Fig. 6. Challenge of hDPP4 KI mice after a single vaccination with the DUB-negative rMERS-CoVMA.
a Timeline for immunization, challenge and evaluation of protective efficacy. At 49 days after immunization, mice were intranasally challenged with a lethal dose 104 PFU of rMERS-CoVMA or mock-challenged with DMEM and monitored daily for (b) weight loss (% from initial weight), (mock-vaccinated and mock-challenged: n = 21; mock-vaccinated and rMERS-CoVMA challenged: n = 16; rMERS-CoVMA-DUBneg vaccinated and rMERS-CoVMA: n = 30), c survival (%) and disease symptoms for 14 days. Statistical comparisons between means were performed by a log-rank test and corrected for multiple comparisons. ****P < 0.0001. d On days 0, 2, 4, 6, and 14 post challenge, lung tissues were collected for virus titration by plaque assay on Huh7 cells. The individual virus titers (PFU) per gram of lung tissue and the mean per group ± SEM are presented for day 0, 2, 4, 6, and 14 p.i. (d). Symbols represent individual mice (n = 6). The limit of detection for infectious viral progeny is 10 PFU/g Lung and is indicated with a dashed line. An unpaired two-tailed t test was used to determine significant differences between the mock-vaccinated and rMERS-CoVMA-challenged (shown in blue) and the DUB-negative rMERS-CoVMA-vaccinated rMERS-CoVMA challenged (shown in red). Day 2 (*P < 0.0117) and day 4 (***P < 0.0002). Source data are provided as a Source Data file.