Entry of equid herpesvirus 1 into CD172a+ monocytic cells

J Gen Virol. 2016 Mar;97(3):733-746. doi: 10.1099/jgv.0.000375. Epub 2015 Dec 18.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antigens, Differentiation / genetics
  • Antigens, Differentiation / immunology*
  • Herpesviridae Infections / immunology
  • Herpesviridae Infections / veterinary*
  • Herpesviridae Infections / virology
  • Herpesvirus 1, Equid / genetics
  • Herpesvirus 1, Equid / immunology
  • Herpesvirus 1, Equid / physiology*
  • Horse Diseases / immunology
  • Horse Diseases / virology*
  • Horses
  • Host-Pathogen Interactions
  • Monocytes / immunology
  • Monocytes / virology*
  • Virus Internalization*

Substances

  • Antigens, Differentiation