Yeast-based vaccines: New perspective in vaccine development and application.

In presently licensed vaccines, killed or attenuated organisms act as a source of immunogens except for peptide-based vaccines. These conventional vaccines required a mass culture of associated or related organisms and long incubation periods. Special requirements during storage and transportation further add to the cost of vaccine preparations. Availability of complete genome sequence, well established genetic, inherent natural adjuvant, and nonpathogenic nature of yeast species viz Saccharomyces cerevisiae, Pichia pastoris makes them an ideal model system for the development of vaccines both for public health and for on-farm consumption. In this review, we compile the work in this emerging field during last two decades with major emphases on S. cerevisiae and P. pastoris which are routinely used worldwide for expression of heterologous proteins with therapeutic value against infectious diseases along with possible use in cancer therapy. We also pointed towards the developments in use of whole recombinant yeast (WRY), yeast surface display (YSD) and virus-like particles (VLPs) as a novel strategy in the fight against infectious diseases and cancer along with other aspects including suitability of yeast in vaccine preparations, yeast cell wall component as an immune stimulator or modulator and present status of yeast-based vaccines in clinical trials.