β-Defensin 1 haplotype associated with postoperative endophthalmitis

Endophthalmitis is a rare but sight-threatening complication of intraocular surgery. β-Defensins are antimicrobial peptides that appear to be important components of the ocular immune response. We propose that variation in defensin genes may alter susceptibility to endophthalmitis.

Post-cataract endophthalmitis patients (n = 28) and post-cataract controls (n = 75) were recruited and DNA samples extracted. The β-defensin 1 gene (DEFB1) was screened for single-nucleotide polymorphisms (SNPs) using bidirectional sequencing. Case-control statistical assessment was undertaken for both the individual polymorphic loci observed and combined haplotypes using PHASE software.

We identified 19 SNPs and observed strong linkage disequilibrium within the gene. We found that the three-SNP haplotype -688C/-44C/-20A was associated strongly with endophthalmitis [odds ratio (OR) = 8.88 (1.74, 45.42), corrected p = 0.0095]. Furthermore, we uncovered several trends, including increased prevalence of the -44CC genotype in the endophthalmitis group.

We have shown previously that the -44CC SNP genotype was present in a single case of bilateral endophthalmitis. In this study, we found this genotype to be more common in the endophthalmitis group and a mini-haplotype including this SNP was associated strongly with endophthalmitis. There is functional evidence that this genetic profile decreases transcription of the β-defensin 1 peptide and could therefore reduce the innate ocular immune defence.