scholarly journals Myeloid Cell Modulation by Tumor-Derived Extracellular Vesicles

2020 ◽  
Vol 21 (17) ◽  
pp. 6319
Author(s):  
Ihor Arkhypov ◽  
Samantha Lasser ◽  
Vera Petrova ◽  
Rebekka Weber ◽  
Christopher Groth ◽  
...  
Keyword(s):  
Extracellular Vesicles ◽  
Tumor Antigens ◽  
High Capacity ◽  
Myeloid Cells ◽  
Suppressor Cells ◽  
Myeloid Cell ◽  
Host Cells ◽  
Central Position ◽  
Tumor Type ◽  
Inflammatory Conditions

Extracellular vesicles (EV) can carry proteins, RNA and DNA, thus serving as communication tools between cells. Tumor cells secrete EV, which can be taken up by surrounding cells in the tumor microenvironment as well as by cells in distant organs. Tumor-derived EV (TEV) contain factors induced by tumor-associated hypoxia such as heat shock proteins or a variety of microRNA (miRNA). The interaction of TEV with tumor and host cells can promote cancer angiogenesis, invasion and metastasis. Myeloid cells are widely presented in tissues, comprise the majority of immune cells and play an essential role in immune reactions and tissue remodeling. However, in cancer, the differentiation of myeloid cells and their functions are impaired, resulting in tumor promotion. Such alterations are due to chronic inflammatory conditions associated with cancer and are mediated by the tumor secretome, including TEV. A high capacity of myeloid cells to clear EV from circulation put them in the central position in EV-mediated formation of pre-metastatic niches. The exposure of myeloid cells to TEV could trigger numerous signaling pathways. Progenitors of myeloid cells alter their differentiation upon the contact with TEV, resulting in the generation of myeloid-derived suppressor cells (MDSC), inhibiting anti-tumor function of T and natural killer (NK) cells and promoting thereby tumor progression. Furthermore, TEV can augment MDSC immunosuppressive capacity. Different subsets of mature myeloid cells such as monocytes, macrophages, dendritic cells (DC) and granulocytes take up TEV and acquire a protumorigenic phenotype. However, the delivery of tumor antigens to DC by TEV was shown to enhance their immunostimulatory capacity. The present review will discuss a diverse and complex EV-mediated crosstalk between tumor and myeloid cells in the context of the tumor type, TEV-associated cargo molecules and type of recipient cells.

scholarly journals Targeted deletion of PD-1 in myeloid cells induces antitumor immunity

2020 ◽  
Vol 5 (43) ◽  
pp. eaay1863 ◽  
Author(s):  
Laura Strauss ◽  
Mohamed A. A. Mahmoud ◽  
Jessica D. Weaver ◽  
Natalia M. Tijaro-Ovalle ◽  
Anthos Christofides ◽  
...  
Keyword(s):  
T Cell ◽  
Antitumor Immunity ◽  
Myeloid Cells ◽  
Suppressor Cells ◽  
Myeloid Cell ◽  
Tca Cycle ◽  
Pentose Phosphate ◽  
Metabolic Reprogramming ◽  
Effector Memory ◽  
Emergency Myelopoiesis

