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Biomedical subjects

T Velu

Publications and source records attributed to T Velu.

At least 37 records · Page 2Linked to original sources
PubMed2000

The role of cellular- and prodrug-associated factors in the bystander effect induced by the Varicella zoster and Herpes simplex viral thymidine kinases in suicide gene therapy.

To investigate the factors influencing the bystander effect--a key element in the efficacy of suicide gene therapy against cancer--we compared the effect triggered by four extremely efficient gene/prodrug combinations, i.e., VZVtk/BVDU, the thymidine kinase of Varicella zoster virus associated with (E)-5-(2-bromovinyl)-2'-deoxyuridine; VZVtk/BVaraU, the same enzyme associated with (E)-5-(2-bromovinyl)-1-beta-D-arabinofuranosyluracil; HSVtk/BVDU, the association of the Herpes simplex virus thymidine kinase with BVDU; and the classical HSVtk/GCV (ganciclovir) paradigm. The cells used, the human MDA-MB-435 breast cancer, and the rat 9L glioblastoma lines were equally sensitive in vitro to these four associations. In both cell types, the combinations involving pyrimidine analogues (BVDU, BVaraU) displayed a smaller bystander killing than the combination involving the purine analogue (GCV). In addition, the bystander effect induced by all the tk/prodrug systems was reduced in MDA-MB-435 cells in comparison to 9L cells; albeit, the viral kinases were produced at a higher level in the breast cancer cells. All systems induced apoptotic death in the two cell types, but the MDA-MB-435 cells, deprived of connexin 43, were noncommunicating in striking contrast with the 9L cells. That functional gap junctions have to be increased in order to improve the breast cancer cell response to suicide gene therapy was demonstrated by transducing the Cx43 gene: this modification enhanced the bystander effect associated in vitro with GCV treatment and, by itself, decreased the tumorigenicity of the untreated cells. However, the noncommunicating MDA-MB-435 cells triggered a significant bystander effect both in vitro and in vivo with the HSVtk/GCV system, showing that communication through gap junctions is not the only mechanism involved.

Animals↗
PubMed2000

Role and expression of CD40 on human retinal pigment epithelial cells.

PURPOSE: To examine the CD40 costimulatory molecule expression on normal resting or activated adult human retinal pigment epithelium (hRPE) cells and to evaluate its role as an activation molecule considering the potential antigen presentation functions of hRPE cells. METHODS: Expression of HLA-DR and costimulatory (CD40, B7.1, B7.2, CD54, and CD58) molecules on hRPE cells was analyzed by flow cytometry. CD40 triggering was performed using soluble CD40L or cocultures with CD40L transfected fibroblasts. Interleukin (IL)-6, -8, -10, and -12 secretions were measured by enzyme-linked immunosorbent assay. Antigen presentation function of hRPE cells was assessed by coculturing hRPE cells with allogeneic T cells. T-cell proliferation was measured by [(3)H]-thymidine incorporation, and T-cell apoptosis by measurement of caspase-3 activity. RESULTS: Interferon (IFN)gamma-activated hRPE cells expressed CD40, but not B7.1 or B7.2. Although interferongamma enhanced IL-6 and IL-8 production, CD40 triggering of IFNgamma-activated hRPE cells did not induce IL-12 secretion. hRPE cells did not stimulate allogeneic resting T cells and downregulated phytohemagglutinin-activated allogeneic T cells via a cell-to-cell contact-dependent mechanism. Some induction of apoptosis was detected. CONCLUSIONS: CD40 is expressed on IFNgamma-activated hRPE cells. Its ligation leads to an increased production of IL-6 and IL-8 but fails to induce B7.1 or B7. 2 expression, or to induce IL-12 secretion. Accordingly, hRPE cells do not activate allogenic T cells but inhibit T-cell proliferation, partly through induction of apoptosis. These results suggest that hRPE cells could be implicated more in a deviant antigen presentation. If the exact molecular mechanisms are unclear, it is likely that CD40-CD40L interaction could play a role in this process.

Animals↗
PubMed1999

Influence of sequence and size of DNA on packaging efficiency of parvovirus MVM-based vectors.

