title: Haptoglobin and sickle cell polymorphisms and risk of active trachoma in Gambian children.
abstract: BACKGROUND
  Susceptibility and resistance to trachoma, the leading infectious cause of blindness, have been associated with a range of host genetic factors. In vitro studies of the causative organism, Chlamydia trachomatis, demonstrate that iron availability regulates its growth, suggesting that host genes involved in regulating iron status and/or availability may modulate the risk of trachoma. The objective was to investigate whether haptoglobin (Hp) haplotypes constructed from the functional polymorphism (Hp1/Hp2) plus the functional promoter SNPs -61A-C (rs5471) and -101C-G (rs5470), or sickle cell trait (HbAS, rs334) were associated with risk of active trachoma when stratified by age and sex, in rural Gambian children.
  
  
  RESULTS
  In two cross sectional surveys of children aged 6-78 months (n = 836), the prevalence of the clinical signs of active trachoma was 21.4%. Within boys, haplotype E (-101G, -61A, Hp1), containing the variant allele of the -101C-G promoter SNP, was associated with a two-fold increased risk of active trachoma (OR = 2.0 [1.17-3.44]). Within girls, an opposite association was non-significant (OR = 0.58 [0.32-1.04]; P = 0.07) and the interaction by sex was statistically significant (P = 0.001). There was no association between trachoma and HbAS.
  
  
  CONCLUSIONS
  These data indicate that genetic variation in Hp may affect susceptibility to active trachoma differentially by sex in The Gambia.
authors.affiliation: MRC International Nutrition Group, London School of Hygiene & Tropical Medicine, London, UK.
authors.forename: Mathilde
authors.initials: M
authors.lastname: Savy
authors.forename: Branwen J
authors.initials: BJ
authors.lastname: Hennig
authors.forename: Conor P
authors.initials: CP
authors.lastname: Doherty
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Fulford
authors.forename: Robin
authors.initials: R
authors.lastname: Bailey
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Holland
authors.forename: Giorgio
authors.initials: G
authors.lastname: Sirugo
authors.forename: Kirk A
authors.initials: KA
authors.lastname: Rockett
authors.forename: Dominic P
authors.initials: DP
authors.lastname: Kwiatkowski
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Prentice
authors.forename: Sharon E
authors.initials: SE
authors.lastname: Cox
mesh_terms: D000755:Anemia, Sickle Cell / Q000235:genetics*; D001483:Base Sequence; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D017931:DNA Primers; D005260:Female; D020022:Genetic Predisposition to Disease; D006239:Haplotypes; D006242:Haptoglobins / Q000235:genetics*; D006801:Humans; D007223:Infant; D008297:Male; D016133:Polymerase Chain Reaction; D020641:Polymorphism, Single Nucleotide; D012307:Risk Factors; D012424:Rural Population; D014141:Trachoma / Q000235:genetics*
chemical_list: D017931:DNA Primers; D006242:Haptoglobins