1. ¹London School of Hygiene and Tropical Medicine, London University, London, UK
2. ²Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
3. ³Medical Research Council Laboratories, Fajara, The Gambia
4. ⁴The National Eye Care Program, Banjul, The Gambia

Correspondence: Ms A Natividad, Clinical Research Unit, Infectious Tropical Disease Department, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK or Childhood Infection Group, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK. E-mail: angels.natividad-sancho@lshtm.ac.uk or angelsn@well.ox.ac.uk

Received 11 November 2004; Revised 14 January 2005; Accepted 14 January 2005; Published online 24 March 2005.

Abstract

Experimental evidence implicates interferon gamma (IFN) in protection from and resolution of chlamydial infection. Conversely, interleukin 10 (IL10) is associated with susceptibility and persistence of infection and pathology. We studied genetic variation within the IL10 and IFN loci in relation to the risk of developing severe complications of human ocular Chlamydia trachomatis infection. A total of 651 Gambian subjects with scarring trachoma, of whom 307 also had potentially blinding trichiasis and pair-matched controls with normal eyelids, were screened for associations between single-nucleotide polymorphisms (SNPs), SNP haplotypes and the risk of disease. MassEXTEND (Sequenom) and MALDI-TOF mass spectrometry were used for detection and analysis of SNPs and the programs PHASE and SNPHAP used to infer haplotypes from population genetic data. Multivariate conditional logistic regression analysis identified IL10 and IFN SNP haplotypes associated with increased risk of both trachomatous scarring and trichiasis. SNPs in putative IFN and IL10 regulatory regions lay within the disease-associated haplotypes. The IFN +874A allele, previously linked to lower IFN production, lies in the IFN risk haplotype and was more common among cases than controls, but not significantly so. The promoter IL10-1082G allele, previously associated with high IL10 expression, is in both susceptibility and resistance haplotypes.