Canine distemper viruses expressing a hemagglutinin without N-glycans lose virulence but retain immunosuppression

J Virol. 2010 Mar;84(6):2753-61. doi: 10.1128/JVI.01813-09. Epub 2009 Dec 30.

Abstract

Paramyxovirus glycoproteins are posttranslationally modified by the addition of N-linked glycans, which are often necessary for correct folding, processing, and cell surface expression. To establish the contribution of N glycosylation to morbillivirus attachment (H) protein function and overall virulence, we first determined the use of the potential N-glycosylation sites in the canine distemper virus (CDV) H proteins. Biochemical characterization revealed that the three sites conserved in all strains were N glycosylated, whereas only two of the up to five additional sites present in wild-type strains are used. A wild-type virus with an H protein reproducing the vaccine strain N-glycosylation pattern remained lethal in ferrets but with a prolonged course of disease. In contrast, introduction of the vaccine H protein in the wild-type context resulted in complete attenuation. To further characterize the role of N glycosylation in CDV pathogenesis, the N-glycosylation sites of wild-type H proteins were successively deleted, including a nonstandard site, to ultimately generate a nonglycosylated H protein. Despite reduced expression levels, this protein remained fully functional. Recombinant viruses expressing N-glycan-deficient H proteins no longer caused disease, even though their immunosuppressive capacities were retained, indicating that reduced N glycosylation contributes to attenuation without affecting immunosuppression.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Chlorocebus aethiops
  • Distemper / immunology
  • Distemper / physiopathology
  • Distemper / virology
  • Distemper Virus, Canine* / immunology
  • Distemper Virus, Canine* / pathogenicity
  • Dogs
  • Ferrets / immunology
  • Ferrets / virology
  • Glycosylation
  • Hemagglutinins, Viral / chemistry*
  • Hemagglutinins, Viral / immunology
  • Humans
  • Immunosuppression Therapy*
  • Male
  • Polysaccharides / immunology*
  • Vero Cells

Substances

  • Hemagglutinins, Viral
  • Polysaccharides