Hepatitis E Virus Lifecycle and Identification of 3 Forms of the ORF2 Capsid Protein

Abstract

We developed a cell culture system and characterized HEV particles; we identified 3 ORF2 capsid proteins (ORF2i, ORF2g, and ORFc). These findings will advance our understanding of the HEV life cycle and improve diagnosis.

Updates in Hepatitis E virus (HEV) field; lessons learned from human liver chimeric mice

“…35,36,59 This evidence suggests that a large amount of ORF2 Ag present in the plasma is attributed to non-infectious particles; a similar conclusion was made from the analysis of HEV infected human sera. 59,65 The viral load and HEV Ag level were higher in gt1 infected mice than in gt3 infected mice, confirming that HEV gt1 is more virulent than gt3. 36,59 Again, similar findings were reported in humans and NHPs.…”

“…Using a robust in vitro cell culture system, Montpellier et al, reported that massive amounts of HEV ORF2 Ag were secreted into the cell culture supernatant and they characterized 3 different forms of ORF2: infectious/intracellular ORF2 (ORF2i), glycosylated ORF2 (ORF2g) and cleaved ORF2 (ORF2c). 65 The ORF2i protein (Mr 80,000) is the structural component of infectious viral particles F I G U R E 1 Production of humanized mice and course of HEV infection. Humanized mice are generated by transplantation of primary human hepatocytes, isolated from human liver fragments and explants, into immunodeficient mice.…”

“…Comparing the virologic parameters in the stool and the plasma of the infected mice revealed high HEV RNA content in the stool compared with the plasma, while HEV ORF2Ag showed an inverse correlation. Stool-derived HEV particles were more infectious than plasma-derived HEV, when they were passaged into naïve mice 65,73 Humanized mice were used to characterize the infectivity of the fraction (fraction 6) of HEVcc that includes only ORF2i. Unlike the HEVcc supernatant, fraction 6 was infectious to the mice indicating that the removal of noninfectious ORF2 Ag increased the infectivity of the HEV preparation, probably due to absence of competitive binding between both infectious and noninfectious ORF2 Ag to the receptor.…”

Convalescent plasma therapy for persistent hepatitis E virus infection

“…Recent studies have identified 3 forms of this ORF2 antigen. 19 It would be informative to understand whether all 3 forms of HEV-Ag fell post-infusion in our patient or whether the secreted form preferentially fell. We anticipate the fall in HEV-Ag levels we observed is due to binding and neutralisation of the secreted form of ORF2, since we would have expected the viral load to fall if virion-associated HEV-Ag had been bound and cleared from the circulation.…”

Elucidating the differences in pathogenicity between hepatitis E virus genotypes: The quest continues

“…The authors also successfully demonstrated HEV infection in JEG‐3 cells after electroporation of full‐length HEV RNA of gt3, including virion assembly and release of infectious viral particles that have similar biophysical characteristics as HEV particles typically produced in HepG2 cells 6. Infection with full‐length gt1 HEV was not successful, but it remains unclear whether this is typical for gt1 viruses in JEG‐3 cells or rather due to the inherent low replicative capacity of Sar55 in cell culture; most likely it is due to the latter.…”