Assembly of bacteriophage Qβ virus-like particles in yeast Saccharomyces cerevisiae and Pichia pastoris

Recombinant bacteriophage Qβ coat protein (CP), which has been proposed as a promising carrier of foreign epitopes via their incorporation either by gene engineering techniques or by chemical coupling, efficiently self-assembles into virus-like particles (VLPs) when expressed in Escherichia coli. Here, we demonstrate expression and self-assembly of Qβ CP in yeast Saccharomyces cerevisiae and Pichia pastoris. Production reached 3–4 mg/1 g of wet cells for S. cerevisiae and 4–6 mg for P. pastoris, which was about 15–20% and 20–30% of the E. coli expression level, respectively. Qβ VLPs were easily purified by size-exclusion chromatography in both cases and contained nucleic acid, shown by native agarose gel electrophoresis. The obtained particles were highly immunogenic in mice and the resulting sera recognized both E. coli- and yeast-derived Qβ VLPs equally well.