With a model peptide, the neutralizing epitope 50-75 of cholera toxin B subunit, two chimeric peptides were constructed. A T-cell epitope, the 174-187 peptide from the G protein of the respiratory syncytial virus, was co-linearly synthesized at the amino-(174-50) or carboxyl-terminus (50-174) of the 50-75 peptide. Although both chimeric peptides were equally immunogenic by the intraperitoneal route, the 50-174 peptide was more immunogenic than the 174-50 peptide by the intranasal (i.n.) route. Both chimeric peptides inhibited the binding of cholera toxin B subunit to GM1 ganglioside with the 50-174 peptide being more effective inhibitor than the 174-50 peptide. In addition, an effective priming of the immune system was achieved after the i.n. administration of immunogens. The observed unresponsiveness after the i.n. co-immunization with the 50-174 peptide and GM1 ganglioside emphasize the role of GM1 binding for the induction of an immune response after i.n. immunization.