Figure 1. MERS-CoV S-2P mRNA protects mice from lethal challenge.

288/330^+/+ mice were immunized at weeks 0 and 3 with 0.01 (green), 0.1 (blue), or 1 μg (red) of MERS-CoV S-2P mRNA. Mock-immunized mice were immunized with PBS (gray). Two weeks post-boost, sera were collected from 3 mice per group and assessed for neutralizing antibodies against MERS m35c4 pseudovirus (a). Four weeks post-boost, 12 mice per group were challenged with a lethal dose of mouse-adapted MERS-CoV (m35c4). Following challenge, mice were monitored for weight loss (b). Two days post-challenge, at peak viral load, lung viral titers (c) and hemorrhage (0 = no hemorrhage, 4 = severe hemorrhage in all lobes) (d) were assessed from 5 animals per group. Dotted line = assay limit of detection. (a, c-d) All dose levels were compared. (b) For weight loss, all comparisons are against PBS-immunized mice.