Mouse models of acute and chronic hepatitis E virus infection.

BACKGROUND & AIMS: Hepatitis E virus (HEV) causes approximately 19.47 million symptomatic cases annually and is an emerging cause of chronic hepatitis in immunocompromised individuals. No definite evidence demonstrates that laboratory mice are susceptible to all known HEV genotypes. The factors that define the host species range of HEV remain unclear. Given the numerous genetic variants and toolkits available for mice, which permit deep mechanistic studies, we aimed to develop an inbred mouse model of HEV infection. METHODS: AG129 and C57BL/6J mice were infected with HEV. Key infection parameters included HEV RNA detection by RT-PCR and RNAscope, liver function tests, histopathological examination. Single-cell RNA sequencing was employed alongside transcriptomic analysis to delineate infection dynamics and investigate virus-host interactions. RESULTS: We show that an emerging human-pathogenic rat-derived HEV-C1 strain can breach the species barrier and robustly infect AG129 mice. Using single-cell sequencing and RNAscope, we demonstrate viral tropism for liver macrophages and hepatocytes, providing a previously unknown single-cell atlas of intrahepatic HEV-C1 infection. We subsequently adapted this HEV-C1 isolate by serial passaging in AG129 mice. After 13 passages, the resulting mouse-adapted strain acquired the ability to infect immunocompetent C57BL/6J mice. Both the immunocompromised and immunocompetent mouse models supported efficient HEV replication and enabled antiviral and vaccine testing. CD4 depletion experiments suggest that impairment of CD4+ T cell responses may contribute to the establishment of persistent infection. CONCLUSIONS: We developed two mouse models using AG129 and C57BL/6J mice, both of which support efficient HEV-C1 replication. This work establishes the first immunocompetent mouse model for HEV infection. These mouse models offer a robust platform for studying HEV immunopathogenesis, evaluating antivirals and vaccines, and investigating mechanisms of cross-species transmission. GENBANK ACCESSION NUMBERS: PX496820, PX572923 RNA-Seq data: https://ngdc.cncb.ac.cn/gsa/ IMPACT AND IMPLICATIONS: HEV research is hampered by the lack of suitable small-animal models, and our study fills this gap by establishing two mouse models, particularly the immunocompetent C57BL/6J mouse model, which should support the use of versatile genetic and immunological tools for deep mechanistic studies in the future. This study also provides a single-cell atlas of HEV infection dynamics, revealing intrahepatic viral tropism. We identified CD4+ T cell depletion as a pivotal driver of chronic infection. These mouse models offer a robust platform for studying HEV immunopathogenesis, evaluating antivirals and vaccines, and investigating mechanisms of cross-species transmission.