TOLLIP inhibits lipid accumulation and the integrated stress response in alveolar macrophages to control Mycobacterium tuberculosis infection

A polymorphism causing deficiencies in Toll-interacting protein (TOLLIP), an inhibitory adaptor protein affecting endosomal trafficking, is associated with increased tuberculosis (TB) risk. It is, however, unclear how TOLLIP affects TB pathogenesis. Here we show that TB severity is increased in Tollip−/− mice, characterized by macrophage- and T cell-driven inflammation, foam cell formation and lipid accumulation. Tollip−/− alveolar macrophages (AM) specifically accumulated lipid and underwent necrosis. Transcriptional and protein analyses of Mycobacterium tuberculosis (Mtb)-infected, Tollip−/− AM revealed increased EIF2 signalling and downstream upregulation of the integrated stress response (ISR). These phenotypes were linked, as incubation of the Mtb lipid mycolic acid with Mtb-infected Tollip−/− AM activated the ISR and increased Mtb replication. Correspondingly, the ISR inhibitor, ISRIB, reduced Mtb numbers in AM and improved Mtb control, overcoming the inflammatory phenotype. In conclusion, targeting the ISR offers a promising target for host-directed anti-TB therapy towards improved Mtb control and reduced immunopathology.