Characterization of Herpes simplex virus internalization into keratinocytes and fibroblasts
Final Report Abstract
The human pathogen herpes simplex virus 1 (HSV-1) penetrates its host via the skin and mucosa, which leads to infection of the epithelium. The open question is how the virus invades this highly protective tissue in vivo and overcomes the effective epithelial barriers to approach its receptors and initiate infection. To explore the viral invasion routes in tissue, we established an ex vivo infection assay using human skin explants. Once the dermis is separated, human epidermal sheets are highly susceptible to HSV-1 via the basal layer upon ex vivo infection; however, the virus cannot penetrate full thickness skin via the apical surface confirming the effective outside-in barrier function of the skin. The general assumption is that skin lesions can serve as entry portals for HSV-1. Remarkably, mechanical wounds of the human skin surface do not provide ad hoc entry portals for HSV-1 after ex vivo infection. Similarly, mechanical wounding of human oral mucosa explants is insufficient for HSV-1 invasion. To address whether pathological skin conditions facilitate viral entry via the skin surface, we ex vivo infected atopic dermatitis (AD) skin characterized by disturbed barrier functions. Lesional AD skin indeed allows HSV-1 penetration via the skin surface suggesting that the impaired epidermal barriers make receptors accessible for HSV-1. In addition to the epidermis, the underlying dermis is a further critical target tissue for HSV-1 in vivo. In murine primary dermal fibroblasts that are deficient in the receptors nectin-1 and HVEM, infection is strongly reduced, while the cells are highly susceptible as long as one of the receptors is present. Ex vivo infection of the dermis revealed that fibroblasts can be rather inefficiently infected which was more pronounced in human than in murine dermis. Interestingly, we found delayed infection efficiency in the dermis of aged mice which correlated with decreased nectin-1 expression during aging while levels of HVEM were unchanged. Our studies on receptor presence and accessibility support the heterogeneity of murine and human dermis and imply that the interplay between dermal barrier functions and receptor presence determine how well HSV-1 penetrates the dermis. Studies in cell culture indicate that HSV-1 infection relies on multiple internalization pathways. Our focus is on viral entry in skin cells. When we addressed the impact of virus internalization via vesicles by blocking endocytic processes at low temperature, we detected viral entry even at 7°C which led to infection of human primary keratinocytes and epidermal tissue. Strikingly, electron microscopy supports that internalization at 7°C is based on fusion of the envelope with the plasma membrane as well as vesicle membranes. In addition, we observed both internalization pathways in dynamin-expressing and dynamin-deficient murine fibroblasts supporting that alternative pathways present upon dynamin depletion can accomplish internalization of HSV-1. Overall, our studies strengthen the role of diverse modes of HSV-1 uptake in skin cells including unconventional endocytic pathways.
Publications
- 2017. Mechanical barriers restrict invasion of herpes simplex virus 1 into human oral mucosa. J. Virol. 91, e01295-17
Thier, K., Petermann, P., Rahn, E., Rothamel, D., Bloch, W., and Knebel-Mörsdorf D.
(See online at https://doi.org/10.1128/jvi.01295-17) - 2018. Entry of herpes simplex virus 1 into epidermis and dermal fibroblasts is independent of the scavenger receptor MARCO. J. Virol. 92, e00490-18
Thier, K., Möckel, M., Palitzsch, K., Döhner, K., Sodeik, B., and Knebel-Mörsdorf D.
(See online at https://doi.org/10.1128/jvi.00490-18) - 2019. Herpes simplex virus 1 can enter dynamin 1 and 2 double-knockout fibroblasts. J. Virol. 93, e00704-19
Möckel, M., Rahn, E., de la Cruz, N., Wirtz, L., van Lent, J.W.M., Pijlman, G.P., and Knebel-Mörsdorf D.
(See online at https://doi.org/10.1128/jvi.00704-19) - 2020. Invasion of herpes simplex virus 1 into murine dermis: The role of nectin-1 and herpesvirus entry mediator as cellular receptors during aging. J. Virol. 94, e02046-19
Wirtz, L., Möckel M, and Knebel-Mörsdorf D.
(See online at https://doi.org/10.1128/jvi.02046-19) - 2021. Endocytic internalization of herpes simplex virus 1 in human keratinocytes at low temperature. J Virol. 2021, e02195-20
De La Cruz, N., and Knebel-Mörsdorf D.
(See online at https://doi.org/10.1128/jvi.02195-20) - 2021. Ex Vivo Infection of Human Skin with Herpes Simplex Virus 1 Reveals Mechanical Wounds as Insufficient Entry Portals via the Skin Surface. J Virol. 95,e0133821
De La Cruz, N.C., Möckel, M., Wirtz, L., Sunaoglu, K., Malter, W., Zinser, M., and Knebel-Mörsdorf, D.
(See online at https://doi.org/10.1128/jvi.01338-21) - 2022. Susceptibility of human and murine dermal fibroblasts to herpes simplex virus 1 in the absence and presence of extracellular matrix. J Virol. 96, e02068-21
Wirtz, L., De La Cruz, N.C., Möckel, M., and Knebel-Mörsdorf, D.
(See online at https://doi.org/10.1128/jvi.02068-21)
