This invention provides a recombinant interferon (rSIFN-co) and its equivalent with changed spatial configuration, high efficacy and low side effects. Therefore, high dose of rSIFN-co may be used. The cytotoxic effect of rSIFN-co is only one-eighth (⅛) of currently clinically available interferons but its anti-viral effect is approximately five to twenty (5-20) times higher, and when used in vivo it has a broader spectrum of clinical applications and longer biofeedback response. This invention further provides methods of using the recombinant interferon to treat proliferative disorders such as cancer or viral diseases.
