Biomedical subjects

G Tosato

Publications and source records attributed to G Tosato.

At least 73 records · Page 4Linked to original sources

PubMed1995

Human interferon-inducible protein 10 is a potent inhibitor of angiogenesis in vivo.

Human interferon-inducible protein 10 (IP-10), a member of the alpha chemokine family, inhibits bone marrow colony formation, has antitumor activity in vivo, is chemoattractant for human monocytes and T cells, and promotes T cell adhesion to endothelial cells. Here we report that IP-10 is a potent inhibitor of angiogenesis in vivo. IP-10 profoundly inhibited basic fibroblast growth factor-induced neovascularization of Matrigel (prepared by H. K. Kleinman) injected subcutaneously into athymic mice. In addition, IP-10, in a dose-dependent fashion, suppressed endothelial cell differentiation into tubular capillary structures in vitro. IP-10 had no effect on endothelial cell growth, attachment, and migration as assayed in vitro. These results document an important biological property of IP-10 and raise the possibility that IP-10 may participate in the regulation of angiogenesis during inflammation and tumorigenesis.

Amino Acid Sequence↗

PubMed1995

Epstein-Barr virus as an agent of haematological disease.

Epstein-Barr virus (EBV) encodes genes that permit its persistence in human B lymphocytes and genes that ensure its replication in epithelial cells. Immune restraints on the virus are usually so effective that most EBV infections are limited to a minute fraction of B lymphocytes and of epithelial cells. As a result, most EBV infections are never symptomatic. Occasionally, the virus causes disease, often with the cooperation of the immune system or other less characterized cofactors. Infectious mononucleosis, a generally self-limited lymphoproliferative illness common in adolescents and young adults, is due to primary EBV infection and to the brisk cellular immune response it elicits. Lymphoproliferative disorders of EBV-infected B cells arise almost exclusively when cellular immunity is grossly compromised. EBV-positive Burkitt's lymphoma contain a translocated and deregulated c-myc oncogene and EBV-positive non-Hodgkin's lymphomas are characterized by the presence of Reed-Sternberg's and Hodgkin's cells, features that have not been directly linked to EBV. Many recent observations, however, including evidence that virus infection precedes malignant transformation and is often associated with a characteristic pattern of viral gene expression, provide continued interest in the relationship between the virus and these haematological malignancies.

Adolescent↗

PubMed1995

Human and viral interleukin-10 in acute Epstein-Barr virus-induced infectious mononucleosis.

Human interleukin 10 (hIL-10), a product of monocytes, T cells, and B cells, shares extensive structural and functional similarity with viral IL-10 (vIL-10), a product of Epstein-Barr virus (EBV) replication. With two ELISAs, one that recognizes both hIL-10 and vIL-10 and the other specific for vIL-10, IL-10 was measured in serum or plasma and in saliva from 50 patients with acute EBV-induced infectious mononucleosis and from 19 normal subjects. In serum or plasma, 60% of the patients had measurable hIL-10 and/or vIL-10 and 18% had measurable vIL-10. In saliva, 20% of the patients had detectable hIL-10 and/or vIL-10 and none had detectable vIL-10. In contrast, hIL-10 and/or vIL-10 was undetectable in all 19 normal serum or plasma samples (P < .001 vs. patient samples). Among normal saliva samples, 21% had detectable hIL-10 and/or vIL-10 but none had detectable vIL-10. Thus, most patients with acute EBV-induced infectious mononucleosis transiently have abnormally high levels of circulating IL-10.

Acute Disease↗

PubMed1995

Regression of experimental human leukemias and solid tumors induced by Epstein-Barr virus-immortalized B cells.

We previously have reported on an experimental athymic mouse model in which regression of human Burkitt's lymphoma is induced by either coinjection with or intratumor inoculation of Epstein-Barr virus (EBV)-immortalized human B cells. In the current study, we were interested in determining whether the powerful antitumor effects of EBV-immortalized B cells could be effective against a variety of human tumors grown in athymic mice, including acute lymphocytic leukemia, malignant melanoma, acute promyelocytic leukemia, neuroblastoma, lung carcinoma, colon adenocarcinoma, Wilms tumor, Hodgkin's lymphoma, rhabdomyosarcoma and breast adenocarcinoma. We report here the results of experiments in nude mice that demonstrated the potent antitumor effect of EBV-immortalized B cells against human tumors derived from a variety of different tissues.

