Regulation of Peripheral Inflammation by a Non-Viable, Non-Colonizing Strain of Commensal Bacteria

The gastrointestinal tract represents one of the largest body surfaces that is exposed to the outside world. It is the only mucosal surface that is required to simultaneously recognize and defend against pathogens, while allowing nutrients containing foreign antigens to be tolerated and absorbed. It differentiates between these foreign substances through a complex system of pattern recognition receptors expressed on the surface of the intestinal epithelial cells as well as the underlying immune cells. These immune cells actively sample and evaluate microbes and other particles that pass through the lumen of the gut. This local sensing system is part of a broader distributed signaling system that is connected to the rest of the body through the enteric nervous system, the immune system, and the metabolic system. While local tissue homeostasis is maintained by commensal bacteria that colonize the gut, colonization itself may not be required for the activation of distributed signaling networks that can result in modulation of peripheral inflammation. Herein, we describe the ability of a gut-restricted strain of commensal bacteria to drive systemic anti-inflammatory effects in a manner that does not rely upon its ability to colonize the gastrointestinal tract or alter the mucosal microbiome. Orally administered EDP1867, a gamma-irradiated strain of Veillonella parvula, rapidly transits through the murine gut without colonization or alteration of the background microbiome flora. In murine models of inflammatory disease including delayed-type hypersensitivity (DTH), atopic dermatitis, psoriasis, and experimental autoimmune encephalomyelitis (EAE), treatment with EDP1867 resulted in significant reduction in inflammation and immunopathology. Ex vivo cytokine analyses revealed that EDP1867 treatment diminished production of pro-inflammatory cytokines involved in inflammatory cascades. Furthermore, blockade of lymphocyte migration to the gut-associated lymphoid tissues impaired the ability of EDP1867 to resolve peripheral inflammation, supporting the hypothesis that circulating immune cells are responsible for promulgating the signals from the gut to peripheral tissues. Finally, we show that adoptively transferred T cells from EDP1867-treated mice inhibit inflammation induced in recipient mice. These results demonstrate that an orally-delivered, non-viable strain of commensal bacteria can mediate potent anti-inflammatory effects in peripheral tissues through transient occupancy of the gastrointestinal tract, and support the development of non-living bacterial strains for therapeutic applications.

CD209a Synergizes with Dectin-2 and Mincle to Drive Severe Th17 Cell-Mediated Schistosome Egg-Induced Immunopathology

The immunopathology caused by schistosome helminths varies greatly in humans and among mouse strains. A severe form of parasite egg-induced hepatic granulomatous inflammation, seen in CBA mice, is driven by Th17 cells stimulated by IL-1β and IL-23 produced by dendritic cells that express CD209a (SIGNR5), a C-type lectin receptor (CLR) related to human DC-SIGN. Here, we show that CD209a-deficient CBA mice display decreased Th17 responses and are protected from severe immunopathology. In vitro, CD209a augments the egg-induced IL-1β and IL-23 production initiated by the related CLRs Dectin-2 and Mincle. While Dectin-2 and Mincle trigger an FcRγ-dependent signaling cascade that involves the tyrosine kinase Syk and the trimolecular Card9-Bcl10-Malt1 complex, CD209a promotes the sustained activation of Raf-1. Our findings demonstrate that CD209a drives severe Th17 cell-mediated immunopathology in a helminthic disease based on synergy between DC-SIGN- and Dectin-2-related CLRs.

Abstract B35: Class IIa HDAC inhibition promotes an antitumor macrophage phenotype that induces breast tumor regression and inhibits metastasis

Tumor macrophages generally promote tumorigenesis and are associated with increased vascular density, resistance to chemotherapy and a worse clinical outcome in the majority of human tumors. Therefore, significant pharmaceutical effort has focused on inhibiting the immunosuppressive effects of tumor macrophages by depleting or inhibiting them. However, macrophage types also exist that can promote tumor clearance. Shifting tumor macrophages to an anti-tumor phenotype offers great hope given their plasticity and high numbers in a variety of solid tumors. We recently reported that a novel, first in class, specific class IIa HDAC inhibitor, TMP195, significantly alters the gene expression signature of human monocytes and promotes their polarization to an anti-tumor phenotype in vitro. Here, we demonstrate that a first in class, class IIa histone deacetylase (HDAC) inhibitor, TMP195, can activate tumor macrophages in vivo to induce tumor regression and inhibit pulmonary metastases in a mouse model of breast cancer. We find that TMP195 induces macrophage recruitment and differentiation of highly phagocytic cells within the tumor, which increases tumor cell death while decreasing angiogenesis. Strikingly, we find that TMP195 enhances chemotherapy and immunotherapy to induce durable tumor reduction. These data reveal a novel role for harnessing the anti-tumor potential of macrophages to enhance cancer therapy.

