Synthesis and Evaluation of Carbohydrate Vaccine Adjuvants

PROJECT SUMMARY The success of vaccination requires the generation of a strong immune response to the inoculated antigens in order to provide long-term protective immunity against many infectious diseases. To achieve this goal often requires the addition of vaccine adjuvants, substances that a substance that boosts the body’s immune response to the vaccine. However, there are only a few human vaccine adjuvants with an extensive safety record and minimal toxicity approved for clinical use. At presence, more studies are needed to identify novel adjuvants that not only significantly enhance the immune response for a particular vaccine, but also must be minimally toxic and maximally safe for clinical use. In efforts to discover novel vaccine adjuvants, an in vivo screening of forty-seven saponins from medicinal plants for their immunostimulatory and hemolytic activities has led to the discovery of new exciting vaccine adjuvants. Among forty- seven saponins evaluated, soyasaponins have emerged as the most potent adjuvants. These newly-discovered carbohydrates exhibited a significantly enhanced adjuvant activity with almost negligible toxicity when directly compared to QS-21 which has emerged as a vaccine adjuvant in numerous clinical trials. However, obtaining them from natural sources is a complicated process of extraction and purification that result in the production of minute. As a result, isolation of soyasaponins is economically unfeasible and unsustainable if sufficient quantities are required for immunological studies and clinical applications. Since FDA has strict regulations regarding to the purity and quality of adjuvants for use in human, a synthetic source must be developed for soyasaponins to be utilized as clinically relevant adjuvants. The objective of this proposal will address these challenges through the chemical synthesis for procuring sufficient quantities of soyasaponins in pure form. This effort will deliver well-defined soyasaponins without batch-to- batch variation and provide tools for studies of their roles as vaccine adjuvants and exploration of structure-adjuvant potency profiles for the discovery of non-natural soyasaponin improved adjuvants.