Biology subjects

Bessou, G.

Publications and source records attributed to Bessou, G..

4 recordsLinked to original sources

bioRxiv2024

Plasmacytoid dendritic cells are dispensable or detrimental in murine systemic or respiratory viral infections

Plasmacytoid dendritic cells (pDCs) are major producers of type I/III interferons. As interferons are crucial for antiviral defense, pDCs are assumed to play an essential role in this process. However, robust evidence supporting this dogma is scarce. Genetic or pharmacological manipulations that eliminate pDC or disrupt their interferon production often affect other cells, confounding interpretation. To overcome this issue, we engineered pDC-less mice that are specifically and constitutively devoid of pDCs by expressing diphtheria toxin under coordinated control of the Siglech and Pacsin1 genes, uniquely co-expressed in pDCs. pDC-less mice mounted protective immunity against systemic infection with mouse Cytomegalovirus and showed higher survival and less lung immunopathology to intranasal infection with influenza virus and SARS-CoV2. Thus, contrary to the prevailing dogma, we revealed that pDCs and their interferons are dispensable or deleterious during several viral infections. pDC-less mice will enable rigorously reassessing the roles of pDCs in health and disease.

immunology↗

bioRxiv2023

M-CSF induces a coordinated myeloid and NK cell differentiation program protecting against CMV after hematopoietic cell transplantation

Immunosuppressed patients are highly susceptible to viral infections. Therapies reconstituting autologous antiviral immunocompetence could therefore represent an important prophylaxis and treatment. Herpesviridae including cytomegalovirus (CMV) are a major cause of morbidity and mortality in patients after hematopoietic cell transplantation (HCT). Here, we show in a mouse model of HCT that macrophage colony-stimulating factor (M-CSF/CSF-1), a key cytokine for myeloid and monocytic differentiation, promoted rapid antiviral activity and protection from viremia caused by murine CMV. Mechanistically, M-CSF stimulated a coordinated myeloid and natural killer (NK) cell differentiation program culminating in increased NK cell numbers and production of granzyme B and interferon-{gamma}. This NK cell response depended upon M-CSF-induced myelopoiesis leading to IL15R-mediated presentation of IL-15 on monocytes. Furthermore, M-CSF also induced differentiation of plasmacytoid dendritic cells producing type I interferons, which supported IL-15-mediated protection. In the context of human HCT, M-CSF induced monopoiesis, increased IL15R expression on monocytes and elevated numbers of functionally competent NK cells in G-CSF-mobilized human hematopoietic stem and progenitor cells. Together, our data show that M-CSF induces an integrated multistep differentiation program that culminates in increased NK cell numbers and activation, thereby protecting graft recipients from CMV infection. Thus, our results identify a mechanism by which M-CSF-induced myelopoiesis can rapidly reconstitute antiviral activity during leukopenia following HCT. Key pointsO_LIM-CSF protects from lethal CMV viremia during leukopenia following hematopoietic cell transplantation, a vulnerable period of immunosuppression. C_LIO_LIEarly action of M-CSF on donor hematopoietic stem and progenitor cells rapidly reconstitutes antiviral immune responses. C_LIO_LIM-CSF stimulates a coordinated myeloid-NK cell-differentiation program resulting in increased NK cell numbers and activity. C_LIO_LIIncreased NK cell differentiation and activity depends on M-CSF-induced myelopoiesis generating IL-15-producing monocytes and I-IFN-producing pDCs. C_LIO_LIM-CSF also stimulates monopoiesis, IL15Ra expression in monocytes and functional NK cell differentiation in G-CSF-mobilized human PBMC. C_LIO_LINo impaired HCT engraftment or proclivity to graft-versus-host-disease by M-CSF. C_LIO_LIM-CSF could provide a single cytokine therapy addressing a major medical need, supporting current antiviral therapies during leukopenia following HCT. C_LI Visual abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=196 SRC="FIGDIR/small/526105v1_ufig1.gif" ALT="Figure 1"> View larger version (43K): org.highwire.dtl.DTLVardef@1b1398eorg.highwire.dtl.DTLVardef@39a9e3org.highwire.dtl.DTLVardef@1c08cc3org.highwire.dtl.DTLVardef@5996b4_HPS_FORMAT_FIGEXP M_FIG C_FIG One Sentence SummaryM-CSF drives myeloid reconstitution to support CMV-directed natural killer cell competence via IL-15/I-IFN after hematopoietic cell transplantation.