Animals↗

PubMed1994

A role for deregulated c-Myc expression in apoptosis of Epstein-Barr virus-immortalized B cells.

When deprived of autocrine growth factors, Epstein-Barr virus (EBV)-immortalized B cells stop growing and die. In this study, we show that death of EBV-immortalized cells deprived of autocrine growth factors occurred by apoptosis. Cycloheximide, a protein synthesis inhibitor, inhibited apoptosis, suggesting that de novo protein synthesis is required. Because p53, Bcl-2, and c-Myc were previously implicated in the induction or prevention of apoptosis in other systems, we assessed their possible involvement here. Unlike normal cells that respond to growth factor deprivation by down-regulating c-Myc expression, EBV-immortalized cells continued to express c-Myc, p53, and Bcl-2 at levels comparable to those measured prior to starvation. Consistent with data demonstrating that c-Myc expression is sufficient to drive quiescent cells into the cell cycle, autocrine growth factor-deprived EBV-immortalized cells did not undergo growth arrest but rather continued to proliferate until death, which occurred randomly throughout the cell cycle. In contrast to EBV-immortalized B cells, normal peripheral blood B cells activated in vitro with anti-CD40 monoclonal antibody and interleukin 4 rapidly down-regulated c-Myc expression and underwent growth arrest in response to growth factors and serum deprivation. These findings demonstrated that c-Myc expression is deregulated in EBV-immortalized cells. Addition of antisense oligonucleotides to c-Myc specifically promoted the survival of starved EBV-immortalized cells and suppressed growth of nonstarved EBV-immortalized cells. Thus, deregulated expression of c-Myc in EBV-immortalized cells promotes proliferation and apoptosis following autocrine growth factor deprivation.

Apoptosis↗

PubMed1994

Interleukin-10 suppresses human immunodeficiency virus-1 replication in vitro in cells of the monocyte/macrophage lineage.

The cytokine interleukin-10 (IL-10) has been implicated in the pathogenesis of a number of disease states, including Epstein-Barr virus and human immunodeficiency virus (HIV-1) infections. In the acquired immunodeficiency syndrome (AIDS), it has been suggested that IL-10 may have a deleterious effect by suppressing cell-mediated immunity. However, there are few data on its direct effects on HIV-1 replication. In the present study, we have found that recombinant human IL-10 (rhIL-10), present during days 0 through 2, potently inhibits HIV production in elutriated monocyte/macrophage (M/M) cultures with a 50% inhibitory concentration (IC50) of approximately 0.03 U/mL. This effect did not appear to be caused by toxicity to M/M because there was no change in cell viability, ability to phagocytose latex beads, or protein synthesis as measured by [3H]-leucine incorporation, at doses of rhIL-10 that inhibit viral replication. In addition, lipopolysaccharide-induced production of IL-1 beta, IL-6, or tumor necrosis factor-alpha was not affected at these doses, nor were human mononuclear cell proliferative responses to phytohemagglutinin, OKT3 antibody, or tetanus toxoid. HIV-1 replication was similarly decreased by rhIL-10 in the monocytoid line U937 without signs of cellular toxicity. However, these effects required much higher concentrations of rhIL-10, and viral production was only partially suppressed. rhIL-10 also slightly inhibited HIV-induced cytopathicity in ATH-8, a tetanus toxoid-specific, retrovirally immortalized T-cell line, but had no effect on HIV replication in the H9 and MOLT-4 T cell lines. Thus, rhIL-10 appears to inhibit HIV replication predominantly in cells of the M/M lineage. This effect may serve to reduce viral production in patients with AIDS. However, additional studies will be needed to more precisely define its physiologic role in this disease.

CD4-Positive T-Lymphocytes↗

PubMed1994

Regression of experimental Burkitt's lymphoma induced by Epstein-Barr virus-immortalized human B cells.

