High-level expression of codon optimized foot-and-mouth disease virus complex epitopes and cholera toxin B subunit chimera in Hansenula polymorpha.

A codon optimized DNA sequence coding for foot-and-mouth disease virus (FMDV) capsid protein complex epitopes of VP1 amino acid residues 21-40, 135-160, and 200-213 was genetically fused to the N-terminal end of a 6x His-tagged cholera toxin B subunit (CTB) gene with the similar synonymous codons preferred by the methylotropic yeast Hansenula polymorpha. The fusion gene was synthesized based on a polymerase chain reaction (PCR) and subsequently overexpressed in H. polymorpha. The chimeric protein was successfully secreted into the culture medium (up to 100mg/L) and retained the antigenicity associated with CTB and FMDV antibodies by Western blot analysis. The chimera after purification through Co(2+)-charged resin column bound specifically to GM1 ganglioside receptor and thus retained the biological activity of CTB. This study has important implications in the construction of CTB chimera for mucosal vaccines against FMDV.