Immunopotentiation by orally-administered Quillaja saponins: effects in mice vaccinated intraperitoneally against rabies.

Orally fed Quillaja saponins amplified the immunopotentiating ability of an intraperitoneally (IP) administered inactivated rabies vaccine in mice. The number of animals surviving rabies infection was markedly higher (90-100%) in groups of animals receiving a combined treatment of oral saponin (SAP) and IP vaccine, compared to groups receiving vaccine alone (25%), or to unimmunized mice (0%). Antibody production was significantly higher in animals fed SAP 2 weeks after primary or secondary sensitization with an IP-injected vaccine. In mice given 2 IP doses of vaccine, 1 week apart, simultaneous feeding of SAP resulted in an enhanced production of rabies-specific (whole Ig) antibodies. On the other hand, animals preconditioned with SAP 3 days prior to administration of the vaccine exhibited greatly increased IgG antibody levels. Moreover, SAP-preconditioned mice vaccinated with a very low dosage produced significantly higher levels of antibodies.