Peripheral T cell expansion predicts tumour infiltration and clinical response.

Despite the resounding clinical success in cancer treatment of antibodies that block the interaction of PD1 with its ligand PDL11, the mechanisms involved remain unknown. A major limitation to understanding the origin and fate of T cells in tumour immunity is the lack of quantitative information on the distribution of individual clonotypes of T cells in patients with cancer. Here, by performing deep single-cell sequencing of RNA and T cell receptors in patients with different types of cancer, we survey the profiles of various populations of T cells and T cell receptors in tumours, normal adjacent tissue, and peripheral blood. We find clear evidence of clonotypic expansion of effector-like T cells not only within the tumour but also in normal adjacent tissue. Patients with gene signatures of such clonotypic expansion respond best to anti-PDL1 therapy. Notably, expanded clonotypes found in the tumour and normal adjacent tissue can also typically be detected in peripheral blood, which suggests a convenient approach to patient identification. Analyses of our data together with several external datasets suggest that intratumoural T cells, especially in responsive patients, are replenished with fresh, non-exhausted replacement cells from sites outside the tumour, suggesting continued activity of the cancer immunity cycle in these patients, the acceleration of which may be associated with clinical response.

CD96 functions as a co-stimulatory receptor to enhance CD8+ T cell activation and effector responses.

CD96 is a member of the poliovirus receptor (PVR, CD155)-nectin family that includes T cell Ig and ITIM domain (TIGIT) and CD226. While CD96, TIGIT, and CD226 have important roles in regulating NK cell activity, and TIGIT and CD226 have also been shown to regulate T cell responses, it is unclear whether CD96 has inhibitory or stimulatory function in CD8+ T cells. Here, we demonstrate that CD96 has co-stimulatory function on CD8+ T cells. Crosslinking of CD96 on human or mouse CD8+ T cells induced activation, effector cytokine production, and proliferation. CD96 was found to transduce its activating signal through the MEK-ERK pathway. CD96-mediated signaling led to increased frequencies of NUR77- and T-bet-expressing CD8+ T cells and enhanced cytotoxic effector activity, indicating that CD96 can modulate effector T cell differentiation. Antibody blockade of CD96 or genetic ablation of CD96 expression on CD8+ T cells impaired expression of transcription factors and proinflammatory cytokines associated with CD8+ T cell activation in in vivo models. Taken together, CD96 has a co-stimulatory role in CD8+ T cell activation and effector function.

Schistosomal-derived lysophosphatidylcholine triggers M2 polarization of macrophages through PPARγ dependent mechanisms.

Mansonic schistosomiasis is a disease caused by the trematode Schistosoma mansoni, endemic to tropical countries. S. mansoni infection induces the formation of granulomas and potent polarization of Th2-type immune response. There is great interest in understanding the mechanisms used by this parasite that causes a modulation of the immune system. Recent studies from our group demonstrated that lipids of S. mansoni, including lysophosphatidylcholine (LPC) have immunomodulatory activity. In the present study, our aim was to investigate the role of lipids derived from S. mansoni in the activation and polarization of macrophages and to characterize the mechanisms involved in this process. Peritoneal macrophages obtained from wild type C57BL/6mice or bone marrow derived macrophages were stimulated in vitro with lipids extracted from adult worms of S. mansoni. We demonstrated that total schistosomal-derived lipids as well as purified LPC induced alternatively activated macrophages/M2 profile observed by increased expression of arginase-1, mannose receptor, Chi3l3, TGFß and production of IL-10 and PGE2 24h after stimulation. The involvement of the nuclear receptor PPARγ in macrophage response against LPC was investigated. Through Western blot and immunofluorescence confocal microscopy we demonstrated that schistosomal-derived LPC induces increased expression of PPARγ in macrophages. The LPC-induced increased expression of arginase-1 were significantly inhibited by the PPAR-γ antagonist GW9662. Together, these results demonstrate an immunomodulatory role of schistosomal-derived LPC in activating macrophages to a profile of the type M2 through PPARγ-dependent mechanisms, indicating a novel pathway for macrophage polarization triggered by parasite-derived LPC with potential implications to disease pathogenesis.

