title: Entry mechanisms of herpes simplex virus 1 into murine epidermis: involvement of nectin-1 and herpesvirus entry mediator as cellular receptors.
abstract: Skin keratinocytes represent a primary entry site for herpes simplex virus 1 (HSV-1) in vivo. The cellular proteins nectin-1 and herpesvirus entry mediator (HVEM) act as efficient receptors for both serotypes of HSV and are sufficient for disease development mediated by HSV-2 in mice. How HSV-1 enters skin and whether both nectin-1 and HVEM are involved are not known. We addressed the impact of nectin-1 during entry of HSV-1 into murine epidermis and investigated the putative contribution of HVEM. Using ex vivo infection of murine epidermis, we showed that HSV-1 entered the basal keratinocytes of the epidermis very efficiently. In nectin-1-deficient epidermis, entry was strongly reduced. Almost no entry was observed, however, in nectin-1-deficient keratinocytes grown in culture. This observation correlated with the presence of HVEM on the keratinocyte surface in epidermis and with the lack of HVEM expression in nectin-1-deficient primary keratinocytes. Our results suggest that nectin-1 is the primary receptor in epidermis, while HVEM has a more limited role. For primary murine keratinocytes, on which nectin-1 acts as a single receptor, electron microscopy suggested that HSV-1 can enter both by direct fusion with the plasma membrane and via endocytic vesicles. Thus, we concluded that nectin-1 directs internalization into keratinocytes via alternative pathways. In summary, HSV-1 entry into epidermis was shown to strongly depend on the presence of nectin-1, but the restricted presence of HVEM can potentially replace nectin-1 as a receptor, illustrating the flexibility employed by HSV-1 to efficiently invade tissue in vivo.
  
  
  OBJECTIVE
  Herpes simplex virus (HSV) can cause a range of diseases in humans, from uncomplicated mucocutaneous lesions to life-threatening infections. The skin is one target tissue of HSV, and the question of how the virus overcomes the protective skin barrier and penetrates into the tissue to reach its receptors is still open. Previous studies analyzing entry into cells grown in vitro revealed nectin-1 and HVEM as HSV receptors. To explore the contributions of nectin-1 and HVEM to entry into a natural target tissue, we established an ex vivo infection model. Using nectin-1- or HVEM-deficient mice, we demonstrated the distinct involvement of nectin-1 and HVEM for HSV-1 entry into epidermis and characterized the internalization pathways. Such advances in understanding the involvement of receptors in tissue are essential preconditions for unraveling HSV invasion of skin, which in turn will allow the development of antiviral reagents.
authors.affiliation: Center for Biochemistry, University of Cologne, Cologne, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Petermann
authors.affiliation: Center for Biochemistry, University of Cologne, Cologne, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Thier
authors.affiliation: Center for Biochemistry, University of Cologne, Cologne, Germany.
authors.forename: Elena
authors.initials: E
authors.lastname: Rahn
authors.affiliation: MRC University of Glasgow Center for Virus Research, Glasgow, United Kingdom.
authors.forename: Frazer J
authors.initials: FJ
authors.lastname: Rixon
authors.affiliation: Department of Molecular and Cellular Sports Medicine, German Sports University, Cologne, Germany.
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Bloch
authors.affiliation: Center for Biochemistry, University of Cologne, Cologne, Germany.
authors.forename: Semra
authors.initials: S
authors.lastname: Özcelik
authors.affiliation: Department of Biological Sciences and Department of Biomedical and Translational Sciences, Rowan University, Glassboro, New Jersey, USA.
authors.forename: Claude
authors.initials: C
authors.lastname: Krummenacher
authors.affiliation: Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Barron
authors.affiliation: Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Dixon
authors.affiliation: Institute of Medical Microbiology and Hospital Hygiene, University of Düsseldorf, Düsseldorf, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Scheu
authors.affiliation: Institute of Medical Microbiology and Hospital Hygiene, University of Düsseldorf, Düsseldorf, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Pfeffer
authors.affiliation: Center for Biochemistry, University of Cologne, Cologne, Germany Department of Dermatology, University of Cologne, Cologne, Germany dagmar.moersdorf@uni-koeln.de.
authors.forename: Dagmar
authors.initials: D
authors.lastname: Knebel-Mörsdorf
mesh_terms: D000818:Animals; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D018259:Herpesvirus 1, Human / Q000502:physiology*; D054884:Host-Pathogen Interactions; D015603:Keratinocytes / Q000821:virology*; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D046529:Microscopy, Electron, Transmission; D000075983:Nectins; D053240:Receptors, Tumor Necrosis Factor, Member 14 / Q000378:metabolism*; D011991:Receptors, Virus / Q000378:metabolism*; D012867:Skin / Q000821:virology; D053586:Virus Internalization
chemical_list: D015815:Cell Adhesion Molecules; C000619010:NECTIN1 protein, human; C000619015:Nectin1 protein, mouse; D000075983:Nectins; D053240:Receptors, Tumor Necrosis Factor, Member 14; D011991:Receptors, Virus