Interferon-stimulated gene 15 in hepatitis B-related liver diseases

This study investigates the association of Interferon-stimulated gene 15 (ISG15) polymorphisms, ISG15 serum levels and expression with HBV-related liver diseases. The ISG15 promoter and the two exons of the gene were screened for polymorphisms in 766 HBV-infected patients and in 223 controls. Soluble ISG15 levels were measured by ELISA. ISG15 mRNA expression was quantified by qRT-PCR in 36 tumor and adjacent non-tumor tissues. The exon 2 allele rs1921A was found associated with decreased progression of HBV-related liver diseases (LC vs. CHB: OR = 0.6, 95%CI = 0.4-0.8, adjusted P = 0.003; HCC vs. CHB: OR = 0.6, 95%CI = 0.4-0.9, adjusted P = 0.005). The rs1921AA genotype was associated with low levels of AST, ALT and total bilirubin, but with high prothrombin levels (P < 0.05). ISG15 serum levels were higher among HBV patients compared to controls (P < 0.0001) and positively associated with HBV-related liver diseases, with highest levels among LC patients. ISG15 levels were correlated with HBV-DNA loads (P = 0.001). In non-tumor tissues from HCC patients, ISG15 mRNA expression was increased in HBV compared to non-HBV infection (P = 0.016). The ISG15 rs1921 variant and ISG15 expression are associated with HBV-related liver diseases. Taken together, ISG15 appears to be a proviral factor involved in HBV replication and triggering progression of HBV-related liver diseases.