Reduced lung viral titers of challenged IFN-α/βR<sup>−/−</sup> mice that received passive transfer of serum from MuV-IA-immunized mice.

<p>BALB/c mice were immunized i.n. with 1x10<sup>6</sup> PFU of MuV in a volume of 100 μL or mock immunized with 100 μL PBS. Mice were boosted at 3 and 6 wpi, and serum was collected and pooled at 8 wpi. Naïve IFN-α/βR<sup>−/−</sup> mice received passive transfer of 300 μL i.p. of inactived serum from MuV-IA immunized mice (50 μL and 150 μL groups received serum diluted in PBS for 300 μL total volume), or 300 μL i.p. inactivated serum from PBS immunized mice. Mice were challenged 24 hours post passive transfer i.n. with 1x10<sup>6</sup> PFU of MuV-IA in a volume of 100 μL. Lungs were collected and homogenized 2 dpi and viral titers were determined by plaque assay in duplicate. The limit of detection of 5.9 PFU/g tissue is represented by the dashed line. ANOVA and Tukey multiple comparison tests were used to calculate <i>P</i> values.</p>