Epstein-Barr virus (EBV)-immortalized human B cells survive only transiently when injected subcutaneously into athymic mice, whereas Burkitt's lymphoma cells give rise to progressively growing subcutaneous tumors. In this study, we tested whether these Burkitt's tumors could be induced to regress via a bystander effect induced by EBV-immortalized B cells. Simultaneous inoculation of EBV-immortalized B cells and Burkitt's lymphoma cells in the same subcutaneous site resulted in tumors that regressed with necrosis and scarring. Similarly, simultaneous inoculation of EBV-immortalized B cells and Burkitt's lymphoma cells in separate subcutaneous sites resulted in regression of a proportion of the Burkitt's tumors. Furthermore, most of the established human Burkitt's tumors regressed with necrosis and scarring after intratumor inoculations with EBV-immortalized B cells. The EBV-immortalized B cells continued to exert this antitumor effect even when killed with irradiation. The experimental approach to Burkitt's lymphoma treatment described here exploits the ability of athymic mice to reject EBV-immortalized B cells to target an effective antitumor response to malignant cells normally incapable of eliciting it.

Animals↗

PubMed1994

Interleukin-10 inhibits apoptotic cell death in infectious mononucleosis T cells.

T lymphocytes from patients with acute EBV-induced infectious mononucleosis rapidly die by apoptosis in vitro. Because human and viral IL-10 are likely to be induced during acute EBV infection and display a variety of functions on human T cells, we examined IL-10 effects on infectious mononucleosis T cell death. After 12 h of incubation in medium alone, only 35.6 (+/- 8.2%) of the originally seeded infectious mononucleosis T cells were viable. Addition of human IL-10 (100 U/ml) to T cell cultures significantly improved recovery of viable cells (71.3 +/- 6.2%, P = 0.0156). Viral IL-10 had comparable effects to human IL-10 in this system. Protection from death by human and viral IL-10 (100 U/ml) was dose dependent and continued over a 6-d culture period. The human IL-10 effect was neutralized by the anti-human IL-10 mAb 19F1. Morphology and analysis of DNA after separation on agarose gels showed that IL-10 inhibits loss of cell volume, chromatin condensation, and DNA fragmentation, characteristics of death by apoptosis. As assessed by [3H]thymidine incorporation, the T cells were not induced to proliferate by IL-10 above the level exhibited when first removed from blood. T cells protected from death by IL-10 proliferated to IL-2 and spontaneously killed sensitive targets as effectively as medium-precultured T cells. Thus, IL-10 promotes the survival of infectious mononucleosis T cells otherwise destined to die by apoptosis and may be critical for the establishment of immunologic memory after resolution of the illness.

Adolescent↗

PubMed1993

Human interleukin-10 can directly inhibit T-cell growth.

Human interleukin-10 (IL-10) inhibits T-cell proliferation and cytokine production in the presence of monocytes. In this study, we have investigated whether IL-10 can directly inhibit T cells. Highly purified peripheral blood T cells containing less than 0.1% CD14+ cells and unresponsive to phytohemagglutinin (PHA), were growth-inhibited by IL-10 when stimulated with immobilized OKT3 monoclonal antibody (MoAb; 55.4% inhibition). This effect was neutralized by the murine MoAb 19F1 directed against human IL-10. In addition, IL-10 inhibited by 52.5% the proliferation of a human tetanus toxoid-specific T-cell clone (TM11) induced by immobilized OKT3 MoAb in the absence of antigen-presenting function. T-cell growth inhibition by IL-10 did not reflect a cytokine-induced change in the kinetics of T-cell response to immobilized OKT3 MoAb, and was observed over a wide range of cell and OKT3 MoAb concentrations. Addition of 1% to 5% monocytes to highly purified peripheral blood T cells resulted in the emergence of proliferation to PHA and to soluble OKT3 MoAb, but did not significantly affect levels of growth inhibition by IL-10 in the presence of immobilized OKT3 MoAb. Similarly, addition of 10% monocytes to the TM11 T-cell clone resulted in the emergence of proliferation in response to tetanus toxoid, but did not significantly influence growth inhibition by IL-10 in the presence of immobilized OKT3 MoAb. When stimulated with immobilized OKT3 MoAb in the absence of accessory cells, T cells secreted IL-2. Secretion of IL-2 under these conditions was inhibited by IL-10 (51.5% inhibition). Thus, IL-10 can directly inhibit growth and IL-2 production in T cells triggered by immobilized OKT3 MoAb in the absence of monocytes.

