Affiliation:
1. Virginia-Maryland Regional College of Veterinary Medicine, University of Maryland, College Park, Maryland 20742
Abstract
ABSTRACT
The hemagglutinin-neuraminidase (HN) protein of Newcastle disease virus (NDV) is an important determinant of its virulence. We investigated the role of each of the four functional N-linked glycosylation sites (G1 to G4) of the HN glycoprotein of NDV on its pathogenicity. The N-linked glycosylation sites G1 to G4 at residues 119, 341, 433, and 481, respectively, of a moderately pathogenic NDV strain Beaudette C (BC) were eliminated individually by site-directed mutagenesis on a full-length cDNA clone of BC. A double mutant (G12) was also created by eliminating the first and second glycosylation sites at residues 119 and 341, respectively. Infectious virus was recovered from each of the cDNA clones of the HN glycoprotein mutants, employing a reverse genetics technique. There was a greater delay in the replication of G4 and G12 mutant viruses than in the parental virus. Loss of glycosylation does not affect the receptor recognition by HN glycoprotein of NDV. The neuraminidase activity of G4 and G12 mutant viruses and the fusogenicity of the G4 mutant virus were significantly lower than those of the parental virus. The fusogenicity of the double mutant virus (G12) was significantly higher than that of the parental virus. Cell surface expression of the G4 virus HN was significantly lower than that of the parental virus. The antigenic reactivities of the mutants to a panel of monoclonal antibodies against the HN protein indicated that removal of glycosylation from the HN protein increased (G1, G3, and G12) or decreased (G2 and G4) the formation of antigenic sites, depending on their location. In standard tests to assess virulence in chickens, all of the glycosylation mutants were less virulent than the parental BC virus, but the G4 and G12 mutants were the least virulent.
Publisher
American Society for Microbiology
Subject
Virology,Insect Science,Immunology,Microbiology
Reference47 articles.
1. Alexander, D. J. 1989. Newcastle disease, p. 114-120. In H. G. Purchase, L. H. Arp, C. H. Domermuth, and J. E. Pearson (ed.), A laboratory manual for the isolation and identification of avian pathogens, 3rd ed. American Association for Avian Pathologists, Inc., Kennett Square, Pa.
2. Alexander, D. J. 1997. Newcastle disease and other avian Paramyxoviridae infection, p. 541-569. In B. W. Calnek (ed.), Diseases of poultry, 10th ed. Iowa State University Press, Ames.
3. Alexander, S., and J. H. Elder. 1984. Carbohydrate dramatically influences immune reactivity of antisera to viral glycoprotein antigens. Science226:1328-1330.
4. Back, N. K. T., L. Smit, J. J. De Jong, W. Keulen, M. Schutten, J. Goudsmit, and M. Tersmette. 1994. An N-glycan within the human immunodeficiency virus type 1 gp120 V3 loop affects virus neutralization. Virology199:431-438.
5. Bagai, S., and R. A. Lamb. 1995. Individual roles in N-linked oligosaccharide chains in the intracellular transport of the paramyxovirus SV5 fusion protein. Virology209:250-256.