immunology↗

bioRxiv2022

A novel mouse model based on intersectional genetics enables unambiguous in vivo discrimination between plasmacytoid and other dendritic cells and their comparative characterization

Plasmacytoid dendritic cells (pDC) were identified about 20 years ago, based on their unique ability to rapidly produce copious amounts of all subsets of type I and type III interferon (IFN-I/III) upon virus sensing, while being refractory to infection. Yet, the identity and physiological functions of pDC are still a matter of debate, in a large part due to their lack of specific expression of any single cell surface marker or gene that would allow to track them in tissues and to target them in vivo with high specificity and penetrance. Indeed, recent studies showed that previous methods that were used to identify or deplete pDC also targeted other cell types, including pDC-like cells and transitional DC (tDC) that were proposed to be responsible for all the antigen presentation ability previously attributed to steady state pDC. Hence, improving our understanding of the nature and in vivo choreography of pDC physiological functions requires the development of novel tools to unambiguously identify and track these cells, including in comparison to pDC-like cells and tDC. Here, we report successful generation of a pDC-reporter mouse model, by using an intersectional genetic strategy based on the unique co-expression of Siglech and Pacsin1 in pDC. This pDC-Tomato mouse strain allows specific ex vivo and in situ detection of pDC. Breeding them with Zbtb46GFP mice allowed side-by-side purification and transcriptional profiling by single cell RNA sequencing of bona fide pDC, pDC-like cells and tDC, in comparison to type 1 and 2 conventional DC (cDC1 and cDC2), both at steady state and during a viral infection, revealing diverging activation patterns of pDC-like cells and tDC. Finally, by breeding pDC-Tomato mice with Ifnb1EYFP mice, we determined the choreography of pDC recruitment to the micro-anatomical sites of viral replication in the spleen, with initially similar but later divergent behaviors of the pDC that engaged or not into IFN-I production. Our novel pDC-Tomato mouse model, and newly identified gene modules specific to combinations of DC types and activations states, will constitute valuable resources for a deeper understanding of the functional division of labor between DC types and its molecular regulation at homeostasis and during viral infections.

immunology↗

bioRxiv2020

cDC1 and interferons promote spontaneous CD4+ and CD8+ T cell protective responses to breast cancer

Here we show that efficient breast cancer immunosurveillance relies on cDC1, conventional CD4+ T cells, CD8+ cytotoxic T lymphocytes (CTL) and later NK/NK T cells. For this process, cDC1 were required constitutively, but especially during the T cell priming phase. In the tumor microenvironment, cDC1 interacted physically and jointly with both CD4+ T cells and tumorspecific CD8+ T cells. We found that interferon (IFN) responses were necessary for the rejection of breast cancer, including cDC1-intrinsic signaling by IFN-{gamma} and STAT1. Surprisingly, cell-intrinsic IFN-I signaling in cDC1 was not required. cDC1 and IFNs shaped the tumor immune landscape, notably by promoting CD4+ and CD8+ T cell infiltration, terminal differentiation and effector functions. XCR1, CXCL9, IL-12 and IL-15 were individually dispensable for breast cancer immunosurveillance. Consistent with our experimental results in mice, high expression in the tumor microenvironment of genes specific to cDC1, CTL, helper T cells or interferon responses are associated with a better prognosis in human breast cancer patients. Our results show that immune control of breast cancer depends on cDC1 and IFNs as previously reported for immunogenic melanoma or fibrosarcoma tumor models, but that the underlying mechanism differ. Revisiting cDC1 functions in the context of spontaneous immunity to cancer should help defining new ways to mobilize cDC1 functions to improve already existing immunotherapies for the benefits of patients. SynopsisType 1 conventional dendritic cells cross-present tumor antigens to CD8+ T cells. Understanding the regulation of their antitumor functions is important. Cell-intrinsic STAT1/IFN-{gamma} signaling licenses them for efficient CD4+ and CD8+ T cell activation during breast cancer immunosurveillance.

immunology↗