CD3 Complex↗

PubMed1993

A mechanism of T cell regulation of Epstein-Barr virus latency.

The tumorigenic potential of B lymphocytes latently infected with EBV is effectively controlled by T cell immunity. The mechanisms of this T cell regulation, however, are incompletely understood. In this study, T lymphocytes were found to proliferate in response to serum-free supernatants of EBV-immortalized cells and to deplete them of growth factors required by the immortalized B cells for autocrine growth. Lactic acid was reported to account for approximately 90% of the autocrine growth factor activity in serum-free supernatants of EBV-immortalized cell lines. Synthetic lactic acid was now found to promote growth in activated T cells. In addition, B cell suppression resulting from coculture of EBV-infected B cells with autologous T cells was reversed by the addition of supernatants from EBV-immortalized cell lines. Thus, T cell competition for growth factors produced and utilized by EBV-immortalized B cells for continuous proliferation may represent an important and novel regulatory mechanism for the maintenance of EBV latency in B lymphocytes.

B-Lymphocytes↗

PubMed1993

NIH conference. Epstein-Barr virus infections: biology, pathogenesis, and management.

Epstein-Barr virus (EBV) encodes genes that ensure its persistence in human B lymphocytes. Some of the genes encourage B-cell proliferation; others are poised to evade or defeat immune recognition. Immune restraints on the virus, however, are typically so effective that most infections are never symptomatic. In contrast, acute infectious mononucleosis, a self-limited lymphoproliferative illness, is common in adolescents and young adults. Unbridled proliferative illnesses arise when cellular immunity is grossly defective. Treatment of EBV-associated syndromes is largely supportive. Antiviral drugs have no proven role except in patients with oral hairy leukoplakia. Vaccine development is technically feasible but is not considered a high priority for developed nations.

B-Lymphocytes↗

PubMed1993

Association of interleukin-6 in the pathogenesis of acutely fatal SIVsmm/PBj-14 in pigtailed macaques.

Infection with a variant of simian immunodeficiency virus (SIVsmm/PBj-14) causes death in juvenile pigtailed macaques within 8 days of infection. The primary pathology is localized to the lymphoid tissues of the gut and spleen. Although the virus is present, the lesions are most consistent with acute reactive inflammation. We studied the serum and tissues for evidence of acute cytokine production often associated with acute inflammation. One factor, IL-6, was found to be significantly increased (> 1000-fold) over all other measured cytokines in all the pigtailed macaques who died acutely. Increased levels of IL-6 were found both in the serum and in the inflamed tissues. mRNA for IL-6 was found in the tissues with the highest protein levels of IL-6. The marked increase in IL-6 and IL-6 mRNA correlated with the virus levels in the tissues and serum as determined by viral isolation, immunohistochemistry, and Northern blot analysis. These findings suggest that the underlying pathogenesis of primary tissue damage, necrosis, and death by PBj-14 is the induction of cytokine production. Although the presence of the virus may be critical for the initiation of these events, the intense inflammatory reaction is associated with the cause of death.

Animals↗

PubMed1993

IL-10 inhibits apoptotic cell death in human T cells starved of IL-2.

