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Biomedical subjects

G Tosato

Publications and source records attributed to G Tosato.

At least 19 recordsLinked to original sources
PubMed2007

Interactions between HIV-1 Tat and KSHV.

Since the advent of the HIV-1 pandemic, a close association between HIV-1 infection and the development of selected types of cancers has been brought to light. The discovery of Kaposi sarcoma-associated herpesvirus (KSHV) has led to significant advances in uncovering the virological and molecular mechanisms involved in the pathogenesis of AIDS-related malignancies. Extensive evidence indicates that HIV-1 trans-activating protein Tat plays an oncogenic role in the development of KSHV-associated neoplasms. Comprehensive knowledge of the functions of Tat-1 together with the KSHV genes will contribute to a better understanding of the pathogenesis of virus-associated cancers and the interaction of viruses with their hosts.

Amino Acid Sequence↗
PubMed2001

Receptor engagement by viral interleukin-6 encoded by Kaposi sarcoma-associated herpesvirus.

Receptor usage by viral interleukin-6 (vIL-6), a virokine encoded by Kaposi sarcoma- associated herpesvirus, is an issue of controversy. Recently, the crystal structure of vIL-6 identified vIL-6 sites II and III as directly binding to glycoprotein (gp)130, the common signal transducer for the IL-6 family of cytokines. Site I of vIL-6, however, comprising the outward helical face of vIL-6, where human IL-6 (hIL-6) would interact with the specific alpha-chain IL-6 receptor (IL-6R), is accessible and not occupied by gp130. This study examined whether this unused vIL-6 surface is available for IL-6R binding. By enzyme-linked immunosorbent assay, vIL-6 bound to soluble gp130 (sgp130) but not to soluble IL-6R (sIL-6R). Using plasmon surface resonance, vIL-6 bound to sgp130 with a dissociation constant of 2.5 microM, corresponding to 1000-fold lower affinity than that of hIL-6/sIL-6R complex for gp130. sIL-6R neither bound to vIL-6 nor affected vIL-6 binding to gp130. In bioassays, vIL-6 activity was neutralized by 4 monoclonal antibodies (mAbs) recognizing a domain within vIL-6 site I, mapped to the C-terminal part of the AB-loop and the beginning of helix B. The homologous region in hIL-6 participates in site I binding to IL-6R. In addition, binding of vIL-6 to sgp130 was interfered with specifically by the 4 neutralizing anti-vIL-6 mAbs. Based on the vIL-6 crystal structure, the vIL-6 neutralizing mAbs map outside the binding interface to gp130, suggesting that they either produce allosteric changes or block necessary conformational changes in vIL-6 preceding its binding to gp130. These results document that vIL-6 does not bind IL-6R and suggest that conformational change may be critical to vIL-6 function.

Allosteric Regulation↗
PubMed2001

Diagnosis of atypical cases of infectious mononucleosis.

The variable manifestations of infectious mononucleosis rarely cause clinicians to suspect primary Epstein-Barr virus or cytomegalovirus infection; consequently, costly diagnostic tests and unnecessary treatments are undertaken. Seventeen cases of clinically atypical and 11 cases of clinically typical infectious mononucleosis were diagnosed through screening for atypical and apoptotic lymphocytes in the peripheral blood samples by means of an automated hematologic analyzer. Atypical and typical cases did not differ significantly with respect to peripheral white blood cell counts; percentages of lymphocytes, atypical lymphocytes, CD4(+) lymphocytes, human leukocyte antigen--DR positivity in CD3 lymphocytes, or apoptotic cells in blood smear after incubation; or levels of aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase. Only the percentage of CD8(+) lymphocytes was significantly higher in patients with typical infectious mononucleosis than it was in patients with atypical infectious mononucleosis. Because certain atypical cases of infectious mononucleosis display laboratory abnormalities that are characteristic of typical infectious mononucleosis, enhanced awareness can help in the diagnosis.

Adult↗
PubMed2001

Hypoxia induces lytic replication of Kaposi sarcoma-associated herpesvirus.

