A single amino acid substitution in the west nile virus nonstructural protein NS2A disables its ability to inhibit alpha/beta interferon induction and attenuates virus virulence in mice

Liu, Wen Jun, Wang, Xiang Ju, Clark, David C., Lobigs, Mario, Hall, Roy A. and Khromykh, Alexander A. (2006) A single amino acid substitution in the west nile virus nonstructural protein NS2A disables its ability to inhibit alpha/beta interferon induction and attenuates virus virulence in mice. Journal of Virology, 80 5: 2396-2404.


Author Liu, Wen Jun
Wang, Xiang Ju
Clark, David C.
Lobigs, Mario
Hall, Roy A.
Khromykh, Alexander A.
Title A single amino acid substitution in the west nile virus nonstructural protein NS2A disables its ability to inhibit alpha/beta interferon induction and attenuates virus virulence in mice
Journal name Journal of Virology   Check publisher's open access policy
ISSN 0022-538X
1070-6321
1098-5514
Publication date 2006-03
Sub-type Article (original research)
DOI 10.1128/JVI.80.5.2396-2404.2006
Volume 80
Issue 5
Start page 2396
End page 2404
Total pages 9
Editor Lynn W. Enquist
Place of publication Washington, DC, U.S.A.
Publisher American Society for Microbiology
Collection year 2006
Language eng
Subject C1
270303 Virology
730101 Infectious diseases
0605 Microbiology
1108 Medical Microbiology
Formatted abstract Alpha/beta interferons (IFN-α/β) are key mediators of the innate immune response against viral infection. The ability of viruses to circumvent IFN-α/β responses plays a crucial role in determining the outcome of infection. In a previous study using subgenomic replicons of the Kunjin subtype of West Nile virus (WNVKUN), we demonstrated that the nonstructural protein NS2A is a major inhibitor of IFN-β promoter-driven transcription and that a single amino acid substitution in NS2A (Ala30 to Pro [A30P]) dramatically reduced its inhibitory effect (W. J. Liu, H. B. Chen, X. J. Wang, H. Huang, and A. A. Khromykh, J. Virol. 78:12225-12235). Here we show that incorporation of the A30P mutation into the WNVKUN genome results in a mutant virus which elicits more rapid induction and higher levels of synthesis of IFN-α/β in infected human A549 cells than that detected following wild-type WNVKUN infection. Consequently, replication of the WNVKUNNS2A/A30P mutant virus in these cells known to be high producers of IFN-α/β was abortive. In contrast, both the mutant and the wild-type WNVKUN produced similar-size plaques and replicated with similar efficiency in BHK cells which are known to be deficient in IFN-α/β production. The mutant virus was highly attenuated in neuroinvasiveness and also attenuated in neurovirulence in 3-week-old mice. Surprisingly, the mutant virus was also partially attenuated in IFN-α/βγ receptor knockout mice, suggesting that the A30P mutation may also play a role in more efficient activation of other antiviral pathways in addition to the IFN response. Immunization of wild-type mice with the mutant virus resulted in induction of an antibody response of similar magnitude to that observed in mice immunized with wild-type WNVKUN and gave complete protection against challenge with a lethal dose of the highly virulent New York 99 strain of WNV. The results confirm and extend our previous original findings on the role of the flavivirus NS2A protein in inhibition of a host antiviral response and demonstrate that the targeted disabling of a viral mechanism for evading the IFN response can be applied to the development of live attenuated flavivirus vaccine candidates.
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
Keyword Virology
Valley-encephalitis-virus
Kunjin virus
Sindbis virus
Dengue virus
Ns1 protein
Viral rplication
Infection
Activation
Flavivirus
Pathway
Q-Index Code C1
Additional Notes This is the first report showing a role for the flavivirus non-structural protein NS2A in attenuation of West Nile virus virulence in mice and this attenuation related with increasing interferon induction in vivo. We also identified a single amino acid in the NS2A responsible for the reduction of viral virulence. The results facilitated the development of live attenuated West Nile virus vaccine candidates by targeted disabling of virus’s ability to inhibit antiviral response. Wang is a Research Assistant in the laboratory and Khromykh is the laboratory head. Hall and Clark are collaborators from University of Queensland and Lobigs is the collaborator from John Curtin School of Medical Research, ANU..

 
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Created: Wed, 15 Aug 2007, 08:19:01 EST