Abstract
Purpose:
To replicate the associations of single nucleotide polymorphisms (SNPs) in interleukin-6 (IL6) gene with the susceptibility of keratitis in a Southern Indian population that was previously associated in a Caucasian population
Methods:
The study included patients with keratitis (n=168) and unaffected controls from the same ethnicity (n=188) who presented to the cornea and contact lens clinic at L. V. Prasad Eye Institute in Southern India between May 2010 and February 2012. DNA was extracted from the peripheral blood of these subjects using an automated extraction machine (MagNA Pure LC, Roche Diagnostics). Two SNPs in IL6 (rs1800795 and rs1800797) were screened by customized genotyping using the goldengate assay (Illumina Inc.) following manufacturer's guidelines. Allele and genotype frequencies were analyzed by the gene counting method and haplotypes were generated with the Haploview software that uses an EM algorithm. The test of statistical significance was set at p=0.05.
Results:
There was no departure from Hardy Weinberg equilibrium for both the SNPs in the normal controls (p>0.05). There were no significant differences in the minor allele frequencies between the cases and controls for the rs1800795 (p=0.208, OR=1.14, 95% CI, 0.74-1.75) and rs1800797 (p=0.562, OR=1.32, 95%CI, 0.85-2.05) SNPs. Further categorization of the cases based on the diagnosis of inflammation and infection did not alter these results. While there was a strong linkage disequilibrium between these two SNPs (D' = 0.978 and r2=0.917), haplotype analysis with the major (C-C; p=0.52, OR=1.15, 95% CI, 0.75-1.75) and minor (T-G; p=0.227, OR=0.76, 95% CI, 0.48-1.19) haplotypes did not reveal any significant association
Conclusions:
The present study could not replicate the association of the two IL6 SNPs in the Indian cohort despite having an adequate power (>80%). This could be attributed either to the ethnic diversity between the two populations or the involvement of other SNPs in the IL6 gene.
Keywords: 480 cornea: basic science •
557 inflammation •
539 genetics