Innate Immune Modulator---Molecular Characterization of Bupleurum kaoi Polysaccharide Fraction and Assessment of Its Immunomodulatory and Antiviral Effects

Current antiviral therapies uses direct acting antivirals (DAAs) targeting specific viral protein, but these are inevitable associated with potential risk of selecting for drug-resistant mutant viruses, such as the case with hepatitis C virus (HCV). As an alternative, targeting the host cell to indirectly produce an antiviral response is a feasible approach of antiviral therapy. This includes the use of modulators of the host cell innate immune system, which is a natural defense against viruses, and there have been intense international studies to identify novel modulating agents. Polysaccharides are naturally occurring glycans that are known to stimulate or modulate host cell innate immunity through interaction(s) with sensors of microbial components or foreign materials such as Toll-like receptors (TLRs). Since Bupleurum roots are commonly used to treat inflammation-related diseases, we hypothesized whether the polysaccharides from this natural medicine could act as an innate immune modulator, and in addition, as an antiviral agent by stimulating the host cell innate immune response. Bupleurum kaoi (B. kaoi) is an endemic species only found in Taiwan, and its polysaccharide fraction has never been fully characterized and evaluated for these functions. Therefore, in this three year grant proposal, we intend to: Year 1- Characterize the glycochemistry of B.kaoi polysaccharide fraction (BKP) to identify its molecular features; Year 2- Evaluate BKP’s immunomodulatory functions in details with mechanistic studies to determine its target receptor(s), activating signaling pathways, and response-associated cytokine profile; and Year 3- Assess its antiviral activities against HCV (which is known to interact with the cell innate immune system) as a model, with regards to direct (enhancing host cell innate immunity), indirect (priming immune cells to elicit an immune response), or modulatory (counter balancing insufficient or over-reactive inflammatory responses) effects. These studies will help characterize and develop BKP as a natural innate immune modulator and antiviral agent for clinical application. Furthermore, the results could provide insight for additional potential applications including treatment against postoperative infections, autoimmune disease therapy, and use as adjuvant for vaccines. Finally, this study will also stimulate local pharmaceutical/agricultural/economic interests in cultivating the unique B. kaoi and develop BKP as an innate immune modulator for these applications.