Adjuvant activity of Quillaja brasiliensis saponins on the immune responses to bovine herpesvirus type 1 in mice

The chemical characterization of aqueous extracts (AE) of barks, leaves and branches and the saponin fraction denominated QB-90 obtained from Quillaja brasiliensis, a native species from Southern Brazil, show remarkable similarities to Quillaja saponaria saponins which are known as adjuvants in vaccine formulations.In vivo toxicity assays of AE and QB-90 showed not to be lethal for mice in doses ranging from 50 to 1600 μg and 50–400 μg, respectively. Experimental vaccines prepared with bovine herpesvirus type 1 (BHV-1) antigen and either AE (barks 100 μg, leaves 400 μg, branches 400 μg) or QB-90 (100 μg) were able to enhance the immune responses of mice in acomparable manner to saponins from Q. saponaria (QuilA, 100 μg). BHV-1 specific IgG, IgG1 and IgG2a antibody levels in serum were also significantly enhanced by AE, QB-90 and QuilA compared to control group (p < 0.05). These results showed that AE and QB-90 from Q. brasiliensis are potential candidates as adjuvants in vaccines.