PD-1, a T cell checkpoint receptor and target of cancer immunotherapy, is also expressed on myeloid cells. The role of myeloid-specific versus T cell–specific PD-1 ablation on antitumor immunity has remained unclear because most studies have used either PD-1–blocking antibodies or complete PD-1 KO mice. We generated a conditional allele, which allowed myeloid-specific (PD-1f/fLysMcre) or T cell–specific (PD-1f/fCD4cre) targeting of Pdcd1 gene. Compared with T cell–specific PD-1 ablation, myeloid cell–specific PD-1 ablation more effectively decreased tumor growth. We found that granulocyte/macrophage progenitors (GMPs), which accumulate during cancer-driven emergency myelopoiesis and give rise to myeloid-derived suppressor cells (MDSCs), express PD-1. In tumor-bearing PD-1f/fLysMcre but not PD-1f/fCD4cre mice, accumulation of GMP and MDSC was prevented, whereas systemic output of effector myeloid cells was increased. Myeloid cell–specific PD-1 ablation induced an increase of T effector memory cells with improved functionality and mediated antitumor protection despite preserved PD-1 expression in T cells. In PD-1–deficient myeloid progenitors, growth factors driving emergency myelopoiesis induced increased metabolic intermediates of glycolysis, pentose phosphate pathway, and TCA cycle but, most prominently, elevated cholesterol. Because cholesterol is required for differentiation of inflammatory macrophages and DC and promotes antigen-presenting function, our findings indicate that metabolic reprogramming of emergency myelopoiesis and differentiation of effector myeloid cells might be a key mechanism of antitumor immunity mediated by PD-1 blockade.

scholarly journals Myeloid Cell-Specific Knockout of NFI-A Improves Sepsis Survival

2017 ◽  
Vol 85 (4) ◽  
Author(s):  
Melissa B. McPeak ◽  
Dima Youssef ◽  
Danielle A. Williams ◽  
Christopher Pritchett ◽  
Zhi Q. Yao ◽  
...  
Keyword(s):  
Ectopic Expression ◽  
Myeloid Cells ◽  
Suppressor Cells ◽  
Myeloid Cell ◽  
Effector Cells ◽  
Conditional Deletion ◽  
Related Transcription Factor ◽  
Nuclear Factor I ◽  
Sepsis Survival ◽  
Myeloid Progenitors

ABSTRACT Myeloid progenitor-derived suppressor cells (MDSCs) arise from myeloid progenitors and suppress both innate and adaptive immunity. MDSCs expand during the later phases of sepsis in mice, promote immunosuppression, and reduce survival. Here, we report that the myeloid differentiation-related transcription factor nuclear factor I-A (NFI-A) controls MDSC expansion during sepsis and impacts survival. Unlike MDSCs, myeloid cells with conditional deletion of the Nfia gene normally differentiated into effector cells during sepsis, cleared infecting bacteria, and did not express immunosuppressive mediators. In contrast, ectopic expression of NFI-A in myeloid progenitors from NFI-A myeloid cell-deficient mice impeded myeloid cell maturation and promoted immune repressor function. Importantly, surviving septic mice with conditionally deficient NFI-A myeloid cells were able to respond to challenge with bacterial endotoxin by mounting an acute inflammatory response. Together, these results support the concept of NFI-A as a master molecular transcriptome switch that controls myeloid cell differentiation and maturation and that malfunction of this switch during sepsis promotes MDSC expansion that adversely impacts sepsis outcome.

scholarly journals Characterization of Myeloid-Derived Suppressor Cells and Tumor Associated Macrophages Using MultiOmyxTM Hyperplexed Immunofluorescence Assay in Hodgkin Lymphoma

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 4135-4135
Author(s):  
Qingyan Au ◽  
Jun Fang ◽  
Anna Juncker-Jensen ◽  
Judy Kuo ◽  
Eric Leones ◽  
...  
Keyword(s):  
Hodgkin Lymphoma ◽  
Hematological Malignancies ◽  
Myeloid Cells ◽  
Suppressor Cells ◽  
Myeloid Cell ◽  
Myeloid Derived Suppressor Cells ◽  
M2 Macrophages ◽  
Tumor Associated Macrophages ◽  
Hla Dr

