We observed significant attenuation of ΔfmvB in pulmonary mouse infections (Fig 7 and Fig H in S1 File) and reduced levels of GM-CSF, IL-3, and IL-10 in the spleens of ΔfmvB-infected mice on day 5 post-infection (Fig 9), indicating that FmvB is involved in F. tularensis virulence. This evidence concerns the gene IL3 and infection.