We have derived a vector from the autonomous parvovirus MVM(p), which expresses human IL-2 specifically in transformed cells (Russell et al., J. Virol 1992;66:2821-2828). Testing the therapeutic potential of these vectors in vivo requires high-titer stocks. Stocks with a titer of 10(9) can be obtained after concentration and purification (Avalosse et al., J. Virol. Methods 1996;62:179-183), but this method requires large culture volumes and cannot easily be scaled up. We wanted to increase the production of recombinant virus at the initial transfection step. Poor vector titers could be due to inadequate genome amplification or to inefficient packaging. Here we show that intracellular amplification of MVM vector genomes is not the limiting factor for vector production. Several vector genomes of different size and/or structure were amplified to an equal extent. Their amplification was also equivalent to that of a cotransfected wild-type genome. We did not observe any interference between vector and wild-type genomes at the level of DNA amplification. Despite equivalent genome amplification, vector titers varied greatly between the different genomes, presumably owing to differences in packaging efficiency. Genomes with a size close to 100% that of wild type were packaged most efficiently with loss of efficiency at lower and higher sizes. However, certain genomes of identical size showed different packaging efficiencies, illustrating the importance of the DNA sequence, and probably its structure.

Bacteriophage lambda↗
PubMed1999

Cellular contaminants of adeno-associated virus vector stocks can enhance transduction.

Transduction efficiency of different types of recombinant (r)AAV-2 based vectors preparations markedly differed, with apparently no correlation with the replicative titers. Using HeLa cells as target for transduction, 105 and 30 infectious units were necessary to observe one transductant using respectively cesium-chloride-purified rAAV and crude lysates of producer cells obtained by sonication. The purified vectors were however able to transduce HEK-193 cells efficiently, but transgene expression was detected with some delay compared with crude lysates. The unexpected high transduction efficiency of sonicated crude lysates was due to virally mediated gene transfer, since similar sonicated crude lysates, but with no AAV rep and cap genes, did not lead to detection of transgene products after incubation with HeLa cells. Furthermore, sonicated cellular extracts of 293 or 293/T cells given in trans stimulate transduction of HeLa cells by purified rAAV. In contrast, neither extracts from the adenovirus E1-transformed 911 cell line, nor from other cell lines not harboring any adenovirus gene, had enhancing effect on rAAV-mediated transduction. These data suggest that 293 sonicated extracts contain factors which stimulate rAAV-mediated transduction of cells that are normally poorly transduced and offer a system to identify such factors and to characterize further the steps limiting the transfer of gene by AAV vectors.

Dependovirus↗
PubMed1999

Sentinel lymph node mapping in the management of high risk malignant melanoma.

In patients with malignant melanoma, the selective biopsy of the first draining lymph node, so-called the sentinel lymph node, allows to identify, with a low morbidity, the patients with nodal metastasis that require radical lymphadenectomy and adjuvant systemic chemotherapy. Herein, we report our initial experience in sentinel lymph node biopsy in 16 patients with malignant melanoma. The sentinel lymph node was localised using preoperative lymphoscintigraphy and injection of dye blue. Intraoperatively, the dissection was guided with a gamma probe and by the recognition of the blue nodes. In the 16 cases the sentinel lymph node was localised. In 50% of the cases, multiple sentinel nodes were demonstrated at lymphoscintigraphy and found during surgery. A limited postoperative morbidity was observed in three cases. Three patients presented nodal metastasis and underwent further radical lymphadenectomy. We conclude that sentinel lymph node mapping is a feasible and reproductive procedure. The preoperative lymphoscintigraphy is essential to identify multiple sentinel nodes and guide surgical dissection. The impact of this approach on the overall survival of patients with high-risk melanoma has still to be demonstrated in studies with a long follow-up.

Adult↗
PubMed1998

Relative contribution of Ki-ras gene analysis and brush cytology during ERCP for the diagnosis of biliary and pancreatic diseases.