Differential TLR2 downstream signaling regulates lipid metabolism and cytokine production triggered by Mycobacterium bovis BCG infection.

The nuclear receptor PPARγ acts as a key modulator of lipid metabolism, inflammation and pathogenesis in BCG-infected macrophages. However, the molecular mechanisms involved in PPARγ expression and functions during infection are not completely understood. Here, we investigate signaling pathways triggered by TLR2, the involvement of co-receptors and lipid rafts in the mechanism of PPARγ expression, lipid body formation and cytokine synthesis in macrophages during BCG infection. BCG induces NF-κB activation and increased PPARγ expression in a TLR2-dependent manner. Furthermore, BCG-triggered increase of lipid body biogenesis was inhibited by the PPARγ antagonist GW9662, but not by the NF-κB inhibitor JSH-23. In contrast, KC/CXCL1 production was largely dependent on NF-κB but not on PPARγ. BCG infection induced increased expression of CD36 in macrophages in vitro. Moreover, CD36 co-immunoprecipitates with TLR2 in BCG-infected macrophages, suggesting its interaction with TLR2 in BCG signaling. Pretreatment with CD36 neutralizing antibodies significantly inhibited PPARγ expression, lipid body formation and PGE2 production induced by BCG. Involvement of CD36 in lipid body formation was further confirmed by decreased BCG-induced lipid body formation in CD36 deficient macrophages. Similarly, CD14 and CD11b/CD18 blockage also inhibited BCG-induced lipid body formation, whereas TNF-α synthesis was not affected. Disruption of rafts recapitulates the latter result, inhibiting lipid body formation, but not TNF-α synthesis in BCG-infected macrophages. In conclusion, our results suggest that CD36-TLR2 cooperation and signaling compartmentalization within rafts, divert host response signaling through PPARγ-dependent and NF-κB-independent pathways, leading to increased macrophage lipid accumulation and down-modulation of macrophage response.

Mycobacterium leprae intracellular survival relies on cholesterol accumulation in infected macrophages: a potential target for new drugs for leprosy treatment.

We recently showed that Mycobacterium leprae (ML) is able to induce lipid droplet formation in infected macrophages. We herein confirm that cholesterol (Cho) is one of the host lipid molecules that accumulate in ML-infected macrophages and investigate the effects of ML on cellular Cho metabolism responsible for its accumulation. The expression levels of LDL receptors (LDL-R, CD36, SRA-1, SR-B1, and LRP-1) and enzymes involved in Cho biosynthesis were investigated by qRT-PCR and/or Western blot and shown to be higher in lepromatous leprosy (LL) tissues when compared to borderline tuberculoid (BT) lesions. Moreover, higher levels of the active form of the sterol regulatory element-binding protein (SREBP) transcriptional factors, key regulators of the biosynthesis and uptake of cellular Cho, were found in LL skin biopsies. Functional in vitro assays confirmed the higher capacity of ML-infected macrophages to synthesize Cho and sequester exogenous LDL-Cho. Notably, Cho colocalized to ML-containing phagosomes, and Cho metabolism impairment, through either de novo synthesis inhibition by statins or depletion of exogenous Cho, decreased intracellular bacterial survival. These findings highlight the importance of metabolic integration between the host and bacteria to leprosy pathophysiology, opening new avenues for novel therapeutic strategies to leprosy.

Immunogenicity of pluripotent stem cells and their derivatives.

