Haplotype analysis finds linkage disequilibrium in the IL-12 gene in patients with HCV.

HCV is a major cause of liver disease worldwide. IL-12 plays an essential role in the balance of T helper 1 (Th1) differentiation versus a T helper 2 (Th2) driven response from its naïve precursor. Linkage disequilibrium measures the degree to which alleles at two loci are associated and the non-random associations between alleles at two loci. Haplotypes of the three IL-12B loci studied were determined in the patient cases and the normal healthy control subjects. The frequency of the 12 possible IL-12B haplotypes on the 3 loci was determined in subjects heterozygous at only one of the loci within the studied haplotype. Haplotype frequencies were compared between the patient groups and controls (n = 49) to determine if any preferential combination of markers occurred using chi-squared and applying the Bonferroni correction. 45 HCV RNA negative patients; 88 HCV RNA positive patients; and 15 uninfected cases at high risk of HCV infection (EU) were studied. The haplotype "C" SNP of the 3'UTR with the "E" 4 bp deletion of the intron 4 region was in linkage disequilibrium (χ(2)  = 45.15, P < 0.001, 95% CL). The haplotype analysis of the insertion allele of the promoter with the deletion allele of the intron 4("E") IL-12B polymorphism showed linkage disequilibrium (χ(2)  = 5.64, P = 0.02). Linkage disequilibrium of polymorphisms is reported in the IL-12 gene in patients with HCV infection and contributes to the understanding of patient genotype and expected production of IL-12, responding to infection.