Lee, James J.

Blood coagulation is essential for physiological hemostasis but simultaneously contributes to thrombotic disease. However, molecular and cellular events controlling initiation and propagation of coagulation are still incompletely understood. In this study, we demonstrate an unexpected role of eosinophils during plasmatic coagulation, hemostasis, and thrombosis. Using a large-scale epidemiological approach, we identified eosinophil cationic protein as an independent and predictive risk factor for thrombotic events in humans. Concurrent experiments showed that eosinophils contributed to intravascular thrombosis by exhibiting a strong endogenous thrombin-generation capacity that relied on the enzymatic generation and active provision of a procoagulant phospholipid surface enriched in 12/15-lipoxygenase–derived hydroxyeicosatetraenoic acid–phosphatidylethanolamines. Our findings reveal a previously unrecognized role of eosinophils and enzymatic lipid oxidation as regulatory elements that facilitate both hemostasis and thrombosis in response to vascular injury, thus identifying promising new targets for the treatment of thrombotic disease.

Abstract Eosinophils and the release of cationic granule proteins have long been implicated in the development of the type 2–induced pathologies linked with respiratory inflammation. Paradoxically, the ablation of the two genes encoding the most abundant of these granule proteins, major basic protein-1 (MBP-1) and eosinophil peroxidase (EPX), results in a near collapse of eosinophilopoiesis. The specificity of this lineage ablation and the magnitude of the induced eosinopenia provide a unique opportunity to clarify the importance of eosinophils in acute and chronic inflammatory settings, as well as to identify potential mechanism(s) of action linked with pulmonary eosinophils in those settings. Specifically, we examined these issues by assessing the induced immune responses and pathologies occurring in MBP-1−/−/EPX−/− mice after 1) ovalbumin sensitization/provocation in an acute allergen-challenge protocol, and 2) crossing MBP-1−/−/EPX−/− mice with a double-transgenic model of chronic type 2 inflammation (i.e., I5/hE2). Acute allergen challenge and constitutive cytokine/chemokine expression each induced the accumulation of pulmonary eosinophils in wild-type controls that was abolished in the absence of MBP-1 and EPX (i.e., MBP-1−/−/EPX−/− mice). The expression of MBP-1 and EPX was also required for induced lung expression of IL-4/IL-13 in each setting and, in turn, the induced pulmonary remodeling events and lung dysfunction. In summary, MBP-1−/−/EPX−/− mice provide yet another definitive example of the immunoregulatory role of pulmonary eosinophils. These results highlight the utility of this unique strain of eosinophil-deficient mice as part of in vivo model studies investigating the roles of eosinophils in health and disease settings.

609 Background: Targeting MEK is of interest in the development of novel agents for treatment of many malignancies. However, better strategies are needed to overcome acquired resistance to MEK inhibitors. Preclinical studies have shown Wnt pathway overexpression in KRAS mutant cell lines resistant to the MEK inhibitor, Selumetinib. The combination of selumetinib and cyclosporin A (CsA), a non-canonical WnT pathway modulator, demonstrated antitumor activity in patient-derived xenograft (PDX) models. We are conducting an NCI CTEP-approved Phase I/IB trial (NCI # 9571/COMIRB # 13-2628) of selumetinib and CsA combination. Biomarkers of response to therapy are being co-developed. We hypothesize that this combination will be safe and potentially effective in patients with mCRC and that upregulation of FZD2 may predict for sensitivity. Methods: Phase I trial with initial dose escalation investigating the combination of selumetinib and CsA in patients with advanced solid tumors (n = 18) followed by an expansion cohort in patients with irinotecan and oxaliplatin-refractory mCRC (n = 20). The expansion cohort utilizes a selumetinib “run-in” to evaluate efficacy in RAS-WT and RAS-MT mCRC to identify those patients most likely to respond to the combination. Results: 18 patients were enrolled in the dose escalation phase and 10 patients have been enrolled in the dose expansion phase as of September 2016. Grade 1 or 2 nausea and rash were reported as the most common AEs. Most commonly reported Grade 3 or 4 toxicities were hypertension, elevated liver enzymes and rash. Three DLTs were reported with Grade 3 hypertension noted at dose level 1 and 2 and grade 3 rash reported at dose level 2. The maximum tolerated dose was defined as Selumetinib 75 mg BID and CsA 2 mg/kg BID on a 28-day cycle. Two partial responses and sixteen stable disease responses have been observed. Six patients have exhibited progressive disease. Conclusions: Selumetinib in combination with cyclosporin A appears to be well-tolerated with evidence of activity in solid tumors. Expansion cohort will complete enrollment this month. Clinical trial information: NCT02188264.

