Serena De Vita

Loss of Function of TET2 Cooperates with Constitutively Active KIT in Murine and Human Models of Mastocytosis

Systemic Mastocytosis (SM) is a clonal disease characterized by abnormal accumulation of mast cells in multiple organs. Clinical presentations of the disease vary widely from indolent to aggressive forms, and to the exceedingly rare mast cell leukemia. Current treatment of aggressive SM and mast cell leukemia is unsatisfactory. An imatinib-resistant activating mutation of the receptor tyrosine kinase KIT (KIT D816V) is most frequently present in transformed mast cells and is associated with all clinical forms of the disease. Thus the etiology of the variable clinical aggressiveness of abnormal mast cells in SM is unclear. TET2 appears to be mutated in primary human samples in aggressive types of SM, suggesting a possible role in disease modification. In this report, we demonstrate the cooperation between KIT D816V and loss of function of TET2 in mast cell transformation and demonstrate a more aggressive phenotype in a murine model of SM when both mutations are present in progenitor cells. We exploit these findings to validate a combination treatment strategy targeting the epigenetic deregulation caused by loss of TET2 and the constitutively active KIT receptor for the treatment of patients with aggressive SM.

Rac signaling in osteoblastic cells is required for normal bone development but is dispensable for hematopoietic development

Hematopoietic stem cells (HSCs) interact with osteoblastic, stromal, and vascular components of the BM hematopoietic microenvironment (HM) that are required for the maintenance of long-term self-renewal in vivo. Osteoblasts have been reported to be a critical cell type making up the HSC niche in vivo. Rac1 GTPase has been implicated in adhesion, spreading, and differentiation of osteoblast cell lines and is critical for HSC engraftment and retention. Recent data suggest a differential role of GTPases in endosteal/osteoblastic versus perivascular niche function. However, whether Rac signaling pathways are also necessary in the cell-extrinsic control of HSC function within the HM has not been examined. In the present study, genetic and inducible models of Rac deletion were used to demonstrate that Rac depletion causes impaired proliferation and induction of apoptosis in the OP9 cell line and in primary BM stromal cells. Deletion of Rac proteins caused reduced trabecular and cortical long bone growth in vivo. Surprisingly, HSC function and maintenance of hematopoiesis in vivo was preserved despite these substantial cell-extrinsic changes. These data have implications for therapeutic strategies to target Rac signaling in HSC mobilization and in the treatment of leukemia and provide clarification to our evolving concepts of HSC-HM interactions.

Changes in inflammatory biomarkers in HCV-infected patients undergoing direct acting antiviral-containing regimens with or without interferon

Background and aims Increased levels of chemokine interferon-gamma (IFN-γ)-inducible protein-10 (CXCL10), soluble CD163 (sCD163) and soluble CD14 (sCD14) have been reported in HCV infection. The aim of this study was to compare, sCD163 and sCD14 levels in HCV-infected patients undergoing direct acting antiviral (DAA)-containing regimens with or without interferon (IFN). Methods sCD163, sCD14 and CXCL10 were longitudinally measured by ELISA in 159 plasma samples from 25 HCV-infected patients undergoing IFN-based treatment plus telaprevir or boceprevir and 28 HCV infected subjects treated with DAA IFN-free regimens. Twenty-five healthy donors (HD) were included as controls. Results At baseline CXCL10, sCD163 and sCD14 levels were higher in HCV-infected patients than in HD. CXCL10 and sCD163 levels were significantly decreased in responder (R) patients who achieved sustained virological response (SVR), with both IFN-based and IFN-free regimens, while they were persistently elevated in non-responders (NR) patients who stopped IFN-based treatments because of failure or adverse events. Conversely, sCD14 levels were apparently unchanged during therapy, but at the end of treatment the levels reached normal ranges. Comparing the two regimens, the extent of CXCL10 reduction was more pronounced in patients undergoing DAA IFN-free therapies, whereas sCD163 and sCD14 reduction was similar in the two groups. Interestingly, only in IFN-based regimens baseline sCD163 levels were significantly higher in NR than in R patients, while in the IFN-free treatment group also patients with high sCD163 plasma levels obtained SVR. At the end of therapy, even if the biomarkers were largely decreased, their levels remained significantly higher compared to HD. Only in the early fibrosis stages, sCD163 values tended to normalize. Conclusions These results indicate that IFN-free regimens including newer DAA induce an early and marked decrease in circulating inflammatory biomarkers. However, the full normalization of biomarkers was not obtained, especially in patients with advanced fibrosis, thus underlying the need for a treatment in the early stages of HCV infection.

