AIM To investigate the impact of IL28 B and OAS gene polymorphisms on interferon treatment responses in children with chronic hepatitis B.METHODS We enrolled 52 children(between the ages of 4 and 18) with hepatitis B e antigen-negative chronic hepatitis B(CHB), who were treated with pegylated interferon alfa for 48 wk. Single nucleotide polymorphisms in the OAS1(rs1131476), OAS2(rs1293747),OAS3(rs2072136), OASL(rs10849829) and IL28B(rs12979860, rs12980275 and rs8099917) genes were studied to examine their associations with responses to IFN treatment in paediatric patients. We adopted two criteria for the therapeutic response, achieving an hepatitis B virus(HBV) DNA level < 2000 IU/m L and normalization of ALT activity(< 40 IU/L). To perform the analyses, we compared the patients in terms of achieving a partial response(PR) and a complete response(CR) upon measurement at the 24-wk posttreatment follow-up. RESULTS The PR and CR rates were 80.8% and 42.3%, respectively. Factors such as age, gender and liver histology had no impact on the type of response(partial or complete). A statistically significant relationship between higher baseline HBV DNA and ALT activity levels and lower rates of PR and CR was shown(P < 0.05). The allele association analysis revealed that only the IL-28 B rs12979860(C vs T) and IL28 B rs12980275(A vs G) markers significantly affected the achievement of PR(P = 0.021, OR = 3.3, 95%CI: 1.2-9.2 and P = 0.014, OR = 3.7, 95%CI: 1.3-10.1, respectively). However, in the genotype analysis, only IL-28 B rs12980275 was significantly associated with PR(AA vs AG-GG, P = 0.014, OR = 10.9, 95%CI: 1.3-93.9). The association analysis for CR showed that the TT genotype of IL28 B rs12979860 was present only in the no-CR group(P = 0.033) and the AA genotype of OASL rs10849829 was significantly more frequent in the noCR group(P = 0.044, OR = 0.26, 95%CI: 0.07-0.88). The haplotype analysis revealed significant associations between PR and CR and OAS haplotype(P = 0.0002 and P = 0.001, respectively), but no association with IL28 B haplotype was observed.CONCLUSION IL28 B and OAS polymorphisms are associated with different clinical outcomes in CHB children treated with interferon. AIM To investigate the impact of IL28 B and OAS gene polymorphisms on interferon treatment responses in children with chronic hepatitis B. METHODS We enrolled 52 children (between ages 4 and 18) with hepatitis B e antigen-negative chronic hepatitis B (CHB) , who were treated with pegylated interferon alfa for 48 wk. Single nucleotide polymorphisms in the OAS1 (rs1131476), OAS2 (rs1293747), OAS3 (rs2072136), OASL (rs10849829) and IL28B (rs12979860, rs12980275 and rs8099917) genes were studied to examine we adopted two criteria for the therapeutic response, achieving an hepatitis B virus (HBV) DNA level <2000 IU / m L and normalization of ALT activity (<40 IU / L). To perform the analyzes, we compared the patients in terms of achieving a partial response (PR) and a complete response (CR) upon measurement at the 24-wk posttreatment follow-up. RESULTS The PR and CR rates were 80.8% and 42.3% respectively. Factors such as ag e, gender and liver histology had no impact on the type of response (partial or complete). A statistically significant relationship between higher baseline HBV DNA and ALT activity levels and lower rates of PR and CR was shown (P <0.05). The allele association analysis revealed that only the IL-28 B rs12979860 (C vs T) and IL28 B rs12980275 (A vs G) markers were significantly affected the achievement of PR (P = 0.021, OR = 3.3, 95% CI: 1.2-9.2 and P = 0.014, OR = 3.7, 95% CI: 1.3-10.1, respectively). However, in the genotype analysis, only IL-28 B rs12980275 was significantly associated with PR (AA vs AG- GG, , 95% CI: 1.3-93.9) The association analysis for CR showed that the TT genotype of IL28 B rs12979860 was present only in the no-CR group (P = 0.033) and the AA genotype of OASL rs 10849829 was significantly more frequent in the nolot group (P = 0.044, OR = 0.26, 95% CI: 0.07-0.88). The haplotype analysis specifically resected between PR and CR and OAS haplotype (P = 0.0002 and P = 0.001, respectively), but no association with IL28 B haplotype was observed. CONCLUSION IL28 B and OAS polymorphisms are associated with different clinical outcomes in CHB children treated with interferon.