title: Mutation of a Single Envelope N-Linked Glycosylation Site Enhances the Pathogenicity of Bovine Leukemia Virus.
abstract: Viruses have coevolved with their host to ensure efficient replication and transmission without inducing excessive pathogenicity that would indirectly impair their persistence. This is exemplified by the bovine leukemia virus (BLV) system in which lymphoproliferative disorders develop in ruminants after latency periods of several years. In principle, the equilibrium reached between the virus and its host could be disrupted by emergence of more pathogenic strains. Intriguingly but fortunately, such a hyperpathogenic BLV strain was never observed in the field or designed in vitro. In this study, we sought to understand the role of envelope N-linked glycosylation with the hypothesis that this posttranslational modification could either favor BLV infection by allowing viral entry or allow immune escape by using glycans as a shield. Using reverse genetics of an infectious molecular provirus, we identified a N-linked envelope glycosylation site (N230) that limits viral replication and pathogenicity. Indeed, mutation N230E unexpectedly leads to enhanced fusogenicity and protein stability.
  
  
  OBJECTIVE
  Infection by retroviruses requires the interaction of the viral envelope protein (SU) with a membrane-associated receptor allowing fusion and release of the viral genomic RNA into the cell. We show that N-linked glycosylation of the bovine leukemia virus (BLV) SU protein is, as expected, essential for cell infection in vitro. Consistently, mutation of all glycosylation sites of a BLV provirus destroys infectivity in vivo. However, single mutations do not significantly modify replication in vivo. Instead, a particular mutation at SU codon 230 increases replication and accelerates pathogenesis. This unexpected observation has important consequences in terms of disease control and managing.
authors.affiliation: Molecular Biology (GxABT) and Molecular and Cellular Epigenetics (GIGA), University of Liege, Gembloux and Liege, Belgium alix.debrogniez@ulg.ac.be luc.willems@ulg.ac.be.
authors.forename: Alix
authors.initials: A
authors.lastname: de Brogniez
authors.affiliation: Molecular Biology (GxABT) and Molecular and Cellular Epigenetics (GIGA), University of Liege, Gembloux and Liege, Belgium.
authors.forename: Amel Baya
authors.initials: AB
authors.lastname: Bouzar
authors.affiliation: Molecular Biology (GxABT) and Molecular and Cellular Epigenetics (GIGA), University of Liege, Gembloux and Liege, Belgium.
authors.forename: Jean-Rock
authors.initials: JR
authors.lastname: Jacques
authors.affiliation: Molecular Biology (GxABT) and Molecular and Cellular Epigenetics (GIGA), University of Liege, Gembloux and Liege, Belgium.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Cosse
authors.affiliation: Molecular Biology (GxABT) and Molecular and Cellular Epigenetics (GIGA), University of Liege, Gembloux and Liege, Belgium.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Gillet
authors.affiliation: IMPMC, CNRS UMR7590, Sorbonne Universités, Université Pierre et Marie Curie-Paris 6, MNHN-IRD, Paris, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Callebaut
authors.affiliation: Department of Pathology, National Veterinary Research Institute, Pulawy, Poland.
authors.forename: Michal
authors.initials: M
authors.lastname: Reichert
authors.affiliation: Molecular Biology (GxABT) and Molecular and Cellular Epigenetics (GIGA), University of Liege, Gembloux and Liege, Belgium alix.debrogniez@ulg.ac.be luc.willems@ulg.ac.be.
authors.forename: Luc
authors.initials: L
authors.lastname: Willems
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002415:Cats; D002459:Cell Fusion; D002522:Chlorocebus aethiops; D006031:Glycosylation; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D001909:Leukemia Virus, Bovine / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity*; D008561:Membrane Fusion / Q000235:genetics; D009154:Mutation; D055550:Protein Stability; D016415:Sequence Alignment; D017423:Sequence Analysis, RNA; D012756:Sheep; D014759:Viral Envelope Proteins / Q000235:genetics* / Q000378:metabolism; D019562:Viral Load; D014779:Virus Replication / Q000235:genetics*
chemical_list: D014759:Viral Envelope Proteins