Abstract Eosinophils are multifunctional cells of the innate immune system linked to allergic inflammation. Asthmatics were more likely to be hospitalized but less likely to suffer severe morbidity and mortality during the 2009 influenza pandemic. These epidemiologic findings were recapitulated in a mouse model of fungal asthma wherein infection during heightened allergic inflammation was protective against influenza A virus (IAV) infection and disease. Our goal was to delineate a mechanism(s) by which allergic asthma may alleviate influenza disease outcome, focused on the hypothesis that pulmonary eosinophilia linked with allergic respiratory disease is able to promote antiviral host defenses against the influenza virus. The transfer of eosinophils from the lungs of allergen-sensitized and challenged mice into influenza virus–infected mice resulted in reduced morbidity and viral burden, improved lung compliance, and increased CD8+ T cell numbers in the airways. In vitro assays with primary or bone marrow–derived eosinophils were used to determine eosinophil responses to the virus using the laboratory strain (A/PR/08/1934) or the pandemic strain (A/CA/04/2009) of IAV. Eosinophils were susceptible to IAV infection and responded by activation, piecemeal degranulation, and upregulation of Ag presentation markers. Virus- or viral peptide–exposed eosinophils induced CD8+ T cell proliferation, activation, and effector functions. Our data suggest that eosinophils promote host cellular immunity to reduce influenza virus replication in lungs, thereby providing a novel mechanism by which hosts with allergic asthma may be protected from influenza morbidity.

Abstract Rationale The release of eosinophil granule proteins in the lungs of patients with asthma has been dogmatically linked with lung remodeling and airway hyperresponsiveness. However, the demonstrated inability of established mouse models to display the eosinophil degranulation occurring in human subjects has prevented a definitive in vivo test of this hypothesis. Objectives To demonstrate in vivo causative links between induced pulmonary histopathologies/lung dysfunction and eosinophil degranulation. Methods A transgenic mouse model of chronic T-helper cell type 2–driven inflammation overexpressing IL-5 from T cells and human eotaxin 2 in the lung (I5/hE2) was used to test the hypothesis that chronic histopathologies and the development of airway hyperresponsiveness occur as a consequence of extensive eosinophil degranulation in the lung parenchyma. Measurement and Main Results Studies targeting specific inflammatory pathways in I5/hE2 mice surprisingly showed that eosinophil-dependent immunoregulative events and not the release of individual secondary granule proteins are the central contributors to T-helper cell type 2–induced pulmonary remodeling and lung dysfunction. Specifically, our studies highlighted a significant role for eosinophil-dependent IL-13 expression. In contrast, extensive degranulation leading to the release of major basic protein-1 or eosinophil peroxidase was not causatively linked to many of the induced pulmonary histopathologies. However, these studies did define a previously unappreciated link between the release of eosinophil peroxidase (but not major basic protein-1) and observed levels of induced airway mucin. Conclusions These data suggest that improvements observed in patients with asthma responding to therapeutic strategies ablating eosinophils may occur as a consequence of targeting immunoregulatory mechanisms and not by simply eliminating the destructive activities of these purportedly end-stage effector cells.

287 Background: Our preliminary immunohistochemical studies of bladder cancer patients have shown that the inflammatory/immune responses associated with bladder cancer appear to be Th2-polarized as judged by the preponderance of tumor infiltrating GATA-3+ (Th2) vs. T-bet+ (Th1) T cells, as well as by evidence of tumor-associated eosinophil infiltration and activation. The standard-of-care treatment for Tis bladder cancer is intravesical administration of BCG, a Th1-polarizing immunomodulator. The aim of the present study was to assess the Th2/Th1 ratio correlation with response to BCG therapy in patients with Tis bladder cancer. Methods: Two groups of patients were studied. Group A included 20 patients that responded to BCG, and Group B included 20 patients that did not respond to therapy. Response to BCG was determined as presence/absence of disease at 6 months post-BCG therapy. The initial diagnostic biopsies of these patients were subjected to immunohistochemical analysis using commercially available antibodies specific for Th2 (GATA-3+) and Th1 (T-bet+) lymphocytes, and our unique monoclonal antibody specific for eosinophil peroxidase (EPX-mAb). Ten random high powered (400X) fields at the maximum focus of mononuclear infiltration were examined and the number of GATA 3+ and T-bet+ tumor infiltrating T cells were counted to define the G/T ratio for each patient sample. Eosinophils and their degranulation activity were counted in the same fields. Results: Patients with response to BCG therapy had a G/T ratio of ≥ 3 and patients with non-response to BCG therapy had a G/T ratio of ≤ 1.5. Correlation of these scores with subsequent patient outcomes following BCG immune therapy demonstrated that patient responsiveness (i.e., tumor elimination at 6 months) trended with the higher G/T ratio patients. In addition, initial biopsies of BCG responsive patients display a higher number of eosinophils and degranulation relative to BCG non-responsive patients. Conclusions: Evaluations of initial biopsies revealed a strong correlation between Th1 and Th2 immune response with BCG therapy outcomes. The development of specific and novel tools to identify/measure Th2 immune responses in Tis bladder cancer provides a unique opportunity to predict outcomes at the time of diagnosis.

