Biomedical subjects

G Tosato

Publications and source records attributed to G Tosato.

At least 55 records · Page 3Linked to original sources

PubMed1998

EBV-NK cells interactions and lymphoproliferative disorders.

Epstein-Barr virus (EBV) usually infects epithelial cells in the oropharynx and B lymphocytes asymptomatically. Occasionally, however, EBV infects T-cells and natural killer (NK) cells, and infection of these cells has been associated with the development of leukemias and lymphomas. EBV-positive lymphoproliferative disorders of NK cells have been reported with increasing frequency, but the interactions between EBV and NK cells are not fully understood, in part because NK cells are not usually infected with EBV in vitro. The lymphoma-derived EBV-positive NK cell line, YT, has been useful in the study of EBV infection of NK cells. YT cells express the EBV-associated nuclear antigen (EBNA)-1, the latent membrane protein (LMP)-1, and LMP-2A, but not EBNA-2 and LMP-2B genes. This pattern of latent gene expression is compatible with a type II latency program, normally associated with nasopharyngeal carcinoma, Hodgkin's disease, and T-cell lymphoma. In this report, we summarize recent information on EBV-NK cell interactions and EBV-positive lymphoproliferative disorders of NK cells.

B-Lymphocytes↗

PubMed1998

Expression of human herpesvirus-8 oncogene and cytokine homologues in an HIV-seronegative patient with multicentric Castleman's disease and primary effusion lymphoma.

Human herpesvirus-8 (HHV-8) has been described in association with two lymphoproliferative disorders: one benign, multicentric Castleman's disease (MCD), and one malignant, primary effusion lymphoma (PEL). The factors that lead to malignant transformation of lymphoid cells are unknown, although most cases of PEL also are positive for EBV, suggesting a role for EBV as a cofactor in malignant transformation. We encountered a rare case of an HHV-8-associated MCD, followed by the development of an HHV-8-positive pleural PEL and a gastric large cell lymphoma in an HIV-seronegative male patient. The lesions were negative for Epstein-Barr virus (EBV). The combination of these diverse HHV-8-associated lymphoproliferative disorders in a single patient afforded us the ability to study potential differences in gene expression in these conditions. HHV-8 DNA was demonstrated by PCR in lymphoid tissues involved by MCD and PEL. By reverse transcriptase-PCR, HHV-8-related transcripts, including vG-coupled protein receptor, vbcl2, vcyclin D, vIL-6, vMIPI, and vMIPII, were detected in the PEL from the pleural cavity and the gastric lymphoma, whereas these transcripts, except for vIL-6, were not detected in a lymph node biopsy with MCD. Expression of hIL-10 was weak in the PEL from the pleural cavity, and expression of hIL-6 was undetectable in all three lesions. These data suggest that vIL-6 may be integral to the pathogenesis of MCD, whereas other viral transcripts that encode oncogene and chemokine homologues are important for HHV-8 tumorigenicity.

Antigens, CD↗

PubMed1997

The role of Mig, the monokine induced by interferon-gamma, and IP-10, the interferon-gamma-inducible protein-10, in tissue necrosis and vascular damage associated with Epstein-Barr virus-positive lymphoproliferative disease.

The mechanisms of tissue necrosis and vascular damage characteristics of certain Epstein-Barr virus (EBV)-associated lymphoproliferative disorders are unknown. The CXC chemokines interferon-gamma-inducible protein-10 (IP-10) and the monokine induced by interferon-gamma (Mig) caused tissue necrosis and vascular damage in Burkitt's lymphoma tumors established in nude mice. We report higher levels of IP-10 and Mig gene expression in tissues with necrosis and vascular damage from EBV-positive lymphomatoid granulomatosis and nasal or nasal-type T/natural killer (NK)-cell lymphomas compared with tissues with lymphoid hyperplasia, which lacked tissue necrosis and vascular damage. By immunohistochemistry, Mig and IP-10 proteins localized with similar patterns in viable tissue surrounding dead tissue, mostly within endothelial cells, monocyte/macrophages, and lymphocytes. Circulating levels of IP-10 were abnormally elevated in patients with EBV-positive lymphomatoid granulomatosis and nasal or nasal-type T/NK-cell lymphomas. These experiments provide the first description of the presence of Mig in any human normal or diseased tissue and the first description of IP-10 in certain lymphoproliferative lesions. These data suggest that Mig and IP-10 play an important role in the pathogenesis of tissue necrosis and vascular damage associated with certain EBV-positive lymphoproliferative processes.

