117(5):1067-73
16675334
Appl Environ Microbiol. 2004 Jan;70(1):262-7
14711650
Pediatr Allergy Immunol. 2008 Aug;19(5):455-65
18221461