The influence of water-miscible alcohols on the conformation of antibodies directed against a defined epitope.
Antiserum was raised against peptide P513 (CSQRSTNSAST) conjugated to diphtheria toxoid. P513 is a sequence derived from the Plasmodium falciparum merozoite surface antigen (MSA-2) containing the STNS epitope recognized by antibodies that inhibit parasite growth. Although antibodies directed against other STNS-containing peptides can bind to the native MSA-2 antigen, polyclonal anti-P513 serum failed to react in immunofluorescence assays with parasites or with MSA-2 by Western blotting. However, addition of methanol, ethanol or 1-propanol modified the specificity of the anti-P513 interaction, resulting in recognition of MSA-2. The effect was concentration dependent: at high alcohol concentrations, the specificity was further modified, and a previously undescribed rhoptry antigen was recognized. These results indicate that addition of alcohols to immunoassays may provide a way of modifying the specificity of antibodies in general, and the reactivity of anti-peptide serum with the parent protein in particular.