Large Extracellular Vesicles From Keratinocytes Expressing Human Papillomavirus Type 16 E6/E7 Suppress...

Human papillomavirus type 16 (HPV16) E6 and E7 are oncogenic proteins that are overexpressed following viral genome integration into the chromosomal DNA of infected mucosal epithelial cells, contributing to viral immune evasion and carcinogenesis. Epithelial cells can shed large extracellular vesicles (LEVs) that may modulate immune responses. We hypothesise that LEVs shed from epithelial cells expressing E6 and E7 modulate CD8⁺ T cell priming by the skin-local antigen presenting cells, the Langerhans cells (LCs). LEVs were isolated from control and E6/E7-expressing murine epithelial PDV cells. PDV-E6/E7 cells shed threefold more LEVs than control PDV cells in vitro. Murine LC 'like' cells were differentiated in vitro, co-cultured with LEVs, and assessed for antigen presentation, co-stimulatory molecule expression and cytokine production. We found that LCs co-cultured with Ctrl-LEVs demonstrated enhanced TAP1-dependent CD8 T cell priming, which was associated with increased co-stimulatory molecule and IL-12 expression. LCs co-cultured with E6/E7-LEVs failed to enhance TAP-1-dependent T cell priming and suppressed IL-12 production despite upregulating MHC-1 and co-stimulatory molecule expression. Our results show that LC priming of T cells is enhanced following treatment with Ctrl-LEVs whereas LEVs from HPV16 E6/E7 expressing cells suppress LC function. Functional impairment of LC priming of T cells by E6/E7-LEVs released in the epithelium may contribute to viral persistence in HPV16-infected skin.