Figure 4.

MHV nsp14 N7-MTase mutants immunization protects mice from death after challenge. (A) Scheme of challenge of C57BL/6 mice. Four-week-old C57BL/6 mice were immunized with 5×10⁵ PFU D330A, Y414A, while the WT virus and DMEM were used as positive and mock control, respectively. At 30 dpi, animals were i.h. challenged with a high lethal dose of 2×10⁷ PFU WT MHV. (B) Body weight change. Means with SD are shown (n = 5). (C) Survival 8 days after challenge (n = 5). (D) Viral loads in livers were measured by plaque assay at 2- and 5- days post challenge. Means with SEM are shown (n = 4). L.O.D: Limit of detection. (E) Liver damage was evaluated by measuring the ALT level in sera. Means with SEM are shown (n = 4). (F) Liver histological changes of mice. Black arrows indicate inflammatory cell infiltration. Scale bar, 100 μm. ****P < 0.0001; **P < 0.01; *P < 0.05 (unpaired Student’s t-test).