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Virus Genes. 2013 Dec;47(3):498-504. doi: 10.1007/s11262-013-0973-4. Epub 2013 Sep 14.

Effects of the HN gene C-terminal extensions on the Newcastle disease virus virulence.

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Southeast Poultry Research Laboratory, Agricultural Research Services, United States Department of Agriculture, 934 College Station Road, Athens, GA, 30605, USA,


The hemagglutinin-neuraminidase (HN) of Newcastle disease virus (NDV) is a multifunctional protein that has receptor recognition, neuraminidase, and fusion promotion activities. Sequence analysis revealed that the HN gene of many extremely low virulence NDV strains encodes a larger open-reading frame (616 amino acids, aa) with additional 45 aa at its C-terminus when compared with that (571 aa) of virulent NDV strains. Therefore, it has been suspected that the 45 aa extension at the C-terminus of the HN may affect the NDV virulence. In this study, we generated an NDV mesogenic strain Anhinga-based recombinant virus with an HN C-terminal extension of 45 aa (rAnh-HN-ex virus) using reverse genetics technology. The biological characterization of the recombinant virus showed that the rAnh-HN-ex virus had similar growth ability to its parental virus rAnh-wt both in embryonating chicken eggs and DF-1 cells. However, the pathogenicity of this recombinant virus in embryonating chicken eggs and day-old chickens decreased, as evidenced by a longer mean death time and lower intracerebral pathogenicity index when compared with the parental virus. This is consistent with our previous finding that the recombinant LaSota virus with a 45-aa extension at its HN C-terminal was attenuated in chickens and embryonating eggs. These results suggest that the HN protein C-terminal extension may contribute to the reduced virulence in some low virulence NDV strains.

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