Background & AimsHepatitis C virus (HCV) induces chronic infection in 50% to 80% of infected persons; approximately 50% of these do not respond to therapy. We performed a genome-wide association study to screen for host genetic determinants of HCV persistence and response to therapy.MethodsThe analysis included 1362 individuals: 1015 with chronic hepatitis C and 347 who spontaneously cleared the virus (448 were coinfected with human immunodeficiency virus [HIV]). Responses to pegylated interferon alfa and ribavirin were assessed in 465 individuals. Associations between more than 500,000 single nucleotide polymorphisms (SNPs) and outcomes were assessed by multivariate logistic regression.ResultsChronic hepatitis C was associated with SNPs in the IL28B locus, which encodes the antiviral cytokine interferon lambda. The rs8099917 minor allele was associated with progression to chronic HCV infection (odds ratio [OR], 2.31; 95% confidence interval [CI], 1.74–3.06; P = 6.07 × 10−9). The association was observed in HCV mono-infected (OR, 2.49; 95% CI, 1.64–3.79; P = 1.96 × 10−5) and HCV/HIV coinfected individuals (OR, 2.16; 95% CI, 1.47–3.18; P = 8.24 × 10−5). rs8099917 was also associated with failure to respond to therapy (OR, 5.19; 95% CI, 2.90–9.30; P = 3.11 × 10−8), with the strongest effects in patients with HCV genotype 1 or 4. This risk allele was identified in 24% of individuals with spontaneous HCV clearance, 32% of chronically infected patients who responded to therapy, and 58% who did not respond (P = 3.2 × 10−10). Resequencing of IL28B identified distinct haplotypes that were associated with the clinical phenotype.ConclusionsThe association of the IL28B locus with natural and treatment-associated control of HCV indicates the importance of innate immunity and interferon lambda in the pathogenesis of HCV infection. Hepatitis C virus (HCV) induces chronic infection in 50% to 80% of infected persons; approximately 50% of these do not respond to therapy. We performed a genome-wide association study to screen for host genetic determinants of HCV persistence and response to therapy. The analysis included 1362 individuals: 1015 with chronic hepatitis C and 347 who spontaneously cleared the virus (448 were coinfected with human immunodeficiency virus [HIV]). Responses to pegylated interferon alfa and ribavirin were assessed in 465 individuals. Associations between more than 500,000 single nucleotide polymorphisms (SNPs) and outcomes were assessed by multivariate logistic regression. Chronic hepatitis C was associated with SNPs in the IL28B locus, which encodes the antiviral cytokine interferon lambda. The rs8099917 minor allele was associated with progression to chronic HCV infection (odds ratio [OR], 2.31; 95% confidence interval [CI], 1.74–3.06; P = 6.07 × 10−9). The association was observed in HCV mono-infected (OR, 2.49; 95% CI, 1.64–3.79; P = 1.96 × 10−5) and HCV/HIV coinfected individuals (OR, 2.16; 95% CI, 1.47–3.18; P = 8.24 × 10−5). rs8099917 was also associated with failure to respond to therapy (OR, 5.19; 95% CI, 2.90–9.30; P = 3.11 × 10−8), with the strongest effects in patients with HCV genotype 1 or 4. This risk allele was identified in 24% of individuals with spontaneous HCV clearance, 32% of chronically infected patients who responded to therapy, and 58% who did not respond (P = 3.2 × 10−10). Resequencing of IL28B identified distinct haplotypes that were associated with the clinical phenotype. The association of the IL28B locus with natural and treatment-associated control of HCV indicates the importance of innate immunity and interferon lambda in the pathogenesis of HCV infection.