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Fabio Malavasi

Publications and source records attributed to Fabio Malavasi.

At least 19 recordsLinked to original sources
PubMed2006

CD molecules 2006--human cell differentiation molecules.

The Human Leucocyte Differentiation Antigens Workshops (HLDA) have since 1984 provided a forum for the characterization and study of leucocyte surface molecules and antibodies against them. HLDA devised the CD nomenclature, which is sanctioned by IUIS. The HLDA Council reviewed and modified the objectives of HLDA in 2004, and changed the name of the organization to Human Cell Differentiation Molecules (HCDM) to reflect the broader objectives. Workshop studies under the HCDM banner proceeded during 2005 and early 2006, culminating in a meeting in May 2006. At that meeting the Council, acting as Nomenclature Committee, approved a number of new CD designations and changes to some pre-existing CD designations, which are summarized in this report.

Antigens, CD↗
PubMed2006

The low-density lipoprotein receptor plays a role in the infection of primary human hepatocytes by hepatitis C virus.

BACKGROUND/AIMS: The direct implication of low-density lipoprotein receptor (LDLR) in hepatitis C virus (HCV) infection of human hepatocyte has not been demonstrated. Normal primary human hepatocytes infected by serum HCV were used to document this point. METHODS: Expression and activity of LDLR were assessed by RT-PCR and LDL entry, in the absence or presence of squalestatin or 25-hydroxycholesterol that up- or down-regulates LDLR expression, respectively. Infection was performed in the absence or presence of LDL, HDL, recombinant soluble LDLR peptides encompassing full-length (r-shLDLR4-292) or truncated (r-shLDLR4-166) LDL-binding domain, monoclonal antibodies against r-shLDLR4-292, squalestatin or 25-hydroxycholesterol. Intracellular amounts of replicative and genomic HCV RNA strands used as end point of infection were assessed by RT-PCR. RESULTS: r-shLDLR4-292, antibodies against r-shLDLR4-292 and LDL inhibited viral RNA accumulation, irrespective of genotype, viral load or liver donor. Inhibition was greatest when r-shLDLR4-292 was present at the time of inoculation and gradually decreased as the delay between inoculation and r-shLDLR4-292 treatment increased. In hepatocytes pre-treated with squalestatin or 25-hydroxycholesterol before infection, viral RNA accumulation increased or decreased in parallel with LDLR mRNA expression and LDL entry. CONCLUSIONS: LDLR is involved at an early stage in infection of normal human hepatocytes by serum-derived HCV virions.

Adolescent↗
PubMed2006

TfR2 localizes in lipid raft domains and is released in exosomes to activate signal transduction along the MAPK pathway.

Transferrin receptor 2 (TfR2) possesses a YQRV motif similar to the YTRF motif of transferrin receptor 1 (TfR1) responsible for the internalization and secretion through the endosomal pathway. Raft biochemical dissection showed that TfR2 is a component of the low-density Triton-insoluble (LDTI) plasma membrane domain, able to co-immunoprecipitate with caveolin-1 and CD81, two structural raft proteins. In addition, subcellular fractionation experiments showed that TfR1, which spontaneously undergoes endocytosis and recycling, largely distributed to intracellular organelles, whereas TfR2 was mainly associated with the plasma membrane. Given the TfR2 localization in lipid rafts, we tested its capability to activate cell signalling. Interaction with an anti-TfR2 antibody or with human or bovine holotransferrin showed that it activated ERK1/ERK2 and p38 MAP kinases. Integrity of lipid rafts was required for MAPK activation. Co-localization of TfR2 with CD81, a raft tetraspanin exported through exosomes, prompted us to investigate exosomes released by HepG2 and K562 cells into culture medium. TfR2, CD81 and to a lesser extent caveolin-1, were found to be part of the exosomal budding vesicles. In conclusion, the present study indicates that TfR2 localizes in LDTI microdomains, where it promotes cell signalling, and is exported out of the cells through the exosome pathway, where it acts as an intercellular messenger.

