ATG5 and infection: It was previously reported that MHV replication was impaired in APG5 (another component of autophagy) deficient embryonic stem cells (Prentice et al., 2004); however, in a more recent study, no significant difference was reported for SARS-CoV titers during infection of wild-type or autophagy-deficient ATG5(−/−) mouse embryonic fibroblasts (Schneider et al., 2012).