Synthetic Gypsogenin Saponins as Synergistic Vaccine Adjuvants

Southern Research Institute, Birmingham AL

Investigators

Abstract

DESCRIPTION (provided by applicant): The objective of this proposal is to develop a glycoside adjuvant or immune agonist capable of concurrently stimulating both innate and adaptive immunity, and driving the induction of both cellular (Th1) and humoral (Th2) immune responses in a synergistic manner. The results of this proposal may lead to the development of a novel subclass of clinically applicable synthetic saponin of triterpene, gypsogenin, which can serve as immune agonists that are stable at room temperature, non-toxic, well characterized, and capable of promoting both innate and adaptive immune responses. To develop this adjuvant, this proposal seeks to add to the triterpene i) oligomannans that can serve as ligands for innate immunity receptors, e.g. toll-like receptors (TLRs) and lectins, and ii) lipophilic chais, that may be designed to serve as ligands for innate immunity receptors. Additionally, the aldehyde group of triterpene, by forming imines with the amino groups of certain cell surface receptor(s), can also provide co-stimulatory signals requisite for eliciting Th1/Th2 immunity. The triterpene group can facilitate the delivery of exogenous antigens to the cytosol of antigen-presenting cells to be processed for presentation to and activation of cytotoxic T lymphocytes (CTL). The concurrent stimulation of both innate and adaptive immunity receptors in the same cell would synergistically drive a much more effective immune response to the immunogen than would be elicited by adjuvants that target these different receptors individually. In this proposal we seek to test the hypothesis that the inclusion of an adjuvant that simultaneously triggers receptors of innate and adaptive immune immunity within the same cell can synergistically improve immune responses to an immunogen as compared to adjuvants that target these receptors individually. This hypothesis will be tested in the following specific aims - 1) Synthesize two immune agonists, having an aldehyde-carrying triterpene (gypsogenin) linked covalently to a mannan oligosaccharide and a lipophilic chain. 2) Assess the ability of the synthetic saponins to enhance cellular and humoral immune responses to the model antigen recombinant hemagglutinin protein (rHA) in mice. Immune responses will be evaluated for the production of IgG2a and IgG2b, antigen-specific lymphoproliferation, the production of Th1 and Th2 cytokines (IL-2, IL-4, IL-5, IFN-r, and TNF-a), and the induction of CTL. 3) Evaluate saponin's critical micellar concentration, haemolytic effect, stability and acute toxicity.