Abstract
To evaluate the contribution of length diversity in the hemagglutinin-neuraminidase (HN) protein to the pathogenicity, replication and biological characteristics of Newcastle disease virus (NDV), we used reverse genetics to generate a series of recombinant NDVs containing truncated or extended HN proteins based on an infectious clone of genotype VII NDV (SG10 strain). The mean death times and intracerebral pathogenicity indices of these viruses showed that the different length mutations in the HN protein did not alter the virulence of NDV. In vitro studies of recombinant NDVs containing truncated or extended HN proteins revealed that the extension of HN protein increased its hemagglutination titer, receptor-binding ability and impaired its neuraminidase activity, fusogenic activity and replication ability. Furthermore, the hemadsorption, neuraminidase and fusogenic promotion activities at the protein level were consistent with those of viral level. Taken together, our results demonstrate that the HN biological activities affected by the C-terminal extension are associated with NDV replication but not the virulence.
Highlights
Includes a stalk region and a large C-terminal globular head domain[5,12]
Mutations in the transmembrane and stalk regions of the HN protein can affect the structure and activities of the protein[13,14], the major amino acids residues involved in the sialic-acid-receptor binding and NA activities are located in the globular head[15,16]
When the open readings frames (ORFs) of the HN protein in different Newcastle disease virus (NDV) strains were compared, it was found that the HN proteins vary in length, and at least nine different length variants have been reported to date: 570 amino acids (570aa), 571aa, 572aa, 577aa, 578aa, 580aa, 582aa, 585aa, and 616aa[26,27,28]
Summary
Includes a stalk region and a large C-terminal globular head domain[5,12]. mutations in the transmembrane and stalk regions of the HN protein can affect the structure and activities of the protein[13,14], the major amino acids residues involved in the sialic-acid-receptor binding and NA activities are located in the globular head[15,16]. In the context of the virulent strains or other length variants, especially the unnatural length of HN protein, the data are lacking These length differences arise from changes in the length of the C-terminal global head, the main functional region of HN, with both receptor-binding activity and neuraminidase activity, and they may influence the activity of the HN protein, and even the biological characteristics of the virus. We chose a representative virulent isolate of NDV genotype VIId circulating in China (SG10) as the model virus upon which to build the recombinant NDVs encoding truncated or extended HN proteins We used these to evaluate the contribution of the HN protein length to the pathogenicity, replication and biological characteristics of the virus
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