IL-10 was originally described as an inhibitory factor produced by murine Th2 lymphocytes that suppresses IFN-gamma production by activated murine Th1 lymphocytes. In this study, we have analyzed the effect of human IL-10 on human T cell death induced by IL-2 deprivation. IL-2-dependent T lymphocytes rapidly die when deprived of IL-2. This cell death was found to involve loss of cell volume, chromatin condensation, and DNA fragmentation, all characteristic of apoptosis. After 2 days incubation in culture medium without IL-2, the viability of TM11 cells (a tetanus toxoid-specific T cell line) and of activated peripheral blood T cells decreased from > 98% to 34.3 (+/- 2.9) and 39.7 (+/- 5.5%) respectively. Addition of purified human IL-10 (100 U/ml) to these IL-2-starved cells significantly improved cell viability (66.0 +/- 6.0 and 73.1 +/- 12.3% respectively, P = 0.0051). This protective effect of IL-10 was dose-dependent and was neutralized by the anti-human IL-10 mAb 19F1. It was neither accompanied by T cell growth stimulation as judged by [3H]thymidine incorporation nor neutralized by anti-IL-2 or anti-IL-2 receptor (CD25) antibodies. Analysis of DNA after separation on agarose gels revealed that IL-10 inhibits DNA fragmentation in IL-2-starved T cells. T cells protected from death by IL-10 were indistinguishable from IL-10-untreated viable T cells in the ability to proliferate in response to IL-2. Thus, another property of IL-10 is to promote the survival of IL-2-dependent T cells otherwise destined to die by apoptosis.

Apoptosis↗

PubMed1993

Heterotransplantation of human Burkitt's lymphoma cell lines in athymic nude mice: tumor-host relationships.

We have explored the factors which influence tumorigenicity of Burkitt's lymphoma (BL) cell lines in athymic nude mice. Four cell lines, Namalwa, CA46, JD38, and ST486 revealed tumor incidence of 63.5, 69.0, 45.5 and 10.0%, respectively, in nude mice, but there was no correlation between tumor incidence and growth rate in vivo. Thus, growth rate and tumorigenicity are dependent upon different biochemical pathways. Evidence of tumor cell heterogeneity was demonstrated in the CA46 parent cell line. Five subclones derived from CA46 revealed varying degrees of tumor incidence (but very similar growth rates) that were consistently less than the parent CA46 line. Line 5, for example, produced 5.7-fold less tumors than the parent line. None of the BL cell lines or clones produced any metastatic lesions in liver, lung, brain, bone marrow or spleen in athymic nude mice. Northern blot analysis of c-myc mRNA levels in different BL cell lines revealed a possible relationship between percent tumor takes (but not growth rates) and the level of c-myc oncogene expression. However, no correlation was observed between c-myc mRNA levels and tumor incidence or growth rates among the CA46 clones. There was no correlation between the ability of the cell lines and the subclones to either secrete growth factors or to respond to growth factors secreted by Epstein-Barr virus-induced lymphoblastoid cells or lipopolysaccharide-activated monocytes, and their growth rates or percent tumor takes in mice. Comparison of tumor incidence and growth rates in irradiated and unirradiated mice showed that host factors influenced the growth of BL in nude mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Interleukin-6 production in posttransplant lymphoproliferative disease.

IL-6, a multifunctional cytokine produced by monocytes, fibroblasts, and endothelial cells, promotes the growth of EBV-immortalized B cells in vitro and renders these cells tumorigenic in athymic mice. In the present study, serum/plasma IL-6 bioactivity was found to be abnormally elevated, albeit transiently, in 17 of 18 solid organ transplant recipients with posttransplant lymphoproliferative disease (PTLD), with a mean maximal level of 196.7 U/ml. This represents a 16.4 increase above the normal mean (11.3 U/ml). In contrast, only 3 of 10 solid organ transplant recipients with uncomplicated courses posttransplant had abnormally elevated serum/plasma IL-6 bioactivity (mean maximal level 41.4 U/ml, P = 0.0007). When transferred to single cell culture, the 11 PTLD tissues produced 640 to 1.25 x 10(6) IL-6 U/ml in the culture supernatant, with a mean maximal level of 35,025 IL-6 U/ml. Cell separation experiments demonstrated that the adherent cells, identified as non-B cells, were the principal source of IL-6 production in vitro by PTLD tissue. Control cultures of inflammatory lymphoid tissue negative for lymphoproliferative disease as well as of PBL from patients with acute EBV-induced infectious mononucleosis consistently produced < 10 IL-6 U/ml. Thus, IL-6 is produced at high levels by PTLD tissues and may play a critical role in the pathogenesis of PTLD.

