title: Entry of equid herpesvirus 1 into CD172a+ monocytic cells.
abstract: Equid herpesvirus 1 (EHV-1) causes respiratory disease, abortion and neurological disorders in horses. Cells from the myeloid lineage (CD172a+) are one of the main target cells of EHV-1 during primary infection. Recently, we showed that EHV-1 restricts and delays its replication in CD172a+ cells as part of an immune-evasive strategy to disseminate to target organs. Here, we hypothesize that a low efficiency of EHV-1 binding to and entry in CD172a+ cells is responsible for this restriction. Thus, we characterized EHV-1 binding and entry into CD172a+ cells, and showed that EHV-1 only bound to 15-20 % of CD172a+ cells compared with 70 % of RK-13 control cells. Enzymic removal of heparan sulphate did not reduce EHV-1 infection, suggesting that EHV-1 does not use heparan sulphate to bind and enter CD172a+ cells. In contrast, we found that treatment of cells with neuraminidase (NA) reduced infection by 85-100 % compared with untreated cells, whilst NA treatment of virus had no effect on infection. This shows that sialic acid residues present on CD172a+ cells are essential in the initiation of EHV-1 infection. We found that αVβ3 integrins are involved in the post-binding stage of CD172a+ cell infection. Using pharmacological inhibitors, we showed that EHV-1 does not enter CD172a+ cells via a clathrin- or caveolae-dependent endocytic pathway, nor by macropinocytosis, but requires cholesterol, tyrosine kinase, actin, dynamin and endosomal acidification, pointing towards a phagocytic mechanism. Overall, these results show that the narrow tropism of EHV-1 amongst CD172a+ cells is determined by the presence of specific cellular receptors.
authors.affiliation: Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium.
authors.forename: Kathlyn
authors.initials: K
authors.lastname: Laval
authors.affiliation: Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium.
authors.forename: Herman W
authors.initials: HW
authors.lastname: Favoreel
authors.affiliation: Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium.
authors.forename: Jolien
authors.initials: J
authors.lastname: Van Cleemput
authors.affiliation: Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium.
authors.forename: Katrien C K
authors.initials: KCK
authors.lastname: Poelaert
authors.affiliation: Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium.
authors.forename: Ivy K
authors.initials: IK
authors.lastname: Brown
authors.affiliation: Department of Clinical Chemistry, Microbiology and Immunology, Ghent University, De Pintelaan 185, 9000 Gent, Belgium.
authors.forename: Bruno
authors.initials: B
authors.lastname: Verhasselt
authors.affiliation: Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium.
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Nauwynck
mesh_terms: D000818:Animals; D000943:Antigens, Differentiation / Q000235:genetics / Q000276:immunology*; D006566:Herpesviridae Infections / Q000276:immunology / Q000662:veterinary* / Q000821:virology; D004861:Herpesvirus 1, Equid / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D006734:Horse Diseases / Q000276:immunology / Q000821:virology*; D006736:Horses; D054884:Host-Pathogen Interactions; D009000:Monocytes / Q000276:immunology / Q000821:virology*; D053586:Virus Internalization
chemical_list: D000943:Antigens, Differentiation