Hepatitis E virus replication and interferon responses in human placental cells

Abstract

Hepatitis E virus (HEV) is a member of the genus Orthohepevirus in the family Hepeviridae and the causative agent of hepatitis E in humans. HEV is a major health problem in developing countries, causing mortality rates up to 25% in pregnant women. However, these cases are mainly reported for HEV genotype (gt)1, while gt3 infections are usually associated with subclinical courses of disease. The pathogenic mechanisms of adverse maternal and fetal outcome during pregnancy in HEV‐infected pregnant women remain elusive. In this study, we observed that HEV is capable of completing the full viral life cycle in placental‐derived cells (JEG‐3). Following transfection of JEG‐3 cells, HEV replication of both HEV gts could be observed. Furthermore, determination of extracellular and intracellular viral capsid levels, infectivity, and biophysical properties revealed production of HEV infectious particles with similar characteristics as in liver‐derived cells. Viral entry was analyzed by infection of target cells and detection of either viral RNA or staining for viral capsid protein by immunofluorescence. HEV gt1 and gt3 were efficiently inhibited by ribavirin in placental as well as in human hepatoma cells. In contrast, interferon‐α sensitivity was lower in the placental cells compared to liver cells for gt1 but not gt3 HEV. Simultaneous determination of interferon‐stimulated gene expression levels demonstrated an efficient HEV‐dependent restriction in JEG‐3. Conclusion: We showed differential tissue‐specific host responses to HEV genotypes, adding to our understanding of the mechanisms contributing to fatal outcomes of HEV infections during pregnancy. Using this cell‐culture system, new therapeutic options for HEV during pregnancy can be identified and evaluated. (Hepatology Communications 2018;2:173–187)

Evidence of the Extrahepatic Replication of Hepatitis E Virus in Human Endometrial Stromal Cells

“…In this study, we showed that HEV RNA and HEV ORF2 Ag were increased over time in PHESCs challenged with HEV preparations, indicating efficient replication in vitro and the life cycle of HEV is completed in these cells. Similar kinetic in HEV RNA and capsid proteins were reported in other cell lines that support HEV replication and represent sites of extrahepatic HEV replication, such as neuron and placenta-derived cell lines [36,37]. HEV-1 replicates more efficiently in PHESCs than HEV-3.…”

“…PHESCs were treated with 50 µM of RBV (Sigma-Aldrich, Darmstadt, Germany) after HEV infection as described previously [29,36,37] with a slight modifications in the procedure. Briefly, 2 × 10 4 cells/well were seeded in a 24-well plate and were incubated at 37 • C. After 24 h, culture medium was removed, and the cells were challenged with HEV preparations (10 6 IU/mL) with or without RBV.…”

The U-Rich Untranslated Region of the Hepatitis E Virus Induces Differential Type I and Type III Interferon Responses in a Host Cell-Dependent Manner

“…The 3= UTR of HEV induced predominantly type I IFN responses in enterocytes. A tissue-specific IFN response has been reported during HEV infection (23,24). Therefore, in addition to liver tissues from HEV-infected pigs and Huh7-S10-3 liver cells, we also determined the IFN mRNA expression levels in HEV SL1-and SL3-stimulated swine enterocyte IPEC-J2 cells using gene-specific RT-qPCR.…”

“…Recent studies showed that HEV induced IFN in both host cell-dependent and genotype-specific manners (23,24). Therefore, in this study, we tested the IFN induction ability by HEV RNA PAMPs in both hepatocytes and enterocytes, since the primary site of HEV replication is the small intestine before reaching the target organ (the liver).…”

“…Studies have also shown that HEV predominantly induces type III IFN in hepatocytes (20), and high serum IFN-3 levels has been observed in patients with acute HEV infection (27). Various IFN subtypes contribute to the antiviral effect against HEV (27,28), and HEV is known to regulate the IFN response dependent on both host and viral factors (23,24,29). Therefore, it is possible that type III IFN may be the predominant IFN to mediate antiviral effects in the liver, while type I IFN may play an important role in enterocytes, the initial site of HEV replication.…”