Conformational changes in pH2-treated human interferon-alpha 2 detected with monoclonal antibodies

Monoclonal antibodies allowed to demonstrate the existence of alternative antigenic forms of the same molecule as of human interferon (IFN)-alpha 2. Exposure of recombinant IFN to pH 2, although not affecting its bioactivity, induced structural modulation of molecular surface. The antigenic structure of IFN-alpha 2 appeared to be built of the acid-stable and acid-labile epitopes. In general, the acid-stable sites determined subtype-specific antigenic properties of the protein, whereas the acid-labile determinants were responsible for antigenic characteristics shared by some other human IFNs. Acidification of IFN-alpha 2 to pH 2 for at least 1-2 h resulted in simultaneous structural rearrangement of all acid-labile sites.