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 falc iparum merozoite surface antigen (MSA-2) containing the STNS epitope r ecognized by antibodies that inhibit parasite growth. Although antibod ies directed against other STNS-containing peptides can bind to the na tive MSA-2 antigen, polyclonal anti-P513 serum failed to react in immu nofluorescence assays with parasites or with MSA-2 by Western blotting . However addition of methanol, ethanol or 1-propanol modified the spe cificity of the anti-P513 interaction resulting in recognition of MSA- 2. The effect was concentration dependent: at high alcohol concentrati ons, 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 specifi city of antibodies in general, and the reactivity of anti-peptide seru m with the parent protein in particular.