Significance of 2',5'-oligoadenylate synthetase activity and HCV genotype in IFN therapy for type C chronic hepatitis.

Although the mechanisms of elimination of HCV by IFN have not been fully elucidated, the 2-5A system was reported to be one of the mechanisms of the anti-viral effect of IFN. Therefore, the relationship between HCV genotype, induction of 2-5AS and clinical effect was investigated. As for the anti-viral effect during IFN therapy, in type III or IV, most patients lost HCV-RNA regardless of serum 2-5AS induction even in high HCV-RNA concentration cases. In contrast, in type II, the negativity rate of HCV-RNA became high along with an increase of serum 2-5AS activity, but in patients with high HCV-RNA concentration, HCV-RNA was persistently positive. As for the long term clinical effect of IFN therapy judged 6 months after completion of IFN therapy, HCV genotypes were closely related to the effect; that is, the patients with type III or type IV HCV genotype showed a higher complete response rate compared with the patients with type II HCV genotype. However, the relationship between the long term clinical effects and induction of serum 2-5AS during IFN therapy was obscure. These results suggest that induction of 2-5AS is closely related to the anti-viral effect during IFN administration, but the viral factors appeared to be related to long term clinical effects after cessation of IFN therapy.