title: The Gene Polymorphism of IL-17 G-152A is Associated with Increased Colonization of Streptococcus pneumoniae in Young Finnish Children.
abstract: BACKGROUND
  Streptococcus pneumoniae is a common respiratory pathogen, and up to 50% of children acquire S. pneumoniae in their nasopharynx during the first 12 months of life. The cytokine interleukin-17A (IL-17A) plays an important role in host defense against extracellular bacterial pathogens. We investigated the effect of IL-17 G-152A polymorphism on pneumococcal colonization in children.
  
  
  METHODS
  Nasopharyngeal swabs and blood samples were collected from healthy Finnish children at 2.6 (N = 405), 13 (N = 198) and 24 (N = 176) months of age. Of them, 160 had both nasopharyngeal swabs and blood samples at each time point. The semiquantitative culture method was used for bacterial culture, Sequenom iPlex Gold System for IL-17A genotyping and Luminex 200 for serum IL-17A determination.
  
  
  RESULTS
  The frequency of IL-17 G-152A genotypes G/G, G/A and A/A was 36%, 45% and 19% in 405 studied subjects, respectively. The colonization rates of S. pneumoniae increased from 10% at 2.6 months to 33% at 24 months of age. Significantly higher pneumococcal colonization was found in subjects with A/A genotype at 13 and 24 months of age compared with those of G/G (RR, 2.30; P = 0.02; RR, 1.91, P = 0.03). This genotype was associated with lower levels of serum IL-17A, and only 6% of subjects with A/A had detectable serum IL-17A compared with 75% and 33% of subjects with G/G and G/A (P < 0.001 and P < 0.01), respectively.
  
  
  CONCLUSIONS
  Our results indicate that IL-17 G-152A is associated with increased colonization rate of S. pneumoniae in young children, suggesting that IL-17A plays an important role in protection against pneumococcal colonization.
authors.affiliation: From the *Department of Infectious Disease Surveillance and Control, National Institute for Health and Welfare, Turku, Finland; †Department of Pediatrics, Turku University Hospital, Turku, Finland; ‡Turku Institute for Child and Youth Research, §The immunogenetics Laboratory, University of Turku, Finland; ¶Department of Clinical Microbiology, University of Eastern Finland, Kuopio, Finland; and ‖Department of Medical Microbiology and Immunology, University of Turku, Finland.
authors.forename: Juho
authors.initials: J
authors.lastname: Vuononvirta
authors.forename: Ville
authors.initials: V
authors.lastname: Peltola
authors.forename: Jorma
authors.initials: J
authors.lastname: Ilonen
authors.forename: Jussi
authors.initials: J
authors.lastname: Mertsola
authors.forename: Qiushui
authors.initials: Q
authors.lastname: He
mesh_terms: D001431:Bacteriological Techniques; D001769:Blood / Q000276:immunology; D002353:Carrier State / Q000453:epidemiology* / Q000276:immunology; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D005387:Finland / Q000453:epidemiology; D060005:Genotyping Techniques; D006801:Humans; D007223:Infant; D020381:Interleukin-17 / Q000235:genetics*; D008297:Male; D009305:Nasopharynx / Q000382:microbiology; D011008:Pneumococcal Infections / Q000453:epidemiology* / Q000276:immunology; D020641:Polymorphism, Single Nucleotide; D013296:Streptococcus pneumoniae / Q000276:immunology* / Q000302:isolation & purification*
chemical_list: C508717:IL17A protein, human; D020381:Interleukin-17