The ability of pluripotent stem cells to self-renew and differentiate into all somatic cell types brings great prospects to regenerative medicine and human health. However, before clinical applications, much translational research is necessary to ensure that their therapeutic progenies are functional and nontumorigenic, that they are stable and do not dedifferentiate, and that they do not elicit immune responses that could threaten their survival in vivo. For this, an in-depth understanding of their biology, genetic, and epigenetic make-up and of their antigenic repertoire is critical for predicting their immunogenicity and for developing strategies needed to assure successful long-term engraftment. Recently, the expectation that reprogrammed somatic cells would provide an autologous cell therapy for personalized medicine has been questioned. Induced pluripotent stem cells display several genetic and epigenetic abnormalities that could promote tumorigenicity and immunogenicity in vivo. Understanding the persistence and effects of these abnormalities in induced pluripotent stem cell derivatives is critical to allow clinicians to predict graft fate after transplantation, and to take requisite measures to prevent immune rejection. With clinical trials of pluripotent stem cell therapy on the horizon, the importance of understanding immunologic barriers and devising safe, effective strategies to bypass them is further underscored. This approach to overcome immunologic barriers to stem cell therapy can take advantage of the validated knowledge acquired from decades of hematopoietic stem cell transplantation.

Microfluidic single-cell analysis shows that porcine induced pluripotent stem cell-derived endothelial cells improve myocardial function by paracrine activation.

RATIONALE: Induced pluripotent stem cells (iPSCs) hold great promise for the development of patient-specific therapies for cardiovascular disease. However, clinical translation will require preclinical optimization and validation of large-animal iPSC models. OBJECTIVE: To successfully derive endothelial cells from porcine iPSCs and demonstrate their potential utility for the treatment of myocardial ischemia. METHODS AND RESULTS: Porcine adipose stromal cells were reprogrammed to generate porcine iPSCs (piPSCs). Immunohistochemistry, quantitative PCR, microarray hybridization, and angiogenic assays confirmed that piPSC-derived endothelial cells (piPSC-ECs) shared similar morphological and functional properties as endothelial cells isolated from the autologous pig aorta. To demonstrate their therapeutic potential, piPSC-ECs were transplanted into mice with myocardial infarction. Compared with control, animals transplanted with piPSC-ECs showed significant functional improvement measured by echocardiography (fractional shortening at week 4: 27.2±1.3% versus 22.3±1.1%; P<0.001) and MRI (ejection fraction at week 4: 45.8±1.3% versus 42.3±0.9%; P<0.05). Quantitative protein assays and microfluidic single-cell PCR profiling showed that piPSC-ECs released proangiogenic and antiapoptotic factors in the ischemic microenvironment, which promoted neovascularization and cardiomyocyte survival, respectively. Release of paracrine factors varied significantly among subpopulations of transplanted cells, suggesting that transplantation of specific cell populations may result in greater functional recovery. CONCLUSIONS: In summary, this is the first study to successfully differentiate piPSCs-ECs from piPSCs and demonstrate that transplantation of piPSC-ECs improved cardiac function after myocardial infarction via paracrine activation. Further development of these large animal iPSC models will yield significant insights into their therapeutic potential and accelerate the clinical translation of autologous iPSC-based therapy.

Genome editing of human embryonic stem cells and induced pluripotent stem cells with zinc finger nucleases for cellular imaging.

RATIONALE: Molecular imaging has proven to be a vital tool in the characterization of stem cell behavior in vivo. However, the integration of reporter genes has typically relied on random integration, a method that is associated with unwanted insertional mutagenesis and positional effects on transgene expression. OBJECTIVE: To address this barrier, we used genome editing with zinc finger nuclease (ZFN) technology to integrate reporter genes into a safe harbor gene locus (PPP1R12C, also known as AAVS1) in the genome of human embryonic stem cells and human induced pluripotent stem cells for molecular imaging. METHODS AND RESULTS: We used ZFN technology to integrate a construct containing monomeric red fluorescent protein, firefly luciferase, and herpes simplex virus thymidine kinase reporter genes driven by a constitutive ubiquitin promoter into a safe harbor locus for fluorescence imaging, bioluminescence imaging, and positron emission tomography imaging, respectively. High efficiency of ZFN-mediated targeted integration was achieved in both human embryonic stem cells and induced pluripotent stem cells. ZFN-edited cells maintained both pluripotency and long-term reporter gene expression. Functionally, we successfully tracked the survival of ZFN-edited human embryonic stem cells and their differentiated cardiomyocytes and endothelial cells in murine models, demonstrating the use of ZFN-edited cells for preclinical studies in regenerative medicine. CONCLUSION: Our study demonstrates a novel application of ZFN technology to the targeted genetic engineering of human pluripotent stem cells and their progeny for molecular imaging in vitro and in vivo.