There is substantial evidence that Kaposi sarcoma-associated herpesvirus (KSHV) plays an important role in the pathogenesis of all forms of Kaposi sarcoma (KS). It has been noted that KS commonly occurs in locations, such as the feet, where tissue may be poorly oxygenated. On the basis of this observation, the potential role of hypoxia in the reactivation of KSHV replication was explored by studying 2 KSHV-infected primary effusion lymphoma B-cell lines (BC-3 and BCBL-1) latently infected with KSHV. Acute and chronic exposure of these cells to hypoxia (1% O(2)) induced KSHV lytic replication, as indicated by an increase in intracellular lytic protein expression and detection of virus in cell supernatants by Western immunoblotting. In addition, hypoxia increased the levels of secreted viral interleukin-6. Moreover, hypoxia enhanced the lytic replication initiated by the viral inducer 12-O-tetradecanoylphorbol-13-acetate. Desferoxamine and cobalt chloride, 2 compounds that increase the intracellular levels of hypoxia-inducible factor 1, were also able to induce KSHV lytic replication. These studies suggest that hypoxia is an inducer of KSHV replication. This process may play an important role in the pathogenesis of KS.

B-Lymphocytes↗
PubMed2001

Detection of viral interleukin-6 in Kaposi sarcoma-associated herpesvirus-linked disorders.

Expression of a viral interleukin-6 (vIL-6) has been detected in certain Kaposi sarcoma (KS)--associated herpesvirus positive (KSHV(+)) lesions. The release of vIL-6 systemically and its contribution to the pathogenesis of HIV-related malignancies was studied. Serum vIL-6 was detected in 13 (38.2%) of 34 HIV(+) patients with KS, in 6 (85.7%) of 7 HIV(+) patients with primary effusion lymphoma (PEL) and/or multicentric Castleman disease (MCD), and in 18 (60.0%) of 30 HIV(+), mostly homosexual, individuals without KS, MCD, or PEL. By contrast, serum vIL-6 was detected in only 3 (23.1%) of 13 patients with classic KS, 1 (2.5%) of 40 blood donors from the United States, and 4 (19.0%) of 21 blood donors from Italy. Circulating vIL-6 levels were associated with HIV(+) status (P <.0001). However, within the HIV(+) cohort, serum vIL-6 levels were not associated with the occurrence of KSHV-associated malignancies (P =.43). (Blood. 2001;97:2173-2176)

Anti-HIV Agents↗
PubMed2001

Chemokine gene expression and clonal analysis of B cells in tissues involved by lymphoid interstitial pneumonitis from HIV-infected pediatric patients.

Lymphoid interstitial pneumonitis (LIP), a frequent pulmonary complication in HIV-infected pediatric patients, is characterized histologically by marked infiltration of lymphoid cells. We sought to evaluate the nature and pathogenesis of the lymphoid infiltrates and to examine the relationship of LIP to pulmonary MALT lymphoma that has been described in pediatric HIV positive patients. To examine the potential contribution of chemokines and cytokines to the inflammatory cell recruitment in tissues involved by lymphoid interstitial pneumonitis from HIV-infected pediatric patients, RNA was extracted from paraffin-embedded tissues from five lung biopsies in four pediatric HIV-positive patients and from five control, normal lung biopsies in five HIV-negative patients and was analyzed by semiquantitative RT-PCR for the expression of cytokines (TNF-alpha, GM-CSF, IFN-gamma, IL-4, IL-6, IL-10, and IL-18) and chemokines (IP-10, Mig, regulated upon activation, normal T expressed and secreted [RANTES], and MIP1-alpha and beta) after normalization for G3PDH. Expression of IL-18 was increased, as well as expression of IFN-gamma-inducible chemokines IP-10 and Mig in LIP tissues compared with controls. RANTES and MIP1-alpha and -beta were also increased in pediatric LIP lesions compared with controls. In contrast, expression of TNF-alpha, GM-CSF, IL-10, and IL-6 was variable in LIP tissues and controls. In addition, clonality of the B-cell population was evaluated by VDJ-PCR. A polyclonal B-cell population was shown in all five biopsies from five patients with LIP; and in one patient with concurrent LIP and MALT lymphoma, a band of increased intensity was observed in the LIP biopsy that was identical in size to the monoclonal band in the concurrent MALT lymphoma biopsy. These results provide evidence of high-level expression of certain chemokines in lymphoid interstitial pneumonitis tissues and suggest that chemokines and cytokines may play an important role in the recruitment of inflammatory cell infiltrates into these tissues. In addition, LIP may represent an early stage of MALT lymphoma or an immunologic response to a chronic antigenic stimulus that may provide a milieu or microenvironment for the evolution of a monoclonal B-cell population.

Adolescent↗
PubMed2001

Macrophage-derived chemokine expression in classical Hodgkin's lymphoma: application of tissue microarrays.

