461773 Systematic Optimization of Protein Secretory Pathways in Saccharomyces Cerevisiae to Increase Production of Hepatitis B Vaccine

Tuesday, November 15, 2016: 8:30 AM
Continental 7 (Hilton San Francisco Union Square)
Jiayuan Sheng1, Hunter Flick2 and Xueyang Feng1, (1)Department of Biological Systems Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, (2)ChE, Virginia Polytechnic Institute and State University, Blacksburg, VA

Systematic Optimization of Protein Secretory Pathways in Saccharomyces cerevisiae to Increase Production of Hepatitis B Vaccine

Hunter Flick, Jiayuan Sheng, Xueyang Feng*

Department of Biological Systems Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24060

Hepatitis B is a major disease that threats over 40% of the population in the world, especially in developing countries. Currently, one of the effective vaccines to treat Hepatitis B is the Hepatitis B Small Antigen (HBsAg), which is produced by the recombinant yeast Saccharomyces cerevisiae.  However, the price for the Hepatitis B vaccine is still too high (~$20/dose) for people in developing countries to afford. In this study, we aim to improve the production of HBsAg by systematically engineering the protein secretory pathways. In general, we screened 194 S. cerevisiae strains with single gene knocked out in four major steps of the secretory pathway: ER degradation (47 genes), protein folding (67 genes), unfolded protein response (39 genes), and translocation and exocytosis (40 genes). From these screenings, we found that the deletion of YPT32 (YGL210W), SBH1 (YER087C-A), and HSP42 (YDR171W) led to the most dramatic increase of HBsAg production, with 1.92, 1.66, and 1.62-fold increases over the wild type S. cerevisiae strain, respectively. During the screening, we also found that the deletion of IRE1 (YHR079C) led to dramatic decrease of HBsAg production. We next overexpressed IRE1 and found that the HBsAg production was increased by 1.29-fold. We then tested the combination of two strategies: gene knockout and gene overexpression and found that deletion of YPT32 with the overexpression of IRE1 led to a 2.12-fold increase in HBsAg production over the wild type which indicates potential synergistic effect among different genes in protein secretory pathways. In summary, our discoveries promoted the bio-manufacturing of a broad scope vaccines in a cost-effective ways, allowing the vaccine to be more accessible throughout the world.


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