Antigens, CD↗
PubMed2006

CD157 plays a pivotal role in neutrophil transendothelial migration.

Paracellular diapedesis, a key step in leukocyte recruitment to the site of inflammation, occurs at endothelial junctions and is regulated by highly coordinated interactions between leukocytes and endothelium. We found that CD157, a glycosylphosphatidylinositol-anchored ectoenzyme belonging to the NADase/ADP-ribosyl cyclase family, plays a crucial role for neutrophil diapedesis, because its ligation with specific monoclonal antibodies (both on neutrophils or endothelial cells) results in altered neutrophil movement on the apical surface of endothelium and, ultimately, in loss of diapedesis. Real-time microscopy revealed that CD157 behaves as a sort of compass during the interaction between neutrophils and endothelial cells; indeed, following CD157 ligation, neutrophils appear disoriented, meandering toward junctions where they eventually stop without transmigrating. These findings are relevant in vivo because CD157-deficient neutrophils obtained from patients with paroxysmal nocturnal hemoglobinuria are characterized by a severely impaired diapedesis.

ADP-ribosyl Cyclase↗
PubMed2006

In-tandem insight from basic science combined with clinical research: CD38 as both marker and key component of the pathogenetic network underlying chronic lymphocytic leukemia.

The absence of mutations in the IgV genes, together with the presence of ZAP-70 and CD38, are the most reliable negative prognostic markers for chronic lymphocytic leukemia (CLL) patients. Several lines of evidence indicate that CD38 may be not only a diagnostic marker but also a key element in the pathogenetic network in CLL. First, CD38 is a receptor that induces proliferation and increases survival of CLL cells. Second, CD38 signals start upon interaction with the CD31 ligand expressed by stromal and nurse-like cells. Third, CD38/CD31 contacts up-regulate CD100, a semaphorin involved in sustaining CLL growth. Fourth, evidence that nurselike cells express high levels of CD31 and plexin-B1, the high-affinity ligand for CD100, offers indirect confirmation for this model of receptor cross-talk. Elements of variation in the clinical course of CD38(+) CLL patients include (1) potential intersection with ZAP-70, a kinase involved in the CD38 signaling pathway in T and natural killer (NK) cells, and (2) the effects of genetic polymorphisms of the receptors involved, at least of CD38 and CD31. Consequently, CD38 together with ZAP-70 appear to be the key elements of a coreceptor pathway that may sustain the signals mediated by the B-cell receptor and potentially by chemokines and their receptors. This would result in acquisition of increased survival potential, providing clues to the poorer prognosis of CD38(+) patients.

ADP-ribosyl Cyclase 1↗
PubMed2006

Role of transferrin receptor 2 in hepatic accumulation of iron in patients with chronic hepatitis C.

BACKGROUND AND AIM: Iron deposition in the liver is a common finding in patients with chronic hepatitis C (CH-C). The mechanism of this hepatic accumulation of iron is not completely understood. This study assessed if the protein expression of transferrin receptor 2 (TfR2) is upregulated in the liver of patients with CH-C and if TfR2 protein mediates iron accumulation during hepatitis C virus (HCV) infection. METHOD: Liver specimens from patients with CH-C that underwent interferon (IFN) therapy (n=23) and from patients with CH-B (n=18) were evaluated. Hepatic expression of TfR2 protein was analyzed by immunohistochemistry. Total hepatic iron score (THIS) was evaluated by Prussian blue staining. RESULTS: TfR2 protein was expressed in the cell membrane and cytosol of hepatocytes. Cytosol TfR2 protein was found to co-localize with Tf. THIS (P=0.0198) and hepatic TfR2 (P=0.0047) expression were significantly higher in CH-C than in CH-B. The change in THIS values (rho=0.580, P=0.0079) and the grade of histological activity (rho=0.444, P=0.0373) were significantly correlated with changes in TfR2 expression after IFN therapy. CONCLUSIONS: The protein expression of TfR2 is significantly associated with iron deposition in the liver in patients with CH-C. HCV infection may affect the hepatic expression of TfR2, leading to iron accumulation in the liver.

