Mice previously infected with rLCMVs were given a lethal dose infection of wtLCMV. Mice that survived inoculation with rLCMVs were further infected intraperitoneally (i.p.) with 1.0 × 103 FFU of wtLCMV 40 days after the first inoculation. (a,b) Changes in body weight and survival rate of CBA/NSlc mice: CBA/NSlc mice previously inoculated with rLCMV-5UTRΔ41–60 (3 mice per group), rLCMV-5UTRΔ60–77 (1 mouse per group), rLCMV-3UTRΔ39–60 (5 mice per group), rLCMV-UTR-comple (5 mice per group), rLCMV-UTR 5-3 change (5 mice per group), rLCMV-Δ26–40 (5 mice per group), or medium (5 mice per group) were used. (c,d) Changes in body weight and survival rate of DBA/1JJmsSlc mice: DBA/1JJmsSlc mice previously inoculated with rwtLCMV (3 mice per group), rLCMV-5UTRΔ41–60 (5 mice per group), rLCMV-5UTRΔ60–77 (5 mouse per group), rLCMV-3UTRΔ39–60 (4 mice per group), rLCMV-UTR-comple (5 mice per group), rLCMV-UTR 5-3 change (5 mice per group), rLCMV-Δ26–40 (5 mice per group), or medium (5 mice per group) were used. Error bars in Figure 5a,c indicate standard errors of the mean.