Genetic variation at the TNF locus and the risk of severe sequelae of ocular Chlamydia trachomatis infection in Gambians

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Abstract
Tumor necrosis factor (TNF) is thought to be a key mediator of the inflammatory and fibrotic response to Chlamydia trachomatis (Ct) infection. A large matched-pair case–control study investigated putative functional single nucleotide polymorphisms (SNPs) across the major histocompatibility complex (MHC) class III region, including TNF and its immediate neighbors nuclear factor of κ light polypeptide gene enhancer in B cells (IκBL), inhibitor like 1 and lymphotoxin alpha (LTA) in relation to the risk of scarring sequelae of ocular Ct infection. Haplotype and linkage disequilibrium analysis demonstrated two haplotypes, differing at position TNF-308, conferring an increased risk of trichiasis. The TNF-308A allele, and its bearing haplotype, correlated with increased TNF production in lymphocyte cultures stimulated with chlamydial elementary body antigen. Thus TNF-308A may determine directly, or be a marker of a high TNF producer phenotype associated with increased risk of sequelae of chlamydial infection. Multivariate analysis provided evidence for the presence of additional risk-associated variants near the TNF locus.