Epitope Localization of a Monoclonal Antibody,LO-22,with Broad Specificity for Interferon-α Subtypes

Abstract

A murine monoclonal antibody, LO-22, with broad cross-reactivity to human interferon-α (HuIFN-α) subtypes and some animal IFN-α species was found to bind less efficiently to IFN-αA (IFN-α_2a*). In contrast, LO-22 bound strongly to IFN-α₂ (IFN-α_2b*) and IFN-α2C (IFN-α_2c*) which differ by one or two amino acids, respectively, from IFN-α; the latter has lysine at position 23 whereas the other closely related IFNs have arginine. LO-22 also bound efficiently to IFN-αD which is only 83% related to IFN-αA, but which also has arginine at position 23. These results strongly suggest that LO-22 recognizes a conserved epitope among IFN-α subtypes in which arginine at position 23 is involved. The specificity of a second monoclonal antibody, MT4/E4, is also reported and compared to that of LO-22.