The gp130 Cytokine Interleukin‐11 Regulates Engraftment of Vav1–/– Hematopoietic Stem and Progenitor Cells in Lethally Irradiated Recipients

During bone marrow transplantation, hematopoietic stem and progenitor cells (HSPCs) respond to signals from the hematopoietic microenvironment by coordinately activating molecular pathways through Rho GTPases, including Rac. We have previously shown that deletion of Vav1, a hematopoietic‐specific activator of Rac, compromises engraftment of transplanted adult HSPCs without affecting steady‐state hematopoiesis in adult animals. Here, we show that Vav1–/– fetal HSPCs can appropriately seed hematopoietic tissues during ontogeny but cannot engraft into lethally irradiated recipients. We demonstrate that the engraftment defect of Vav1–/– HSPCs is abrogated in the absence of irradiation and demonstrate that Vav1 is critical for the response of HSPCs to the proinflammatory cytokine interleukin‐11 (IL‐11) that is upregulated in the marrow of irradiated recipients. Vav1–/– HSPCs display abnormal proliferative responses to IL‐11 in vitro and dysregulated activation of pathways critical to engraftment of HSPCs. The engraftment of Vav1–/– HSPCs can be partially rescued in irradiated recipients treated with an anti‐IL‐11 antibody. These data suggest that HSPCs may respond to different functional demands by selective usage of the IL‐11‐Vav‐Rac pathway, contextualizing further the recent view that HSPCs capable of reconstituting the blood system following transplantation might be distinct from those supporting hematopoiesis during homeostatic conditions. Stem Cells 2018; 36:446–457

Persistent high plasma levels of sCD163 and sCD14 in adult patients with measles virus infection

Background and aims Measles is an infectious disease that represents a serious public health problem worldwide, being associated with increased susceptibility to secondary infections, especially in the respiratory and gastrointestinal tracts. The aim of this study was to evaluate sCD163 and sCD14 levels in measles virus (MV) infected patients, as markers of immune activation, in order to better understand their role in the pathogenesis of the disease. TNF-α plasma levels were also evaluated. Methods sCD163, sCD14 and TNF-α were measured by ELISA in plasma samples of 27 MV infected patients and 27 healthy donors (HD) included as controls. Results At the time of hospital admission, sCD163 and sCD14 levels were significantly higher in MV infected patients than in HD, while a decrease in TNF-α levels were found even if without statistical significance. sCD163 and sCD14 levels were significantly decreased after two months from acute infection compared to hospital admission although they remained significantly higher compared to HD. TNF-α levels increased significantly during the follow-up period. Considering clinical parameters, sCD163 levels positively correlated with aspartate aminotransferase, white blood cell count and neutrophils rate, while negatively correlated with the lymphocyte percentage. sCD14 levels positively correlated with the neutrophil and lymphocyte percentages. Conclusions These results indicate that, despite the resolution of symptoms, an important macrophage/monocyte activation persists in measles patients, even after two months from infection.

Overproduction of IL-6 and Type-I IFN in a Lethal Case of Chikungunya Virus Infection in an Elderly Man during the 2017 Italian Outbreak

Abstract Chikungunya fever is caused by Chikungunya virus (CHIKV) and is generally considered a self-limiting disease. However, severe clinical presentations with a high mortality rate have been reported in association with underlying medical conditions. This study reports the molecular characterization of the virus and an abnormal pattern of circulating cytokines in a unique lethal CHIKV case during the 2017 outbreak in Italy, which involved an elderly patient with underlying cardiac disease. Analysis of inflammatory cytokines revealed a strong increase of interferon (IFN)-α and IFN-β, as well as interleukin-6, suggesting a possible role of type-I IFN in the cytokine storm, which may be correlated with unfavorable prognosis of CHIKV infection.