Adult↗

PubMed1993

Parameters affecting the development of non-Hodgkin's lymphoma in patients with severe human immunodeficiency virus infection receiving antiretroviral therapy.

PURPOSE: To investigate the occurrence of non-Hodgkin's lymphoma (NHL) in human immunodeficiency virus (HIV)-infected patients receiving long-term antiretroviral therapy and factors associated with the development of these lymphomas. PATIENTS AND METHODS: The charts of 55 patients with advanced HIV infection receiving zidovudine (formerly known as azidothymidine [AZT])-based therapy and 61 patients receiving dideoxyinosine (ddI) were examined for the occurrence of NHL. Stored samples from the AZT-based treatment cohort were examined retrospectively for parameters predictive of the subsequent development of lymphoma. RESULTS: Eight of 55 patients receiving AZT-based therapy developed NHL, yielding an estimated probability of 12% (95% confidence interval [CI], 4.7% to 27.1%) after 24 months, and 29.2% (95% CI, 15.2% to 48.7%) after 36 months. Four of 61 patients receiving ddI developed NHL, yielding a 6.2% (95% CI, 2.1% to 17%) estimated probability after 24 months, and 9.5% (95% CI, 3.6% to 22.8%) after 36 months. The difference between these cohorts was not significant (two-tailed P [P2] = .13). Patients with less than 50 CD4 cells/microL developed NHL at a significantly higher rate (P2 = .0085). This was particularly true for patients who presented with primary CNS lymphoma (PCNSL). For patients receiving AZT-based therapy, pretreatment serum interleukin-6 (IL-6) levels were somewhat higher in those who subsequently developed NHL than in those who did not (P2 = .048). CONCLUSION: HIV-infected patients with profound immunodeficiency, especially those with less than 50 CD4 cells/microL, are at substantial risk of developing NHL and particularly PCNSL. Additional studies are needed to define the role of other factors such as IL-6 in the pathogenesis of these opportunistic tumors.

CD4-Positive T-Lymphocytes↗

PubMed1992

IL-10 inhibits human T cell proliferation and IL-2 production.

Human IL-10 has been reported previously to inhibit the secretion of IFN-gamma in PBMC. In this study, we have found that human IL-10 inhibits T cell proliferation to either mitogen or anti-CD3 mAb in the presence of accessory cells. Inhibited T cell growth by IL-10 was associated with reduced production of IFN-gamma and IL-2. Studies of T cell subset inhibition by human IL-10 showed that CD4+, CD8+, CD45RA high, and CD45RA low cells are all growth inhibited to a similar degree. Dose response experiments demonstrated that IL-10 inhibits secretion of IFN-gamma more readily than T cell proliferation to mitogen. In addition, IL-2 and IL-4 added exogenously to IL-10 suppressed T cell cultures reversed completely the inhibition of T cell proliferation, but had little or no effect on inhibition of IFN-gamma production. Thus, in addition to its previously reported biologic properties, IL-10 inhibits human T cell proliferation and IL-2 production in response to mitogen. Inhibition of IFN-gamma production by IL-10 appears to be independent of the cytokine effect of IL-2 production.

Humans↗

PubMed1992

Regulation of B-cell growth and immunoglobulin gene transcription by interleukin-6.

Interleukin-6 (IL-6) stimulates growth and immunoglobulin (lg) secretion in Epstein-Barr virus (EBV)-infected B cells. In this study, we demonstrate that B-cell activation by IL-6 is associated with an initial induction of c-myc, a gene believed to act as a competence factor for increased RNA transcription and DNA replication, and by increases in DNA, RNA, and protein synthesis, as well as cell number. IL-6 increased the levels of lg mRNA per cell in comparison to a non-cycle-dependent cellular mRNA, tubulin. However, two other cell cycle-dependent cellular mRNAs, c-myc and actin, were also induced by IL-6 comparable to lg mRNAs. Increased levels of lg mRNA were not due to significant changes in RNA turnover, but appeared to reflect increased levels of RNA transcription. Together, these findings support the notion that IL-6 plays an important role as a stimulator of DNA and RNA synthesis in EBV-activated B cells.

Actins↗