title: Toll-like receptor 9 (TLR9) polymorphism associated with symptomatic malaria: a cohort study.
abstract: BACKGROUND
  In areas mesoendemic for malaria transmission, symptomatic individuals play a significant role as reservoirs for malaria infection. Understanding the pathogenesis of symptomatic malaria is important in devising tools for augmenting malaria control. In this study, the effect of TLR9 polymorphisms on susceptibility to symptomatic malaria was investigated among Ghanaian children.
  
  
  METHODS
  Four hundred and twenty nine (429) healthy Ghanaian children, aged three to eleven years (3-11 years), were enrolled into a cohort study and actively followed up for symptomatic malaria for one year. Four TLR9 single nucleotide polymorphisms (SNPs) namely: rs187084 (C-1486 T), rs5743836(C-1237 T), rs352139 (G + 1174A) and rs352140 (G + 2848A) were genotyped by direct sequencing, and their attributable and relative risks for symptomatic malaria determined. TLR9 haplotypes were inferred using the PHASE software and analysed for the risk of symptomatic malaria. A luciferase assay was performed to investigate whether the TLR9 haplotypes influence TLR9 promoter activity.
  
  
  RESULTS
  The rs352139 GG genotype showed a significantly increased relative risk of 4.8 for symptomatic malaria (P = 0.0024) and a higher mean parasitaemia (P = 0.04). Conversely, the rs352140 GG genotype showed a significantly reduced relative risk of 0.34 (P = 0.048). TLR9 haplotypes analyses showed that TTAG haplotype was significantly associated with reduced relative risk of 0.2 for symptomatic malaria (P = 4×10⁻⁶) and a lower mean parasitaemia (0.007), while CTGA haplotype had an increased relative risk of 3.3 (P = 0.005). Functional luciferase reporter gene expression assay revealed that the TTA haplotype had a significantly higher promoter activity than the CCG, CTG and TCG haplotypes.
  
  
  CONCLUSIONS
  Taken together, these findings indicate a significant association of TLR9 gene polymorphisms with symptomatic malaria among Ghanaian children in Dangme-West district.
authors.affiliation: Department of Immunogenetics, Institute of Tropical Medicine-NEKKEN and Global COE Program, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan.
authors.forename: Ahmeddin H
authors.initials: AH
authors.lastname: Omar
authors.forename: Michio
authors.initials: M
authors.lastname: Yasunami
authors.forename: Akiko
authors.initials: A
authors.lastname: Yamazaki
authors.forename: Hiroki
authors.initials: H
authors.lastname: Shibata
authors.forename: Michael F
authors.initials: MF
authors.lastname: Ofori
authors.forename: Bartholomew D
authors.initials: BD
authors.lastname: Akanmori
authors.forename: Mohammed Nasir
authors.initials: MN
authors.lastname: Shuaibu
authors.forename: Mihoko
authors.initials: M
authors.lastname: Kikuchi
authors.forename: Kenji
authors.initials: K
authors.lastname: Hirayama
mesh_terms: D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D020022:Genetic Predisposition to Disease; D005838:Genotype; D005869:Ghana; D006239:Haplotypes; D006801:Humans; D008137:Longitudinal Studies; D008288:Malaria / Q000235:genetics* / Q000276:immunology*; D020641:Polymorphism, Single Nucleotide; D017422:Sequence Analysis, DNA; D051217:Toll-Like Receptor 9 / Q000235:genetics*
chemical_list: C495371:TLR9 protein, human; D051217:Toll-Like Receptor 9