Complex Human hear bearing SkiOrganoids reveal Cell- Type Specific Susceptibility and Innate Immune Responses to Herpes Simplex Virus 1

Epithelial surfaces are the initial site of Herpes Simplex Virus 1 (HSV-1) infection. After latencyestablishment in the peripheral nervous system, reactivation can lead to skin pathologies likecold sores. To reflect the complexity of human skin, we used complex human hair bearing skinorganoids as a new model system for HSV-1 infection. Using microscopy and spatialtranscriptomics with single cell resolution, we found a restricted viral infection in keratinocytesof the epidermis and in hair follicles. The immediate early response 3 protein (IER3) wasspecifically upregulated at the leading edge of the infection in papillary fibroblasts of the dermis.In keratinocytes of the stratum basale, we found interferon regulatory factor 3 (IRF3)upregulated in infected but also virus negative cells, suggesting a signaling mechanism toinitiate antiviral responses. Furthermore, we found that infection of keratinocytes andfibroblasts led to activation of TNF and TNFSF9 genes, respectively, with TNFalpha target genesinduced in neighboring cells. We postulate that this spatially coordinated production ofsignaling molecules orchestrates an efficient immune response to HSV-1 aiming to suppressviral infection after reactivation. Taken together, we demonstrate how organoids can be used toinvestigate progression of an infection and cellular reactions in tissue.