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 9

SLAMF7 or SLAMF8 triggers NF-κB, IRF7, and STAT-1 signaling in human pDCs.

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SLAMF7 or SLAMF8 triggers NF-κB, IRF7, and STAT-1 signaling in human pDC...
(A–C) CAL-1 and stably transduced (shCTRL, shSLAMF7, shSLAMF8) CAL-1 cells were infected with DsRed–S. Typhimurium (MOI 25) for 3 hours, and then processed for phospho-flow cytometry or confocal microscopy. (A) Heatmap showing MFI levels for p-IRF7, p–NF-κB p65, p–STAT-1, p-p38, p–ERK-1/2, p-AKT, and p-IRF3 of Salmonella-infected cells relative to mock condition. Multiple-comparison Kruskal-Wallis test followed by post hoc Dunn’s test. n = 4–5. (B) Column graphs showing relative MFI of selected phosphorylated proteins in infected cells. Mean ± SD. n = 5. (C) Confocal images (scale bars: 20 μm) (left) and quantification (right) of p–NF-κB p65 in Salmonella-infected CAL-1 and stably transduced CAL-1 cells. n = 3. One-way ANOVA followed by Dunnett’s multiple-comparison test. (D) Primary human pDCs were infected and analyzed as in B but, after 1 hour, SLAMF7 or SLAMF8 were engaged by cross-linking with a specific antibody or its isotype control. One donor per n; n = 10. (E) Flow cytometry histogram of EAT-2 expression (fluorescence intensity [FI]) in primary human pDCs with positivity indicated by a vertical gray bar. One donor per n; n = 3. (F) Left: Flow cytometry histogram of EAT-2 FI in CAL-1 cells at resting state with positivity bar. Right: Percentages of EAT-2+ CAL-1 and stably transduced cells, infected (green) or not (gray) as in B. n = 2. (G) CAL-1 and stably transduced CAL-1 cells were infected as in B; after 1 hour, washes, and gentamicin addition, MitoTEMPO (100 μM) was added for 2 hours. Then cells were processed for phospho-flow cytometry. Column graphs showing relative MFI of selected phosphorylated proteins in infected cells. Mean ± SD. n = 3. Two-way ANOVA followed by Šidák’s multiple-comparison test. Only statistically significant differences are shown. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001. No P value indicates not significant.