Loss of CDKN2B promotes p53-dependent smooth muscle cell apoptosis and aneurysm formation.

OBJECTIVE: Genomewide association studies have implicated allelic variation at 9p21.3 in multiple forms of vascular disease, including atherosclerotic coronary heart disease and abdominal aortic aneurysm. As for other genes at 9p21.3, human expression quantitative trait locus studies have associated expression of the tumor suppressor gene CDKN2B with the risk haplotype, but its potential role in vascular pathobiology remains unclear. METHODS AND RESULTS: Here we used vascular injury models and found that Cdkn2b knockout mice displayed the expected increase in proliferation after injury, but developed reduced neointimal lesions and larger aortic aneurysms. In situ and in vitro studies suggested that these effects were attributable to increased smooth muscle cell apoptosis. Adoptive bone marrow transplant studies confirmed that the observed effects of Cdkn2b were mediated through intrinsic vascular cells and were not dependent on bone marrow-derived inflammatory cells. Mechanistic studies suggested that the observed increase in apoptosis was attributable to a reduction in MDM2 and an increase in p53 signaling, possibly due in part to compensation by other genes at the 9p21.3 locus. Dual inhibition of both Cdkn2b and p53 led to a reversal of the vascular phenotype in each model. CONCLUSIONS: These results suggest that reduced CDKN2B expression and increased smooth muscle cell apoptosis may be one mechanism underlying the 9p21.3 association with aneurysmal disease.

In vivo functional and transcriptional profiling of bone marrow stem cells after transplantation into ischemic myocardium.

OBJECTIVE: Clinical trials of bone marrow-derived stem cell therapy for the heart have yielded variable results. The basic mechanism(s) that underlies their potential efficacy remains unknown. In the present study, we evaluated the survival kinetics, transcriptional response, and functional outcome of intramyocardial bone marrow mononuclear cell (BMMC) transplantation for cardiac repair in a murine myocardial infarction model. METHODS AND RESULTS: We used bioluminescence imaging and high-throughput transcriptional profiling to evaluate the in vivo survival kinetics and gene expression changes of transplanted BMMCs after their engraftment into ischemic myocardium. Our results demonstrate short-lived survival of cells following transplant, with less than 1% of cells surviving by 6 weeks posttransplantation. Moreover, transcriptomic analysis of BMMCs revealed nonspecific upregulation of various cell regulatory genes, with a marked downregulation of cell differentiation and maturation pathways. BMMC therapy caused limited improvement of heart function as assessed by echocardiography, invasive hemodynamics, and positron emission tomography. Histological evaluation of cell fate further confirmed findings of the in vivo cell tracking and transcriptomic analysis. CONCLUSIONS: Collectively, these data suggest that BMMC therapy, in its present iteration, may be less efficacious than once thought. Additional refinement of existing cell delivery protocols should be considered to induce better therapeutic efficacy.

Preclinical derivation and imaging of autologously transplanted canine induced pluripotent stem cells.

Derivation of patient-specific induced pluripotent stem cells (iPSCs) opens a new avenue for future applications of regenerative medicine. However, before iPSCs can be used in a clinical setting, it is critical to validate their in vivo fate following autologous transplantation. Thus far, preclinical studies have been limited to small animals and have yet to be conducted in large animals that are physiologically more similar to humans. In this study, we report the first autologous transplantation of iPSCs in a large animal model through the generation of canine iPSCs (ciPSCs) from the canine adipose stromal cells and canine fibroblasts of adult mongrel dogs. We confirmed pluripotency of ciPSCs using the following techniques: (i) immunostaining and quantitative PCR for the presence of pluripotent and germ layer-specific markers in differentiated ciPSCs; (ii) microarray analysis that demonstrates similar gene expression profiles between ciPSCs and canine embryonic stem cells; (iii) teratoma formation assays; and (iv) karyotyping for genomic stability. Fate of ciPSCs autologously transplanted to the canine heart was tracked in vivo using clinical positron emission tomography, computed tomography, and magnetic resonance imaging. To demonstrate clinical potential of ciPSCs to treat models of injury, we generated endothelial cells (ciPSC-ECs) and used these cells to treat immunodeficient murine models of myocardial infarction and hindlimb ischemia.

