Identification and characterization of the neutralization epitope(s) of the hepatitis E virus

The neutralization epitope(s) of the hepatitis E virus (HEV) was studied by an in vitro neutralization assay using antibodies obtained by immunization of mice with 51 overlapping 30-mer synthetic peptides spanning the region 221-660 amino acids (aa) of the HEV open reading frame 2 encoded protein (p ORF2) and 31 overlapping recombinant proteins of different sizes derived fr om the entire pORF2 of the HEV Burma strain. Antibodies against synthetic p eptides and short recombinant proteins of similar to 100 as did not neutral ize HEV, suggesting the HEV neutralization epitope(s) is conformation-depen dent. However, one recombinant protein of similar to 400 as in length compr ising the pORF2 sequence at position 274-660 as as well as all truncated de rivatives of this protein containing region 452-617 as elicited antibodies, demonstrating HEV neutralizing activity. These findings establish for the first time that the minimal size fragment, designated pB166, that can effic iently model the neutralization epitope(s) is 166 as in length and is locat ed at position 452-617 as of the HEV pORF2. Additionally, antibodies agains t pB166 were found to cross-neutralize three different HEV genotypes, sugge sting that a common neutralization epitope(s) may exist within the differen t HEV genotypes. Thus, recombinant proteins constructed in this study may b e considered as potential candidates for the development of an HEV subunit vaccine as well as for the development of highly sensitive and specific dia gnostic tests. (C) 2001 Academic Press.