BACKGROUND: Ki-ras mutation analysis from material collected during ERCP has been claimed to improve the diagnosis of pancreatic and bile duct carcinomas as compared with conventional cytology. Our aim was to study the relative contribution of both Ki-ras analysis and brush cytology in patients with a significant stricture at ERCP. METHODS: Brushings were collected in duplicate for both analyses in 142 patients in whom a definitive diagnosis was obtained by histology or a minimal follow-up of 6 months. RESULTS: For pancreatic strictures, sensitivity, specificity, and accuracy of Ki-ras analysis vs. cytology in detecting malignancy were 81% vs. 66%, 72% vs. 100%, and 70% vs. 74%, respectively. For biliary strictures, they were 25% vs. 42%, 100% vs. 100%, and 35% vs. 43%, respectively. The combination of the two methods only marginally increased their sensitivity and accuracy in both types of strictures. CONCLUSION: Ki-ras analysis is a sensitive method for diagnosing pancreatic but not biliary carcinoma. However, its specificity is lowered by a high frequency of Ki-ras mutations in patients with chronic pancreatitis (25%) who did not manifest cancer development within a 6-month follow-up period. In pancreatic duct strictures, brush cytology appears to be more specific in detecting malignancy; specificity for Ki-ras and cytology are equivalent for the diagnosis of malignant bile duct strictures. Therefore, making a clinical decision on the sole basis of Ki-ras analysis is probably not justified in the majority of the cases.

Adult↗
PubMed1997

Disseminated angiosarcoma presenting as a hemophagocytic syndrome in a renal allograft recipient.

A case of angiosarcoma arising in the setting of transplantation is reported. This rare and malignant tumor of the endothelial system is seldom observed in allograft recipients, with only seven cases having been previously reported. What is interesting about the present observation is that the tumor is thought to have developed in the vicinity of a Dacron graft and that it showed prominent erythrophagocyte-like activity. This activity was associated with a particular clinical syndrome that shared some attributes with infection-associated hemophagocytic syndrome.

Diagnosis, Differential↗
PubMed1997

Morphologic and phenotypic changes of the leukemic cells in a case of marginal zone B-cell lymphoma.

A particular case of marginal zone B-cell lymphoma (MZBCL) presenting with leukemic lymphocytes is reported. In the present observation, the leukemic cells not only displayed a remarkable morphological fluctuation but also had an unusual phenotype, changing with time. These phenotypic features, which have been functionaly investigated by in vitro assays, might simply reflect an activation state depending on the microenvironment. Because of its disconcerting similarities with hairy cell leukemia (HCL) and splenic lymphoma with villous lymphocytes (SLVL), this case relaunches the debate about whether close relationships might exist between the splenic marginal zone, SLVL and HCL.

Antigens, CD19↗
PubMed1997

Interleukin-10 modulates susceptibility in experimental cerebral malaria.

In this study, we examined the effects of interleukin-10 (IL-10) on the outcome of experimental cerebral malaria (CM), a lethal neurological syndrome that occurs in susceptible strains of mice after infection with Plasmodium berghei ANKA (PbA). Constitutive IL-10 mRNA levels were significantly higher in the spleen and brain of resistant animals. In vivo neutralization of endogenous IL-10 in CM-resistant mice induced the neurological syndrome in 35.7% of these mice, as opposed to 7.7% in controls. IL-10 inhibited PbA antigen-specific interferon-gamma (IFN-gamma) production in vitro but not tumour necrosis factor (TNF) serum levels in vivo. Susceptible mice, on the other hand, were significantly protected against CM when injected with recombinant IL-10. Overall, our findings suggest that IL-10 plays a protective role against experimental cerebral malaria.

Animals↗
PubMed1997

Nature of the T lymphocytes in lymphocyte predominance Hodgkin's disease.

Little is known about the function of the T lymphocytes in lymphocyte predominance Hodgkin's disease. We report here the case of a 37-year-old man with a diffuse LPHD, featuring a similar increase in T lymphocytes in both the peripheral blood and the tumor, thus allowing for their characterization by functional assays. These cells were CD4+CD45RO+ and produced high amounts of IL-2 and IFN-gamma, consistent with a TH1-type profile. This subset of T helper cells is involved in cellular immunity and could reflect a cytotoxic reaction directed against the neoplastic cells.

Adult↗
PubMed1996

Gene therapy: socioeconomic and ethical issues. A roundtable discussion.

Gene therapy research has the potential to revolutionize the way in which many human diseases are treated. Despite its enormous potential, roundtable panelists concluded that the field needs time to mature scientifically without pressure to develop a marketable therapeutic product. In addition, health care decision makers, physicians, and the lay public need to be educated on the future medical, economic, and ethical ramifications of gene therapy.

Clinical Trials as Topic↗
PubMed1996

Curative potential of herpes simplex virus thymidine kinase gene transfer in rats with 9L gliosarcoma.