Citation Format: Jennifer L. Guerriero, Alaba Sotayo, Holly E. Ponichtera, Jessica A. Castrillon, Alexandra L. Pourzia, Sara Schad, Shawn F. Johnson, Ruben D. Carrasco, Susan B. Lazo, Roderick T. Bronson, Scott P. Davis, Mercedes X. Lobera, Michael A. Nolan, Anthony Letai. Class IIa HDAC inhibition promotes an antitumor macrophage phenotype that induces breast tumor regression and inhibits metastasis [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr B35.

Abstract P3-05-05: Class IIa HDAC inhibition promotes an anti-tumor macrophage phenotype that induces breast tumor regression and inhibits metastasis

While tumor-associated macrophages (TAMs) often have net pro-tumor effects, their embedded location and their untapped potential provide impetus to the discovery of strategies to turn them against tumors. We recently reported that a first in class selective class IIa HDAC inhibitor (TMP195) influenced human monocyte responses to colony stimulating factors CSF-1 and CSF-2 in vitro. Here, we utilize a macrophage-dependent autochthonous mouse model of breast cancer to demonstrate that in vivo TMP195 treatment alters the tumor microenvironment and reduces tumor burden and pulmonary metastases through macrophage modulation. TMP195 induces recruitment and differentiation of highly phagocytic and stimulatory macrophages within tumors. Furthermore, combining TMP195 with chemotherapy regimens or T-cell checkpoint blockade in this model significantly enhances the durability of tumor reduction. These data introduce class IIa HDAC inhibition as a novel means to harness the anti-tumor potential of macrophages to enhance cancer therapy.

Citation Format: Guerriero JL, Sotayo A, Ponichtera HE, Castrillon JA, Pourzia AL, Schad S, Johnson SF, Carrasco RD, Lazo S, Bronson RT, Davis SP, Lobera M, Nolan MA, Letai A. Class IIa HDAC inhibition promotes an anti-tumor macrophage phenotype that induces breast tumor regression and inhibits metastasis [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-05-05.

Abstract 5030: Polarizing tumor associated macrophages (TAMs) towards an anti-tumor phenotype with a novel compound reveals a new subset of TAMs within breast tumors which facilitate tumor regression

Manipulation of the innate immune system is a relatively understudied strategy for anti-cancer immunotherapy. The current focus on immunotherapy is centered on the adaptive immune system. However, there is growing evidence that manipulation of the innate immune system, including macrophages, is also a promising method to combat cancer.

Tumor associated macrophages (TAMs) are one of the major infiltrating leukocyte populations associated with solid tumors. There are two major types of macrophages: classically activated macrophages, which can kill bacteria, pathogens, and similarly tumor cells; and alternatively activated macrophages which facilitate wound repair and are generally found in the tumor microenvironment. TAMs are generally alternatively activated cells with immunosuppressive properties that have been shown to enhance tumorogenesis by facilitating metastasis, angiogenesis, and inhibiting a protecting adaptive immune response. The presence of macrophages in the tumor microenvironment correlates with poor prognosis. Here we describe a novel, first in class compound that activates macrophages to an anti-tumor phenotype. While this compound has no direct cytotoxic activity, we show in the PyMT mouse model of breast cancer that breast tumors regress in response to therapy in a manner dependent on myeloid cells. Through the use of flow cytometry, we have been able to identify different subpopulations of TAMs using the markers CD45, MHCII, and CD11b. Correlating with tumor regression, we see an increase in PARP and cleaved caspase 3, indicating apoptotic cell death. Here we show that a novel compound effectively polarize macrophages to an anti-tumor phenotype to induce tumor regression. This strategy may have great therapeutic promise.

Citation Format: Alaba O. Sotayo, Jennnifer L. Guerriero, Holly E. Ponichtera, Anthony G. Letai. Polarizing tumor associated macrophages (TAMs) towards an anti-tumor phenotype with a novel compound reveals a new subset of TAMs within breast tumors which facilitate tumor regression. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5030. doi:10.1158/1538-7445.AM2015-5030

Abstract 460: Novel compound elicits anti-tumor macrophages associated with tumor regression in breast cancer

Cancer immuno-therapies targeting components of the immune system have shown great promise for the treatment of various forms of cancer. Most of the immuno-therapies currently under trial intervene in adaptive immune cell pathways; however, the innate immune system has also recently been shown to play a potent immunomodulatory role in the tumor microenvironment. Tumor associated macrophages (TAMs) compose up to 50% of tumor volume. Presently, we demonstrate that administration of a novel compound stimulates rapid tumor regression that is associated with the infiltration of F4/80+ macrophages into tumors in the MMTV-PyMT murine model of breast cancer. A significant increase in tumor-infiltrating macrophages was visible by immunohistochemistry after five days of treatment and macrophages were necessary for tumor regression as demonstrated by cell depletion assays in vivo. Of note, macrophage infiltration correlated with an increase in tumor cell death as shown by elevated expression of the apoptotic protein cleaved-caspase-3 (CC3); conversely, cell proliferation factor Ki67 was decreased. Additionally, compound-treated animals exhibited striking changes in tumor vascularization, with a marked decrease in overall endothelial cell marker expression as displayed by immunohistochemistry. Taken together, these findings reveal a novel role for macrophages in breast tumor regression during treatment with a novel compound that alters the tumor microenvironment.

