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Identification and characterization of hepatitis E virus factories

Although Hepatitis E virus (HEV) is the major leading cause of enterically transmitted viral hepatitis worldwide, many gaps remain in the understanding of the HEV lifecycle. Notably, viral factories induced by HEV have not been documented yet and it is currently unknown whether HEV infection leads to cellular membrane modelling as many positive-strand RNA viruses.

HEV genome encodes the ORF1 replicase, the ORF2 capsid protein and the ORF3 protein involved in virion egress. Previously, Laurence Cocquerel's research group demonstrated that HEV produces different ORF2 isoforms including the virion-associated ORF2i form. In the study of Bentaleb, Hervouet et al.,they generated monoclonal antibodies that specifically recognize the ORF2i form, and antibodies that recognize the different ORF2 isoforms. One antibody, named P1H1 and targeting the ORF2i N-terminus, recognized delipidated HEV particles from cell culture and patient sera. Importantly, AlphaFold2 modelling demonstrated that the P1H1 epitope is exposed on HEV particles. Next, they used the anti-ORF2 antibodies to probe viral factories in HEV-producing/infected cells. By confocal microscopy, they identified subcellular nugget-like structures enriched in ORF1, ORF2 and ORF3 proteins and viral RNA. Electron microscopy analyses revealed an unprecedented HEV-induced membrane network containing tubular and vesicular structures. They showed that these structures are dependent on ORF2i capsid protein assembly and ORF3 expression. An extensive colocalization study of viral proteins with subcellular markers, and silencing experiments demonstrated that these structures are derived from the endocytic recycling compartment (ERC) for which Rab11 is a central player. Hence, HEV hijacks the ERC and forms a membrane network of vesicular and tubular structures that might be the hallmark of HEV infection. This work opens new diagnostic and therapeutic perspectives to fight HEV.

The Endocytic Recycling Compartment Serves as a Viral Factory for Hepatitis E Virus

Bentaleb C*, Hervouet K*, Montpellier C§, Camuzet C§, Ferrié M§, Burlaud-Gaillard J, Bressanelli S, Metzger K, Werkmeister E, Ankavay M, Janampa NL, Marlet J, Roux J, Deffaud C, Goffard A, Rouillé Y, Dubuisson J, Roingeard P, Aliouat-Denis C-M$, Cocquerel L$.

Cellular and Molecular Life Sciences, 2022 Dec 3;79(12):615. doi: 10.1007/s00018-022-04646-y