Both mutant and WT viruses began to replicate at 8 h post-infection (p.i.), and reached maximal titers at 12 h p.i. The maximal titer of MHV-nsp1-27D was about 5×105 pfu/ml, a little lower than that of WT MHV-A59 (1×106 pfu/ml). Here, SH2D3A is linked to infection.