Greg Smith, PhD Associate Professor Microbiology-Immunology Herpesvirus transport in the nervous system Curricula: Immunology and Microbial Pathogenesis Cell Biology Neurobiology E-mail:   g-smith3@northwestern.edu

Some of the most traumatic diseases result from infections of the nervous system. Diseases such as polio, rabies and encephalitis are typically debilitating or lethal. In contrast, herpesviruses are highly proficient at infecting the nervous system, yet normally do not cause neurological disease. This is achieved in part by self-imposed restrictions encoded within the viruses that limit viral reproduction and prevent dissemination into the brain. For the individual, this results in a relatively benign infection, yet the virus becomes a life-long occupant of the nervous system that will periodically reemerge at body surfaces to infect others.

Research in the lab is interdisciplinary. Bacterial genetics and molecular biology are used to manipulate the herpesvirus genome. We have cloned the entire 150 kb DNA viral genome in E.coli as a bacterial artificial chromosome (BAC). Bacterial genetic methods are used to mutate the cloned genome in bacteria, and the virus is subsequently produced by transfection of the mutated viral genome into cultured eukaryotic cells. This approach allows for fast wide spread screening of viral genes in a number of biological assays employed in the lab.

Many of our assays are based in cell biology and microscopy. Advanced methods in fluorescent and video microscopy are commonly used to examine mutant viruses made in the lab.  For example, by fusing the green fluorescent protein (GFP) to a structural component of the viral capsid, individual viral particles can be tracked within the axons of living neurons during both entry and egress phases of the viral life cycle. Although herpesviruses are smaller than the spatial resolution of visual optics, GFP emissions from single capsids can be detected and time-lapse microscopy with high temporal resolution allow for detailed tracking of the capsids in cultured neurons. Studies in culture are often complemented by examining the pathogenesis of mutant viruses in rodent models of infection.

Initial characterization of viral transport indicates that the virus regulates directional spread in axons by associating with multiple microtubule motors. Viral egress in axons is mediated by bi-directional transport that has net anterograde (away from the cell body) travel. This is accomplished with greater capsid velocity, travel distances and frequencies in the anterograde direction. Conversely, viral entry in axons is also bi-directional, but the anterograde component is severely diminished, allowing the retrograde component to be dominant. Our preliminary findings indicate that viral assembly and cell-to-cell spread are coupled processes. Current studies are focusing on identifying the viral components responsible for axonal transport and how regulation of viral transport relates to disease.

Selected Publications:

Lee JI, Sollars PJ, Baver SB, Pickard GE, Leelawong M, Smith GA. 2009. A herpesvirus encoded deubiquitinase is a novel neuroinvasive determinant. PLoS Pathog. 5(4):e1000387. Epub 2009 Apr 17.

Coller KE, Smith GA. 2008. Two viral kinases are required for sustained long distance axon transport of a neuroinvasive herpesvirus. Traffic. 9(9):1458-70.

Coller KE, Lee JI, Ueda A, Smith GA. 2007. The capsid and tegument of the alphaherpesviruses are linked by an interaction between the UL25 and VP1/2 proteins. J Virol. 81(21):11790-7.

Antinone, S.E., G.A. Smith. 2006. Two modes of herpesvirus trafficking in neurons: membrane acquisition directs motion. J. Virol. 80(22): 11235-11240

Lee, J.I., G.W. Luxton, G.A. Smith. 2006. Mapping Essential Domains of the Herpesvirus VP1/2 Tegument Protein: the Carboxy Terminus Directs Incorporation Into Capsid Assemblons. J. Virol. 80(24): 12086-12094

Antinone, S.E., G.T. Shubeita, K.E. Coller, J.I. Lee, S. Haverlock-Moyns, S.P. Gross, and G.A. Smith. 2006. The herpesvirus capsid surface protein, VP26, and the majority of the tegument proteins are dispensable for capsid transport toward the nucleus. J Virol 80: 5494-5498

Luxton, G. W., J. I. Lee, S. Haverlock-Moyns, J. M. Schober, and G. A. Smith. 2006. The Pseudorabies Virus VP1/2 Tegument Protein Is Required for Intracellular Capsid Transport. J Virol 80:201-9.

Luxton GW, Haverlock S, Coller KE, Antinone SE, Pincetic A, Smith GA. Targeting of herpesvirus capsid transport in axons is coupled to association with specific sets of tegument proteins. Proc Natl Acad Sci U S A. 2005 Mar 28

Smith GA, Pomeranz L, Gross SP, Enquist LW. Local modulation of plus-end transport targets herpesvirus entry and egress in sensory axons. Proc Natl Acad Sci U S A. 2004 Nov 9;101(45):16034-9.

Smith GA, Enquist LW. Break ins and break outs: viral interactions with the cytoskeleton of Mammalian cells. Annu Rev Cell Dev Biol. 2002;18:135-61.

View Publications by Greg Smith listed in the National Library of Medicine (PubMed).