A natural carrier effect and the generation of specific antibodies to biologically active peptides

Production of specific antibodies to haptens, especially antipeptides, without interference by carrier protein, is desirable. The bradykinin-potentiating peptides (BPPs) are a family of pyroglutamyl proline-rich oligopeptides with strong antihypertensive properties. In this work, the production of antibodies to BPPs by use of an efficient immunization protocol in mice genetically modified for the high antibody responsiveness (HIII line) is described. Although it was possible to induce antibody production by single-dose administration of free BPPs, higher antibody titers were obtained in mice preimmunized with carrier protein before administration of peptides conjugated to this carrier. Interestingly, both mouse groups had a higher titer of IgG1 than IgG2a isotypes, regardless of prior immunization with the carrier protein. However, a lower titer of IgG2a was observed in unprimed mice. A single band of about 27 kDa corresponding to the BPP precursor protein was recognized by these antibodies in the cytosol of the Bothrops jararaca venom gland. This work proposes an efficient immunization protocol based on classic studies described for the hapten-carrier effect for generating specific antibodies against biologically active peptides.