Hodgkin's disease (HD) is a lymphoid malignancy characterized by the presence of Reed-Sternberg (RS) and Hodgkin's cells in a background of mixed inflammatory cells and stromal reaction. Studies have documented that HD is a neoplasm associated with abnormal cytokine and chemokine production. To define the expression of macrophage-derived chemokine (MDC) in HD, 57 cases (18 lymphocyte predominant, 11 mixed cellularity, 28 nodular sclerosis) were stained for MDC by immunohistochemistry and compared with reactive lymph nodes as controls. MDC was expressed by RS cells in classical HD (CHD) and showed a distinct cytoplasmic and Golgi localization. Accumulating evidence suggests that lymphocyte-predominant HD (LPHD) represents an entity distinct from CHD, with different biological properties and clinical course. On the basis of the high level of MDC staining alone, CHD could be distinguished from LPHD (P <.001), which showed only faint staining of scattered histiocytes similar to control tissues. CHD cases with high MDC mRNA levels showed high levels of MDC protein expression by immunohistochemistry (P <.001) and significant eosinophil infiltration, suggesting that MDC may represent another molecule that plays a critical role in eosinophil recruitment. We also analyzed 102 cases of non-Hodgkin's lymphoma and normal spleen, lymph node, and thymic tissue. High levels of MDC expression were specific to CHD cases because only low levels of MDC were observed in a minor subset of LPHD, NHL or normal lymphoid tissues.

Adolescent↗
PubMed2001

The angiogenesis inhibitor vasostatin does not impair wound healing at tumor-inhibiting doses.

Inhibition of tumor angiogenesis represents a promising new approach for the treatment of human cancers. It has remained unclear, however, whether inhibition of tumor angiogenesis may also result in impaired wound healing, a process thought to be angiogenesis dependent. To determine the effects of the angiogenesis inhibitor vasostatin, a 180 amino acid calreticulin fragment, on wound healing at tumor inhibiting doses, full-thickness wounds were generated on the back of nude mice that were also injected intradermally with CA46 Burkitt lymphoma cells. Mice were treated with daily injections of vasostatin or vehicle control at a site between the wounds and the transplanted tumor cells over 14 d. Vasostatin potently inhibited tumor growth and significantly reduced tumor angiogenesis, as measured by computer-assisted image analysis of CD31-stained tumor sections. Moreover, vasostatin treatment resulted in an increased fraction of mature tumor-associated blood vessels. In contrast, no impairment of wound healing was observed in vasostatin-treated mice, despite a significantly reduced vascularity of the wound granulation tissue. Our results reveal a different sensitivity of malignant tumor growth and physiologic wound healing to inhibition of angiogenesis, and they suggest that therapeutic inhibition of tumor angiogenesis may be achieved without impairment of tissue repair.

Angiogenesis Inhibitors↗
PubMed2001

Vascular endothelial growth factor/vascular permeability factor in the pathogenesis of primary effusion lymphomas.

Primary effusion lymphomas (PEL), rare lymphomas associated with Kaposi's sarcoma-associated herpesvirus (KSHV or HHV-8) infection, present as malignant lymphomatous effusions in body cavities. We have recently found that PEL effusions contain high levels of vascular endothelial growth factor/vascular permeability factor (VEGF/VPF). VEGF/VPF, an important regulator of tumor-angiogenesis in vivo, exerts its effects acting through the receptors KDR/Flk-1 and Flt-1 on the endothelial cell membrane. In vitro, the PEL cell lines BC-1, BCP-1 and BCBL-1 produce high levels of VEGF. RT-PCR analysis of RNA from the PEL cell lines amplified the three VEGF/VPF secreted isoforms, VEGF/VPF(121), VEGF/VPF(145) and VEGF/VPF(165). Two of the PEL cell lines express the VEGF/VPF receptor Flt-1, but VEGF did not stimulate proliferation in these cells. SCID/beige mice inoculated intraperitoneally with BCBL-1 cells developed effusion lymphoma of human cell origin with prominent bloody ascites. In contrast, none of the mice treated with a neutralizing anti-human VEGF/VPF antibody developed ascites and effusion lymphoma. Although the precise mechanisms by which VEGF/VPF can promote vascular permeability are not fully understood, VEGF/VPF stimulation of vascular leakage may be critical to the pathogenesis of PEL.

Animals↗
PubMed2001

Interleukin-18 expression induced by Epstein-Barr virus-infected cells.

