OBJECTIVE:: Multiple viral and host factors are related to the treatment response to pegylated-interferon (Peg-IFN) and ribavirin (RBV) combination therapy; however, the clinical relevance and relationship of these factors have not yet been fully evaluated.

METHODS:: We studied 168 patients with chronic hepatitis C who received Peg-IFN and RBV combination therapy. Gene expression profiles in the livers of 91 patients were analyzed using an Affymetrix genechip. The expression of interferon-stimulated genes (ISGs) was evaluated in all samples by real-time PCR. Genetic variation in interleukin 28B (IL28B; rs8099917) was determined in 91 patients.

RESULTS:: Gene expression profiling of the liver differentiated patients into two groups: patients with up-regulated ISGs (Up-ISGs) and patients with down-regulated ISGs (Down-ISGs). A high proportion of patients with no response (NR) to treatment was found in the Up-ISGs group (p=0.002). Multivariate logistic regression analysis showed that ISGs (<3.5) (Odds=16.2, p<0.001), fibrosis stage (F1-2) (Odds=4.18, p=0.003), and ISDR mutation (>==2) (Odds=5.09, p=0.003) were strongly associated with the viral response. The IL28B polymorphism of 91 patients showed that 66% were major homozygotes (TT), 30% were heterozygotes (TG), and 4% were minor homozygotes (GG). Interestingly, hepatic ISGs were associated with the IL28B polymorphism (Odds=18.1, p<0.001) and its expression was significantly higher in patients with the minor genotype (TG or GG) than in those with the major genotype (TT).

CONCLUSIONS:: The expression of hepatic ISGs is strongly associated with treatment response and genetic variation of IL28B. The differential role of host and viral factors as predicting factors may also be present.