The response elicited by QB-90U, specifically the profile of IgG subclasses and the positive DTH reaction, led us to

analyze the expression of Th1 cytokines to confirm the capacity of this saponin preparation to induce the differentiation of T cells with a Th1 phenotype. Fig. 5 shows the relative expression levels of IFN-γ and IL-2, in antigen-stimulated and non-stimulated splenocytes, 120 days after the second immunization. Higher levels of IFN-γ and IL-2 mRNA relative to the control group were observed in mice from the QB-90U and Quil A groups. In the case of IFN-γ, the differences were statistically significant in non-stimulated splenocytes from mice of the QB-90U group (P < 0.05) and in antigen stimulated splenocytes from animals immunized with Quil A (P < 0.05). In the case of IL-2, significant differences were observed in all assayed samples, buy Screening Library that is, in antigen stimulated and non-stimulated splenocytes from mice of the QB-90U (P < 0.01 and P < 0.05, respectively) and Quil A (P < 0.01 and P < 0.05, respectively) groups. As somehow expected, no significant differences were detected in the expression of IFN-γ or IL-2 in mice from the alum group. see more The expression pattern of Th1

cytokines in mice from the QB-90U group – very similar to the one of the Quil A group and markedly different from the alum group – showed that this saponin fraction from Q. brasiliensis did promote the generation of CD4+ T cells with a Th1 phenotype. Considered globally, our results show that the saponin fraction from Q. brasiliensis that we named QB-90U is a safe preparation whose adjuvant effect resembles the one of Quil A, when used for immunization with a viral antigen (BoHV-5). Indeed, both saponin fractions stimulated Thiamine-diphosphate kinase the production of high antibody titres, containing neutralizing antibodies, and a strong DTH response. Similar patterns of IgG subclasses were observed in immunized mice, which suggested the involvement of Th2 (high IgG1

levels) as well as Th1 (high IgG2a and IgG3 levels) CD4+ cells in the antibody response; the participation of the latter was specifically confirmed through the detection of increased expression of IL-2 and INF-γ. The low in vitro (this work) and in vivo (our previous study [17]) toxicity of QB-90U and its high effectiveness to generate strong humoral and cellular responses towards a co-administered viral antigen allow us to propose that this saponin fraction can be considered as an interesting alternative to Quil A adjuvants. Prof. Eduardo Alonso of the Botany Department of Facultad de Química is gratefully acknowledged for the identification of the plant material.