Human Epstein-Barr virus (EBV)-negative Burkitt lymphomas cells usually grow as malignant subcutaneous tumors in athymic mice, but these tumors regress when the Burkitt cells are injected in conjunction with EBV-positive lymphoblastoid cells or when the Burkitt cells are transfected with the EBV latent membrane protein-1 (LMP-1) gene. Tumor regression is mediated, in part, by murine interferon gamma (IFN-gamma) and the IFN-gamma-induced murine chemokine IFN-gamma-inducible protein-10 (IP-10). The mechanisms by which EBV-LMP-1 promotes the expression of IFN-gamma has remained unclear. Here we show that murine interleukin (IL)-18 was consistently expressed in regressing Burkitt tumors but was either expressed at low levels or absent from progressively growing Burkitt tumors. By immunohistochemical methods, IL-18 protein was visualized in regressing but not in progressively growing Burkitt tumors. In contrast, IL-12 p35 and IL-12 p40 were only rarely expressed in regressing Burkitt tumors. In splenocyte cultures, EBV-infected lymphoblastoid cells and LMP-1-transfected Burkitt cells promoted the expression of IL-18 but not the expression of IL-12 p35 and IL-12 p40. A neutralizing antibody directed at murine IL-18 reduced murine IP-10 expression induced by EBV-immortalized cells in splenocyte cultures. These results provide evidence for IL-18 expression in response to a viral latency protein and suggest that IL-18 may play an important role as an endogenous inducer of IFN-gamma expression, thereby contributing to tumor regression.

Animals↗
PubMed2000

Effective targeting of tumor vasculature by the angiogenesis inhibitors vasostatin and interleukin-12.

Solid tumors are dependent on preexisting vasculature and neovascularization for their growth. Successful cancer therapies targeting the tumor vasculature would be expected to block the existing tumor blood supply and to prevent tumor neovascularization. We tested the antitumor activity of experimental therapy with 2 distinct antiangiogenic drugs. Vasostatin inhibits endothelial cell growth and neovascularization, and interleukin-12 (IL-12) targets the tumor vasculature acting through interferon-gamma (IFN-gamma) and the downstream chemokines interferon-inducible protein-10 (IP-10) and monokine induced by IFN-gamma. Individually, vasostatin and IL-12 produced distinct efficacy profiles in trials aimed at reducing tumor growth in athymic mice. In combination, these inhibitors halted the growth of human Burkitt lymphoma, colon carcinoma, and ovarian carcinoma. Thus, cancer therapy that combines distinct inhibitors of angiogenesis is a novel, effective strategy for the experimental treatment of cancer. (Blood. 2000;96:1900-1905)

Angiogenesis Inhibitors↗
PubMed2000

Viral and cellular cytokines in AIDS-related malignant lymphomatous effusions.

Kaposi sarcoma-associated herpesvirus encodes viral IL-6 (vIL-6). To investigate the potential role of vIL-6 in the pathogenesis of human immunodeficiency virus (HIV)- related primary effusion lymphomas (PEL), a sensitive enzyme-linked immunosorbent assay was developed for vIL-6 and applied to the study of PEL. Whereas vIL-6 was detectable in 6 of 8 PEL effusions (range, 1390-66 630 pg/mL), it was not detectable in any of the control effusions. As expected, all PEL effusions contained human IL-6 (range, 957-37 494 pg/mL), and 7 of 8 contained detectable human IL-10 (range, 66-2,521,297 pg/mL). Human and vIL-6 have previously been shown to induce vascular endothelial growth factor, which in turn can increase vascular permeability. The results of the current study suggest that these cytokines play a central role in the pathogenesis and manifestations of PEL. (Blood. 2000;96:1599-1601)

Body Fluids↗
PubMed2000

Contribution of automated hematology analysis to the detection of apoptosis in peripheral blood lymphocytes.

Automated hematology analyzers (analyzers) can provide complete blood counts and white blood cell (WBC) differentials in clinical laboratories and alert users to the presence of quantitative and qualitative cell abnormalities through cautionary flags. In this study, we applied analyzers to the screening of apoptotic cells in peripheral blood and examined the triggering capacity of cautionary flags to detect apoptotic cell populations. EDTA-anticoagulated fresh peripheral blood from patients with acute infectious mononucleosis containing atypical lymphocytes comprising 12.3 +/- 4. 0% of WBC was applied to a Beckman-Coulter MAXM A/L Retic (MAXM) analyzer. The lymphocyte cluster spread upward in VOLUME/DF1 scattergrams and the threshold lines between lymphocyte and monocyte clusters shifted upward. Flags for the number and percentage of lymphocytes, variant lymphocytes, and blast cells were generally present for samples containing atypical lymphocytes. After the blood from acute infectious mononucleosis patients was incubated for 4 h at 37 degrees C, peripheral blood smears revealed the presence of morphologically apoptotic cells comprising 9.0 +/- 4.2% of WBC and a comparable reduction of lymphocytes. On the MAXM analyzer, the apoptotic lymphocyte cluster appeared under the lymphocyte cluster in VOLUME/DF1 scattergrams. However, no specific flag was present to alert users to the presence of the apoptotic lymphocyte cluster. We conclude that visual inspection of scattergrams generated by the MAXM analyzer can be useful for the detection of apoptotic lymphocytes in peripheral blood. Cytometry (Comm. Clin. Cytometry) 42:209-214, 2000. Published 2000 Wiley-Liss, Inc.