Adult↗
PubMed2005

CD38 orchestrates migration, survival, and Th1 immune response of human mature dendritic cells.

CD38, an ectoenzyme and a signaling receptor, is a novel marker of human mature monocyte-derived dendritic cells (MDDCs). The working hypothesis is that CD38 is not only a marker but also contributes to functions specifically gained by MDDCs with maturation. This was tested by assessing the role(s) of CD38 after signaling with agonistic anti-CD38 monoclonal antibodies or by blocking the interactions taking place between CD38 and CD31, its counterreceptor. The results indicate the following: (1) CD38 engagement in MDDCs ensures efficient chemotaxis and transendothelial migration driven by CC chemokine ligand 21 (CCL21); (2) CD38 is laterally associated with the CCL21-specific CC chemokine receptor 7 and with CD83 and CD11b; (3) CD38 localizes in membrane lipid domains; (4) CD38 signaling contributes to support longevity of lipopolysaccharide (LPS)-matured MDDCs after growth factor withdrawal; and (5) IFN-gamma is produced by cocultured T lymphocytes, thus affecting T-helper 1 (Th1) polarization. These data suggest that the localization of CD38 in lipid rafts and its multiple interactions with signaling receptors rule innate and adaptive immune responses by tuning DC migration, survival, and Th1-polarization ability. These findings may lay out the basis to assess the functional role(s) of human CD38 in infections, autoimmune diseases, and neoplastic disorders.

ADP-ribosyl Cyclase 1↗
PubMed2005

Use of genetic immunization to raise antibodies recognizing toxin-related cell surface ADP-ribosyltransferases in native conformation.

ADP-ribosyltransferases (ARTs) transfer ADP-ribose from NAD to arginine, asparagine, or cysteine residues in target proteins. This post-translational protein modification is the mechanism by which cholera-toxin and other bacterial toxins cause pathology in human host cells. Molecular cloning has identified five toxin-related GPI-anchored cell surface ARTs in the mouse (ART1, ART2.1, ART2.2, ART3, and ART4) and three in the human (ART1, ART3, and ART4). ART2-which has sparked interest because of its ability to activate the cytolytic P2X7 purinergic receptor by ADP-ribosylation-is encoded by two functional gene copies in the mouse genome while the human genome carries two inactivated ART2 pseudogenes. We generated stable transfectants for FLAG-tagged versions of each of the functional human and mouse ARTs. Using genetic immunization we raised monoclonal antibodies that recognize the native human ARTs on the surface of living cells. Some of these mAbs recognize an epitope shared with the mouse ART orthologue but not with more distant ART paralogues. Screening of primary cells and established cell lines by FACS revealed expression of ART1 by monocytes, neutrophils and myeloid leukemia cell lines but not by cell lines derived from solid tumors. ART1 and ART4 have been assigned the designations: CD296, and CD297, respectively.

ADP Ribose Transferases↗
PubMed2005

A panel of monoclonal antibodies recognizing GPI-anchored ADP-ribosyltransferase ART4, the carrier of the Dombrock blood group antigens.

