title: Scarring trachoma is associated with polymorphism in the tumor necrosis factor alpha (TNF-alpha) gene promoter and with elevated TNF-alpha levels in tear fluid.
abstract: Tumor necrosis factor alpha (TNF-alpha) may play a central role in the disease pathogenesis which occurs as a consequence of chlamydial infection. To investigate the importance of TNF-alpha gene promoter polymorphisms and TNF-alpha levels in tear fluid in scarring trachoma, a large matched-pair case-control study was performed in The Gambia. The -308A allele was present in a higher proportion of patients (28.4%) than controls (18.4%), with an increasing association for homozygotes (chi2 for trend, P = 0.032; allele frequency, 0.163 in patients and 0.099 in controls; chi2, P = 0.025). For the -238A allele, the association was similar but not significant. The disease association was highly significant when the number of either -308A or -238A sites in an individual was considered (P = 0.003). TNF-alpha promoter alleles are tightly linked to some HLA class I and II alleles, but multivariate analysis confirmed that the disease associations were independent of HLA, although a class I allele, A*6802, is also associated with disease. TNF-alpha was more frequently detected in tear samples from patients (27.6%) than from controls (15.9%), increasingly so for higher levels of detectable TNF-alpha (P = 0.015). Among patients, detectable TNF-alpha in tears was highly associated with the presence of ocular chlamydial infection (P < 0.001). The results indicate that TNF-alpha plays a major role in the tissue damage and scarring which occurs as a consequence of Chlamydia trachomatis infection.
authors.affiliation: Department of Clinical Sciences, London School of Hygiene and Tropical Medicine, United Kingdom. d.conway@lshtm.ac.uk
authors.forename: D J
authors.initials: DJ
authors.lastname: Conway
authors.forename: M J
authors.initials: MJ
authors.lastname: Holland
authors.forename: R L
authors.initials: RL
authors.lastname: Bailey
authors.forename: A E
authors.initials: AE
authors.lastname: Campbell
authors.forename: O S
authors.initials: OS
authors.lastname: Mahdi
authors.forename: R
authors.initials: R
authors.lastname: Jennings
authors.forename: E
authors.initials: E
authors.lastname: Mbena
authors.forename: D C
authors.initials: DC
authors.lastname: Mabey
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D002648:Child; D002690:Chlamydia Infections / Q000175:diagnosis; D002921:Cicatrix / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D011401:Promoter Regions, Genetic; D013666:Tears / Q000378:metabolism*; D014141:Trachoma / Q000209:etiology* / Q000235:genetics; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics*
chemical_list: D014409:Tumor Necrosis Factor-alpha