Immunomodulatory Effects of Orally-Administered Saponins and Nonspecific Resistance against Rabies Infection

Abstract

We present evidence that orally fed Quillaja saponins offer nonspecific resistance to mice against rabies viral infection. Adoptive transfer of spleen cells and thymocytes from animals preconditioned with saponin (SAP), inactivated rabies antigen (AG), or a mixture of AG+SAP has offered significant protection against an intracerebral challenge with live rabies virus. Levels of serum rabies-neutralizing antibodies in the different groups of recipient animals did not correlate with the respective survival rates. Culture supernatants of concanavalin A-stimulated spleen cells from animals fed SAP or AG+SAP induced marked T cell and B cell proliferation, and also greatly enhanced the plaque-forming cell activity of unprimed spleen B cells. Irrespective of the presence or absence of rabies-specific antibodies, sera from animals fed a mixture of AG+SAP induced significant levels of cell proliferation and augmented phytohemagglutinin (PHA)-induced responsiveness of spleen lymphocytes in vitro. The addition of sera from animals fed AG alone resulted in inhibition of cell proliferation and suppressed PH A-induced responses.

Immune stimulating complexes as mucosal vaccines

“…However, ISCOMs have been found to be exceptionally stable structures, able to resist degradation by exposure to low pH and bile salts 47 . Furthermore, it has been known for many years that the saponins themselves are effective adjuvants when given orally, inducing serum antibodies, antigen‐specific proliferation and CTL activity 48 , 49 . These indications, that ISCOMs could be an effective oral vaccine, were confirmed by our initial findings that a single feed of ISCOMs‐containing OVA could induce primary OVA‐specific IgG, DTH and MHC class I‐restricted CTL responses in mice 23 .…”

“…A further possible explanation for the adjuvant effect of ISCOMs is the inherent inflammatory properties of the Quil A contained in the ISCOMs matrix. It has been known for many years that saponins have adjuvant properties, being effective when given both parenterally 37 and orally 48 , 49 . Recently, we have found that oral administration of OVA together with free Quil A reproduces most of the local and systemic immune responses found after feeding intact OVA ISCOMs (Figure 4).…”

Adjuvant effects of saponins on animal immune responses

“…Purified Quillaja saponins boosted antibody production without producing any reaginic antibodies (So et al, 1997). Chavali and Campbell (1987a;1987b) found that mice fed Quillaja saponins exhibited increased cell proliferation in spleen and mesenteric lymph nodes and increased and prolonged natural killer (NK) cell activity, suggesting that saponins act directly on T-helper cells of the mucosal immune system to induce secretion of soluble mediators. Other studies also suggest that Quillaja saponin has mitogenic activity and induces T cell and B cell proliferation (Chavali et al, 1987;Mowat et al, 1991).…”

Chemical Evaluation and Nutritive Value of Cultivated and Wild Gongronema latifolium Obtained in Etinan, Akwa Ibom State, Nigeria

“…Saponins serve as antioxidants as they prevent degeneration of DNA and also help to reduce colon damage and risk of cancer. Saponins are used as adjuvant in vaccines and their oral intake has been used to help in managing retroviral infections [51]. Alkaloid level in the cultivated sample was 27.88 ± 0.03% while that of the wild sample was 28.25 ± 0.02%.…”