Hepatitis E Virus Produced from Cell Culture Has a Lipid Envelope

Abstract

The absence of a productive cell culture system hampered detailed analysis of the structure and protein composition of the hepatitis E virion. In this study, hepatitis E virus from a robust HEV cell culture system and from the feces of infected monkeys at the peak of virus excretion was purified by ultra-centrifugation. The common feature of the two samples after ultracentrifugation was that the ORF2 protein mainly remained in the top fractions. The ORF2 protein from cell culture system was glycosylated, with an apparent molecular weight of 88 kDa, and was not infectious in PLC/PRF/5 cells. The ORF2 protein in this fraction can bind to and protect HEV RNA from digestion by RNase A. The RNA-ORF2 product has a similar sedimentation coefficient to the virus from feces. The viral RNA in the cell culture supernatant was mainly in the fraction of 1.15g/cm3 but that from the feces was mainly in the fraction of 1.21 g/cm3. Both were infectious in PLC/PRF/5 cells. And the fraction in the middle of the gradient (1.06g/cm3) from the cell culture supernatant,but not that from the feces, also has ORF2 protein and HEV RNA but was not infectious in PLC/PRF/5.The infectious RNA-rich fraction from the cell culture contained ORF3 protein and lipid but the corresponding fraction from feces had no lipid and little ORF3 protein. The lipid on the surface of the virus has no effect on its binding to cells but the ORF3 protein interferes with binding. The result suggests that most of the secreted ORF2 protein is not associated with HEV RNA and that hepatitis E virus produced in cell culture differs in structure from the virus found in feces in that it has a lipid envelope.

Cutthroat Trout Virus—Towards a Virus Model to Support Hepatitis E Research

“…Hepatitis A virus (HAV), for example, has been shown to be enveloped when produced in cell culture [29,30]. Similarly, it was reported that HEV released from infected cells has a lipid envelope [31,32]. The presence of an envelope in HEV depends on the environment the virus encounters.…”

Evaluation of High-Pressure Processing in Inactivation of the Hepatitis E Virus

“…HEV is a quasi-enveloped virus (47, 48), and the presence of a lipid envelope may have a protective role. If so the impact HPP could potentially be enhanced in the presence of detergents or other membrane disrupting molecules.…”

New insights into the ORF2 capsid protein, a key player of the hepatitis E virus lifecycle

“…HEV is a quasi-enveloped virus (6–8) containing a linear, single-stranded, positive-sense RNA genome that contains three open reading frames (ORFs), namely, ORF1, ORF2 and ORF3 (9). ORF1 encodes a non-structural polyprotein (ORF1 protein) that is essential for viral replication (10).…”

“…The ORF2 protein has been largely studied and is the most characterized HEV viral protein. However, whether using various heterologous expression systems (14–17) or infectious systems (8, 13), the glycosylation status of ORF2 and the biological relevance of this post-translational modification was still controversial until recently. Indeed, by combining the highly replicative and cell culture-selected gt3 p6 strain (18) and a highly transfectable subclone of PLC/PRF/5 cells (PLC3 cells), we recently developed an efficient HEV cell culture system and demonstrated for the first time that, during its lifecycle, HEV produces 3 forms of the ORF2 capsid protein ( Figure 1A ): infectious/intracellular ORF2 (ORF2i), glycosylated ORF2 (ORF2g), and cleaved ORF2 (ORF2c) (19).…”