[Characterization of antigenic epitopes of ORF2 encoded proteins of hepatitis E virus genotype 4 identified in China].

To characterize antigenic epitopes of hepatitis E virus (HEV) genotype 4 that was first identified in China a few years ago, a recombinant protein, p166Chn, encoded by HEV genotype 4 ORF2 was used to prepare anti-p166Chn McAbs. Simultaneously, twenty N- or C-terminal truncated p166Chn proteins were generated. Immunoreactivity between the McAbs and the truncated proteins as well as seven p166 recombinant proteins derived from different HEV genotypes and subgenotypes was detected by indirect ELISA, Western blot and competition inhibition ELISA. Two reactive profiles were observed with different McAbs and different truncated proteins. The McAbs, represented by 1G10, reacted with those N-terminal truncated proteins beginning at upstream of aa477 and those C-terminal truncated proteins ending at down-stream of aa613, suggesting that the epitope recognized by 1G10 relied on the region of aa477aa613 and was conformation-dependent. While McAb 2F11 was reactive to those truncated p166Chn proteins beginning at upstream of aa474 or ending at downstream of aa617, indicating that the epitope recognized by 2F11 was also conformation-dependent and relied on a longer peptide of aa474aa617. However, the two groups of McAbs didn't inhibit each other when tested by a competition inhibition ELISA, which confirmed the different spatial positions of the two epitopes. Furthermore, when p166 proteins derived from different HEV genotypes and subtypes were applied, all of the McAbs prepared against pChn166 of genotype 4 identified in China could react with the proteins of genotype 1, 2 and 3 distributed worldwide. The data suggested that the two identified epitopes were HEV genotype-common and played significant effects on cross immunoreactivity between different HEV genotypes.