A study of the association between chronic superficial keratitis and polymorfisms in the upstream regulatory regions of DLA-DRB 1, DLA-DQB 1 and DLA-DQA1

BARRIENTOS, LAURA S.; ZAPATA, GUSTAVO; CRESPI, JULIAN A.; POSIK DIEGO M; DIAZ SILVINA; IT, VERONICA; PERAL GARCIA P; GIOVAMBATTISTA GUILLERMO

Salta

Congreso; XLII CONGRESO ARGENTINO DE GENETICA - III REUNION REGIONAL SAG - NOA; 2013

Canine chronic superficial keratitis (CSK) is an inflammatory corneal disease that leads to blindness if not treated. CSK occurs most frequently in the German Shepherd dog (GSDs). While the normal central cornea has little MHC class II expression, aberrant expression occurs in CSK, associated with secretion of gamma interferon by infiltrating CD4-expressing lymphocytes. Several evidences lend support to the hypothesis that CSK is an immune-mediated disease. Accordingly, to investigate the molecular genetic factors that may be associated to CSK development, upstream regulatory regions (URR) of DLA class II DLA-DRB, DLA-DQA and DLA-DQB genes were genotyped in 68 dogs, including 40 CSK animals. DNA direct-sequencing of the URR of these genes revealed two SNPs in the DLA-DRB1, two SNPs in the DLA-DQA1, six SNPs in the DLA-DQB1, and one indel in the DLA-DQB1 URRs. None new polymorphisms were observed. LD analysis allowed us to identify two blocks (r2 ≤ 45), with two DLA-DRB1 haplotypes and five DLA-DQB1 haplotypes, respectively; the remaining two DQB haplotypes were detected for the first time in GSDs. The association between CSK and DLA-URR alleles/haplotypes, evaluated using a classical case-control study design, showed a significant association between DQB1*-154 [C/T] (p = 0.014), suggesting that T variant may increase the risk for developing CSK disease (OR = 2.93, 95% CI = 1.18-7.54). When haplotype associations were performed, the URR-DQB*TATC haplotype was significantly associated with CSK (p = 0.014), increasing over two folds the risk of develop this disease (OR= 2.87, 95%, CI = 1.16-7.37). The obtained results showed that dogs that carried homozygote genotype at DRB1*69 [C/T] had a risk for developing CSK disease over four times than those dogs with heterozygote genotypes. In addition, a suggestive association between homozygote genotype at DRB1*-128 [C/T] and risk of CSK developing was observed (p = 0.09; OR = 3.01, 95% CI = 0.86 - 11.46). This genetic association also supports the previous clinical, histological and pharmacological studies of CSK as an immune-mediated disease and could potentially be used to identify susceptibly animals that require monitoring for early pathological changes to reduce blindness.