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Endotoxin exposure, CD14 and wheeze among farmers: a gene–environment interaction
  1. Lidwien A M Smit1,
  2. Dick Heederik1,
  3. Gert Doekes1,
  4. Gerard H Koppelman2,
  5. Renske W B Bottema3,
  6. Dirkje S Postma4,
  7. Inge M Wouters1
  1. 1Institute for Risk Assessment Sciences, Division Environmental Epidemiology, Utrecht University, Utrecht, The Netherlands
  2. 2Department of Pediatric Pulmonology and Pediatric Allergology, Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
  3. 3Department of Pediatrics, Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
  4. 4Department of Pulmonology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
  1. Correspondence to Dr Lidwien Smit, Institute for Risk Assessment Sciences, Division Environmental Epidemiology, PO Box 80178, 3508 TD Utrecht, The Netherlands; l.a.smit{at}uu.nl

Abstract

Objectives Endotoxin-exposed workers are at an increased risk of non-atopic asthma and lung-function decline. Genetic variants may influence susceptibility to these effects. The objective of the present study was to assess whether the association between occupational endotoxin exposure and wheeze is modified by innate immunity gene variants.

Methods Twenty-four single nucleotide polymorphisms (SNPs) in CD14, Toll-like receptor 4 (TLR4), TLR2, MD2 and MyD88 were genotyped in 408 agricultural workers with spirometry and questionnaire data on asthma symptoms available. Personal airborne endotoxin exposure levels were estimated in 249 exposure measurements.

Results The association between endotoxin exposure and wheeze was modified by three CD14 SNPs: -260 C/T (rs2569190), -1247 T/C (rs2569191) and -1721 A/G (rs2915863), and one MD2 SNP (rs10808798 T/C). In individuals carrying the CD14 and MD2 major allele variants, the prevalence of wheeze increased with increasing endotoxin concentration, whereas this was the opposite in minor allele homozygotes. Interaction between endotoxin exposure and genotype was statistically significant under the best-fitting recessive model (p=0.05 to 0.006). Correction for multiple comparisons resulted in marginally significant p values for interaction (p<0.06) for CD14 -260 C/T and -1247 T/C, and for MD2 rs10808798 T/C. The CD14 SNPs appeared to modify associations between endotoxin exposure and forced expiratory volume in 1 s in a similar direction (p interaction=0.07 to 0.15).

Conclusions The association between occupational endotoxin exposure and wheeze in agricultural workers was significantly modified by genetic variants in CD14 and MD2. Our study suggests that carriers of the functional CD14/-260 C allele are more responsive to endotoxin exposure than T allele homozygotes.

  • Asthma
  • epidemiology
  • farming
  • gene–environment interaction
  • innate immunity
  • respiratory
  • genetic susceptibility
  • organic dusts

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Footnotes

  • Funding Funded by The Netherlands Asthma Foundation (Grant no 3.2.03.70). DSP received funding for research from AstraZeneca, GSK, Nycomed. Travel to ERS or ATS has been partially funded by Astra Zeneca, GSK, Chiesi, Nycomed.

  • Competing interests DSP has been consultant to AstraZeneca, Boehringer Ingelheim, Chiesi, GSK, Nycomed, TEVA. GHK has received a research grant from GSK (<€10 000, money to institution), and has spoken at an annual Dutch conference for Paediatricians on asthma organised by an independent committee (GSK; €1250, money to institution).

  • Ethics approval Ethics approval was provided by the University Medical Center Utrecht.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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