Adult↗

PubMed1997

Role of the p53 tumor suppressor gene in the tumorigenicity of Burkitt's lymphoma cells.

Burkitt's lymphoma (BL) cell lines carry a translocated c-myc gene and, in 60-80% of cases, exhibit mutations in the p53 tumor suppressor gene. We examined the potential role of the p53 gene in BL tumorigenicity using an in vitro assay that measures p53-dependent cell cycle arrest in the G1 phase of the cell cycle and an in vivo athymic murine model that detects differences in the tumorigenicity of BL cell lines. A highly significant inverse correlation was found between the ability of BL cells to arrest in G1 after irradiation and their tumorigenicity in athymic mice, consistent with the notion that loss of p53 function is associated with increased tumorigenicity. Inactivation of wild-type (wt) p53 function by expression of the human papillomavirus E6 protein in the AG876V BL cell line, which carries both wt and mutant p53 proteins, rendered the cell line significantly more tumorigenic in athymic mice. Transfection of the wt p53 gene into the p53 mutant and highly tumorigenic BL-41 cell line caused it to acquire wt p53 function and rendered it less tumorigenic in mice. In addition to confirming a role for the loss of p53 function in tumor progression, the data demonstrate that wt p53 protein can reduce BL tumorigenicity in vivo.

Animals↗

PubMed1997

Mig, the monokine induced by interferon-gamma, promotes tumor necrosis in vivo.

Mig, the monokine induced by interferon-gamma, is a CXC chemokine active as a chemoattractant for activated T cells. Mig is related functionally to interferon-inducible protein 10 (IP-10), with which it shares a receptor, CXCR3. Previously, IP-10 was found to have antitumor activity in vivo. In the present study, murine Mig RNA was found to be expressed at higher levels in regressing Burkitt's lymphoma tumors established in nude mice compared with progressively growing tumors. Daily inoculations of purified recombinant human Mig into Burkitt's tumors growing subcutaneously in nude mice consistently caused tumor necrosis associated with extensive vascular damage. These effects were indistinguishable from those produced by intratumor inoculations of Burkitt's tumors with IP-10. These results support the notion that Mig, like IP-10, has antitumor activity in vivo.

Animals↗

PubMed1997

Interleukin-15 promotes angiogenesis in vivo.

IL-15, a cytokine with biological functions on cells of lymphoid lineage similar to those of IL-2, mediates its activities through the beta and gamma chains of the IL-2/15R and its own alpha chain. Unlike IL-2, IL-15 also binds to endothelial cells with high affinity. We report here that IL-15 is a stimulator of angiogenesis in vivo. When injected subcutaneously into nude mice, IL-15 consistently induced neovascularization of Matrigel plugs. Endothelial cells were found to express the IL-15R alpha chain and the IL-2/15R beta and common gamma chains. IL-15 induced the rapid tyrosine phosphorylation of proteins in endothelial cells, but did not stimulate endothelial cell proliferation in vitro. These findings document a previously unrecognized biological property of IL-15 and emphasize the role of IL-15 as an important mediator outside the immune system.

Animals↗

PubMed1997

Viral interleukin-10 in chronic active Epstein-Barr virus infection.

Viral interleukin-10 (IL-10), a product of the Epstein-Barr virus (EBV) replication gene BCRF1, shares extensive structural and functional similarity with the human cytokine IL-10. Both viral and human IL-10 inhibit T cell growth and interferon-gamma production. With two ELISAs, one that recognized both human and viral (total) IL-10 and the other specific for viral IL-10, IL-10 was measured in serum or plasma from 34 patients with chronic active EBV infection (CAEBV) and from 15 healthy controls. Of the patients, 56% had measurable total IL-10 and 29% had measurable viral IL-10. In contrast, total IL-10 was detectable in only 2 of 15 controls and viral IL-10 was undetectable. Thus, many patients with CAEBV have abnormally high levels of circulating IL-10 that may contribute to disease pathogenesis by inhibiting host immunity.

Adolescent↗

PubMed1997

Infectious mononucleosis as a disease of early childhood in Japan caused by primary Epstein-Barr virus infection.

