Human Lung Conventional Dendritic Cells Orchestrate Lymphoid Neogenesis during Chronic Obstructive Pulmonary Disease.

Rationale: Emerging evidence supports a crucial role for tertiary lymphoid organs (TLOs) in chronic obstructive pulmonary disease (COPD) progression. However, mechanisms of immune cell activation leading to TLOs in COPD remain to be defined.Objectives: To examine the role of lung dendritic cells (DCs) in T follicular helper (Tfh)-cell induction, a T-cell subset critically implicated in lymphoid organ formation, in COPD.Methods: Myeloid cell heterogeneity and phenotype were studied in an unbiased manner via single-cell RNA sequencing on HLA-DR+ cells sorted from human lungs. We measured the in vitro capability of control and COPD lung DC subsets, sorted using a fluorescence-activated cell sorter, to polarize IL-21+CXCL13+ (IL-21-positive and C-X-C chemokine ligand type 13-positive) Tfh-like cells. In situ imaging analysis was performed on Global Initiative for Chronic Obstructive Lung Disease stage IV COPD lungs with TLOs.Measurements and Main Results: Single-cell RNA-sequencing analysis revealed a high degree of heterogeneity among human lung myeloid cells. Among these, conventional dendritic type 2 cells (cDC2s) showed increased induction of IL-21+CXCL13+ Tfh-like cells. Importantly, the capacity to induce IL-21+ Tfh-like cells was higher in cDC2s from patients with COPD than in those from control patients. Increased Tfh-cell induction by COPD cDC2s correlated with increased presence of Tfh-like cells in COPD lungs as compared with those in control lungs, and cDC2s colocalized with Tfh-like cells in TLOs of COPD lungs. Mechanistically, cDC2s exhibited a unique migratory signature and (transcriptional) expression of several pathways and genes related to DC-induced Tfh-cell priming. Importantly, blocking the costimulatory OX40L (OX40 ligand)-OX40 axis reduced Tfh-cell induction by control lung cDC2s.Conclusions: In COPD lungs, we found lung EBI2+ (Epstein-Barr virus-induced gene 2-positive) OX-40L-expressing cDC2s that induced IL-21+ Tfh-like cells, suggesting an involvement of these cells in TLO formation.

Immunogenic cell death of dendritic cells following modified vaccinia virus Ankara infection enhances CD8+ T cell proliferation.

"Immunogenic cell death" (ICD) is associated with the emission of so-called damage-associated molecular patterns (DAMPs) which trigger the immune response against dead-cell associated antigens. The secretion of the DAMP, adenosine triphosphate (ATP) has been shown to be autophagy-dependent. Here, we demonstrate that Modified Vaccinia virus Ankara (MVA), a highly attenuated strain of vaccinia virus, induces both cell death and autophagy in murine bone marrow-derived dendritic cells (BMDCs), which in turn confer the (cross-)priming of OVA-specific cytotoxic T cells (OT-I cells). Additionally, we show that MVA infection leads to increased extracellular ATP (eATP) as well as intracellular ATP (iATP) levels, with the latter being influenced by the autophagy. Furthermore, we show that the increased eATP supports the proliferation of OT-I cells and inhibition of the P2RX7 receptors results in an abrogation of the proliferation. These data reveal novel mechanisms on how MVA enhances adaptive immunity in vaccine strategies.

Lipid nanoparticle-mediated siRNA delivery for safe targeting of human CML in vivo.

Efficient and safe delivery of siRNA in vivo is the biggest roadblock to clinical translation of RNA interference (RNAi)-based therapeutics. To date, lipid nanoparticles (LNPs) have shown efficient delivery of siRNA to the liver; however, delivery to other organs, especially hematopoietic tissues still remains a challenge. We developed DLin-MC3-DMA lipid-based LNP-siRNA formulations for systemic delivery against a driver oncogene to target human chronic myeloid leukemia (CML) cells in vivo. A microfluidic mixing technology was used to obtain reproducible ionizable cationic LNPs loaded with siRNA molecules targeting the BCR-ABL fusion oncogene found in CML. We show a highly efficient and non-toxic delivery of siRNA in vitro and in vivo with nearly 100% uptake of LNP-siRNA formulations in bone marrow of a leukemic model. By targeting the BCR-ABL fusion oncogene, we show a reduction of leukemic burden in our myeloid leukemia mouse model and demonstrate reduced disease burden in mice treated with LNP-BCR-ABL siRNA as compared with LNP-CTRL siRNA. Our study provides proof-of-principle that fusion oncogene specific RNAi therapeutics can be exploited against leukemic cells and promise novel treatment options for leukemia patients.

