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Journal of Virology, August 2008, p. 7828-7836, Vol. 82, No. 16
0022-538X/08/$08.00+0     doi:10.1128/JVI.00578-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

The Large Polymerase Protein Is Associated with the Virulence of Newcastle Disease Virus{triangledown}

Subrat N. Rout and Siba K. Samal*

Virginia-Maryland Regional College of Veterinary Medicine, University of Maryland, 8075 Greenmead Drive, College Park, Maryland 20742

Received 14 March 2008/ Accepted 27 May 2008

Naturally occurring Newcastle disease virus (NDV) strains vary greatly in virulence, ranging from no apparent infection to severe disease causing 100% mortality in chickens. The viral determinants of NDV virulence are not completely understood. Cleavage of the fusion protein is required for the initiation of infection, and it acts as a determinant of virulence. The attachment protein HN was found to play a minor role in virulence. In this study, we have evaluated the role of the internal proteins (N, P, and L) in NDV virulence by using a chimeric reverse-genetics approach. The N, P, and L genes were exchanged individually between an avirulent NDV strain, LaSota, and an intermediate virulent NDV strain, Beaudette C (BC), and the N and P genes were also exchanged together. The recovered chimeric viruses were evaluated for their pathogenicity in the natural host, chickens. Our results showed that the pathogenicities of N and P chimeric viruses were similar to those of their respective parental viruses, indicating that the N and P genes probably play minor roles in virulence. However, replacement of the L gene of BC with that of LaSota significantly increased the pathogenicity of the L-chimeric virus, suggesting that the L gene probably contributes to the virulence of NDV. The L-chimeric BC virus was found to replicate at a 100-fold-higher level than its parental virus in chicken brain, suggesting that the increase in pathogenicity may be due to the increased replication level of the chimeric virus. Our findings offer new insights into the pathogenesis of NDV infection.

* Corresponding author. Mailing address: 8075 Greenmead Drive, College Park, MD 20770. Phone: (301) 314-6813. Fax: (301) 314-6855. E-mail: ssamal{at}umd.edu

{triangledown} Published ahead of print on 11 June 2008.

Journal of Virology, August 2008, p. 7828-7836, Vol. 82, No. 16
0022-538X/08/$08.00+0     doi:10.1128/JVI.00578-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

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