Acta Univ Latv (2008) 745: 75–85

High-level expression and purification of bacteriophage GA virus-like particles from yeast Saccharomyces cerevisiae and Pichia pastoris

Abstract

The recombinant virus-like particles (VLPs) generated by heterologous expression of RNA bacteriophage coat protein genes have been proposed as promising carriers of foreign epitopes and nucleic acids for development of novel vaccines and gene therapy tools. Here, we investigated the possibility to produce bacteriophage GA coat protein-derived VLPs in yeast Saccharomyces cerevisiae and Pichia pastoris. To optimize growth conditions, three expression systems have been explored: GAL1 and GAL10 promoter-directed expression in S. cerevisiae as well as AOX1 promoter-directed expression in P. pastoris. Synthesis of GA coat protein and formation of VLPs was observed in all three cases. GA VLPs were purified by a single size-exclusion chromatography step till 80 to 90 % of homogeneity. The final amount of purified VLPs varied between 0.6 to 2.0 mg per 1 g of cells for S. cerevisiae, while expression in P. pastoris resulted in VLP yield of up to 3 mg from the same amount of cells. The recombinant VLPs obtained may be further used for exposition of foreign epitopes on their surface via chemical coupling and/or packaging of immunostimulatory DNA sequences internally.