Likewise, studies aimed at examining the critical role played by the S1Pmediated processing of arenavirus GPC in the virus life cycle were aided by the use of recombinant viruses where the S1P cleavage site within GPC was replaced by a canonical furin cleavage site (Albarino et al., 2009; Rojek et al., 2010; Urata et al., 2011) .