Purification of an Immunoadjuvant Saponin Fraction from Quillaja brasiliensis Leaves by Reversed-Phase Silica Gel Chromatography.

Saponins include a large variety of molecules that find several applications in pharmacology. The use of Quillaja saponaria saponins as immunological adjuvants in vaccines is of interest due to their capacity to stimulate both humoral and cellular responses. The congener species Q. brasiliensis has saponins with chemical similarities and adjuvant activity comparable to that of Q. saponaria fraction Quil-A®, with additional advantages of showing lower toxicity and reduced hemolytic activity. Here we describe in detail the methods for preparing the aqueous extract from Q. brasiliensis leaves, as well as the purification of the bioactive saponin fraction QB-90 using silica reversed-phase chromatography.

Quillaja brasiliensis saponins induce robust humoral and cellular responses in a bovine viral diarrhea virus vaccine in mice.

A saponin fraction extracted from Quillaja brasiliensis leaves (QB-90) and a semi-purified aqueous extract (AE) were evaluated as adjuvants in a bovine viral diarrhea virus (BVDV) vaccine in mice. Animals were immunized on days 0 and 14 with antigen plus either QB-90 or AE or an oil-adjuvanted vaccine. Two-weeks after boosting, antibodies were measured by ELISA; cellular immunity was evaluated by DTH, lymphoproliferation, cytokine release and single cell IFN-γ production. Serum anti-BVDV IgG, IgG1 and IgG2b were significantly increased in QB-90- and AE-adjuvanted vaccines. A robust DTH response, increased splenocyte proliferation, Th1-type cytokines and enhanced production of IFN-γ by CD4(+) and CD8(+) T lymphocytes were detected in mice that received QB-90-adjuvanted vaccine. The AE-adjuvanted preparation stimulated humoral responses but not cellular immune responses. These findings reveal that QB-90 is capable of stimulating both cellular and humoral immune responses when used as adjuvant.