Peptides composed of variants of a B-cell epitope followed by a T-cell determinant of rabies virus ribonucleoprotein (RNP) have been synthesized to elicit antibody production in mice. Conformation of the peptides was characterized by secondary structural prediction and circular dichroism measurements. It was found that only synthetic peptides with disrupted helical structure in the antigenic region were active on immunoblot assay, performed against a natural anti-protein monoclonal antibody (MAb) and provoked virus-neutralizing antibody production.