Abstract Although eosinophils as a group are readily identified by their unique morphology and staining properties, flow cytometry provides an important means for identification of subgroups based on differential expression of distinct surface Ags. Here, we characterize an eosinophil subpopulation defined by high levels of expression of the neutrophil Ag Gr1 (CD45+CD11c−SiglecF+Gr1hi). SiglecF+Gr1hi eosinophils, distinct from the canonical SiglecF+Gr1− eosinophil population, were detected in allergen-challenged wild-type and granule protein-deficient (EPX−/− and MBP-1−/−) mice, but not in the eosinophil-deficient ΔdblGATA strain. In contrast to Gr1+ neutrophils, which express both cross-reacting Ags Ly6C and Ly6G, SiglecF+Gr1hi eosinophils from allergen-challenged lung tissue are uniquely Ly6G+. Although indistinguishable from the more-numerous SiglecF+Gr1− eosinophils under light microscopy, FACS-isolated populations revealed prominent differences in cytokine contents. The lymphocyte-targeting cytokines CXCL13 and IL-27 were identified only in the SiglecF+Gr1hi eosinophil population (at 3.9 and 4.8 pg/106 cells, respectively), as was the prominent proinflammatory mediator IL-13 (72 pg/106 cells). Interestingly, bone marrow-derived (SiglecF+), cultured eosinophils include a more substantial Gr1+ subpopulation (∼50%); Gr1+ bmEos includes primarily a single Ly6C+ and a smaller, double-positive (Ly6C+Ly6G+) population. Taken together, our findings characterize a distinct SiglecF+Gr1hi eosinophil subset in lungs of allergen-challenged, wild-type and granule protein-deficient mice. SiglecF+Gr1hi eosinophils from wild-type mice maintain a distinct subset of cytokines, including those active on B and T lymphocytes. These cytokines may facilitate eosinophil-mediated immunomodulatory responses in the allergen-challenged lung as well as in other distinct microenvironments.

Abstract Proinflammatory consequences have been described for lysophosphatidylcholine, a lipid product of cellular injury, signaling via the G protein–coupled receptor G2A on myeloid and lymphoid inflammatory cells. This prompted the hypothesis that genetic deletion of G2A would limit intestinal inflammation in a mouse model of colitis induced by dextran sodium sulfate. Surprisingly, G2A−/− mice exhibited significantly worsened colitis compared with wild-type mice, as demonstrated by disease activity, colon shortening, histology, and elevated IL-6 and IL-5 in colon tissues. Investigation of inflammatory cells recruited to inflamed G2A−/− colons showed significantly more TNF-α+ and Ly6ChiMHCII− proinflammatory monocytes and eosinophils than in wild-type colons. Both monocytes and eosinophils were pathogenic as their depletion abolished the excess inflammation in G2A−/− mice. G2A−/− mice also had less IFN-γ in inflamed colon tissues than wild-type mice. Fewer CD4+ lymphocytes were recruited to inflamed G2A−/− colons, and fewer colonic lymphocytes produced IFN-γ upon ex vivo stimulation. Administration of IFN-γ to G2A−/− mice during dextran sodium sulfate exposure abolished the excess colitic inflammation and reduced colonic IL-5 and eosinophil numbers to levels seen in wild-type mice. Furthermore, IFN-γ reduced the numbers of TNF-α+ monocyte and enhanced their maturation from Ly6ChiMHCII− to Ly6CintMHCII+. Taken together, the data suggest that G2A signaling serves to dampen intestinal inflammation via the production of IFN-γ, which, in turn, enhances monocyte maturation to a less inflammatory program and ultimately reduces eosinophil-induced injury of colonic tissues.

Abstract Respiratory viruses cause asthma exacerbations. Because eosinophils are the prominent leukocytes in the airways of 60–70% of patients with asthma, we evaluated the effects of eosinophils on a common respiratory virus, parainfluenza 1, in the lung. Eosinophils recruited to the airways of wild-type mice after ovalbumin sensitization and challenge significantly decreased parainfluenza virus RNA in the lungs 4 days after infection compared with nonsensitized animals. This antiviral effect was also seen in IL-5 transgenic mice with an abundance of airway eosinophils (NJ.1726) but was lost in transgenic eosinophil-deficient mice (PHIL) and in IL-5 transgenic mice crossed with eosinophil-deficient mice (NJ.1726-PHIL). Loss of the eosinophil granule protein eosinophil peroxidase, using eosinophil peroxidase–deficient transgenic mice, did not reduce eosinophils’ antiviral effect. Eosinophil antiviral mechanisms were also explored in vitro. Isolated human eosinophils significantly reduced parainfluenza virus titers. This effect did not involve degradation of viral RNA by eosinophil granule RNases. However, eosinophils treated with a nitric oxide synthase inhibitor lost their antiviral activity, suggesting eosinophils attenuate viral infectivity through production of nitric oxide. Consequently, eosinophil nitric oxide production was measured with an intracellular fluorescent probe. Eosinophils produced nitric oxide in response to virus and to a synthetic agonist of the virus-sensing innate immune receptor, Toll-like receptor (TLR) 7. IFNγ increased expression of eosinophil TLR7 and potentiated TLR7-induced nitric oxide production. These results suggest that eosinophils promote viral clearance in the lung and contribute to innate immune responses against respiratory virus infections in humans.