['IL15 is an essential cytokine in both innate and adaptive immune response against hepatitis C virus (HCV) infection. The aim was to analyze whether IL15 rs10833 is associated with liver disease severity and response to pegylated-interferon-alpha plus ribavirin (pegIFN-alpha/RBV) therapy in human immunodeficiency virus (HIV)-/HCV-co-infected patients.', 'A retrospective study was performed in 315 patients who started pegIFN-alpha/RBV therapy. Liver fibrosis stage was characterized in 286 patients. IL15 rs10833 and IL28B rs12980275 were genotyped by GoldenGate. The primary outcomes were: (a) advanced liver fibrosis evaluated by liver biopsy (F3-F4) or transient elastography (liver stiffness values ≥9.5 Kpa); (b) sustained virological response (SVR). The secondary outcome variable was the levels of serum biomarkers of inflammation.', 'Patients with rs10833 AA genotype had increased odds of having advanced fibrosis (adjusted odds ratio (aOR) = 2.30; P = 0.019), particularly in males (aOR = 2.24; P = 0.040), patients with HCV serum viral load (HCV-RNA) <500 000 IU/ml (aOR = 5.14; P = 0.018) and patients with IL28B rs12980275 AG/GG genotypes (aOR = 2.51; P = 0.046). Moreover, rs10833 AA genotype was significantly associated with higher levels of hepatocyte growth factor (adjusted arithmetic mean ratio (aAMR) = 1.50; P = 0.016), sICAM-1 (aAMR = 1.57; P = 0.025) and sVCAM-1 (aAMR = 1.56; P = 0.007). Finally, patients with rs10833 AA genotype had increased odds of achieving SVR (aOR = 3.12; P = 0.006), particularly in males (aOR = 3.69; P = 0.005), GT1/4 patients (aOR = 3.59; P = 0.006), patients with advanced fibrosis (aOR = 4.64; P = 0.021), HCV-RNA ≥500 000 IU/ml (aOR = 3.92; P = 0.007) and patients with IL28B rs12980275 AG/GG genotype (aOR = 2.98; P = 0.041).'] Is iL15 polymorphism associated with advanced fibrosis , inflammation-related biomarkers and virological response in human immunodeficiency virus/hepatitis C virus coinfection?