Hepatitis E Vaccine: Current Status and Future Prospects

Samad Amini-Bavil-Olyaee; Christian Trautwein; Frank Tacke


Future Virology. 2009;4(2):143-154. 

In This Article

HEV Virology

Human HEV was initially identified by electron microscopy from the feces of infected patients and could be cloned in the early 1990s.[8] According to the eighth report of the International Committee on the Taxonomy of Viruses, HEV belongs to a separated family and genus named Hepeviridae and Hepevirus, respectively.[76] HEV is an icosahedral, round nonenveloped virus (27-34 nm), with a single-stranded polyadenylated (+)RNA of approximately 7.5 kb in length. The virus consists of three open-reading frames (ORFs) comprising nonstructural and structural proteins, as well as two conserved nontranslated regions at the 5´ and 3´ termini of the genome (Figure 2). ORF1 encodes a nonstructural multifunctional polyprotein that the viral RNA-dependent RNA polymerase synthesizes. The virus major capsid protein, the main structural protein of HEV, is encoded by ORF2. The last and the smallest ORF3, which overlaps ORF1 (slightly) and ORF2 (mostly), encodes a small protein with unknown function, possibly mediating interactions between virus and host; for example, anchoring of the virus with the cytoskeleton.[19]

Figure 2.

Genomic organization of HEV.

The diagram depicts the HEV genome organization, mostly of genotype 1-3. HEV is an RNA virus with three ORFs (ORF1-3) encoding for nonstructural and structural proteins. ORF2 encodes for the capsid protein that is used as the antigen for vaccination strategies. Genomic (~7.5 kb) and subgenomic viral RNA can be detected in infected cells.

NTR = Nontranslatable region; ORF = Open-reading frame.


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