Production and characterization of a fusion form of hepatitis E virus <i>t</i>ORF2 capsid protein in <i>Escherichia coli</i>

Hepatitis E virus (HEV) is a nonenveloped virus causing an emerging zoonotic disease posing a severe threat to the public health in the world, especially to pregnant women. In this study, a truncated form (aa 368-606) of the open reading frame 2 of the capsid protein (<i>t</i>ORF2-HEV), a major structural protein of HEV, was expressed in <i>Escherichia coli</i>. This work characterizes for the first time, the fused Glutathione-S-Transferase-tagged <i>t</i>ORF2 (GST-<i>t</i>ORF2) and <i>t</i>ORF2-HEV forms in <i>E. coli</i>. The fusion protein was purified by affinity chromatography with a purity higher than 90% and to yield about 27% after thrombin digestion. The purified GST-<i>t</i>ORF2 protein was then characterized by western blot, using anti-GST antibodies, and CD spectroscopy. The GST-<i>t</i>ORF2 and <i>t</i>ORF2-HEV proteins were shown to be efficient to develop an ELISA test to detect anti-HEV IgG in mice sera immunized with a recombinant full length ORF2 protein. Sera showed a significant increase of the absorbance signal at 450 nm, in plate wells coated with a quantity of 0.5, 1 and 2 µg of proteins. ELISA plates coated with the purified GST-<i>t</i>ORF2 and <i>t</i>ORF2-HEV showed similar response when compared to the HEV ELISA where total insect cell lysate, infected with the recombinant baculovirus expressing full ORF2, was used as positive control.