Abstract Tumor microenvironment (TME) consists of heterogeneous subsets of myeloid cells and plays a crucial role in promoting cancer development and metastasis. Tumor associated macrophages (TAMs) and myeloid-derived suppressor cells (MDSCs) all contribute to an immunologically permissive microenvironment for cancer cells. On basis of the expression of surface markers, MDSC can be further subdivided into granulocytic MDSC (G-MDSC, polymorphonuclear MDSC) and monocytic MDSC (M-MDSC). In solid tumors, these different myeloid cell populations are well characterized and extensively studied. However, in hematological malignancies the role of myeloid cell subsets has been less studied. A recent study showed increase in MDSC in the bone marrow (BM) at time of diagnosis in acute myeloid leukemia (AML) patients (Sun H. et al. Int J Hematol. 2015). Significantly higher numbers of G-MDSC and M-MDSC were present at diagnosis in classic Hodgkin lymphoma (cHL) (Romano A. et al. Br J Haematol. 2015). The accumulation of TAMs was also reported to be associated with poor prognosis in cHL (Steidl C. et al. N Engl J Med. 2010). Collectively, these results indicate that the tumor-resident myeloid cells play an important clinical role, thus highlighting the need for monitoring and deeper characterization of various myeloid subsets in hematological malignancies, especially in the tumor FFPE sections. Herein, we report an analysis of MDSCs and 'protumoral' M2 macrophages using MultiOmyx hyperplexed immunofluorescence (IF) assay in 9 clinical samples diagnosed with HL. MultiOmyx is a proprietary multi 'omic' technology that enables detection and visualization of up to 60 biomarkers on a single 4µM FFPE slide (Gerdes MJ. et al. PNAS 2013). The HL FFPE sections were stained with a 13-marker panel including Arginase 1, CD11b, CD14, CD15, CD16, CD33, CD68, CD163, HLA-DR, CD3, CD4, CD8 and FOXP3. We observed that both M-MDSC (Fig 1A, characterized as CD11b+CD14+CD15-CD33+HLA-DR-) and G-MDSC (Fig 1B, identified as CD11b+CD14-CD15+CD33+HLA-DR-) accumulated within the TME in all 9 HL samples, with higher frequency of G-MDSCs over M-MDSCs. Arg1 expression was detected exclusively in G-MDSC population (Fig 1C). The data also revealed an abundant M2 macrophages (Fig 1D, characterized as CD68+CD163+) present in all HL samples. The detection of both MDSCs and M2 macrophages in HL samples supports the hypothesis that these cells contribute to the establishment of an immunosuppressive TME. Using the MultiOmyx proprietary algorithm, which takes into account the staining patterns, we will next quantify the counts and density of different tumor-resident myeloid subsets and measure the spatial distance between each subset of tumor-resident myeloid cells to the neoplastic Reed-Sternberg cells. Correlation study will also be performed to determine if significant correlations exist between MDSCs and TAMs and how these immunosuppressive myeloid cells are related to the Regulatory T cells (CD3+CD4+FOXP3+) in HL samples. In addition to HL samples, the same 13-plexed panel will be utilized to characterize the myeloid cell population from AML patients. TAMs and MDSCs are emerging as potential biomarkers for diagnosis and prognosis of cancer as well as therapeutic targets. The comprehensive myeloid cells phenotyping offered by MultiOmyx 13-plexed panel has the potential to monitor the changes of immunosuppressive myeloid cells in response to immune modulating drugs such as MDSC-targeting drugs (e.g. PDE-5 inhibitors, COX-2 inhibitors), TAM-targeting agents (e.g. anti-CSF1R) and combined therapy in treatment of lymphoma and leukemia. Disclosures No relevant conflicts of interest to declare.

scholarly journals Immune Regulation by Dendritic Cell Extracellular Vesicles in Cancer Immunotherapy and Vaccines

Cancers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3558
Author(s):  
Irene Fernández-Delgado ◽  
Diego Calzada-Fraile ◽  
Francisco Sánchez-Madrid
Keyword(s):  
Extracellular Vesicles ◽  
Cancer Vaccines ◽  
Suppressor Cells ◽  
Cancer Therapeutics ◽  
Myeloid Cell ◽  
Tumor Rejection ◽  
Myeloid Derived Suppressor Cells ◽  
Histocompatibility Complex ◽  
Peptide Complexes ◽  
Unique Composition

