The administration of rabies ribonucleocapsid (RNP) by oral as well as parenteral routes was found to prime specific T cells and elicit N-protein-specific antibodies. per os and intramuscular immunization led to the production of antibodies of the IgA and IgG isotypes, respectively. Mice primed orally with RNP produced significantly enhanced amounts of virus-neutralizing antibody, compared with non-immune controls, upon subsequent parenteral booster immunization with inactivated rabies virus. Thus oral immunization with rabies RNP primed cells capable of mediating a secondary systemic response to rabies virus. The results of experiments in which peptide and protein antigens were administered either physically coupled to or mixed with RNP indicate that RNP has an inherent capacity to enhance immune responses.