Association of tumour necrosis factor alpha variants with the CF pulmonary phenotype.
BACKGROUND
The pulmonary phenotype in patients with cystic fibrosis (CF), even in those with the same CF transmembrane conductance regulator (CFTR) genotype, is variable and must therefore be influenced by secondary genetic factors as well as environmental factors. Possible candidate genes that modulate the CF lung phenotype may include proinflammatory cytokines. One such protein is tumour necrosis factor alpha (TNFalpha), a member of the immune system.


METHODS
Three polymorphic loci in the promoter (-851c/t, -308g/a, -238g/a) and one polymorphic locus in intron 1 (+691g ins/del) of the TNFalpha gene were typed by a single nucleotide primer extension assay in CF patients and healthy controls. Spirometric data and first age of infection with Pseudomonas aeruginosa were collected retrospectively from patients' medical records.


RESULTS
An association was found between the TNFalpha +691g ins/del polymorphic locus and severity of CF lung disease. Patients heterozygous for +691g ins and +691g del were more likely to have better pulmonary function (mean (SD) forced expiratory volume in 1 second (FEV1) 79.7 (12.8)% predicted) than patients homozygous for +691g ins (mean (SD) FEV1 67.5 (23.0)% predicted; p = 0.008, mean difference 12.2%, 95% CI 3.5 to 21.0). Also, patients heterozygous for +691g ins and +691g del were more likely to have an older first age of infection with P aeruginosa (mean (SD) 11.4 (6.0) years) than patients homozygous for +691g ins (mean (SD) 8.3 (4.6) years; p = 0.018, mean difference 3.1 years, 95% CI 0.5 to 5.6). An association was also found with the -851c/t polymorphic locus. In the group of patients with more severe FEV1% predicted, a higher proportion of patients were homozygous for the -851c allele than in the other group of patients (p = 0.04, likelihood ratio chi2, odds ratio = 2.4).


CONCLUSIONS
TNFalpha polymorphisms are associated with the severity of CF lung disease in Czech and Belgian patients with CF.
Yarden
J
J
Department for Human Genetics, KULeuven, Herestraat 49, O&N6, 3000 Leuven, Belgium.
Radojkovic
D
D
De Boeck
K
K
Macek
M
M
Zemkova
D
D
Vavrova
V
V
Vlietinck
R
R
Cassiman
J-J
JJ
Cuppens
H
H
D000293:Adolescent; D000704:Analysis of Variance; D002648:Child; D003550:Cystic Fibrosis / Q000235:genetics* / Q000503:physiopathology; D005260:Female; D005541:Forced Expiratory Volume / Q000235:genetics; D005838:Genotype; D006720:Homozygote; D006801:Humans; D008297:Male; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D011110:Polymorphism, Genetic / Q000235:genetics*; D011552:Pseudomonas Infections / Q000150:complications; D011550:Pseudomonas aeruginosa; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics*
D014409:Tumor Necrosis Factor-alpha