A Study on the Virus-Like Particle Formation of Hepatitis E Virus ORF2 and Rotavirus NSP4 Protein in the Eukaryotic and Prokaryotic Expression Systems

Background: Hepatitis E virus (HEV) is able to induce fulminant hepatitis E infection in immunosuppressed individuals. Previous studies showed that the Baculovirus expression system (BES) could be used for developing hepatitis E virus-like particles (VLPs). Objectives: In the present study, the formation of VLPs of the recombinant proteins of HEV truncated open reading frame 2 (ORF2; 112-607) and Rotavirus non-structural protein 4 (NSP4) (OSU-a) were investigated in BES and Escherichia. coli. Methods: To construct VLPs, the truncated ORF2-NSP4 protein was expressed in BES. The expression of protein was confirmed by western blot. This protein was expressed in E. coli. The truncated ORF2-NSP4 gene was subcloned in pET28a, and then transformed into E. coli DH5 alpha. The confirmed colonies were transformed into E. coli BL21. The solubility of protein were checked by SDS-PAGE and western blot analysis. In the final step, to verify the VLP formation in BES and E. coli, the recombinant proteins were stained with 2% uranyl acetate and checked by transmission electron microscopy (TEM). Results: The 75 KDa truncated ORF2-NSP4 protein was successfully expressed in Sf9 cells, assembled, and formed VLP according to TEM results. In the prokaryotic expression system (E. coli), the ORF2-NSP4 gene was successfully subcloned and expressed in BL21 but VLP was not detected in TEM analysis. Conclusions: The truncated ORF2-NSP4 VLP were efficiently expressed in the SF9 cells, as a potential mucosal vaccine against HEV and Rotavirus. In the prokaryotic expression system (E. coli), the ORF2-NSP4 gene was successfully expressed.