The present study investigated 54 pediatric patients with acute Epstein-Barr virus (EBV)-induced infectious mononucleosis (IM) in Japan. Most of the acute cases clustered within the first 5 years of life, and the peak incidence was observed at around 4 years of age. These patients were arbitrarily separated into three age groups (less than 3 years, 3-5 years, and 6-14 years). Fever, pharyngitis, lymphadenopathy and hepatomegaly were detected in more than 80% of all cases. Tonsillitis and splenomegaly were present in about 60% of cases. Skin manifestations and eyelids edema were less often detected in the older age group than in the young age groups. In addition to an increase of total white blood cell and lymphocyte counts in the peripheral blood, a significant increase in the percentage of CD3+ CD8+ HLA-DR+ T cells was always observed. Epstein-Barr virus seropositivity increased soon after birth and reached approximately 70% around 3 years of age. Close to 100% of the adult controls were EBV seropositive. The results suggest that EBV-induced acute IM is a disease of early childhood in Japan.

Adolescent↗

PubMed1996

Virus-cell interactions in a natural killer-like cell line from a patient with lymphoblastic lymphoma.

Lymphoproliferative disorders involving Epstein-Barr virus (EBV) infected natural killer (NK) cells are reported with increasing frequency, but the nature and role of EBV infection in these cells remains undefined. In this study, we have investigated virus-cell interactions in the EBV-positive YTN10 cell line, an NK-like cell line established from a patient with lymphoblastic lymphoma. Low level expression of the EBV receptor CD21 molecule was detected by FACS and reverse transcriptase polymerase chain reaction (RT-PCR) analysis. Immunoblotting and RT-PCR analysis identified a latency II pattern of EBV gene expression, consisting of EBNA-1 transcription from the Qp promoter, in the absence of other EBNA gene expression, and accompanied by LMP-1 and LMP-2A expression. The EBV genome was present in episomal form and there was evidence for lytic viral replication. This latency pattern is typical of EBV gene expression in nasopharyngeal carcinoma and Hodgkin's disease, and differs from the full spectrum of EBV latent gene expression in most posttransplant lymphoproliferative disorders and from the restricted EBNA-1 expression in Burkitt's lymphoma tissues. The interaction between EBV and NK cells described here has important implications for the pathogenesis and treatment of EBV-infected NK malignancies.

Adolescent↗

PubMed1996

Interferon-inducible protein-10 identified as a mediator of tumor necrosis in vivo.

Human Burkitt lymphoma cell lines give rise to progressively growing subcutaneous tumors in athymic mice. These tumors are induced to regress by inoculation of Epstein-Barr virus-immortalized normal human lymphocytes. In the present study, analysis of profiles of murine cytokine/chemokine gene expression in Burkitt tumor tissues excised from the nude mice showed that expression of the murine alpha-chemokine interferon-inducible protein-10 (IP-10) was higher in the regressing than in the progressive Burkitt tumors. We tested the effects of IP-10 on Burkitt tumor growth in nude mice. Inoculation of established Burkitt tumors either with crude preparations of murine IP-10 or with purified human IP-10 caused visible tumor necrosis in a proportion of the animals, although no complete tumor regressions were observed. Constitutive expression of murine IP-10 in Burkitt cells reduced their ability to grow as subcutaneous tumors, and caused visible tumor necrosis in a proportion of the animals. Histologically, IP-10-treated and IP-10-expressing Burkitt tumors had widespread evidence of tumor tissue necrosis and of capillary damage, including intimal thickening and vascular thrombosis. Thus, IP-10 is an antitumor agent that promotes damage in established tumor vasculature and causes tissue necrosis in human Burkitt lymphomas established subcutaneously in athymic mice.

Animals↗

PubMed1996

The apoptosis-associated gamma-ray response of BCL-X(L) depends on normal p53 function.

We have investigated the effect of DNA damage on the expression of BCL-X, a member of the BCL-2 family. BCL-X mRNA levels were found to increase upon exposure human cells to ionizing radiation (IR). The Bcl-X(L) protein, but not Bcl-X(S), was identified to be induced by IR. Like BAX, another member of the BCL-2 family and a p53-regulated gene, the induction of BCL-X(L) was dependent on normal p53 function and required that cells have an apoptosis-susceptible phenotype. The induction of BCL-X(L) was rapid, transient and dose-dependent. The mRNA level peaked at 4 h and returned to baseline by 24 h post-irradiation. In agreement with the increased transcript level, Bcl-X(L) protein level was also observed to increase in cells with wild-type p53 where IR triggered apoptosis. In addition, a survey of the BCL-X(L) mRNA basal levels in human cells with known apoptotic responses showed that low basal levels of BCL-X(L) mRNA in cells were highly correlated with a strong ability of cells to undergo IR-induced apoptosis. On the other hand, high levels of basal BCL-X(L) were correlated with the resistance of cells to IR-induced apoptosis regardless of p53 status. These results indicate that BCL-2 and BCL-X(L) behave differently in response to DNA damage treatment even though they both are able to protect cells from p53-mediated apoptosis; along with down-regulation of BCL-2, BCL-X(L) was up-regulated by IR in human cells with wild-type p53 and susceptibility to IR-induced apoptosis. We speculate that the physiological function of increased BCL-X(L) protein would be expected to probably limit the severity and length of BAX effect in order to maintain a proper threshold for apoptosis and to complete cell cycle arrest activated by p53.