ART4 (CD297) is a member of the family of toxin-related ADP-ribosyltransferases (ARTs) and is the carrier of the Dombrock blood group alloantigens (Do). Two mouse monoclonal antibodies (MIMA-52 and MIMA-53), and two rat monoclonal antibodies (N0NI-B4 and NONI-B63) were obtained following immunization of mice with human Do/ART4-transfected cells and of rats with human Do/ART4 cDNA, respectively. All four mAbs recognize Do/ART4-transfected Jurkat cells but not untransfected cells by FACS analysis. Staining of Do/ART4-transfected cells by these mAbs was reduced following treatment of cells with PI-PLC, confirming that Do/ART4 is anchored in the cell membrane by linkage to glycosylphosphatidylinositol as predicted from its amino acid sequence. The four mAbs did not react with Gy(a-) (Dombrock null) erythrocytes but agglutinated other red blood cells. By flow cytometric analysis, all mAbs reacted prominently with erythrocytes, and weakly with peripheral blood monocytes and splenic macrophages, but not with B-lymphocytes or T-lymphocytes. The mAbs reacted weakly also with human umbilical vein endothelial cells and the basophilic leukemia KU-812. Immunohistology revealed staining of epithelia and endothelia on sections of tonsils. In FACS analyses NONI-B4 competed with MIMA-52 for binding to Do/ART4-transfected cells and erythrocytes, whereas NONI-B63 competed with MIMA-53. Neither of the mAbs reacted with mouse ART4-transfected cells, but NONI-B63 and MIMA-53 did react with a mouse/human ART4 chimera, indicating that the epitope recognized by these mAbs lies in the C-terminal half of the protein.

ADP Ribose Transferases↗
PubMed2005

CD molecules 2005: human cell differentiation molecules.

The immune system works through leukocytes interacting with each other, with other cells, with tissue matrices, with infectious agents, and with other antigens. These interactions are mediated by cell-surface glycoproteins and glycolipids. Antibodies against these leukocyte molecules have provided powerful tools for analysis of their structure, function, and distribution. Antibodies have been used widely in hematology, immunology, and pathology, and in research, diagnosis, and therapy. The associated CD nomenclature is commonly used when referring to leukocyte surface molecules and antibodies against them. It provides an essential classification for diagnostic and therapeutic purposes. The most recent (8th) Workshop and Conference on Human Leukocyte Differentiation Antigens (HLDA), held in Adelaide, Australia, in December 2004, allocated 95 new CD designations and made radical changes to its aims and future operational strategy in order to maintain its relevance to modern human biology and clinical practice.

Antigens, CD↗
PubMed2005

Immunodetection of anti-MAG IgM antibody by cross-reactivity to LA-N-1 neuroblastoma cells.

Demyelinating polyneuropathiy associated with IgM paraproteinemia and high titers of anti-MAG IgM antibodies (MAG-PN) is considered different from chronic inflammatory demyelinating polyneuropathy, particularly because of the poorer response to treatment of MAG-PN patients. Therefore, anti-MAG anitbodies may have relevant prognostic value. Available anti-MAG antibody assays require central nervous system myelin proteins from autopsied human brains. This study investigated the feasibility of detecting anti-MAG antibody by immunofluorescence and flow cytometry using a panel of human neuroblastoma cell lines as targets. We report here on the evaluation of the LA-N-1 cell line as an appropriate substrate for the detection of anti-MAG antibody by indirect immunoflourescence.

Adult↗
PubMed2004

CD38 and CD100 lead a network of surface receptors relaying positive signals for B-CLL growth and survival.

This work addresses the question whether CD38, a negative prognostic marker in B-cell chronic lymphocytic leukemia (B-CLL), plays a role in neoplastic B-cell growth and survival. We show that CD38+ B-CLL cells bind to murine fibroblasts transfected with the CD31 ligand. The interaction triggers an extensive remodeling of the B-CLL membrane, with relocalization of BCR/CD19 to the CD38/CD31 contact areas, and it also increases cell survival and proliferation. A second event is the up-modulation of the survival receptor CD100, restricted to proliferating cells, and a concomitant decrease of CD72 (low-affinity CD100 ligand and negative regulator of immune responses). The most efficient signals are delivered through sequential interactions between CD38/CD31 and CD100/plexin-B1 (high-affinity CD100 ligand), as inferred by coculture experiments using specific transfectants and blocking monoclonal antibodies (mAbs). The finding that nurselike cells from B-CLL patients express CD31 and plexin-B1, which deliver growth and survival signals to CD38+/CD100+ B-CLL cells, further confirms the model proposed. These findings show that a set of normal receptors and ligands ruling physiologic signaling pathways in B lymphocytes becomes detrimental when expressed in the context of B-CLL cells, ultimately leading to the generation of a tumor reservoir.