Double knockdown of prolyl hydroxylase and factor-inhibiting hypoxia-inducible factor with nonviral minicircle gene therapy enhances stem cell mobilization and angiogenesis after myocardial infarction.

BACKGROUND: Under normoxic conditions, hypoxia-inducible factor (HIF)-1α is rapidly degraded by 2 hydroxylases: prolyl hydroxylase (PHD) and factor-inhibiting HIF-1 (FIH). Because HIF-1α mediates the cardioprotective response to ischemic injury, its upregulation may be an effective therapeutic option for ischemic heart failure. METHODS AND RESULTS: PHD and FIH were cloned from mouse embryonic stem cells. The best candidate short hairpin (sh) sequences for inhibiting PHD isoenzyme 2 and FIH were inserted into novel, nonviral, minicircle vectors. In vitro studies after cell transfection of mouse C2C12 myoblasts, HL-1 atrial myocytes, and c-kit(+) cardiac progenitor cells demonstrated higher expression of angiogenesis factors in the double-knockdown group compared with the single-knockdown and short hairpin scramble control groups. To confirm in vitro data, shRNA minicircle vectors were injected intramyocardially after left anterior descending coronary artery ligation in adult FVB mice (n=60). Functional studies using MRI, echocardiography, and pressure-volume loops showed greater improvement in cardiac function in the double-knockdown group. To assess mechanisms of this functional recovery, we performed a cell trafficking experiment, which demonstrated significantly greater recruitment of bone marrow cells to the ischemic myocardium in the double-knockdown group. Fluorescence-activated cell sorting showed significantly higher activation of endogenous c-kit(+) cardiac progenitor cells. Immunostaining showed increased neovascularization and decreased apoptosis in areas of injured myocardium. Finally, western blots and laser-capture microdissection analysis confirmed upregulation of HIF-1α protein and angiogenesis genes, respectively. CONCLUSIONS: We demonstrated that HIF-1α upregulation by double knockdown of PHD and FIH synergistically increases stem cell mobilization and myocardial angiogenesis, leading to improved cardiac function.

Intratumoral plasma cells predict outcomes to PD-L1 blockade in non-small cell lung cancer.

Inhibitors of the programmed cell death-1 (PD-1/PD-L1) signaling axis are approved to treat non-small cell lung cancer (NSCLC) patients, based on their significant overall survival (OS) benefit. Using transcriptomic analysis of 891 NSCLC tumors from patients treated with either the PD-L1 inhibitor atezolizumab or chemotherapy from two large randomized clinical trials, we find a significant B cell association with extended OS with PD-L1 blockade, independent of CD8+ T cell signals. We then derive gene signatures corresponding to the dominant B cell subsets present in NSCLC from single-cell RNA sequencing (RNA-seq) data. Importantly, we find increased plasma cell signatures to be predictive of OS in patients treated with atezolizumab, but not chemotherapy. B and plasma cells are also associated with the presence of tertiary lymphoid structures and organized lymphoid aggregates. Our results suggest an important contribution of B and plasma cells to the efficacy of PD-L1 blockade in NSCLC.

In vivo bioluminescence for tracking cell fate and function.

Tracking the fate and function of cells in vivo is paramount for the development of rational therapies for cardiac injury. Bioluminescence imaging (BLI) provides a means for monitoring physiological processes in real time, ranging from cell survival to gene expression to complex molecular processes. In mice and rats, BLI provides unmatched sensitivity because of the absence of endogenous luciferase expression in mammalian cells and the low background luminescence emanating from animals. In the field of stem cell therapy, BLI provides an unprecedented means to monitor the biology of these cells in vivo, giving researchers a greater understanding of their survival, migration, immunogenicity, and potential tumorigenicity in a living animal. In addition to longitudinal monitoring of cell survival, BLI is a useful tool for semiquantitative measurements of gene expression in vivo, allowing a better optimization of drug and gene therapies. Overall, this technology not only enables rapid, reproducible, and quantitative monitoring of physiological processes in vivo but also can measure the influences of therapeutic interventions on the outcome of cardiac injuries.

