An assay for the detection of interferon dependent and interferon independent antibody activities

A spectrophotometric assay is described for the detection of interferon (IFN) dependent antibody (IDA) activity (i.e., antibodies that act with IFN to synergistically inhibit virus infection) and IFN independent antibody (IIA) activity (i.e., antibodies that act additively with IFN to inhibit virus infection). Four neutralizing monoclonal antibodies (mAb) against poliovirus type 1 (PV-1) were tested. Three mAb exhibited IDA activity and one mAb exhibited IIA activity against PV-1 strain Sabin. Concomitantly, the respective IDA and IIA activities were confirmed by a yield reduction assay. Also, the spectrophotometric assay detected IIA activity against PV-1 and IDA activity against PV-2 and PV-3 in human serum. Interestingly, antibody to a synthetic peptide of PV-1 capsid protein VP2 exhibited IIA activity against PV-2 strain MEF. Thus, this assay can facilitate the identification and investigation of IDA and IIA activities. Further, the assay adds economic feasibility to studying the natural occurrence of these antibody activities in the general population and can be useful in assessing the therapeutic potential of vaccine induced and hyperimmune antibodies.