Extracellular vesicles (EVs) play a crucial role in intercellular communication as vehicles for the transport of membrane and cytosolic proteins, lipids, and nucleic acids including different RNAs. Dendritic cells (DCs)-derived EVs (DEVs), albeit variably, express major histocompatibility complex (MHC)-peptide complexes and co-stimulatory molecules on their surface that enable the interaction with other immune cells such as CD8+ T cells, and other ligands that stimulate natural killer (NK) cells, thereby instructing tumor rejection, and counteracting immune-suppressive tumor microenvironment. Malignant cells oppose this effect by secreting EVs bearing a variety of molecules that block DCs function. For instance, tumor-derived EVs (TDEVs) can impair myeloid cell differentiation resulting in myeloid-derived suppressor cells (MDSCs) generation. Hence, the unique composition of EVs makes them suitable candidates for the development of new cancer treatment approaches including prophylactic vaccine targeting oncogenic pathogens, cancer vaccines, and cancer immunotherapeutics. We offer a perspective from both cell sides, DCs, and tumor cells, on how EVs regulate the antitumor immune response, and how this translates into promising therapeutic options by reviewing the latest advancement in DEV-based cancer therapeutics.

scholarly journals Myeloid Cells in the Tumor Microenvironment: Modulation of Tumor Angiogenesis and Tumor Inflammation

2010 ◽  
Vol 2010 ◽  
pp. 1-10 ◽  
Author(s):  
Michael C. Schmid ◽  
Judith A. Varner
Keyword(s):  
Tumor Microenvironment ◽  
Tumor Angiogenesis ◽  
Malignant Tumors ◽  
Critical Role ◽  
Myeloid Cells ◽  
Suppressor Cells ◽  
Myeloid Cell ◽  
Promote Tumor Growth ◽  
Bone Marrow Derived Cells

Myeloid cells are a heterogeneous population of bone marrow-derived cells that play a critical role during growth and metastasis of malignant tumors. Tumors exhibit significant myeloid cell infiltrates, which are actively recruited to the tumor microenvironment. Myeloid cells promote tumor growth by stimulating tumor angiogenesis, suppressing tumor immunity, and promoting metastasis to distinct sites. In this review, we discuss the role of myeloid cells in promoting tumor angiogenesis. Furthermore, we describe a subset of myeloid cells with immunosuppressive activity (known as myeloid-derived suppressor cells). Finally, we will comment on the mechanisms regulating myeloid cell recruitment to the tumor microenvironment and on the potential of myeloid cells as new targets for cancer therapy.

scholarly journals Immune Suppression by Myeloid Cells in HIV Infection: New Targets for Immunotherapy

2014 ◽  
Vol 8 (1) ◽  
pp. 66-78 ◽  
Author(s):  
Vikram Mehraj ◽  
Mohammad-Ali Jenabian ◽  
Kishanda Vyboh ◽  
Jean-Pierre Routy
Keyword(s):  
T Cell ◽  
Hiv Infection ◽  
Cell Function ◽  
Myeloid Cells ◽  
Suppressor Cells ◽  
Myeloid Cell ◽  
Immune Dysfunction ◽  
Hiv Pathogenesis ◽  
Host Restriction