The transfer of the gene coding for the thymidine kinase of the herpes simplex virus (HSV-tk), followed by ganciclovir (GCV) administration, has been described for the treatment of several types of cancer, especially brain tumors. We further studied the efficacy of this approach by using the 9L rat gliosarcoma model, and cells producing 5 x 10(3), 9 x 10(4), 3 x 10(5) HSV-tk retroviral particles per milliliter. Their stereotactic injection in 9L brain tumors and GCV treatment did not result in any increase of survival. To study a model of optimal in vivo transduction, we examined the survival of rats with tumors growing from 9L cells that had been previously transduced in vitro with the HSV-tk vectors (9LTk cells). We observed that GCV administration cured 26% (n = 42) of the animals with 9LTk brain tumors, with most of the relapsing tumors remaining HSV-tk positive. The increase of either the dose or the duration of GCV treatment did not improve the survival rate. But the cerebral localization of the tumor played an important role, because this survival rate reached 67% (n = 12) when similar tumors were growing subcutaneously. No or only marginal antitumoral responses were induced by the presence of a selectable marker gene in the HSV-tk vectors. These results demonstrate that in vitro HSV-tk gene transfer in 9L tumor cells, but not in vivo gene transfer, followed by GCV treatment, is able to cure rats at a rate that is higher for subcutaneous than for intracerebral tumors.

Animals↗
PubMed1996

Interleukin 10 inhibits inflammatory cells infiltration in endotoxin-induced uveitis.

BACKGROUND: Endotoxin-induced uveitis (EIU) is a model for acute anterior uveitis associated with a variety of pro-inflammatory cytokines and nitric oxide production. Interleukin 10 (IL-10) down-regulates these inflammatory mediators. We report a study of the effect of systemic administration of IL-10 on the inflammatory parameters of EIU. METHODS: Uveitis was induced in C3H/HeN mice by subcutaneous injection of 200 micrograms lipopolysaccharide (LPS) per mouse. Intraocular inflammation was assessed by leukocyte count and measurement of the protein concentration in the aqueous humor (AH). Mouse recombinant IL-10 at 1000 U or its vehicle alone were administered by three intravenous injections given 4.0 h and 0.5 h before and 8.0 h after LPS injection. RESULTS: The inflammatory cell infiltration in the eyes was significantly reduced in four of five experiments from 40% to 64% in the groups treated with IL-10 compared to the control groups (P < 0.05). In contrast, the level of protein exudation in the anterior chamber (AC) was not significantly affected by IL-10 treatment. CONCLUSION: IL-10 reduces the cellular infiltration in the ocular inflammation produced by endotoxin. This result suggests potential usefulness for IL-10 in the treatment of severe anterior uveitis with a strong cellular component.

Animals↗
PubMed1996

Transfer of p16inka/CDKN2 gene in leukaemic cell lines inhibits cell proliferation.

The gene encoding for p16ink4a, a negative regulator of transition between G1 and S phase, is homozygously deleted in a large proportion of acute lymphoblastic leukaemias (ALL). Transfer of p16ink4a gene in several solid tumour cell lines with functional pRb and lacking both p16ink4a alleles has resulted in a dramatic reduction of cell proliferation, and the aim of this work was to confirm this effect in leukaemic (especially ALL) cell lines. We tested the proliferation in liquid medium and in soft agar after transfer of p16ink4a gene by a retroviral vector in leukaemic cell lines with homozygous p16ink4a gene deletion (K562, CEM, Jurkat cell lines) or with p16ink4a gene hemizygous deletion and a point mutation inactivating the remaining allele (HL60 cell line). The viral titre obtained after transfection of PA317 amphotropic packaging cell line, which has a p16ink4a gene homozygous deletion, was low, suggesting that p16ink4a gene expression could impair viral production of retroviral packaging cell lines derived from the NIH3T3 cell line. After retroviral transfer of p16ink4a in cell lines and G418 selection in liquid medium, a strong cell proliferation inhibition was observed for K562, CEM and Jurkat, but no inhibition was seen for HL60. A strong growth reduction in soft agar was also observed with p16ink4a-transduced CEM, Jurkat and K562 cells, with a moderate growth reduction in the HL60 cell line. The growth inhibition in liquid culture, of K562 and Jurkat cell lines, was confirmed by electroporation transfer of the p16ink4a gene. Our findings show that p16ink4a gene transfer has a growth-inhibitory effect in leukaemic cell lines with p16ink4a gene homozygous deletion. These data suggest that p16 could be a suitable gene for gene therapy in ALL.

Cell Division↗