Genetic Modification in Mammalian Orthoreoviruses

Amino acids substitutions in σ1 and μ1 outer capsid proteins of a Vero cell-adapted mammalian orthoreovirus are required for optimal virus binding and disassembly

“…Viruses selected for their large-plaque phenotype using L929 cells, somewhat reminiscent of larger plaques formed by VeroAV on Vero cells in the absence of chymotrypsin, were shown to be better oncolytic viruses both in vitro and in animal models (Shmulevitz et al, 2012). A recent report (van den Wollenberg et al, 2012) also suggests that the ability to infect cells independently of the JAM receptor, possibly due to increased binding to sialic acids, could be a useful strategy against cancer cell types that express low levels of JAM and are thus relatively resistant to reovirus (van den Hengel et al, 2013;van den Wollenberg et al, 2009;van Houdt et al, 2008). Furthermore, a virus harboring a deletion of the JAM binding domain and binding solely onto cell surface sialic acids, was shown to be attenuated in nontransformed cells while retaining an oncolytic potential and exhibiting reduced host toxicity (Kim et al, 2011).…”

“…This has led to numerous clinical studies as reviewed by others (Black and Morris, 2012;Clements et al, 2014;Harrington et al, 2010;Kelly et al, 2009;Maitra et al, 2012). Despite the fact that reoviruses are naturally oncolytic without prior genetic modifications, there is still a significant research effort ongoing to obtain novel virus variants better adapted to infect, replicate in, and kill cancer cells while sparing non-transformed cells (van den Hengel et al, 2013;Kim et al, 2011;Rudd and Lemay, 2005;Shmulevitz et al, 2012;van den Wollenberg et al, 2009van den Wollenberg et al, , 2012. One possible approach is to take advantage of novel viral variants that could be selected during establishment of viral persistence in different cell types.…”

“…An altered disassembly of its outer capsid, as evidenced by different kinetics of in vitro cleavage by chymotrypsin, was also observed. The novel plasmid-based reverse genetics system (Kobayashi et al, 2007(Kobayashi et al, , 2010reviewed in: Boehme et al, 2011;van den Hengel et al, 2013;Lemay, 2011) preferential infection of Vero cells is actually due to the σ1 amino acid substitutions, although the co-adaptation of μ1 appears necessary to optimize viral infection. Altogether, these results indicate that the establishment of viral persistence can select for different viral variants depending on the cell type.…”

Multiple proteins differing between laboratory stocks of mammalian orthoreoviruses affect both virus sensitivity to interferon and induction of interferon production during infection

“…This could possibly lead to better optimization of viral strains toward oncolytic activity, as many investigators believe to be possible, and as recently reviewed (Mohamed et al, 2015;Kemp et al, 2016). This is especially envisaged since the advent of plasmid-based reverse genetics to manipulate the viral genome (Lemay, 2011;van den Hengel et al, 2013;Stuart et al, 2017). In the present study, reverse genetics was thus used to introduce each of the T3D K gene in the T3D S genetic background, either separately or in different combinations, in order to determine which protein(s) is responsible for this difference in interferon response.…”