Hepatitis E virus (HEV) is widespread worldwide, particularly in East and South Asia, and sporadically in developed countries such as Japan, the United States, and Western Europe. HEV is usually acute or latent, but in special populations such as pregnant women, patients who have received organ transplantation, or have underlying liver disease, HEV infection can lead to severe, chronic, extrahepatic injury, and even death from hepatitis E. Effective in vitro models are essential to study the pathogenesis of hepatitis E, virus-host interactions, and drug development.
At present, hepatocellular carcinoma cell lines are the most commonly used in vitro models for the study of hepatitis E, but their characteristics are far from normal hepatocytes, and there are certain limitations in exploring the host response and antiviral drug evaluation after infection. Organoids are formed by the differentiation of pluripotent stem cells or organ progenitor cells, which have a highly similar structure to tissues or organs of the same source in vivo, and therefore have a unique advantage in maintaining the structure, composition, diversity and function of the source tissue/organ cell type as an in vitro model.
Recently, Professor Pan Qiuwei of Erasmus University Medical Center in the Netherlands and Professor Wang Yijin's research group at Southern University of Science and Technology published a paper entitled "Retractulating hepatitis E virus–host interactions" and facilitating antiviral drug discovery in human liver– Derived organoids research paper. The study successfully established an in vitro replication and infection model of HEV using human liver organoids, which supports the entire life cycle of HEV infection and is suitable for studying viral-host interactions as well as antiviral drug screening.
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In the previous period and in the study, the research group found that hepatocytes and cholangiocytes of the liver parenchymal cells (hepatocytes) and cholangiocytes in patients with hepatitis E could be directly infected with HEV. There are populations of stem cells in the human liver that can be cultured into organoids. These stem cells are located in the biliary chamber and produce organoids with a bile duct cell phenotype that can differentiate into hepatic parenchymal cells under specific culture conditions. The study first used normal human liver tissue to obtain 3D cultured organoids, and then transfected HEV RNA or directly infected organoids through viral particles, confirming that differentiated (with hepatic phenotype) and undifferentiated (with bile ducts and liver phenotype cells) can effectively support HEV replication and infection (Figure 1).
Figure 1. 3D culture of human liver organoids can effectively support HEV replication and infection in both differentiated (right) and undifferentiated (left) states
The researchers then used the Transwell culture system, where 3D liver organoids could be converted into 2D single-cell layers. Differentiated and undifferentiated 2D liver organoid cells are also effective in supporting HEV replication and infection. It was further found that viral particles in this system are more likely to be released from the top of the cell to the supernatant than from the basal end, so the model somehow simulates the detoxification pattern of the human liver (Figure 2).
Figure 2. 2D cultured human liver organoid cells effectively support HEV replication and infection and its viral release patterns.
Through transcriptomics and tRNA omics, the study explored the interaction between HEV and the host, validating interferon pathway activation and its antiviral effects. In addition, the study also used a 3D organoid HEV replication model for broad-spectrum antiviral drugs screening, and the results showed that homoharringtonine has a highly effective anti-HEV effect, stronger than the antihev drug virazole that has been used clinically at the same concentration (Figure 3). At present, high-spinel is mainly used for the treatment of leukemia, and its anti-HEV effect has yet to be verified by later in vivo tests.
Figure 3. Using the 3D organoid HEV replication model, the spectral antiviral drug library was screened to find the highly effective antiHEV effect of high-spinel
In summary, the study successfully established a novel in vitro model of HEV based on human liver organoids. The system will greatly advance research on heV-host interactions and screening of antiviral drugs. At present, this model is mainly suitable for genotype 3 HEV, and other genotype models need to be further explored and optimized.
Doctoral student Li Pengfei is the first author of the paper, and Professor Pan Qiuwei and Professor Wang Yijin are co-corresponding authors
原文链接：Li P, Li Y, Wang Y, et al. Recapitulating hepatitis E virus-host interactions and facilitating antiviral drug discovery in human liver-derived organoids. Sci Adv. 2022 Jan 21;8( 3):eabj5908.
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