Fig. 3.

Vaccine efficacy in the mouse model. Mean VEEV titer in organs of SIN/ZPC vaccinated wild type and immunodeficient mice at 3 and 7 days post-challenge with ZPC738. Mice were immunized on day − 42 and day − 14 with chimeric SIN/ZPC vaccine at a dose of 5 × 10⁵ plaque-forming units (PFU) in 100 μl of PBS or with PBS (WT* Mock) via subcutaneous route and challenged intranasally with 2 × 10⁵ PFU of virulent VEEV (ZPC738) per animal in 20 μl of PBS. Asterisk (^⁎) indicates parental C57BL/6 mice (wild type, WT) and the characteristics of immunodeficient mice are described in Materials and methods (Table 1). Animals were sacrificed at (A) 3 days and (B) 7 days post-challenge and organs were harvested for viral titration. The limit of detection was 40 PFU/g, as indicated by the solid line.