Over thirty years of extensive research has not yet solved the complexity of HIV pathogenesis leading to a continued need for a successful cure. Recent immunotherapy-based approaches are aimed at controlling the infection by reverting immune dysfunction. Comparatively less appreciated than the role of T cells in the context of HIV infection, the myeloid cells including macrophages monocytes, dendritic cells (DCs) and neutrophils contribute significantly to immune dysfunction. Host restriction factors are cellular proteins expressed in these cells which are circumvented by HIV. Guided by the recent literature, the role of myeloid cells in HIV infection will be discussed highlighting potential targets for immunotherapy. HIV infection, which is mainly characterized by CD4 T cell dysfunction, also manifests in a vicious cycle of events comprising of inflammation and immune activation. Targeting the interaction of programmed death-1 (PD-1), an important regulator of T cell function; with PD-L1 expressed mainly on myeloid cells could bring promising results. Macrophage functional polarization from pro-inflammatory M1 to anti-inflammatory M2 and vice versa has significant implications in viral pathogenesis. Neutrophils, recently discovered low density granular cells, myeloid derived suppressor cells (MDSCs) and yolk sac macrophages provide new avenues of research on HIV pathogenesis and persistence. Recent evidence has also shown significant implications of neutrophil extracellular traps (NETs), antimicrobial peptides and opsonizing antibodies. Further studies aimed to understand and modify myeloid cell restriction mechanisms have the potential to contribute in the future development of more effective anti-HIV interventions that may pave the way to viral eradication.

scholarly journals Mechanisms and Functional Significance of Human Tumor-infiltrating Myeloid Cells

2019 ◽  
Vol 4 (2) ◽  
pp. 41-49
Author(s):  
Amin Ramezani ◽  
Fatemeh Sadat Toghraie
Keyword(s):  
Stromal Cells ◽  
Cancer Biology ◽  
Critical Role ◽  
Myeloid Cells ◽  
Human Tumor ◽  
Suppressor Cells ◽  
Myeloid Cell ◽  
Myeloid Derived Suppressor Cells ◽  
Patient Prognosis ◽  
Tumor Associated Neutrophils

Myeloid cells as the major components of tumor-infiltrating leukocytes play critical roles in anti-tumor immunity. However, emerging evidences have revealed that soluble factors produced by tumor/stromal cells skew myeloid cells toward a tumor-promoting phenotype. Tumor-infiltrating myeloid cells (TIMs) including tumor-associated macrophages (TAMs), tumor-associated neutrophils (TANs), myeloid-derived suppressor cells (MDSCs), and tumor-associated dendritic cells (TADCs) are considered as the key mediators of tumor microenvironment (TME). TIMs have been shown to play important roles in various aspects of cancer biology and their presence is often linked to altered patient prognosis and survival. Regarding their critical role in TME, TIMs have been proposed as relevant targets of therapeutic strategies aimed at expanding immunostimulatory myeloid cell populations and depleting or modulating immunosuppressive ones. In this review, we briefly describe TIMs subsets and discuss the mechanisms by which TIMs induce immunosuppression, angiogenesis, and metastasis.

Acute Myeloid Leukemia Cells Export c-Myc in Extracellular Vesicles Driving a Proliferation of Immune-Suppressive Myeloid-Derived Suppressor Cells

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 703-703
Author(s):  
Athalia Rachel Pyzer ◽  
Dina Stroopinsky ◽  
Hasan Rajabi ◽  
Abigail J. Washington ◽  
Leandra Cole ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Extracellular Vesicles ◽  
Research Funding ◽  
Healthy Donor ◽  
Myeloid Cells ◽  
Suppressor Cells ◽  
Negative Regulator ◽  
Myeloid Derived Suppressor Cells ◽  
Antigen Presenting ◽  
Donor Pbmcs

