Investigating the long-term stability of protein immunogen(s) for whole recombinant yeast-based vaccines

Even today vaccine(s) remains a mainstay in combating infectious diseases. Many yeast-based vaccines are currently in different phases of clinical trials. Despite the encouraging results of whole recombinant yeast (WRY) and yeast display (YD), the systematic study assessing the long-term stability of protein antigen(s) in yeast cells is still missing. Therefore, in the present study, I investigate the stability of heterologous protein antigen in the cellular environment of S. cerevisiae through E. coli surface protein (major curlin or CsgA). Present biochemical data showed that the stationary phase yeast cells were able to keep the antigen stable for almost one year when stored at 2-8°C and 23-25°C. Further, iTRAQ based quantitative proteomics of yeast whole cell lysate showed that the level of heterologous fusion protein was low in cells stored at 23-25°C compared to those at 2-8°C. In the end, I also proposed a workable strategy to test integrity or completeness of heterologous protein in the yeast cell. I believe that the observations made in the present study will be really encouraging for those interested in the development of a whole recombinant yeast-based vaccine(s).