06: Visualization of hepatitis E virus RNA and proteins in the human liver
2017
Background: Although hepatitis E constitutes a substantial disease burden
worldwide, surprisingly little is known about the localization of hepatitis E Virus (HEV) in the human liver. We therefore aimed to visualize HEV
RNA and proteins in situ.
Methods: Twelve antibodies against HEV open reading frame (ORF) 1–3
proteins for immunohistochemistry (IHC) and two probes for in situ
hybridization (ISH) were tested on formalin-fixed, paraffin-embedded
(FFPE) Huh-7 cells transfected with HEV ORF1-3 Expression vectors.
IHC (and partly ISH) were then applied to Hep293TT cells replicating infectious
HEV and liver specimens from patients with hepatitis E (n=20)
and controls (n=134).
Results: Whereas ORF1-3 proteins were all detectable in HEV protein expressing
cells, only ORF2 and 3 proteins were traceable in cells replicating
infectious HEV. In liver specimens from patients with hepatitis E, only the
ORF2encoded capsid protein was unequivocally detectable. IHC for ORF2
protein revealed a patchy expression in individual or grouped hepatocytes,
generally stronger in cases of chronic compared to acute hepatitis. Besides
cytoplasmic and canalicular, ORF2 protein also displayed a hitherto not
described nuclear localization. Furthermore, positivity for ORF2 protein
in defined areas correlated with HEV RNA detection by ISH. IHC was specific
and comparably sensitive as PCR for HEV RNA.
Conclusions: In livers from patients with hepatitis E, the ORF2 protein can
be visualized reliably by IHC, allowing sensitive and specific detection of
HEV in FFPE samples. Therefore, HEV ORF2 IHC can be used as a rapid,
handy and not expensive ancillary tool in histopathologic diagnostics of
HEV. In addition, its variable subcellular distribution in individual hepatocytes
of the same liver suggests an interaction with nuclear components
and thus a redistribution of ORF2 protein during infection.
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