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Journal of Virology, February 2009, p. 1546-1554, Vol. 83, No. 4
0022-538X/09/$08.00+0     doi:10.1128/JVI.01684-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Expression of the A56 and K2 Proteins Is Sufficient To Inhibit Vaccinia Virus Entry and Cell Fusion ^,

Timothy R. Wagenaar and Bernard Moss^*

Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892-0310

Received 7 August 2008/ Accepted 18 November 2008

Many animal viruses induce cells to fuse and form syncytia. For vaccinia virus, this phenomenon is associated with mutations affecting the A56 and K2 proteins, which form a multimer (A56/K2) on the surface of infected cells. Recent evidence that A56/K2 interacts with the entry/fusion complex (EFC) and that the EFC is necessary for syncytium formation furnishes a strong connection between virus entry and cell fusion. Among the important remaining questions are whether A56/K2 can prevent virus entry as well as cell-cell fusion and whether these two viral proteins are sufficient as well as necessary for this. To answer these questions, we transiently and stably expressed A56 and K2 in uninfected cells. Uninfected cells expressing A56 and K2 exhibited resistance to fusing with A56 mutant virus-infected cells, whereas expression of A56 or K2 alone induced little or no resistance, which fits with the need for both proteins to bind the EFC. Furthermore, transient or stable expression of A56/K2 interfered with virus entry and replication as determined by inhibition of early expression of a luciferase reporter gene, virus production, and plaque formation. The specificity of this effect was demonstrated by restoring entry after enzymatically removing a chimeric glycophosphatidylinositol-anchored A56/K2 or by binding a monoclonal antibody to A56. Importantly, the antibody disrupted the interaction between A56/K2 and the EFC without disrupting the A56-K2 interaction itself. Thus, we have shown that A56/K2 is sufficient to prevent virus entry and fusion as well as formation of syncytia through interaction with the EFC.

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* Corresponding author. Mailing address: Laboratory of Viral Diseases, NIAID, NIH, 33 North Drive, MSC 3210, Bethesda, MD 20892-3210. Phone: (301) 496-9869. Fax: (301) 480-1535. E-mail: bmoss{at}nih.gov

Published ahead of print on 26 November 2008.

Supplemental material for this article may be found at http://jvi.asm.org/.

Present address: National Institute of Child Health and Development, NIH, 18T Center Drive, Bethesda, MD 20892.

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Journal of Virology, February 2009, p. 1546-1554, Vol. 83, No. 4
0022-538X/09/$08.00+0     doi:10.1128/JVI.01684-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Satheshkumar, P. S., Moss, B. (2009). Characterization of a Newly Identified 35-Amino-Acid Component of the Vaccinia Virus Entry/Fusion Complex Conserved in All Chordopoxviruses. J. Virol. 83: 12822-12832 [Abstract] [Full Text]  
• Ching, Y.-C., Chung, C.-S., Huang, C.-Y., Hsia, Y., Tang, Y.-L., Chang, W. (2009). Disulfide Bond Formation at the C Termini of Vaccinia Virus A26 and A27 Proteins Does Not Require Viral Redox Enzymes and Suppresses Glycosaminoglycan-Mediated Cell Fusion. J. Virol. 83: 6464-6476 [Abstract] [Full Text]