(EN) A method of monitoring treatment of HCV by oral administration of ovine IFN-$g(t) is disclosed. The method includes measuring the blood levels of 2', 5'-oligoadenylate synthetase prior to and after such oral administration, and if necessary, adjusting the dose of IFN-$g(t) until a measurable increase in blood 2', 5'-oligoadenylate synthetase level, relative to the level observed prior to administration, is observed. Also disclosed are oral-delivery compositions for use in treating HCV in an HCV-infected patient comprising ovine IFN-$g(t), in a dosage effective to stimulate bloodstream levels of 2', 5'-oligoadenylate synthetase.