Mycobacterium bovis bacillus Calmette-Guérin infection induces TLR2-dependent peroxisome proliferator-activated receptor gamma expression and activation: functions in inflammation, lipid metabolism, and pathogenesis.

Macrophages have important roles in both lipid metabolism and inflammation and are central to immunity to intracellular pathogens. Foam-like, lipid-laden macrophages are present during the course of mycobacterial infection and have recently been implicated in mycobacterial pathogenesis. In this study, we analyzed the molecular mechanisms underlying the formation of macrophage lipid bodies (lipid droplets) during Mycobacterium bovis bacillus Calmette-Guérin (BCG) infection, focusing on the role of the lipid-activated nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma). We found that BCG infection induced increased expression of PPARgamma that paralleled the augmented lipid body formation and PGE(2) synthesis in mouse peritoneal macrophages. BCG-induced PPARgamma expression and lipid body formation were diminished in macrophages from TLR2-deficient mice, suggesting a key role for TLR2. The function of PPARgamma in modulating BCG infection was demonstrated by the capacity of the PPARgamma agonist BRL49653 to potentiate lipid body formation and PGE(2) production; furthermore, pretreatment with the PPARgamma antagonist GW9662 inhibited BCG-induced lipid body formation and PGE(2) production. BCG-induced MIP-1alpha, IL12p70, TNF-alpha, and IL6 production was not inhibited by GW9662 treatment. Nonpathogenic Mycobacterium smegmatis failed to induce PPARgamma expression or lipid body formation. Moreover, inhibition of PPARgamma by GW9662 enhanced the mycobacterial killing capacity of macrophages. Our findings show that PPARgamma is involved in lipid body biogenesis, unravels a cross-talk between the innate immune receptor TLR2 and the lipid-activated nuclear receptor PPARgamma that coordinates lipid metabolism and inflammation in BCG-infected macrophages, thereby potentially affecting mycobacterial pathogenesis.

Schistosomal­derived lysophosphatidylcholine are involved in eosinophil activation and recruitment through Toll­like receptor-2-dependent mechanisms.

Parasite­derived lipids may play important roles in host­pathogen interactions and escape mechanisms. Herein, we evaluated the role of schistosomal­derived lipids in Toll­like receptor (TLR)-2 and eosinophil activation in Schistosoma mansoni infection. Mice lacking TLR2 exhibited reduced liver eosinophilic granuloma, compared with that of wild­type animals, following S. mansoni infection. Decreased eosinophil accumulation and eosinophil lipid body (lipid droplet) formation, at least partially due to reduced production of eotaxin, interleukin (IL)­5, and IL­13 in S. mansoni-infected TLR2-/- mice, compared with the corresponding production in wild­type mice, was noted. Although no differences were observed in survival rates during the acute schistosomal infection (up to 50 days), increased survival of TLR2-/- mice, compared with survival of wild­type mice, was observed during the chronic phase of infection. Schistosomal lipid extract­ and schistosomal­derived lysophosphatidylcholine (lyso­PC)-stimulated macrophages in vitro induced TLR2­dependent NF­kB activation and cytokine production. Furthermore, in vivo schistosomal lyso­PC administration induced eosinophil recruitment and cytokine production, in a mechanism largely dependent on TLR2. Taken together, our results suggest that schistosomal­derived lyso­PC may participate in cytokine production and eosinophil activation through a TLR2­dependent pathway in S. mansoni infection. Moreover, our results suggest that TLR2­dependent inflammatory reaction, cytokine production, and eosinophil recruitment and activation may contribute to the pathogenesis and lethality in the chronic phase of infection.

Anti-VEGF Treatment Enhances CD8+ T-cell Antitumor Activity by Amplifying Hypoxia.

