Figure 4. SeV DVGs reduce virulence in vivo.

(A–C) Mice were infected with 10⁵ TCID₅₀/mouse of SeV Cantell HD (HD) or SeV Cantell LD (LD). (A) Weight loss (***p<0.001, ****p<0.0001; Two-way ANOVA with Bonferroni's post hoc test), (B) Virus titers in the lung, (n = 11 for day 1, n = 6 for day 3), and (C) expression of Ifnb mRNA by RT-qPCR. Gene expression is shown as copy number relative to the housekeeping genes Tuba1b and Rps11 (***p<0.001, Unpaired, two tailed, t student test). (D–F) Mice were infected with 10⁴ TCID₅₀/mouse SeV Cantell LD alone, in the presence of 5,000 HA Units/mouse purified defective particles (DPs) or in the presence of UV-inactivated DPs (UVDP). Mice received DPs or UVDPs immediately following virus inoculation. (D) Weight loss, (†, mice sacrificed due to severe weight loss; ***p<0.001, ****p<0.0001; Two-way ANOVA with Bonferroni's post hoc test), (E) lung lesion score at day 7 post-infection (n = 3)(*p<0.05, Mann-Whitney test). (F) Photos of the lung of a representative mouse at day 7 post-infection. Arrowhead indicates areas of lesions. (G) Lungs from mice infected with SeV Cantell LD alone, or in the presence of DPs or UVDPs were analyzed by flow cytometry for the expression of the SeV NP protein.