SLAMF7 and SLAMF8 receptors shape human plasmacytoid dendritic cell responses to intracellular bacteria
Joaquín Miguel Pellegrini, Anne Keriel, Laurent Gorvel, Sean Hanniffy, Vilma Arce-Gorvel, Mile Bosilkovski, Javier Solera, Stéphane Méresse, Sylvie Mémet, Jean-Pierre Gorvel
Joaquín Miguel Pellegrini, Anne Keriel, Laurent Gorvel, Sean Hanniffy, Vilma Arce-Gorvel, Mile Bosilkovski, Javier Solera, Stéphane Méresse, Sylvie Mémet, Jean-Pierre Gorvel
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Research Article Immunology Infectious disease Microbiology

SLAMF7 and SLAMF8 receptors shape human plasmacytoid dendritic cell responses to intracellular bacteria

Abstract

Plasmacytoid dendritic cells (pDCs), professional type I IFN–producing cells, have been implicated in host responses against bacterial infections. However, their role in host defense is debated, and the operating molecular mechanisms are unknown. Certain signaling lymphocyte activation molecule family (SLAMF) members act as microbial sensors and modulate immune functions in response to infection. Here, human blood transcriptomic analyses reveal the involvement of SLAMF7 and SLAMF8 in many infectious diseases, with elevated levels associated with type I IFN responses in salmonellosis and brucellosis patients. We further identify SLAMF7 and SLAMF8 as key regulators of human pDC function. They activate pDC maturation and cytokine production during infection with bacteria that induce acute (Salmonella) or chronic (Brucella) inflammation. SLAMF7 and SLAMF8 signal through NF-κB, IRF7, and STAT-1, and limit mitochondrial ROS accumulation upon Salmonella infection. Remarkably, this SLAMF7/8-dependent control of mitochondrial ROS levels favors bacterial persistence and NF-κB activation. Overall, our results unravel essential shared multifaceted roles of SLAMF7 and SLAMF8 in finely tuning human pDC responses to intracellular bacterial infections with potential for future diagnostic and therapeutic applications.

Authors

Joaquín Miguel Pellegrini, Anne Keriel, Laurent Gorvel, Sean Hanniffy, Vilma Arce-Gorvel, Mile Bosilkovski, Javier Solera, Stéphane Méresse, Sylvie Mémet, Jean-Pierre Gorvel

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Figure 8

SLAMF7 and SLAMF8 restrict Salmonella clearance by limiting mitochondrial ROS accumulation in human pDCs.

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SLAMF7 and SLAMF8 restrict Salmonella clearance by limiting mitochondria...
(A) Global cellular ROS in CAL-1 and SLAMF7- or SLAMF8-KD cells loaded with CellROX Deep Red fluorogenic probe, infected with S. Typhimurium (green) for 4 hours and analyzed by flow cytometry. Left: Column graphs of the relative MFI (rMFI) of CellROX Deep Red to mock-treated CAL-1 (gray) cells put arbitrarily at 1. Each individual point represents 1 independent experiment. Mean ± SD. n = 3. Right: Histograms for total ROS content upon Salmonella infection (FMO, fluorescence minus one negative control). (B) Oxidative stress detection by intracellular Salmonella. CAL-1 and SLAMF-silenced cells were infected with the ROS-sensing mutant Salmonella strain carrying the ahpC-gfp (left, scheme). Cells were lysed at different time points p.i., and GFP fluorescence intensity of intracellular bacteria was determined by flow cytometry. Results (right) are representative of n = 3. (C and D) Mitochondrial superoxide detection in CAL-1 and SLAMF-silenced cells infected with DsRed–S. Typhimurium for 4 hours using MitoSOX and flow cytometry. (C) Column graphs show MitoSOX MFI in the total population. Each individual point represents 1 independent experiment. Mean ± SD. n = 3. (D) mtROS levels in gated Salmonella-infected cells from C. (E and F) After internalization (2 hours p.i.), DsRed-Salmonella–infected cells were treated or not with MitoTEMPO (100 μM) and further incubated for the indicated times. n = 4 for CAL-1; n = 3 for SLAMF-KD. (E) Proportion of DsRed-Salmonella–infected cells determined at 48 hours p.i. by flow cytometry. Each individual point represents 1 independent experiment. Mean ± SD. (F) Intracellular bacterial burden determined by CFU quantification at 24 hours p.i. Each individual point corresponds to 1 independent experiment. (A–F) Two-way ANOVA followed by Šidák’s multiple-comparison test. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001.