The association of Interleukin 8 gene SNP with severe inflammatory complications in contact lens wearers experiencing Acanthamoeba Keratitis

Nicole Carnt, Chi N Ignatius Pang, Kathryn P Burdon, Virginia L Calder, John K G Dart, Dinesh Subedi, Alison J Hardcastle

Research output: Contribution to conferenceAbstract


Purpose : Over a third of patients with Acanthamoeba keratitis (AK) experience severe inflammatory complications (SICs) thought to be unrelated to the infective process. This study aimed to determine if some contact lens (CL) wearers with AK were predisposed to SICs due to variations in key immune genes.

Methods : CL wearers with AK attending Moorfields Eye Hospital for diagnosis and/or ongoing treatment were recruited prospectively between April 2013 and October 2014. Clinical data was collected using the REDCap database platform (Vanderbilt University, TN,USA). SICs were defined as scleritis and/or stromal ring infiltrate. Genomic DNA was collected by a cheek swab (FLOQswabs, Copan Diagnostics,CA,USA ) or a sputum kit (DNAGenotek, ON, CA or DNAgard, Biomatricia, CA, USA). DNA was extracted and processed with an Illumina Low Input Custom Amplicon assay (Illumina Corp, CA, USA) of 69 SNP targets across 19 genes using the Illumina MiSeq platform. The MiSeq reporter software generated variant calling files (.vcf) for each sample using BWA-MEM for read alignment and GATK for variant calling. The files were merged in vcftools software suite, accounting for missing values and tested for association analysis in PLINK. Covariates included clinical predictors of SIC: steroids pre-diagnosis and Herpes Simplex Keratitis (HSK) misdiagnosis along with sex and age.

Results : Genomic DNA was obtained and analyzed for 105 cases of AK, 40 (38%) of whom experienced SICs. A SNP in the interleukin 8 (IL-8) gene was significantly associated with protection from SICs (chr4: rs11266474 OR 0.3, p=0.005) after adjusting for age, sex, steroids pre-diagnosis and HSK misdiagnosis. The average age at the time of presentation for all AK cases was 36.9±15.5 years, and there was no difference in age between those with SICs compared to those without (38.7±15.6 compared to 36.0±15.5, p=0.19). Likewise, there was no difference in sex between the two groups (Females: 23/43, 53% vs 42/76, 55%, p=0.85).

Conclusions : The current study identifies a biologically relevant gene variation in AK patients with SICs; IL-8 is associated with a strong neutrophil response in the cornea in AK. Further work is needed but this data confirms that genetically screening patients who present with keratitis to predict severity and assist in the management of the disease, is viable.
Original languageEnglish
Number of pages1
Publication statusPublished - Jun 2020

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