G Model VIRUS-96006; No. of Pages 17 ARTICLE IN PRESS Virus Research xxx (2013) xxx–xxx Contents lists available at SciVerse ScienceDirect Virus Research jo urnal homepage: www.elsevier.com/locate/virusres Review Understanding and altering cell tropism of vesicular stomatitis virus ∗ Eric Hastie, Marcela Cataldi, Ian Marriott, Valery Z. Grdzelishvili Department of Biology, University of North Carolina at Charlotte, 9201 University City Boulevard, Charlotte, NC 28223, United States a r t i c l e i n f o a b s t r a c t Article history: Vesicular stomatitis virus (VSV) is a prototypic nonsegmented negative-strand RNA virus. VSV’s broad Received 30 March 2013 cell tropism makes it a popular model virus for many basic research applications. In addition, a lack of Received in revised form 6 June 2013 preexisting human immunity against VSV, inherent oncotropism and other features make VSV a widely Accepted 7 June 2013 used platform for vaccine and oncolytic vectors. However, VSV’s neurotropism that can result in viral Available online xxx encephalitis in experimental animals needs to be addressed for the use of the virus as a safe vector. Therefore, it is very important to understand the determinants of VSV tropism and develop strategies to Keywords: alter it. VSV glycoprotein (G) and matrix (M) protein play major roles in its cell tropism. VSV G protein Vesicular stomatitis virus VSV is responsible for VSV broad cell tropism and is often used for pseudotyping other viruses. VSV M affects Tropism cell tropism via evasion of antiviral responses, and M mutants can be used to limit cell tropism to cell Host factors types defective in interferon signaling. In addition, other VSV proteins and host proteins may function as Oncolytic determinants of VSV cell tropism. Various approaches have been successfully used to alter VSV tropism Neurotropism to benefit basic research and clinically relevant applications. Neurotoxicity © 2013 Elsevier B.V. All rights reserved. Contents 1. Introduction . 00 2. Entry. 00 2.1. Biology of VSV entry . 00 2.2. Altering VSV tropism by targeting entry . 00 3. Replication . 00 3.1. Biology of VSV replication . 00 3.2. Altering VSV tropism by targeting replication . 00 4. Exit . 00 5. Neurotropism of VSV. 00 5.1. VSV neurotropism . 00 5.2. Role of T-cells and glial cells in VSV neurotoxicity . 00 5.3. Altering VSV neurotropism. 00 6. Concluding remarks . 00 Acknowledgments . 00 Appendix A. Supplementary data. 00 References . 00 Understanding viral tropism is important for basic virology, but also 1. Introduction for development of effective gene therapy, vaccines and oncolytic virus therapies. This review focuses on the cellular tropism of vesic- Viral tropism commonly refers to the specificity of a virus for ular stomatitis virus (VSV), one of the best-studied RNA viruses, a particular cell type, tissue, organ or species. Here, we define which is extensively exploited in various applications. cell tropism as the specificity of VSV for cell types supporting Studies of virus cell tropism reveal not only viral but also host virus infection, replication and production of infectious progeny. components, which if present or absent may provide a hospitable environment for the virus life cycle (Fig. 1). Permissive cells usually contain required factors for virus attachment, entry, biosynthe- ∗ sis and exit, but lack effective antiviral mechanisms. The complex Corresponding author. Tel.: +1 704 687 7778; fax: +1 704 687 1488. E-mail address: [email protected] (V.Z. Grdzelishvili). interaction of viral and host components determines the rates of 0168-1702/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.virusres.2013.06.003 Please cite this article in press as: Hastie, E., et al., Understanding and altering cell tropism of vesicular stomatitis virus. Virus Res. (2013), http://dx.doi.org/10.1016/j.virusres.2013.06.003 G Model VIRUS-96006; No. of Pages 17 ARTICLE IN PRESS 2 E. Hastie et al. / Virus Research xxx (2013) xxx–xxx Fig. 1. Known and putative determinants of cell tropism of VSV. Host and viral proteins are involved (positively or negatively) in VSV infection and replication. Different viral and host proteins are involved in VSV attachment, entry, replication, assembly, or release. Proteins known to be involved in the VSV life cycle are shown at each step: green indicates viral or host proteins known to assist VSV while red indicates putative host proteins as well as host proteins responsible for an antiviral response. infection, replication, and production of progeny. Understanding large polymerase (L). All 5 gene products assemble to create these interactions helps to develop various strategies to manipulate an enveloped, bullet-shaped virion that measures approximately VSV tropism. 