Abstract Myeloid-derived suppressor cells (MDSCs) play a critical role in promoting immune tolerance and disease growth. We have previously shown that MDSCs are expanded in patients with AML and can be induced from healthy donor PBMCs by co-culture with leukemic cells; a mechanism dependent on expression of the MUC1-C oncoprotein. We sought to elucidate the precise mechanism by which MUC1-C signaling mediates the expansion of this immune suppressive population of immature myeloid cells. We have previously demonstrated that AML cells release membrane bound extracellular vesicles, which traffic to co-cultured cells. We hypothesized that AML EVs may mediate the expansion of MDSCs. MOLM-14 and THP-1 AML EVs were isolated using the ExoQuick precipitation technique, and analyzed by flow cytometry, and compared to size standardized beads, demonstrating particles between 200-300nM in diameter. Furthermoreisolated AML EVs were visualised using Transmission Electron Microscopy demonstrating multiple rounded structures measuring 100-200nM in diameter and bound by darkly staining membrane. Subsequently, healthy donor PBMCs were cultured for three days with GFP tagged AML EVs and then quantified for CD33+/HLADR-/CD11b+ MDSCs and HLADR+/CD11c+ antigen presenting myeloid cells by flow cytometry. In the PBMCs co-cultured with EVs, the proportion of MDSCs increased 8-fold, whilst the proportion of HLADR+/CD11c+ antigen presenting myeloid cells decreased by 10 fold (n=3, p<0.05). We subsequently investigated how MUC1-C signaling, necessary for the expansion of MDSCs, might alter AML extracellular vesicles composition. We evaluated AML EVs for the presence of the pro-proliferative oncoprotein c-Myc by immune-blotting, demonstrating that AML cells secrete EVs containing c-Myc, which is abrogated by downregulation of MUC1-C. Furthermore, EVs containing MUC1 and c-myc led to an up-regulation of the c-Myc downstream targets cyclin D2 and cyclin E1 in co-cultured MDSCs, indicating that c-Myc containing EVs may drive MDSC proliferation. Critically, EVs from MUC1-C silenced AML cells failed to elicit this increase in c-Myc and cyclin D2 and E1 expression in EV exposed MDSCs. Interestingly, exposure of MDSCs to AML EVs lead to an increased expression of PD-L1, which was abrogated in EVs from MUC1-C silenced AML cells. We then sought to determine how MUC1 signaling promotes c-Myc signaling in AML. MUC1-C silencing did not alter c-Myc mRNA levels suggesting a post-transcriptional level of regulation. Micro RNAs are small non-encoding RNA molecules involved in post-translational regulation of gene expression. MiR34a, a known p53 inhibitor, has been implicated in regulating the expansion of MDSCs and it is known that tumor cells suppress MiR34a expression as part of their self-protective armoury. Furthermore, MiR34a is a predicted negative regulator of c-Myc, due to a complementary sequence for MiR34a in the c-Myc promoter region. Using qPCR, we have demonstrated that MUC1-C silencing results in increased expression of MiRNA34a. Furthermore, over-expression of MiR34a in AML cells led to a dramatic down-regulation of c-Myc protein expression, and conversely silencing of MiR34a led to a significant upregulation of c-Myc expression, confirming that MiR34a regulates c-Myc expression in AML. To confirm MiR34a as a critical negative regulator of MDSC expansion, MiR34a altered cells were interrogated for their ability to elicit an expansion of MDSCs in co-cultured PBMCs. Overexpression of MiR34a in AML cells partially abrogated their ability to induce MDSCs from co-cultured donor PBMCs. In concert, silencing of MiR34a in MUC1-C silenced AML cells, recapitulated their ability to induce MDSCs in this model. Taken together, this study illustrates a novel role of the MUC1-C and c-Myc oncoproteins in driving MDSC proliferation and MDSC PD-L1 expression. We have demonstrated that AML EVs alter the tumor microenvironment away from antigen presentation capable myeloid cells and towards immature immune suppressive MDSCs. Disclosures Arnason: Gilead: Consultancy. Küfe:Genus Oncology: Equity Ownership. Rosenblatt:Astex: Research Funding; BMS: Research Funding; DCPrime: Research Funding. Avigan:Astex: Research Funding; DCPrime: Research Funding.