Herpes simplex virus 1 interferes with autophagy of murine dendritic cells and impairs their ability to stimulate CD8+ T lymphocytes.

The MHC class I presentation is responsible for the presentation of viral proteins to CD8+ T lymphocytes and mainly depends on the classical antigen processing pathway. Recently, a second pathway involving autophagy has been implicated in this process. Here, we show an increase in the capacity of murine dendritic cells (DCs) to present viral antigens on MHC class I after infection with a mutant herpes simplex virus 1 (HSV-1-Δ34.5), lacking infected cell protein 34.5 (ICP34.5), when compared to its parental HSV-1 strain. The ICP34.5 protein counteracts host cell translational arrest and suppresses macroautophagy, and the lack of this protein resulted in a low viral protein abundance, which was processed and presented in an efficient way. Our study demonstrates an important role of autophagy in processing endogenous viral proteins in HSV-1-infected DCs.

Autolysosomal activation combined with lysosomal destabilization efficiently targets myeloid leukemia cells for cell death.

Introduction: Current cancer research has led to a renewed interest in exploring lysosomal membrane permeabilization and lysosomal cell death as a targeted therapeutic approach for cancer treatment. Evidence suggests that differences in lysosomal biogenesis between cancer and normal cells might open a therapeutic window. Lysosomal membrane stability may be affected by the so-called 'busy lysosomal behaviour' characterized by higher lysosomal abundance and activity and more intensive fusion or interaction with other vacuole compartments. Methods: We used a panel of multiple myeloid leukemia (ML) cell lines as well as leukemic patient samples and updated methodology to study auto-lysosomal compartment, lysosomal membrane permeabilization and lysosomal cell death. Results: Our analyses demonstrated several-fold higher constitutive autolysosomal activity in ML cells as compared to human CD34+ hematopoietic cells. Importantly, we identified mefloquine as a selective activator of ML cells' lysosomal biogenesis, which induced a sizeable increase in ML lysosomal mass, acidity as well as cathepsin B and L activity. Concomitant mTOR inhibition synergistically increased lysosomal activity and autolysosomal fusion and simultaneously decreased the levels of key lysosomal stabilizing proteins, such as LAMP-1 and 2. Discussion: In conclusion, mefloquine treatment combined with mTOR inhibition synergistically induced targeted ML cell death without additional toxicity. Taken together, these data provide a molecular mechanism and thus a rationale for a therapeutic approach for specific targeting of ML lysosomes.

Increased expression and accumulation of GDF15 in IPF extracellular matrix contribute to fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a chronic disease of unmet medical need. It is characterized by formation of scar tissue leading to a progressive and irreversible decline in lung function. IPF is associated with repeated injury, which may alter the composition of the extracellular matrix (ECM). Here, we demonstrate that IPF patient-derived pulmonary ECM drives profibrotic response in normal human lung fibroblasts (NHLF) in a 3D spheroid assay. Next, we reveal distinct alterations in composition of the diseased ECM, identifying potentially novel associations with IPF. Growth differentiation factor 15 (GDF15) was identified among the most significantly upregulated proteins in the IPF lung-derived ECM. In vivo, GDF15 neutralization in a bleomycin-induced lung fibrosis model led to significantly less fibrosis. In vitro, recombinant GDF15 (rGDF15) stimulated α smooth muscle actin (αSMA) expression in NHLF, and this was mediated by the activin receptor-like kinase 5 (ALK5) receptor. Furthermore, in the presence of rGDF15, the migration of NHLF in collagen gel was reduced. In addition, we observed a cell type-dependent effect of GDF15 on the expression of cell senescence markers. Our data suggest that GDF15 mediates lung fibrosis through fibroblast activation and differentiation, implicating a potential direct role of this matrix-associated cytokine in promoting aberrant cell responses in disease.