Herpes Simplex Virus 1 (HSV-1) establishes itself primarily within sensory neurons of the trigeminal ganglia. Inside the neurons, the virus persists in a latent state and can potentially reactivate, leading to recurrent infections. Research on HSV-1 latency has traditionally been conducted in animal models, primarily mice, due to their ability to provide integrative insights into the pathophysiology of the infection. Various cell cultures are emerging as alternative models for studying HSV-1 latency at the molecular level, including primary mouse neurons, immortalized human neurons, and neuron-like cells. Human induced pluripotent stem cell (hiPSC)-derived neurons are increasingly utilized due to their ease of production and maintenance, along with their relevance as a human-based model.

We have developed a straightforward protocol that allows us to obtain neurons with characteristic features of sensory neurons, including the expression of specific molecular markers and the ability to generate action potentials. These neurons can be used in 2D culture and in 3D spheroids, offering a versatile system to study HSV-1. In collaboration with the CellTechs team (CEA/SupBiotech, Fontenay-aux-Roses), we are also developing a 3D model of neuro-ectodermal organoids for infections. These organoids mimic the complex cellular environment of the nervous system, providing a more physiologically relevant context for studying HSV-1 latency and reactivation. The integration of neurons with supporting cells, such as astrocytes and neural progenitors, within these organoids allows for the examination of cell-cell interactions and signaling pathways that may influence viral latency. Our preliminary data show that we can efficiently infect our hiPSC-derived sensory neurons and neuro-ectodermal organoids, establishing latent infection and/or reactivation of the virus.

The development of these advanced models is crucial for gaining deeper insights into the molecular mechanisms governing HSV-1 persistence and reactivation, particularly in terms of epigenetic regulation.