A method of monitoring treatment of HCV by oral administration of ovine IFN- 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- 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-, in a dosage effective to stimulate bloodstream levels of 2,5-oligoadenylate synthetase.