ADP-ribosyl Cyclase↗
PubMed2004

Characterization and phylogenetic epitope mapping of CD38 ADPR cyclase in the cynomolgus macaque.

BACKGROUND: The CD38 transmembrane glycoprotein is an ADP-ribosyl cyclase that moonlights as a receptor in cells of the immune system. Both functions are independently implicated in numerous areas related to human health. This study originated from an inherent interest in studying CD38 in the cynomolgus monkey (Macaca fascicularis), a species closely related to humans that also represents a cogent animal model for the biomedical analysis of CD38. RESULTS: A cDNA was isolated from cynomolgus macaque peripheral blood leukocytes and is predicted to encode a type II membrane protein of 301 amino acids with 92% identity to human CD38. Both RT-PCR-mediated cDNA cloning and genomic DNA PCR surveying were possible with heterologous human CD38 primers, demonstrating the striking conservation of CD38 in these primates. Transfection of the cDNA coincided with: (i) surface expression of cynomolgus macaque CD38 by immunofluorescence; (ii) detection of approximately 42 and 84 kDa proteins by Western blot and (iii) the appearance of ecto-enzymatic activity. Monoclonal antibodies were raised against the cynomolgus CD38 ectodomain and were either species-specific or cross-reactive with human CD38, in which case they were directed against a common disulfide-requiring conformational epitope that was mapped to the C-terminal disulfide loop. CONCLUSION: This multi-faceted characterization of CD38 from cynomolgus macaque demonstrates its high genetic and biochemical similarities with human CD38 while the immunological comparison adds new insights into the dominant epitopes of the primate CD38 ectodomain. These results open new prospects for the biomedical and pharmacological investigations of this receptor-enzyme.

ADP-ribosyl Cyclase↗
PubMed2004

CD157 is an important mediator of neutrophil adhesion and migration.

CD157, a glycosylphosphatidylinositol (GPI)-anchored protein encoded by a member of the CD38 NADase/ADP-ribosyl cyclase gene family, is expressed on the surface of most human circulating neutrophils. This work demonstrates that CD157 is a receptor that induces reorganization of the cytoskeleton and significant changes in cell shape, and that signals mediated by CD157 act through modulation of cytosolic Ca(2+) concentration. These signals are independent of the products of CD157's enzymatic activities (ie, cyclic adenosine diphosphate [ADP]-ribose and ADP-ribose). Indeed, the enzymatic activities of CD157 in circulating neutrophils as well as in dimethyl sulfoxide (DMSO)-differentiated (CD157(+)/CD38(-)) HL-60 cells, are hardly detectable. This work also shows that the receptorial activity relies on cross-talk between CD157 and beta(2) integrin. CD157 localizes in GM1-enriched lipid rafts and, upon activation, it migrates to the uropod, a structure specialized in motility and adhesive functions. Indeed, CD157 is involved in adhesion to extracellular matrix proteins and in chemotaxis induced in vitro by formyl-methionyl-leucyl-phenylalanine (fMLP). These findings were consistent with the results obtained in neutrophils from patients with paroxysmal nocturnal hemoglobinuria (PNH), in which CD157 is deficient. These neutrophils showed constant defects in adhesion and migration. Our data attribute specific and crucial roles to CD157 in the regulation of innate immunity during inflammation.

ADP-ribosyl Cyclase↗
PubMed2004

Transferrin receptor 2 protein is not expressed in normal erythroid cells.

