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In patients with autoimmune pulmonary alveolar proteinosis, the use of inhaled recombinant granulocyte–macrophage colony-stimulating factor resulted in a significantly better alveolar–arterial oxygen gradient at 25 weeks than the use of placebo. The beneficial effect was not observed in smokers.

Oncolytic viruses are under development for tumor treatment. David Kirn and colleagues now report their results of a randomized phase 2 dose-finding trial of JX-594, an oncolytic immunotherapeutic vaccinia virus, in patients with advanced hepatocellular carcinoma. The study shows that high-dose JX-594 was associated with significantly improved overall survival and induced radiographic responses and antitumor immunity. Oncolytic viruses and active immunotherapeutics have complementary mechanisms of action (MOA) that are both self amplifying in tumors, yet the impact of dose on subject outcome is unclear. JX-594 (Pexa-Vec) is an oncolytic and immunotherapeutic vaccinia virus. To determine the optimal JX-594 dose in subjects with advanced hepatocellular carcinoma (HCC), we conducted a randomized phase 2 dose-finding trial ( n = 30). Radiologists infused low- or high-dose JX-594 into liver tumors (days 1, 15 and 29); infusions resulted in acute detectable intravascular JX-594 genomes. Objective intrahepatic Modified Response Evaluation Criteria in Solid Tumors (mRECIST) (15%) and Choi (62%) response rates and intrahepatic disease control (50%) were equivalent in injected and distant noninjected tumors at both doses. JX-594 replication and granulocyte-macrophage colony-stimulating factor (GM-CSF) expression preceded the induction of anticancer immunity. In contrast to tumor response rate and immune endpoints, subject survival duration was significantly related to dose (median survival of 14.1 months compared to 6.7 months on the high and low dose, respectively; hazard ratio 0.39; P = 0.020). JX-594 demonstrated oncolytic and immunotherapy MOA, tumor responses and dose-related survival in individuals with HCC.

A study in patients with chronic GVHD evaluated three doses of axatilimab, a colony-stimulating factor 1 receptor antibody. The lowest dose appeared to maximize response with the fewest adverse effects.

Many risk genes for the development of Alzheimer’s disease (AD) are exclusively or highly expressed in myeloid cells. Microglia are dependent on colony-stimulating factor 1 receptor (CSF1R) signaling for their survival. We designed and synthesized a highly selective brain-penetrant CSF1R inhibitor (PLX5622) allowing for extended and specific microglial elimination, preceding and during pathology development. We find that in the 5xFAD mouse model of AD, plaques fail to form in the parenchymal space following microglial depletion, except in areas containing surviving microglia. Instead, Aβ deposits in cortical blood vessels reminiscent of cerebral amyloid angiopathy. Altered gene expression in the 5xFAD hippocampus is also reversed by the absence of microglia. Transcriptional analyses of the residual plaque-forming microglia show they exhibit a disease-associated microglia profile. Collectively, we describe the structure, formulation, and efficacy of PLX5622, which allows for sustained microglial depletion and identify roles of microglia in initiating plaque pathogenesis. Genetics implicate microglia in Alzheimer’s disease pathogenesis, but their roles remain unclear. Here, the authors find that microglial depletion in a mouse model of Alzheimer’s disease impairs plaque formation and that Aβ-induced changes in neuronal gene expression are microglia-mediated.

The proliferation, differentiation and survival of mononuclear phagocytes depend on signals from the receptor for macrophage colony-stimulating factor, CSF1R. The mammalian Csf1r locus contains a highly conserved super-enhancer, the fms -intronic regulatory element (FIRE). Here we show that genomic deletion of FIRE in mice selectively impacts CSF1R expression and tissue macrophage development in specific tissues. Deletion of FIRE ablates macrophage development from murine embryonic stem cells. Csf1r ΔFIRE/ΔFIRE mice lack macrophages in the embryo, brain microglia and resident macrophages in the skin, kidney, heart and peritoneum. The homeostasis of other macrophage populations and monocytes is unaffected, but monocytes and their progenitors in bone marrow lack surface CSF1R. Finally, Csf1r ΔFIRE/ΔFIRE mice are healthy and fertile without the growth, neurological or developmental abnormalities reported in Csf1r −/− rodents. Csf1r ΔFIRE/ΔFIRE mice thus provide a model to explore the homeostatic, physiological and immunological functions of tissue-specific macrophage populations in adult animals. The lineage-specific receptor CSF1R controls macrophage development and homeostasis. Here the authors show that deletion of a conserved Csf1r enhancer (FIRE) selectively depletes brain microglia and resident macrophages in the epidermis, kidney, heart and peritoneum of otherwise healthy mice.

Patients with autoimmune pulmonary alveolar proteinosis received inhaled molgramostim or matching placebo for 24 weeks. Patients receiving molgramostim had greater improvement in pulmonary gas transfer and alleviation of symptoms than those receiving placebo.

