Antigenic domains of the open reading frame 2-encoded protein of hepatitisE virus

The antigenic composition of the hepatitis E virus (HEV) protein encoded by open reading frame 2 (ORF2) was determined by using synthetic peptides. Th ree sets of overlapping 18-, 25-, and 30-mer peptides, with each set spanni ng the entire ORF2 protein of the HEV Burma strain, were synthesized. All s ynthetic peptides were tested by enzyme immunoassay against a panel of 32 a nti-HEV-positive serum specimens obtained from acutely HEV-infected persons . Six antigenic domains within the ORF2 protein were identified. Domains 1 and 6 located at the N and C termini of the ORF2 protein, respectively, con tain strong immunoglobulin G (IgG) and IgM antigenic epitopes that can be e fficiently modeled with peptides of different sizes. In contrast, antigenic epitopes identified within the two central domains (3 and 4) were modeled more efficiently with 30-mer peptides than with either 18- or 25-mers. Doma in 2 located at amino acids (aa) 143 to 222 was modeled best with 25-mer pe ptides. A few 30-mer synthetic peptides derived from domain 5 identified at aa 490 to 579 demonstrated strong IgM antigenic reactivity. Several 30-mer synthetic peptides derived from domains 1, 4, and 6 immunoreacted with IgG or IgM with more than 70% of anti-HEV-positive serum specimens. Thus, the results of this study demonstrate the existence of six diagnostically relev ant antigenic domains within the HEV ORF2 protein.