Apoptosis↗
PubMed2000

Large deletion of the X-linked lymphoproliferative disease gene detected by fluorescence in situ hybridization.

The X-linked lymphoproliferative disease (XLP) is an inherited immunodeficiency characterized by an abnormal responses to infection with Epstein-Barr virus (EBV), resulting in fatal infectious mononucleosis, hypogammaglobulinemia, virus-associated hemophagocytic syndrome, and malignant lymphoma. Mutations in the gene coding for a T cell-specific SLAM-associated protein (SAP) have been recently identified in XLP patients. We report on a 1-year-old boy representing fulminant hemophagocytic syndrome. He developed high fever, lymphadenopathy, hepatosplenomegaly with liver dysfunction, and pancytopenia with marrow hemophagocytosis. EBV DNA was abnormally increased in the blood. Polymerase chain reaction failed to amplify SAP mRNA and genomic DNA products from the patient' As peripheral blood. A large deletion of the SAP gene was confirmed by fluorescence in situ hybridization (FISH). FISH analysis also disclosed that the patient's mother was a carrier. We conclude that FISH can be useful in the diagnosis of XLP with large deletions of the SAP gene and its carrier state.

Carrier Proteins↗
PubMed2000

Kaposi's sarcoma-associated herpesvirus-encoded interleukin-6.

Since the discovery of the virus in 1994, the rapid pace with which Karposi's sarcoma-associated herpesvirus (KSHV) research has progressed has quickly led to a broad understanding of the structure of the virus and its biology and pathology in humans. Molecular piracy of potentially useful cellular genes has emerged as a characteristic feature of this virus. The viral homolog of human IL-6, vIL-6 is an example in kind. Studies in vitro and in vivo have shown that vIL-6 can stimulate the growth of KSHV-infected primary infusion lymphoma (PEL) cells, can promote hematopoiesis, and act as an angiogenic factor through the induction of vascular endothelial growth factor (VEGF). It is not difficult to envision how vIL-6, through these properties and perhaps others yet to be identified, can contribute to KSHV survival and spread in the human population.

Hematopoiesis↗
PubMed2000

Activity of thalidomide in AIDS-related Kaposi's sarcoma.

PURPOSE: To assess the toxicity and activity of oral thalidomide in Kaposi's sarcoma (KS) in a phase II dose-escalation study. PATIENTS AND METHODS: Human immunodeficiency virus (HIV)-seropositive patients with biopsy-confirmed KS that progressed over the 2 months before enrollment received an initial dose of 200 mg/d of oral thalidomide in a phase II study. The dose was increased to a maximum of 1,000 mg/d for up to 1 year. Anti-HIV therapy was maintained during the study period. Toxicity, tumor response, immunologic and angiogenic factors, and virologic parameters were assessed. RESULTS: Twenty patients aged 29 to 49 years with a median CD4 count of 246 cells/mm(3) (range, 14 to 646 cells/mm(3)) were enrolled. All patients were assessable for toxicity, and 17 for response. Drowsiness in nine and depression in seven patients were the most frequent toxicities observed. Eight (47%; 95% confidence interval [CI], 23% to 72%) of the 17 assessable patients achieved a partial response, and an additional two patients had stable disease. Based on all 20 patients treated, the response rate was 40% (95% CI, 19% to 64%). The median thalidomide dose at the time of response was 500 mg/d (range, 400 to 1,000 mg/d). The median duration of drug treatment was 6.3 months, and the median time to progression was 7.3 months. CONCLUSION: Oral thalidomide was tolerated in this population at doses up to 1,000 mg/d for as long as 12 months and was found to induce clinically meaningful anti-KS responses in a sizable subset of the patients. Additional studies of this agent in KS are warranted.

Acquired Immunodeficiency Syndrome↗