Abstract Rationale Sustained sepsis-associated immunosuppression is associated with uncontrolled infection, multiple organ dysfunction, and death. Objectives In the first controlled biomarker-guided immunostimulatory trial in sepsis, we tested whether granulocyte–macrophage colony-stimulating factor (GM-CSF) reverses monocyte deactivation, a hallmark of sepsis-associated immunosuppression (primary endpoint), and improves the immunological and clinical course of patients with sepsis. Methods In a prospective, randomized, double-blind, placebo-controlled, multicenter trial, 38 patients (19/group) with severe sepsis or septic shock and sepsis-associated immunosuppression (monocytic HLA-DR [mHLA-DR] <8,000 monoclonal antibodies (mAb) per cell for 2 d) were treated with GM-CSF (4 μg/kg/d) or placebo for 8 days. The patients' clinical and immunological course was followed up for 28 days. Measurements and Main Results Both groups showed comparable baseline mHLA-DR levels (5,609 ± 3,628 vs. 5,659 ± 3,332 mAb per cell), which significantly increased within 24 hours in the GM-CSF group. After GM-CSF treatment, mHLA-DR was normalized in 19/19 treated patients, whereas this occurred in 3/19 control subjects only (P < 0.001). GM-CSF also restored ex-vivo Toll-like receptor 2/4–induced proinflammatory monocytic cytokine production. In patients receiving GM-CSF, a shorter time of mechanical ventilation (148 ± 103 vs. 207 ± 58 h, P = 0.04), an improved Acute Physiology and Chronic Health Evaluation-II score (P = 0.02), and a shorter length of both intrahospital and intensive care unit stay was observed (59 ± 33 vs. 69 ± 46 and 41 ± 26 vs. 52 ± 39 d, respectively, both not significant). Side effects related to the intervention were not noted. Conclusions Biomarker-guided GM-CSF therapy in sepsis is safe and effective for restoring monocytic immunocompetence. Use of GM-CSF may shorten the time of mechanical ventilation and hospital/intensive care unit stay. A multicenter trial powered for the improvement of clinical parameters and mortality as primary endpoints seems indicated. Clinical trial registered with www.clinicaltrials.gov (NCT00252915).

Tissue-specific Langerhans cells and microglia develop in situ before birth. Colonna and colleagues identify IL-34 produced by keratinocytes and neurons as the relevant ligand of CSF1R necessary for their generation. The differentiation of bone marrow–derived progenitor cells into monocytes, tissue macrophages and some dendritic cell (DC) subtypes requires the growth factor CSF1 and its receptor, CSF1R. Langerhans cells (LCs) and microglia develop from embryonic myeloid precursor cells that populate the epidermis and central nervous system (CNS) before birth. Notably, LCs and microglia are present in CSF1-deficient mice but absent from CSF1R-deficient mice. Here we investigated whether an alternative CSF1R ligand, interleukin 34 (IL-34), is responsible for this discrepancy. Through the use of IL-34-deficient ( Il34 LacZ/LacZ ) reporter mice, we found that keratinocytes and neurons were the main sources of IL-34. Il34 LacZ/LacZ mice selectively lacked LCs and microglia and responded poorly to skin antigens and viral infection of the CNS. Thus, IL-34 specifically directs the differentiation of myeloid cells in the skin epidermis and CNS.

Exosomes are small membrane vesicles that are secreted by a multitude of cell types. The exosomes derived from dendritic cells (Dex), tumor cells (Tex), and malignant effusions demonstrate immunomodulatory functions, and are even under clinical trial for cancer treatments. In this study we report the phase I clinical trial of the ascites-derived exosomes (Aex) in combination with the granulocyte–macrophage colony-stimulating factor (GM-CSF) in the immunotherapy of colorectal cancer (CRC). The Aex isolated by sucrose/D2O density gradient ultracentrifugation are 60–90-nm vesicles that contain the diverse immunomodulatory markers of exosomes and tumor-associated carcinoembryonic antigen (CEA). Totally 40 patients (HLA-A0201+CEA+) with advanced CRC were enrolled in the study, and randomly assigned to treatments with Aex alone or Aex plus GM-CSF. Patients in both groups received a total of four subcutaneous immunizations at weekly intervals. We found that both therapies were safe and well tolerated, and that Aex plus GM-CSF but not Aex alone can induce beneficial tumor-specific antitumor cytotoxic T lymphocyte (CTL) response. Therefore, our study suggests that the immunotherapy of CRC with Aex in combination with GM-CSF is feasible and safe, and thus can serve as an alternative choice in the immunotherapy of advanced CRC.

Microenvironment contributes to follicular lymphoma (FL) pathogenesis and impacts survival with macrophages playing a controversial role. In the present study, using FL primary samples and HK follicular dendritic cells (FDC) to mimic the germinal center, together with mouse models, we have analyzed the three-way crosstalk of FL-FDC-macrophages and derived therapeutic opportunities. Ex vivo primary FL-FDC co-cultures ( n  = 19) and in vivo mouse co-xenografts demonstrated that FL-FDC crosstalk favors tumor growth and, via the secretion of CCL2 and CSF-1, promotes monocyte recruitment, differentiation, and polarization towards an M2-like protumoral phenotype. Moreover, FL-M2 co-cultures displayed enhanced angiogenesis, dissemination, and immunosuppression. Analysis of the CSF-1/CSF-1R pathway uncovered that CSF-1 was significantly higher in serum from grade 3A FL patients, and that high CSF-1R expression in FL biopsies correlated with grade 3A, reduced overall survival and risk of transformation. Furthermore, CSF-1R inhibition with pexidartinib (PLX3397) preferentially affected M2-macrophage viability and polarization program disrupting FL-M2 positive crosstalk. In vivo CSF1-R inhibition caused M2 reduction and repolarization towards M1 macrophages and antitumor effect cooperating with anti-CD20 rituximab. In summary, these results support the role of macrophages in FL pathogenesis and indicate that CSF-1R may be a relevant prognostic factor and a novel therapeutic target cooperating with anti-CD20 immunotherapy.