Antiangiogenic therapies that target the VEGF pathway have been used clinically to combat cancer for over a decade. Beyond having a direct impact on blood vessel development and tumor perfusion, accumulating evidence indicates that these agents also affect antitumor immune responses. Numerous clinical trials combining antiangiogenic drugs with immunotherapies for the treatment of cancer are ongoing, but a mechanistic understanding of how disruption of tumor angiogenesis may impact immunity is not fully discerned. Here, we reveal that blockade of VEGF-A with a mAb to VEGF augments activation of CD8+ T cells within tumors and potentiates their capacity to produce cytokines. We demonstrate that this phenomenon relies on the disruption of VEGFR2 signaling in the tumor microenvironment but does not affect CD8+ T cells directly. Instead, the augmented functional capacity of CD8+ T cells stems from increased tumor hypoxia that initiates a hypoxia-inducible factor-1α program within CD8+ T cells that directly enhances cytokine production. Finally, combinatorial administration of anti-VEGF with an immunotherapeutic antibody, anti-OX40, improved antitumor activity over single-agent treatments. Our findings illustrate that anti-VEGF treatment enhances CD8+ T-cell effector function and provides a mechanistic rationale for combining antiangiogenic and immunotherapeutic drugs for cancer treatment.

Function of CSF1 and IL34 in Macrophage Homeostasis, Inflammation, and Cancer.

Colony-stimulating factor 1 (CSF1) and interleukin 34 (IL34) signal via the CSF1 receptor to regulate macrophage differentiation. Studies in IL34- or CSF1-deficient mice have revealed that IL34 function is limited to the central nervous system and skin during development. However, the roles of IL34 and CSF1 at homeostasis or in the context of inflammatory diseases or cancer in wild-type mice have not been clarified in vivo. By neutralizing CSF1 and/or IL34 in adult mice, we identified that they play important roles in macrophage differentiation, specifically in steady-state microglia, Langerhans cells, and kidney macrophages. In several inflammatory models, neutralization of both CSF1 and IL34 contributed to maximal disease protection. However, in a myeloid cell-rich tumor model, CSF1 but not IL34 was required for tumor-associated macrophage accumulation and immune homeostasis. Analysis of human inflammatory conditions reveals IL34 upregulation that may account for the protection requirement of IL34 blockade. Furthermore, evaluation of IL34 and CSF1 blockade treatment during Listeria infection reveals no substantial safety concerns. Thus, IL34 and CSF1 play non-redundant roles in macrophage differentiation, and therapeutic intervention targeting IL34 and/or CSF1 may provide an effective treatment in macrophage-driven immune-pathologies.

Lipid Bodies as Sites of Prostaglandin E2 Synthesis During Chagas Disease: Impact in the Parasite Escape Mechanism.

During Chagas disease, the Trypanosoma cruzi can induce some changes in the host cells in order to escape or manipulate the host immune response. The modulation of the lipid metabolism in the host phagocytes or in the parasite itself is one feature that has been observed. The goal of this mini review is to discuss the mechanisms that regulate intracellular lipid body (LB) biogenesis in the course of this parasite infection and their meaning to the pathophysiology of the disease. The interaction host-parasite induces LB (or lipid droplet) formation in a Toll-like receptor 2-dependent mechanism in macrophages and is enhanced by apoptotic cell uptake. Simultaneously, there is a lipid accumulation in the parasite due to the incorporation of host fatty acids. The increase in the LB accumulation during infection is correlated with an increase in the synthesis of PGE2 within the host cells and the parasite LBs. Moreover, the treatment with fatty acid synthase inhibitor C75 or non-steroidal anti-inflammatory drugs such as NS-398 and aspirin inhibited the LB biogenesis and also induced the down modulation of the eicosanoid production and the parasite replication. These findings show that LBs are organelles up modulated during the course of infection. Furthermore, the biogenesis of the LB is involved in the lipid mediator generation by both the macrophages and the parasite triggering escape mechanisms.

Corrigendum: Lipid Bodies as Sites of Prostaglandin E2 Synthesis During Chagas Disease: Impact in the Parasite Escape Mechanism.

[This corrects the article on p. 499 in vol. 9, PMID: 29616011.].