Failure to detect antiviral activity in serum and plasma of healthy individuals displaying high activity in ELISA for IFN-alpha and IFN-beta

The presence of constitutively produced interferon (IFN)-alpha in the blood of healthy individuals has been the subject of contradictory discussions f or years. Immunologic as well as biologic test procedures have demonstrated striking differences regarding serum IFN-alpha under physiologic condition s. We investigated the presence of immunoreactive IFN-alpha in serum sample s of 923 healthy blood donors by means of a widely used commercially availa ble ELISA, Of these, 254 (27.5%) exhibited detectable serum IFN-alpha level s. The sera of 85.1% of these people also contained IFN-beta, Both IFN were also demonstrated in EDTA-anticoagulated plasma. However, none of these sa mples exhibited any antiviral effect on human A549 lung carcinoma cells cha llenged with encephalomyocarditis virus. Samples,vith high IFN-alpha ELISA activity did not abolish the antiviral action of added natural IFN-alpha, t hus excluding IFN-alpha inhibitory factors. The experiments suggest that th e detected compounds probably did not represent IFN-alpha but were the resu lt of a cross-reaction with unknown serum components, A variety of disorder s has been associated with elevated serum IFN-alpha levels that in most cas es were detected by ELISA, In view of our data, these findings need to be c arefully reevaluated. For the purpose of monitoring IFN-alpha levels in the rapy of atopic, autoimmune, or malignant disorders, an appropriate detectio n system for IFN-alpha is advisable.