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

A murine monoclonal antibody, LO-22, with broad cross-reactivity to human interferon-alpha (HuIFN-alpha) subtypes and some animal IFN-alpha species was found to bind less efficiently to IFN-alpha A (IFN-alpha 2a). In contrast, LO-22 bound strongly to IFN-alpha 2 (IFN-alpha 2b) and IFN-alpha 2C (IFN-alpha 2c) which differ by one or two amino acids, respectively, from IFN-alpha A; the latter has lysine at position 23 whereas the other closely related IFNs have arginine. LO-22 also bound efficiently to IFN-alpha D which is only 83% related to IFN-alpha A, but which also has arginine at position 23. These results strongly suggest that LO-22 recognizes a conserved epitope among IFN-alpha 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.