Genome & Morphology

Hepatitis E viruses consist of a naked virion with icosahedral symmetry and diameter of 30-34 nm. Although not as pronounced as the cup-like depressions in caliciviruses, each facet of the capsid contains indentations. The nonsegmented, positive-sense, single-stranded RNA genome is 7.5 kb in length. Little is known about the replicative strategies of HEV in comparison to those of other viral families, but it is clear that the capped genome contains three different open reading frames (ORFs), which overlap with one another and utilize different coding frames. Situated at the 5'-terminus, ORF1 contains 5,073 to 5,124 nucleotides and gives rise to nonstructural proteins such as an RNA-dependent RNA polymerase. The 1977 to 1980 base pairs of ORF2 encodes components of the viral capsid. They attach to a polyA tail at the 3'-end of the RNA strand. Overlapping with ORF1 and ORF2, ORF3 may produce regulatory proteins. To date, virologists have detected only a single neutralization epitope between amino acids 578 and 607 of ORF2 protein (Li 12999).

Partial nucleotide sequences from ORF1 and 2 fall into four major genotypes: Asian/African, Chinese, Mexican, and U.S. strains. This genetic heterogeneity suggests HEV is an ancient virus that evolved and diverged over time and space.

 

Organization of the hepatitis E virus genome. Fields Virology.
Model of a Hepatitic E Particle. Running like Water--The Omnipresence of Hepatitis E.