Human TFR2 (transferrin receptor 2) is a membrane-bound protein homologous with TFR1. High levels of TFR2 mRNA were found mainly in the liver and, to a lesser extent, in erythroid precursors. However, although the presence of the TFR2 protein in hepatic cells has been confirmed in several studies, evidence is lacking about the presence of the TFR2 protein in normal erythroid cells. Using two anti-TFR2 monoclonal antibodies, G/14C2 and G/14E8, we have provided evidence that TFR2 protein is not expressed in normal erythroid cells at any stage of differentiation, from undifferentiated CD34+ cells to mature orthochromatic erythroblasts. In contrast, erythroleukaemic cells (K562 cells) exhibited a high level of expression of TFR2 at both the mRNA and the protein level. We can therefore conclude that an elevated expression of TFR2 protein is observed in leukaemic cells, but not in normal erythroblasts. The implications of this observation for the understanding of the phenotypic features of haemochromatosis due to mutation of the TFR2 gene are discussed.

Antibodies↗
PubMed2004

CD38 is expressed on human mature monocyte-derived dendritic cells and is functionally involved in CD83 expression and IL-12 induction.

Dendritic cell (DC) maturation is characterized by the gain or loss of immunological functions and by expression of distinctive surface receptors. CD38 is an ectoenzyme that catalyzes the synthesis of cyclic ADP ribose (a potent second messenger for Ca(2+) release), as well as a receptor that initiates transmembrane signaling upon engagement with its counter-receptor CD31 or with agonistic monoclonal antibodies. Since CD38 is expressed by resting monocytes, we aimed to monitor CD38 expression during the differentiation of human monocyte-derived DC (MDDC) and to investigate the possibility that CD38 plays a functional role during DC maturation. CD38 is down-modulated during differentiation into immature MDDC and expressed again upon maturation. The extent of CD38 expression is dependent on the stimulus adopted (LPS > IFN-gamma > CD40 cross-linking). Although weak, IFN-gamma consistently induces DC maturation. De novo-synthesized CD38 is enzymatically active, and its expression in mature (m) MDDC is dependent on NF-kappa B activity. However, CD38 is not merely a maturation marker but also mediates signaling in mMDDC, where it maintains its functions as a receptor. Activation via agonistic anti-CD38 mAb induces up-regulation of CD83 expression and IL-12 secretion, whereas disruption of CD38/CD31 interaction inhibits CD83 expression, IL-12 secretion and MDDC-induced allogeneic T cell proliferation.

ADP-ribosyl Cyclase↗
PubMed2004

Radioimmunotherapy in advanced ovarian cancer: is there a role for pre-targeting with (90)Y-biotin?

OBJECTIVES: Despite recent advances in the management of ovarian cancer, this tumor remains the leading cause of death among gynecologic malignancies. Moreover, advanced ovarian carcinoma has a poor prognosis, thus requiring new therapeutic modalities. Previous studies have indicated a survival advantage for ovarian cancer patients (pts) treated with radioimmunotherapy (RIT). Pre-targeting RIT, based on the avidin-biotin system, has been the objective of previous studies performed by our group. PATIENTS AND METHODS: In the present study, the therapeutic efficacy and toxicity of RIT in 38 advanced ovarian cancer patients have been retrospectively evaluated. RIT was performed according to the following three-step protocol: biotinylated monoclonal antibodies (MoAb) and avidin were intraperitoneally (ip) injected (1st and 2nd step), and 12-18 h later (90)Y-labeled biotin either iv or ip was injected as 3rd step. Sixteen out of 38 patients were treated by intraperitoneal injection only, whereas other 22 pts received the combined treatment (ip + iv); the dose range was 10-100 mCi of (90)Y-biotin. RESULTS: Both of the two therapy regimens were well tolerated; no acute side effects were observed. Two patients (5%) showed temporary hematological grade III-IV toxicity. As regards to the therapeutic efficacy, in the ip group we observed 6% of objective tumor reduction, stabilization in 31% of pts, and progression in 50%. In the group of combined treatment, 9% of patients achieved objective responses, 32% showed stable disease, and 41% had a progression. CONCLUSIONS: These data show the excellent tolerability (maximum tolerated dose (MTD) has not been determined yet) and the potential therapeutic role of RIT in advanced ovarian cancer. Patients with minimal residual disease would probably take the best advantages of RIT with (90)Y-biotin (electrons). These data warrant further prospective studies.

Adult↗