A model of impaired Langerhans cell maturation associated with HPV induced epithelial hyperplasia.

Langerhans cells (LC) are skin-resident antigen-presenting cells that regulate immune responses to epithelial microorganisms. Human papillomavirus (HPV) infection can promote malignant epithelial transformation. As LCs are considered important for controlling HPV infection, we compared the transcriptome of murine LCs from skin transformed by K14E7 oncoprotein and from healthy skin. We identified transcriptome heterogeneity at the single cell level amongst LCs in normal skin, associated with ontogeny, cell cycle, and maturation. We identified a balanced co-existence of immune-stimulatory and immune-inhibitory LC cell states in normal skin that was significantly disturbed in HPV16 E7-transformed skin. Hyperplastic skin was depleted of immune-stimulatory LCs and enriched for LCs with an immune-inhibitory gene signature, and LC-keratinocyte crosstalk was dysregulated. We identified reduced expression of interleukin (IL)-34, a critical molecule for LC homeostasis. Enrichment of an immune-inhibitory LC gene signature and reduced levels of epithelial IL-34 were also found in human HPV-associated cervical epithelial cancers.

Single-cell RNA sequencing reveals cell type-specific HPV expression in hyperplastic skin lesions.

Human Papillomavirus infection is highly prevalent worldwide. While most types of HPV cause benign warts, some high-risk types are known to cause cervical cancer, as well as cancer of the oral cavity and head and neck. Persistent cutaneous HPV infection can be particularly problematic in patients with chronic immunosuppression, for example following organ transplantation. Due to unknown mechanisms, these patients may develop numerous warts, as well as present with a dramatically increased skin cancer prevalence. Despite an association between HPV persistence in the epidermis and excessive wart or squamous cancer development, the molecular mechanisms linking immunosuppression, HPV expression and excessive epidermal proliferation have not been determined, largely due to low-sensitivity methodology to capture rare viral transcription events. Here, we use single-cell RNA sequencing to profile HPV-positive skin lesions from an immunosuppressed patient that were found to express the alphapapillomavirus HPV78 in basal keratinocytes, suprabasal keratinocytes and hair follicle stem cells. This method can be applied to detect and investigate HPV transcripts in cutaneous lesions, allowing mechanistic links between immunosuppression-induced HPV life cycle and epidermal hyperproliferation to be uncovered.