The aim of this work was to investigate single-nucleotide polymorphisms (SNPs) in multiple genes on chromosome 6p in corneal transplant recipients known to be at increased risk of failure through immunologic rejection (ie, "high-risk" corneal transplants). Tumor necrosis factor alpha (TNF-α) is a key immunoregulatory cytokine in the ocular environment, interacting with a variety of factors in a synergistic way and playing a crucial role in many stages of the inflammatory response. Vascular endothelial growth factor (VEGF) is one of the most important angiogenic factors, supporting both hemangiogenesis and lymphangiogenesis, both key in transplant tolerance and rejection. Interleukin-17 (IL-17) is a multifunctional cytokine produced by T-helper 17 cells, exerting specific effector functions during an immune response. Association of SNPs in all 3 genes with corneal transplant outcome was therefore investigated.
Three hundred five corneal transplant recipients were followed for 3 years, and episodes of allograft rejection were recorded. With the use of patient DNA, 6 SNPs of 3 different genes on chromosome 6p were investigated. The TNF-α promoter SNP -308 G/A (rs1800629) was analyzed with the use of induced heteroduplex generation; 2 VEGF-A functional variants were analyzed, -2578 (rs699947) C/A and -1154 (rs1570360) G/A, with the use of Taqman genotyping assays; and 3 nonsynonymous IL-17F SNPs in exon 3 (negative strand), (rs2397084) A/G, (rs11465553) G/A, and (rs763780) A/G, were investigated with the use of direct sequencing. Haplotypes were inferred with the use of PHASE using positive strand alleles, and exact measures of association were determined with the use of Mid-P exact chi-square.
Six common haplotypes were inferred, with the haplotype TNF-α (rs1800629), VEGF-A (rs699947), (rs1570360), IL-17F (rs763780), (rs11465553), and (rs2397084) ACGTCT having a significant association with corneal transplant rejection (odds ratio, 1.78; 95% confidence interval, 1.01-3.11; P = .04).
The results suggest that patients carrying a combination of SNPs for TNF-α, VEGF-A, and IL-17F of ACGTCT haplotype may have an increased risk of corneal allograft rejection compared with patients carrying other haplotypes.