ABSTRACT
Objective To characterize the dimerization and the antigenicity of the ORF2 polypep-tide of hepatitis E virus (HEV, genotype 4). Methods HEV ORF2 gene was cloned from the serum of a patient with hepatitis E. The genotype was determined by sequencing. Three ORF2 polypeptides differing in size and other polypeptides with point mutations were produced in E. coli. The recombinant polypeptides were purified and analyzed by SDS-PAGE and Western blot. Results The ORF2 polypeptide containing 459-607 amino acid formed homedimer even in 8 mol/L urea. The truncated polypeptides containing amino acid 472-607 or 459-594 formed monomer only. The mutations at amino acid 562 or 595 disrupted the ho-modimer, whereas the mutations at amino acid 476 or 580 did not. Anti-HEV from hepatitis E patients only reacted with the homodimer form of the polypeptide 459-607 and did not react with monomer or tnmcated pol-ypeptides. Conclusion The amino acid 459-607 of HEV ORF2 is essential for dimerization of the ORF2 polypeptide. Residues at amino acid 562 and 595 are critical for the dimerization. The antigenicity of the polypeptide 459-607 mainly depends on its homodimer form.