Quantitative omics reveals that type I and II IFNs alter bacterial vacuole compositions to restrict infection in macrophages and lungs. Mus musculus

The innate defense mechanisms that control infections with intracellular bacteria are still incompletely understood. Here we show that type I and II IFNs are key regulators of the early gene expression and the host-protective immune response during Legionella pneumophila-induced pneumonia. Using mixed bone marrow-chimeric mice and isolated cells we indicate that both IFNs protect against L. pneumophila by activating an alveolar macrophage-intrinsic antibacterial defense pathway. Quantitative mass spectrometry analysis reveals that both IFNs markedly alter the protein composition of purified Legionella-containing vacuoles, and integrated network analysis defines distinct subsets of IFN-regulated proteins. Subsequent experiments uncover Immunoresponsive gene 1 (Irg1) as a central effector that restricts the bacteria through production of itaconic acid. Collectively, we provide a comprehensive analysis of IFN-mediated effects on gene expression and the bacterial vacuole proteome, and show that L. pneumophila is restricted by an Irg1-dependent production of a bactericidal metabolite. Overall design: Microarray experiments were performed as dual-color hybridizations on Agilent mouse whole genome catalog 44K arrays. To compensate for dye-specific effects, a dye-reversal color-swap was applied.