Citation Format: Holly E. Ponichtera, Jennifer L. Guerriero, Alaba O. Sotayo, Anthony Letai. Novel compound elicits anti-tumor macrophages associated with tumor regression in breast cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 460. doi:10.1158/1538-7445.AM2015-460

Dendritic cell expression of the C-type lectin receptor CD209a: A novel innate parasite-sensing mechanism inducing Th17 cells that drive severe immunopathology in murine schistosome infection

Following infection with the trematode helminth Schistosoma mansoni, CBA mice develop severe parasite egg-induced hepatic granulomatous inflammation as well as prominent CD4(+) T helper 17 (Th17) cell responses driven by dendritic cell (DC)-derived IL-1β and IL-23. By comparison, C57BL/6 mice develop mild hepatic immunopathology, egg stimulation of DCs does not result in IL-1β and IL-23 production, and Th17 cells fail to develop. To investigate the reasons for strain-specific differences in antigen presenting cell (APC) reactivity to eggs, we performed a comparative gene profiling analysis of normal bone marrow-derived DCs (BMDCs) and found that CBA DCs display markedly elevated expression of C-type lectin receptors (CLRs). In particular, expression of CD209a, a murine homologue of human DC-specific ICAM-3-grabbing non-integrin (DC-SIGN, CD209), was strikingly higher in CBA than BL/6 DCs. High CD209a surface expression was observed in various CBA splenic and granuloma APC subpopulations; however, only DCs, and not macrophages, B cells or neutrophils, were able to induce Th17 cell differentiation in response to schistosome eggs. Lentiviral gene silencing in CBA DCs, and over-expression in BL/6 DCs, demonstrated CD209a to be critical for egg-induced DC IL-1β and IL-23 production necessary for Th17 cell differentiation and expansion. These findings reveal a novel innate parasite-sensing mechanism promoting CD4(+) Th17 cells that mediate severe immunopathology in schistosomiasis.

CD209a expression on dendritic cells is critical for the development of pathogenic Th17 cell responses in murine schistosomiasis

In murine schistosomiasis, immunopathology and cytokine production in response to parasite eggs are uneven and strain dependent. CBA/J (CBA) mice develop severe hepatic granulomatous inflammation associated with prominent Th17 cell responses driven by dendritic cell (DC)-derived IL-1β and IL-23. Such Th17 cells fail to develop in low-pathology C57BL/6 (BL/6) mice, and the reasons for these strain-specific differences in APC reactivity to eggs remain unclear. We show by gene profiling that CBA DCs display an 18-fold higher expression of the C-type lectin receptor CD209a, a murine homolog of human DC-specific ICAM-3-grabbing nonintegrin, compared with BL/6 DCs. Higher CD209a expression was observed in CBA splenic and granuloma APC subpopulations, but only DCs induced Th17 cell differentiation in response to schistosome eggs. Gene silencing in CBA DCs and overexpression in BL/6 DCs demonstrated that CD209a is essential for egg-elicited IL-1β and IL-23 production and subsequent Th17 cell development, which is associated with SRC, RAF-1, and ERK1/2 activation. These findings reveal a novel mechanism controlling the development of Th17 cell-mediated severe immunopathology in helminthic disease.

Induction and regulation of pathogenic Th17 cell responses in schistosomiasis

Schistosomiasis is a major tropical disease caused by trematode helminths in which the host mounts a pathogenic immune response against tissue-trapped parasite eggs. The immunopathology consists of egg antigen-specific CD4 T cell-mediated granulomatous inflammation that varies greatly in magnitude in humans and among mouse strains in an experimental model. New evidence, covered in this review, intimately ties the development of severe pathology to IL-17-producing CD4 T helper (Th17) cells, a finding that adds a new dimension to the traditional CD4 Th1 vs. Th2 cell paradigm. Most examined mouse strains, in fact, develop severe immunopathology with substantial Th17 as well as Th1 and Th2 cell responses; a solely Th2-polarized response is an exception that is only observed in low-pathology strains such as the C57BL/6. The ability to mount pathogenic Th17 cell responses is genetically determined and depends on the production of IL-23 and IL-1β by antigen presenting cells following recognition of egg antigens; analyses of several F2 progenies of (high × low)-pathology strain crosses demonstrated that quantitative trait loci governing IL-17 levels and disease severity vary substantially from cross to cross. Low pathology is dominant, which may explain the low incidence of severe disease in humans; however, coinfection with intestinal nematodes can also dampen pathogenic Th17 cell responses by promoting regulatory mechanisms such as those afforded by alternatively activated macrophages and T regulatory cells. A better understanding of the pathways conducive to severe forms of schistosomiasis and their regulation should lead to interventions similar to those presently used to manage other immune-mediated diseases.