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Vitamin D-related gene polymorphism predict treatment response to pegylated interferon-based therapy in Thai chronic
Kessarin Thanapirom1,2, Sirinporn Suksawatamnuay1,2, Wattana Sukeepaisarnjaroen3
1Divisions of Gastroenterology, Department of Medicine, Faculty of Medicine, Chulalongkorn University, King Chulalongkorn Memorial Hospital, Thai Red Cross Society, No. 1873 Rama IV road, Pathumwan District, Bangkok, 10330, Thailand.
Background:
Patients with chronic hepatitis C (HCV) infection have high prevalence of vitamin D deficiency. Genome-wide association study data has showed that several genetic variants within vitamin D cascade affect vitamin D function. This study aimed to determine whether genetic polymorphisms of genes in the vitamin D pathway are associated with treatment responses to pegylated interferon (PEG-IFN)-based therapy in patients with chronic HCV infection.
Methods:
The study included 623 Thai patients from 2 university hospitals diagnosed with chronic HCV infection who were treated with a PEG-IFN and ribavirin. Patients were genotyped for functional variants on vitamin D synthetic pathway including GC (rs4588, rs7041, rs22020, rs2282679), CYP2R1 (rs2060793, rs12794714), CYP27B1 (rs10877012), and DHCR7 (rs12785878). Pre-treatment predictors of sustained virologic response (SVR) at 24 weeks following discontinuation of therapy were identified using a logistic regression analysis.
Results:
SVR was achieved by 60.5% of patients (52.9% with HCV genotype 1; 66.7% with HCV non-genotype 1). In 44.6% of HCV genotype 1-infected patients, only the variant rs12785878 in the DHCR7 locus was significantly associated with an SVR. HCV genotype 1 patients who had DHCR7 rs12785878 GT/TT had a higher rate of SVR than those with the GG allele (59.7% vs. 43.4%, P = 0.03), but in HCV non-genotype 1-infected patients, the SVR rate did not differ between the two groups (63.3% and 59.1% for GT/TT and GG allele, P = 0.54). By multivariate analysis, liver fibrosis stage 0-1 (OR = 5.00; 95% CI, 2.02-12.37; P < 0.001), and DHCR7 rs12785878 GT/TT allele (OR = 2.69; 95% CI, 1.03-7.05; P = 0.04) were independent pre-treatment predictors of SVR following PEG-IFN-based therapy in HCV genotype 1 patients. Baseline HCV RNA < 400,000 IU/ml (OR = 1.96; 95% CI, 1.13-3.39; P = 0.02) was the only independent predictor of SVR in HCV non-genotype 1 patients. The polymorphisms of GC, CYP2R1 and CYP27B1 were not associated with treatment outcome even in genotype 1 or non-genotype 1 HCV infection.
Conclusion:
The DHCR7 polymorphism may be a pre-treatment predictive marker for response to PEG-IFN-based therapy in chronic HCV genotype 1 infection.