Research Overview

The Poxviridae family includes some of the largest DNA viruses known. While variola (the causative agent of smallpox) remains the most deadly member of the family, several other members, including monkeypox, tanapox, cowpox, vaccinia, Yaba-like disease virus and molluscum contagiosum, are capable of causing disease in humans. Orthopoxviruses, which include variola, monkeypox and vaccinia, have a double stranded genome of about 200 kb and are predicted to encode for approximately 200 functional open reading frames making them some the most complex animal viruses known. This complexity is best demonstrated during viral morphogenesis that results in a virion that is predicted to incorporate approximately 100 viral polypeptides and several morphologically distinct forms.

Viral replication occurs entirely in the cytoplasm in discrete areas know as viral factories and results in the first infectious form termed intracellular mature virions (IMV). A subset of IMV receives an extra double membrane wrapping derived from the trans-Golgi or endosomal cisternae and are referred to as intracellular enveloped virions (IEV). After wrapping, IEV are transported via microtubules to the cell periphery where the outer membrane of the IEV fuses with the plasma membrane depositing one of the newly acquired membranes into the plasma membrane and releasing the enveloped virion from the cell. Many enveloped virions remain attached to the plasma membrane and are termed cell-associated-virus (CEV). Viral proteins deposited into the plasma membrane, by the fusion of IEV at the plasma membrane, direct the polymerization of actin on the cytosolic side forming what are called actin tails, which serve to propel CEV away from the cell and towards adjacent cells. CEV released from the plasma membrane are termed extracellular enveloped virus (EEV). IEV, CEV and EEV make up the enveloped form of vaccinia virus and IMV are considered unenveloped. While IMV represents the majority of progeny virions they are not released from the cell making the enveloped form responsible for cell-to-cell spread. Presently only seven viral proteins have been found to be specific to the enveloped form, and of these seven only six have been shown to be required for efficient envelope virus production. The major focus of my laboratory is the study of poxvirus morphogenesis, emphasizing the intracellular envelopment process. We employ molecular virological techniques along with state of the art live video microscopy and cell biology to study viral egress with the goal of understanding the molecular mechanism employed by poxviruses to produce intracellular enveloped virions. Furthermore, our research should also provide insight into such cellular processes as protein trafficking, membrane and vesicle formation and intracellular trafficking.

Recent Publications

• Ward BM. Visualization and Characteri zation of the Intracellular Movement of Vaccinia Virus Intracellular Mature Virions. J. Virol. 2005;79 4755-4763.

• Ward BM. Pox, Dyes, and Videotape: Making Movies of Fluorescently Labeled Vaccinia Virions. In S.N. Isaacs (ed.), Poxvirus Protocols. Methods Mol Biol. 2004;269:205-18.
  

  Quicktime movie showing the entire time-lapse sequence used for Figure 2. Time ratio is 1:30.

• Ward BM, Moss B. Vaccinia Virus A36R Membrane Protein Provides a Direct Link between Intracellular Enveloped Virions and the Microtubule Motor Kinesin. J. Virol. 2004;78 2486-2493
• Senkevich TG, Ward BM, Moss B. Vaccinia Virus A28L Gene Encodes an Essential Protein Component of the Virion Membrane with Intramolecular Disulfide Bonds Formed by the Viral Cytoplasmic Redox Pathway. J. Virol. 78 2348-2356, 2004
• Senkevich TG, Ward BM, Moss B. Vaccinia Virus Entry into Cells Is Dependent on a Virion Surface Protein Encoded by the A28L Gene. J. Virol. 78 2357-2366, 2004
• Katz E, Ward BM, Weisberg AS, Moss, B. Mutations in the vaccinia virus A33R andB5R envelope proteins that enhance release of extracellular virions and eliminat formation of actin-containing microvilli without preventing tyrosing phosphorylation of the A36R protein. J.Virol. 77 12266-12275, 2003
• Ward BM, Weisberg AS, Moss B. Mapping and functional analysis of interaction sites within the cytoplasmic domains of the vaccinia virus A33R and A36R envelope proteins. J Virol. 77:4113-26, 2003.
  Supplemental Material (Movies)
• Moss B, Ward BM. High-speed mass transit for poxviruses on microtubules. Nat Cell Biol. 3:E245-6, 2001.
  Supplemental Material (Movies)
• Ward BM, Moss B. Vaccinia virus intracellular movement is associated with microtubules and independent of actin tails. J Virol. 75:11651-63, 2001.
• Ward BM, Moss B. Visualization of intracellular movement of vaccinia virus virions containing a green fluorescent protein-B5R membrane protein chimera. J Virol. 75:4802-13, 2001.
  Supplemental Material (Movies)
• Ward BM, Moss B. Golgi network targeting and plasma membrane internalization signals in vaccinia virus B5R envelope protein. J Virol. 74:3771-80, 2000.

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