Apoptosis↗

PubMed1996

A role for the interferon-inducible protein 10 in inhibition of angiogenesis by interleukin-12.

We have developed a nude mouse model in which tumor regression is reproducibly induced by coinjection with or intratumor inoculation of EBV-immortalized B cells. A wide spectrum of tumor-derived human cell lines can be established as subcutaneous tumors in sublethally irradiated athymic mice. Most of these tumors are induced to regress by human B cells immortalized with EBV. The tumor regression process is characterized by superficial necrosis and scarring that progressively extends itself to involve all or most of the tumor. Microscopically, tumor regression is characterized by tumor tissue necrosis, evidence of vascular damage with intimal thickening and capillary thrombosis, and macrophage, but not lymphocyte or neutrophil, infiltration. Profiles of cytokine expression differed between progressive and regressive Burkitt's tumors in that regressive tumors expressed larger levels of TNF-alpha, IL-6, IFN-gamma, IP-10, Mig, and IL-12 p35, but not other chemokines/cytokines. IP-10 and IL-12 were found to act as potent inhibitors of angiogenesis in vivo. IL-12 is an inducer of IFN-gamma and indirectly of IP-10, an IFN-gamma-inducible protein, raising the possibility that the antiangiogenic effect of IL-12 is mediated by IP-10. Previous studies have demonstrated that IL-12 has potent antitumor activity in vivo. Much of this activity was dependent on the presence of IFN-gamma and of immune T cells. The observation, made in our studies, that IP-10 is an inhibitor of angiogenesis raises the possibility that IP-10 might contribute to the antitumor effects of IL-12 by inhibiting angiogenesis. Inhibition of angiogenesis by IP-10 and IL-12 is T-cell independent, suggesting that IL-12 targets at least two compartments, T cells and capillaries, each capable of mediating antitumor effects.

Animals↗

PubMed1996

Activation of naive and memory T cells by interleukin-15.

Interleukin-15 (IL-15), a product of monocytes and other cells, has biological activities similar to those of IL-2, including growth stimulation of activated T cells, induction of cytolytic effector cells, and B-cell costimulation for proliferation and lg production. We report that IL-15 at optimal concentrations rapidly induced memory (CD45RO+) CD4+ and CD8+ T cells and naive (CD45RO-) CD8+ T cells to express the CD69 activation marker followed by proliferation. By contrast, IL-15 failed to induce naive (CD45RO-) CD4+ T cells to express CD69 or to proliferate. Similar findings were obtained with IL-2. Unlike the other T-cell subsets, CD4+ T cells with a naive phenotype expressed little or no IL-2R beta chain, a shared component of the IL-2 and IL-15 receptors required for receptor function. A monoclonal antibody to the IL-2R beta chain, Mik beta 1, reduced CD69 expression and proliferation in CD4+ memory, CD8+ memory, and CD8+ naive T cells activated by IL-15. These results confirm the biological similarities of IL-2 and IL-15. They further document that the pool of naive CD4+ cells, unlike the pool of memory CD4+, memory CD8+, and naive CD8+ cells, is not regulated directly by the T-cell growth factors IL-2 or IL-15.

Antibodies, Monoclonal↗

PubMed1996

Inhibition of angiogenesis by interleukin-12 is mediated by the interferon-inducible protein 10.

Interleukin 12 (IL-12), a multifunctional cytokine produced by macrophages and B-cell lines, induces interferon-gamma (IFN-gamma) production, stimulates growth of both T and natural killer cells, promotes Th1-type helper T-cell responses, and inhibits neovascularization. Because the human interferon-inducible protein 10 (IP-10) can also inhibit neovascularization, we tested whether IP-10, induced by IL-12 through the intermediate IFN-gamma, might be a mediator of IL-12 angiogenesis inhibition. We report here that murine IL-12 profoundly inhibited basic fibroblast growth factor (bFGF)-induced Matrigel neovascularization in vivo, and that this effect of IL-12 was neutralized by systemic administration of antibodies to either murine IFN-gamma or IP-10. Murine IL-12 induced murine IP-10 expression in mouse splenocytes, and human IFN-gamma induced human IP-10 expression in purified human endothelial cells, suggesting that IL-12 can induce IP-10 expression in certain cells. These results document the important role of IP-10 as a mediator of angiogenesis inhibition by IL-12, and raise the possibility that IP-10 may also contribute to the antitumor effect of IL-12.

