Abstract
Herpes simplex virus 1 (HSV-1) establishes latency in both peripheral nerve ganglia and the central nervous system (CNS). The outcomes of acute and latent infections in these different anatomic sites appear to be distinct. It is becoming clear that many of the existing culture models using animal primary neurons to investigate HSV-1 infection of the CNS are limited and not ideal, and most do not recapitulate features of CNS neurons. Human induced pluripotent stem cells (hiPSCs) and neurons derived from them are documented as tools to study aspects of neuropathogenesis, but few have focused on modeling infections of the CNS. Here, we characterize functional two-dimensional (2D) CNS-like neuron cultures and three-dimensional (3D) brain organoids made from hiPSCs to model HSV-1-human-CNS interactions. Our results show that (i) hiPSC-derived CNS neurons are permissive for HSV-1 infection; (ii) a quiescent state exhibiting key landmarks of HSV-1 latency described in animal models can be established in hiPSC-derived CNS neurons; (iii) the complex laminar structure of the organoids can be efficiently infected with HSV, with virus being transported from the periphery to the central layers of the organoid; and (iv) the organoids support reactivation of HSV-1, albeit less efficiently than 2D cultures. Collectively, our results indicate that hiPSC-derived neuronal platforms, especially 3D organoids, offer an extraordinary opportunity for modeling the interaction of HSV-1 with the complex cellular and architectural structure of the human CNS.IMPORTANCE This study employed human induced pluripotent stem cells (hiPSCs) to model acute and latent HSV-1 infections in two-dimensional (2D) and three-dimensional (3D) CNS neuronal cultures. We successfully established acute HSV-1 infections and infections showing features of latency. HSV-1 infection of the 3D organoids was able to spread from the outer surface of the organoid and was transported to the interior lamina, providing a model to study HSV-1 trafficking through complex neuronal tissue structures. HSV-1 could be reactivated in both culture systems; though, in contrast to 2D cultures, it appeared to be more difficult to reactivate HSV-1 in 3D cultures, potentially paralleling the low efficiency of HSV-1 reactivation in the CNS of animal models. The reactivation events were accompanied by dramatic neuronal morphological changes and cell-cell fusion. Together, our results provide substantive evidence of the suitability of hiPSC-based neuronal platforms to model HSV-1-CNS interactions in a human context.
Highlights
Herpes simplex virus 1 (HSV-1) establishes latency in both peripheral nerve ganglia and the central nervous system (CNS)
We recently reported the sensitivity of human 2D Human induced pluripotent stem cells (hiPSCs)-derived neuronal cultures to herpes simplex virus 1 (HSV-1) infection [11]
In order to further study the interaction of HSV-1 with CNS neurons, we investigated the expression of the immediate early protein ICP4 in the nuclei of HSV-1 infected MAP2-positive hiPSC-derived CNS neurons, generated as previously described [17] (Fig. 1)
Summary
Herpes simplex virus 1 (HSV-1) establishes latency in both peripheral nerve ganglia and the central nervous system (CNS). The absence of an adequate human cellular model and the limited availability of primary human neuronal cultures have hindered progress to investigate HSV-1 latency, the chromatin organization of HSV-1 genomes, and the transcription of viral miRNAs in human neurons These difficulties have impeded models of the interactions of HSV-1 with the human central nervous system (CNS). Human in vitro systems are critically needed to investigate HSV-1 genetics and epigenetics, to model HSV-1 infection of the human CNS, and to advance our understanding of the molecular mechanisms involved in HSV-1 latency and reactivation Such models would facilitate the development of more efficacious and long-lasting therapies for prophylaxis and treatment of HSV-1 infections, with a goal of improving the neurological sequelae in encephalitis survivors
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