title: Functional polymorphisms in IL13 are protective against high Schistosoma mansoni infection intensity in a Brazilian population.
abstract: BACKGROUND
  IL-13 is a signature cytokine of the helper T cell type 2 (TH2) pathway which underlies host defense to helminthic infection and activates production of IgE in both parasitized populations and in urban settings after allergen exposure.
  
  
  RESULTS
  Two functional polymorphisms in IL13, rs1800925 (or c.1-1111C>T) and rs20541 (or R130Q) were previously found to be associated with Schistosoma hematobium infection intensity. They have not been thoroughly explored in S. mansoni-endemic populations, however, and were selected along with 5 tagging SNPs for genotyping in 812 individuals in 318 nuclear families from a schistosomiasis-endemic area of Conde, Bahia, in Brazil. Regression models using GEE to account for family membership and family-based quantitative transmission disequilibrium tests (QTDT) were used to evaluate associations with total serum IgE (tIgE) levels and S. mansoni fecal egg counts adjusted for non-genetic covariates. We identified a protective effect for the T allele at rs20541 (P = 0.005) against high S. mansoni egg counts, corroborated by QTDT (P = 0.014). Our findings also suggested evidence for protective effects for the T allele at rs1800925 and A allele at rs2066960 after GEE analysis only (P = 0.050, 0.0002).
  
  
  CONCLUSIONS
  The two functional variants in IL13 are protective against high S. mansoni egg counts. These markers showed no evidence of association with tIgE levels, unlike tIgE levels previously studied in non-parasitized or atopic study populations.
authors.affiliation: Department of Epidemiology, Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, Maryland, United States of America. audrey.grant@inserm.fr
authors.forename: Audrey V
authors.initials: AV
authors.lastname: Grant
authors.forename: Maria Ilma
authors.initials: MI
authors.lastname: Araujo
authors.forename: Eduardo Vieira
authors.initials: EV
authors.lastname: Ponte
authors.forename: Ricardo Riccio
authors.initials: RR
authors.lastname: Oliveira
authors.forename: Peisong
authors.initials: P
authors.lastname: Gao
authors.forename: Alvaro A
authors.initials: AA
authors.lastname: Cruz
authors.forename: Kathleen C
authors.initials: KC
authors.lastname: Barnes
authors.forename: Terri H
authors.initials: TH
authors.lastname: Beaty
mesh_terms: D000328:Adult; D000818:Animals; D001938:Brazil / Q000453:epidemiology; D019353:Endemic Diseases / Q000517:prevention & control; D005260:Female; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood; D018793:Interleukin-13 / Q000235:genetics*; D015810:Linkage Disequilibrium; D008297:Male; D020641:Polymorphism, Single Nucleotide; D012550:Schistosoma mansoni / Q000472:pathogenicity*; D012555:Schistosomiasis mansoni / Q000453:epidemiology / Q000235:genetics* / Q000276:immunology / Q000517:prevention & control*; D018418:Th2 Cells / Q000276:immunology
chemical_list: D018793:Interleukin-13; D007073:Immunoglobulin E