Herpes Simplex Virus (HSV) is sexually transmitted through the anogenital epithelium and infects keratinocytes and Dendritic Cells (DCs), via the receptor Nectin-1. We established a human foreskin explant model to investigate HSV entry and spread and found that microtrauma was essential in viral infection beyond the superficial layers of the inner foreskin epidermis. Rapid lateral infection occurred in keratinocytes within 24 hpi, due to the redistribution of Nectin-1 partially mediated by the production of chemokines from infected keratinocytes. We previously showed that Langerhans cells (LCs) and Epidermal (Epi-) DCs are infected with HSV-1 and undergo apoptosis while migrating into the dermis. Dermal DCs are recruited to the region and take up the viral antigen, to be presented to T cells as shown in mice. Here, using RNAscope to detect viral DNA and cyclic immunofluorescence (IF), we visualised clusters of dermal conventional type 1 and type 2 DCs (cDC1s & cDC2s) under epidermal “foci” of infection compared to regions far from infection. Flow cytometry, Legendplex and chemotaxis assays were utilised to determine the specific chemokines involved in recruitment of dermal DCs to the upper dermis, including CXCL9/10 produced by HSV infected LCs and Epi-DCs, which bind to CXCR3 on cDC1s, and CCL3/4 produced by Epi-DCs, which bind to CCR5 on cDC2s.
HSV also infects cutaneous nerve fibres, through which the virus can travel up the neurons into the DRG and establish latency and lifelong infection. IF staining of nerve fibres labelling PGP9.5 and RNAscope of HSV infected inner foreskin showed individual HSV particles colocalised or in close proximity to nerve fibres in dermal papillae at 24 hpi. This data indicates there is a narrow window of opportunity for targeting HSV in early infection to prevent the establishment of latency, thus informing the design for potential prophylactic vaccines.