185 nm × 75 nm (Ge et al., 2010). In addition to G, an attachment VSV is a prototypic, non-segmented negative sense RNA virus protein, that enables infection of very wide range of cells, other (order Mononegavirales, family Rhabdoviridae). Five genes are VSV proteins may also play roles in directing VSV tropism, includ- encoded by the 11-kb VSV genome: nucleocapsid protein (N), ing evasion of the innate immune response and interaction with phosphoprotein (P), matrix protein (M), glycoprotein (G), and host factors (discussed later). VSV’s broad cell tropism, relative Please cite this article in press as: Hastie, E., et al., Understanding and altering cell tropism of vesicular stomatitis virus. Virus Res. (2013), http://dx.doi.org/10.1016/j.virusres.2013.06.003 G Model VIRUS-96006; No. of Pages 17 ARTICLE IN PRESS E. Hastie et al. / Virus Research xxx (2013) xxx–xxx 3 independence on cell cycle, rapid replication, high virus yields, clinically relevant applications. The neurotropism of VSV is a and small, easily manipulated genome make it a popular model particularly important issue to address for development of safe virus for many basic research applications. In addition, a lack of VSV-based vectors, and will be reviewed in detail. While the format preexisting human immunity against VSV and its inability to trans- of this review does allow us to describe all the details of VSV biol- form host cells make VSV a widely used experimental platform for ogy, we would like to refer readers to an excellent review by Lyles vaccine vectors (Bukreyev et al., 2006). Moreover, VSV is a promis- and Rupprecht in Fields Virology, Rhabdoviridae chapter (Lyles and ing oncolytic virus (OV), preferentially infecting and killing cancer Rupprecht, 2007). cells while leaving nonmalignant “normal” cells unharmed. Numer- ous preclinical studies demonstrated effectiveness of VSV against various malignancies (Hastie and Grdzelishvili, 2012) and a VSV 2. Entry recombinant encoding the IFN-␤ gene is currently in a phase I clin- ical trial against hepatocellular carcinoma (clinicaltrials.gov, 2012, 2.1. Biology of VSV entry Trial ID: NCT01628640). The major VSV serotypes, Indiana (IN) and New Jersey (NJ), are VSV enters the cell via the endocytic pathway and subsequently endemic to parts of the United States as well as much of Central fuses with a cellular membrane within the acidic environment of and South America. Among VSV’s natural hosts are cattle, pigs, the endosome. This penetration process is relatively inefficient for horses and other mammals and their insect vectors (Drolet et al., VSV. Many virions that attach to the cell surface are not internal- 2005; Hansen et al., 1985). Instances of VSV infection of humans ized, and many of the internalized virions appear to be degraded are rare, but cases have been documented for agricultural and lab- by proteases and other enzymes (Matlin et al., 1982). Differences oratory workers (Reif et al., 1987). VSV infection can cause mild among cell types in the efficiency of each step may lead to altered flu-like symptoms in adults. However, viral encephalitis has been infection efficacy, thereby, affecting the cellular tropism. A siRNA reported in a 3-year-old child in Panama (Quiroz et al., 1988). In screen of the human kinome (the genomic collection of human pro- nature, VSV can be transmitted to mammalian hosts by arthropod tein, lipid and carbohydrate kinases) in HeLa cells showed that the vectors that include sandflies, houseflies, and mosquitos, or direct productive entry of VSV involves a large cohort of kinases from dif- contact with infected animals (Bergold et al., 1968; Cupp et al., ferent families, suggesting that multiple cellular proteins involved 1992; Drolet et al., 2005, 2009; Letchworth et al., 1999; Mead et al., with endocytosis may determine the VSV tropism at the level of 2004; Tesh et al., 1971). Experimental studies of VSV pathology entry (Pelkmans et al., 2005). have reported varied outcomes dependent on the route of admin- The VSV G protein is the main viral determinant of the entry istration. In the laboratory, due mainly to VSV’s ability to cause (Roche et al., 2008), and is involved in two of the initial steps of the experimental encephalitis, studies generally focus on intranasal infectious process: virus attachment to the host cell surface and (i.n.) injection in murine and non-human primate models. Non- viral-induced pH-dependent endosomal membrane fusion. VSV G human primate models were also used with no evidence of VSV enables infection of most, if not all, human cell types, and of organ- in the brain, spinal cord, or plasma found following i.n. injection ism as distant as zebrafish and Drosophila (Gillies and Stollar, 1980; (Johnson et al., 2007). However, intrathalmic (i.t.) injection resulted Mudd et al., 1973; Seganti et al., 1986). in neurological disease and animal sacrifice (Johnson et al., 2007; The membrane lipid phosphatidylserine (PS) has long been con- Mire et al., 2012). VSV spread within the CNS (mouse and pri- sidered to play an important role in VSV entry and may be involved mate models) will be discussed in detail in a later section of this in attachment or triggering endocytosis, although this possible role review.