The Myeloid Cell Compartment—Cell by Cell

2019 ◽  
Vol 37 (1) ◽  
pp. 269-293 ◽  
Author(s):  
Kevin Bassler ◽  
Jonas Schulte-Schrepping ◽  
Stefanie Warnat-Herresthal ◽  
Anna C. Aschenbrenner ◽  
Joachim L. Schultze
Keyword(s):  
Single Cell ◽  
Developmental Trajectories ◽  
Myeloid Cells ◽  
Cell Subset ◽  
Myeloid Cell ◽  
Cell Compartment ◽  
Protein Marker ◽  
Tissue Macrophage ◽  
Inflammatory Conditions ◽  
Compartment Cell

Myeloid cells are a major cellular compartment of the immune system comprising monocytes, dendritic cells, tissue macrophages, and granulocytes. Models of cellular ontogeny, activation, differentiation, and tissue-specific functions of myeloid cells have been revisited during the last years with surprising results; for example, most tissue macrophages are yolk sac derived, monocytes and macrophages follow a multidimensional model of activation, and tissue signals have a significant impact on the functionality of all these cells. While these exciting results have brought these cells back to center stage, their enormous plasticity and heterogeneity, during both homeostasis and disease, are far from understood. At the same time, the ongoing revolution in single-cell genomics, with single-cell RNA sequencing (scRNA-seq) leading the way, promises to change this. Prevailing models of hematopoiesis with distinct intermediates are challenged by scRNA-seq data suggesting more continuous developmental trajectories in the myeloid cell compartment. Cell subset structures previously defined by protein marker expression need to be revised based on unbiased analyses of scRNA-seq data. Particularly in inflammatory conditions, myeloid cells exhibit substantially vaster heterogeneity than previously anticipated, and work performed within large international projects, such as the Human Cell Atlas, has already revealed novel tissue macrophage subsets. Based on these exciting developments, we propose the next steps to a full understanding of the myeloid cell compartment in health and diseases.

scholarly journals Proteomic Analysis of Anaplasma phagocytophilum during Infection of Human Myeloid Cells Identifies a Protein That Is Pronouncedly Upregulated on the Infectious Dense-Cored Cell

2011 ◽  
Vol 79 (11) ◽  
pp. 4696-4707 ◽  
Author(s):  
Matthew J. Troese ◽  
Amandeep Kahlon ◽  
Stephanie A. Ragland ◽  
Andrew K. Ottens ◽  
Nore Ojogun ◽  
...  
Keyword(s):  
Anaplasma Phagocytophilum ◽  
Myeloid Cells ◽  
Surface Protein ◽  
Myeloid Cell ◽  
Hypothetical Protein ◽  
Extensive Study ◽  
Host Cells ◽  
Developmental Cycle ◽  
Cell Infection ◽  
Content Type

ABSTRACTAnaplasma phagocytophilumis an obligate intracellular bacterium that invades neutrophils to cause the emerging infectious disease human granulocytic anaplasmosis.A. phagocytophilumundergoes a biphasic developmental cycle, transitioning between an infectious dense-cored cell (DC) and a noninfectious reticulate cell (RC). To gain insights into the organism's biology and pathogenesis during human myeloid cell infection, we conducted proteomic analyses onA. phagocytophilumorganisms purified from HL-60 cells. A total of 324 proteins were unambiguously identified, thereby verifying 23.7% of the predictedA. phagocytophilumproteome. Fifty-three identified proteins had been previously annotated as hypothetical or conserved hypothetical. The second most abundant gene product, after the well-studied major surface protein 2 (P44), was the hitherto hypothetical protein APH_1235. APH_1235 homologs are found in otherAnaplasmaandEhrlichiaspecies but not in other bacteria. Theaph_1235RNA level is increased 70-fold in the DC form relative to that in the RC form. Transcriptional upregulation of and our ability to detect APH_1235 correlate with RC to DC transition, DC exit from host cells, and subsequent DC binding and entry during the next round of infection. Immunoelectron microscopy pronouncedly detects APH_1235 on DC organisms, while detection on RC bacteria minimally, at best, exceeds background. This work represents an extensive study of theA. phagocytophilumproteome, discerns the complement of proteins that is generated during survival within human myeloid cells, and identifies APH_1235 as the first known protein that is pronouncedly upregulated on the infectious DC form.

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