Parasite-induced IFN-γ regulates host defense via CD115 and mTOR-dependent mechanism of tissue-resident macrophage death.

Host resistance to a common protozoan parasite Toxoplasma gondii relies on a coordinated immune response involving multiple cell types, including macrophages. Embryonically seeded tissue-resident macrophages (TRMs) play a critical role in maintaining tissue homeostasis, but their role in parasite clearance is poorly understood. In this study, we uncovered a crucial aspect of host defense against T. gondii mediated by TRMs. Through the use of neutralizing antibodies and conditional IFN-γ receptor-deficient mice, we demonstrated that IFN-γ directly mediated the elimination of TRMs. Mechanistically, IFN-γ stimulation in vivo rendered macrophages unresponsive to macrophage colony-stimulating factor (M-CSF) and inactivated mTOR signaling by causing the shedding of CD115 (CSFR1), the receptor for M-CSF. Further experiments revealed the essential role of macrophage IFN-γ responsiveness in host resistance to T. gondii. The elimination of peritoneal TRMs emerged as an additional host defense mechanism aimed at limiting the parasite's reservoir. The identified mechanism, involving IFN-γ-induced suppression of CD115-dependent mTOR signaling in macrophages, provides insights into the adaptation of macrophage subsets during infection and highlights a crucial aspect of host defense against intracellular pathogens.

T-bet-dependent ILC1- and NK cell-derived IFN-γ mediates cDC1-dependent host resistance against Toxoplasma gondii.

Host resistance against intracellular pathogens requires a rapid IFN-γ mediated immune response. We reveal that T-bet-dependent production of IFN-γ is essential for the maintenance of inflammatory DCs at the site of infection with a common protozoan parasite, Toxoplasma gondii. A detailed analysis of the cellular sources for T-bet-dependent IFN-γ identified that ILC1s and to a lesser degree NK, but not TH1 cells, were involved in the regulation of inflammatory DCs via IFN-γ. Mechanistically, we established that T-bet dependent innate IFN-γ is critical for the induction of IRF8, an essential transcription factor for cDC1s. Failure to upregulate IRF8 in DCs resulted in acute susceptibility to T. gondii infection. Our data identifies that T-bet dependent production of IFN-γ by ILC1 and NK cells is indispensable for host resistance against intracellular infection via maintaining IRF8+ inflammatory DCs at the site of infection.

Publisher Correction: Orthogonal Cas9-Cas9 chimeras provide a versatile platform for genome editing.

The original version of this Article contained errors in the author affiliations. Mehmet Fatih Bolukbasi was incorrectly associated with Bluebird Bio., Cambridge, MA, USA and Ankit Gupta was incorrectly associated with Exonics Therapeutics, Watertown, MA, USA. This has now been corrected in the HTML version of the Article. The PDF version of the Article was correct at the time of publication.

Orthogonal Cas9-Cas9 chimeras provide a versatile platform for genome editing.

The development of robust, versatile and accurate toolsets is critical to facilitate therapeutic genome editing applications. Here we establish RNA-programmable Cas9-Cas9 chimeras, in single- and dual-nuclease formats, as versatile genome engineering systems. In both of these formats, Cas9-Cas9 fusions display an expanded targeting repertoire and achieve highly specific genome editing. Dual-nuclease Cas9-Cas9 chimeras have distinct advantages over monomeric Cas9s including higher target site activity and the generation of predictable precise deletion products between their target sites. At a therapeutically relevant site within the BCL11A erythroid enhancer, Cas9-Cas9 nucleases produced precise deletions that comprised up to 97% of all sequence alterations. Thus Cas9-Cas9 chimeras represent an important tool that could be particularly valuable for therapeutic genome editing applications where a precise cleavage position and defined sequence end products are desirable.