Fig. 2: IFNγ is required for iv BCG-induced protection against early SARS-CoV-2 infection.

Mice of the indicated genotypes were inoculated with BCG or PBS iv 40–45 days prior to intranasal challenge with SARS-CoV-2 (SCV2). Lungs were harvested 3–5 days after viral challenge. A Schematic of experimental protocol. B Viral titers in lung homogenate from B6, Ifngr1^−/− or Tcra^−/− mice as measured by TCID₅₀ assay 3 days after viral challenge (Left panel: B6 PBS n = 10, B6 BCG n = 8, Ifngr1^−/− PBS n = 10. Ifngr1^−/− n = 10. Right panel: B6 n = 10/group, Tcra^−/− PBS n = 10, Tcra^−/− BCG n = 9. Both panels: pooled from two independent experiments; Kruskal-Wallis with Dunn’s post-test). C Schematic of experimental protocol with anti-IFNγ and anti-IFNAR treatment. D Viral titers in lung homogenate as measured by TCID₅₀ assay 3 days after viral challenge (Left panel: PBS isotype n = 24, BCG isotype n = 24, PBS αIFNγ n = 23, BCG αIFNγ n = 22; pooled from 5 independent experiments. Right panel: n = 10/group; pooled from two independent experiments. Both panels: Kruskal–Wallis with Dunn’s post test). E Schematic of the experimental protocol with anti-IFNγ treatment in the K18-hACE2 mouse model. F Percentage of starting weight at 5 dpi. Hashed gray box shows percentage of animals with greater than 10% body weight loss. G Viral titers in lung homogenate as measured by TCID₅₀ assay 5 days after SARS-CoV-2 WA/2020 challenge (n = 10/group; pooled from two independent experiments; Kruskal–Wallis with Dunn’s post-test). Not significant (ns) p > 0.05. Gray boxes denote values below the limit of detection. Source data are provided as a Source Data file.