Animals↗

PubMed1996

Target-induced death by apoptosis in human lymphokine-activated natural killer cells.

Activated human natural killer (NK) cells undergo rapid apoptotic cell death after ligand binding to the Fc receptor (CD16). We examined whether human NK cells die after engagement in cytolytic functions. Peripheral blood NK cells, with and without prior activation in vitro with interleukin-2 (IL-2), were tested for the occurrence of cell death after incubation with K562, the prototype NK-sensitive target cell. A proportion (15.2%) of NK cells that were stimulated for 3 days with IL-2 and then incubated for 4 hours with K562 cells showed rapid cell death, but NK cells not stimulated with IL-2 did not. This cell death was found to involve nuclear condensation and fragmentation and DNA cleavage, all of which are characteristic of apoptosis. These data indicate that a proportion of activated human NK cells undergo apoptosis as they engage in target cell lysis. Target-induced NK cell death may represent an important mechanism for regulation of inflammatory processes involving NK cells.

Apoptosis↗

PubMed1996

Chronic persistent Epstein-Barr virus infection of natural killer cells and B cells associated with granular lymphocytes expansion.

B lymphocytes and epithelial cells are the only cell types known to be infected with Epstein-Barr virus (EBV) in normal individuals. Rarely, EBV also infects other cells, including natural killer (NK) cells, almost always in the context of fatal leukaemias or lymphoproliferative disorders. We report on a 6-year-old previously healthy girl who developed fevers and liver function abnormalities for 3 months. The peripheral blood revealed an abnormal expansion of large granular lymphocytes, comprising 24% of the white blood cells. Flow cytometric analysis of the peripheral blood mononuclear cells showed an abnormal increase of CD16-positive NK cells, 62% of which were EBV-infected by in situ EBER-1 hybridization. The circulating B cells were normal in number, but 18% were infected with EBV by in situ EBER-1 hybridization. Approximately 2 years after resolution of all symptoms and continued good health. 35% of the circulating mononuclear cells were EBV-infected, indicative of persistent expansion of EBV-infected cells. We conclude that abnormal expansions of EBV-infected NK and B cells can be associated with a chronic benign course.

B-Lymphocytes↗

PubMed1996

Juvenile idiopathic stabbing headache.

We report on 83 juvenile patients with idiopathic stabbing headache, subjectively perceived as lasting from a fraction of a second to a few minutes. This sample was selected from among 2543 outpatients referred because of recurrent headache to the Paediatric Neurology Services of Ferrara and Padua (Italy). Other painful syndromes were excluded by clinical examination and appropriate tests. Idiopathic stabbing headache in the pediatric age group, contrary to the adult form, is usually not associated with other primary headache syndromes. We suggest that this clinical picture should be more clearly defined in the future, in order to better understand its relationships with other primary headaches.

Adolescent↗

PubMed1995

Infection of human endothelial cells with Epstein-Barr virus.

Interleukin-6 (IL-6) promotes growth and tumorigenicity of Epstein-Barr virus (EBV)-immortalized B cells, and is abnormally elevated in the serum of solid organ transplant recipients who develop EBV-positive posttransplant lymphoproliferative disease (PTLD), but not in control transplant recipients. Endothelial cells derived from PTLD lesions were found to secrete spontaneously high levels of IL-6 in vitro for up to 4 mo. We examined possible mechanisms for sustained IL-6 production by endothelial cells. Here, we show that EBV can infect endothelial cells in vitro. After 3-4 wk incubation with lethally irradiated EBV-positive, but not EBV-negative cell lines, a proportion of human umbilical cord-derived endothelial cells (HUVECs) expressed in situ the EBV-encoded small RNAs (EBER). Southern blot analysis after polymerase chain reaction showed EBV DNA in HUVEC that had been incubated with lethally irradiated EBV-positive cells, but not in the controls. Exposure of HUVECs to lethally irradiated EBV-positive but not EBV-negative cell lines induced IL-6 production that was sustained for up to 120 d of culture. These studies identify endothelial cells as targets for EBV infection and raise the possibility that this infection may be important in the life cycle and pathology of EBV.

Base Sequence↗