Modeling extrahepatic hepatitis E virus infection in induced human primary neurons
Hepatitis E virus (HEV) infections are one of the most common causes of acute viral hepatitis, annually causing over 3 million symptomatic cases and 70,000 deaths worldwide. Historically, HEV was described as a hepatotropic virus, but has recently been associated with various extrahepatic manifestations including neurological disorders such as Guillain-Barré syndrome and neuralgic amyotrophy. However, the underlying pathogenesis of these neurological diseases remains largely unknown. The aim of this study was to investigate extrahepatic HEV manifestations in a neuronal model system using human induced primary neurons (iPNs). Renal epithelial cells from human urine were reprogrammed to induced pluripotent stem cells (iPSCs) to generate neuronal progenitor cells, which were subsequently differentiated into iPNs over 21 days. These iPNs supported HEV infection preferentially in neurite-bearing cells. Transcriptional profiling of the neuronal development process as well as viral infection dynamics in iPNs uncovered a lack of antiviral innate immune responses to HEV infection with only an intrinsic expression of distinct interferon-regulated genes (ISGs) and signaling molecules. Viral open reading frame 2 (ORF2) encoded capsid protein could be visualized by volumetric three-dimensional reconstitution within the neurites, which were reduced in length in an HEV inoculation-dependent manner. In conclusion, this neuron-derived human model system provides a powerful tool for studying extrahepatic manifestations of HEV infection. It further indicates a potential mechanism of pathogenesis driven by the interaction between host and viral factors. Overall design: Different differentiation stages of induced primary neurons (days 2, 7, 14, and 21) were subjected to HEV infection for five days. As a control, medium without viral particles was used for each differentiation stage and incubated for five days or for 48 hours for cells that were two days old. Analysis was performed to characterize the global gene expression changes during the differentiation process, followed by a comparison of Mock versus infected samples. Particular emphasis was placed on innate immune genes and interferon-regulated genes. For each sample an individual run was performed.