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ABSTRACT: Bovine leukemia virus (BLV) is closely associated with the development of B-cell leukemia and lymphoma in cattle. BLV infection has also been studied extensively in an in vivo ovine model that provides a unique system for studying B-cell leukemogenesis. There is no evidence that BLV can directly infect ovine B cells in vitro, and there are no direct data regarding the oncogenic potential of the viral Tax transactivator in B cells. Therefore, we developed ovine B-cell culture systems to study the interaction between BLV and its natural target, the B cell. In this study, we used murine CD154 (CD40 ligand) and gamma-chain-common cytokines to support the growth of B cells isolated from ovine lymphoid tissues. Integrated provirus, extrachromosomal forms, and viral transcripts were detected in BLV-exposed populations of immature, rapidly dividing surface immunoglobulin M-positive B cells from sheep ileal Peyer's patches and also in activated mature B cells isolated from blood. Conclusive evidence of direct B-cell infection by BLV was obtained through the use of cloned B cells derived from sheep jejunal Peyer's patches. Finally, inoculation of sheep with BLV-infected cultures proved that infectious virus was shed from in vitro-infected B cells. Collectively, these data confirm that a variety of ovine B-cell populations can support productive infection by BLV. The development of ovine B-cell cultures permissive for BLV infection provides a controlled system for investigating B-cell leukemogenic processes and the pathogenesis of BLV infection.
Journal of Virology 03/2001; 75(3):1095-103. · 5.40 Impact Factor
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ABSTRACT: CD40 signaling induces B cell proliferative and differentiation responses that can be modulated by many different cytokines. Cytokines in the IL-2 receptor gamma chain (gammac)-common family are known to play an integral role in B cell development. Therefore, we investigated the possibility that CD40 signaling induced B cell responsiveness to multiple gammac-common cytokines and that individual gammac-common cytokines induced distinct B cell responses. B cells were isolated from lymphoid follicles of sheep Peyer's patches (PP) and co-cultured with murine CD40 ligand (mCD40L). CD40 signaling induced PP B cell responsiveness to recombinant human IL-2, IL-4, IL-7 and IL-15. mCD40L-induced B cell growth was enhanced by combining IL-4 with a second gammac-common cytokine and sustained B cell growth required co-stimulation with IL-4 plus IL-2, IL-7 and IL-15. gammac-common cytokine responsiveness remained dependent upon CD40 signaling, and removal of mCD40L resulted in B cell differentiation and cell death. Similar proliferative responses to mCD40L and gammac-common cytokines were observed for both immature (ileal) and mature (jejunal) PP B cells. Finally, the capacity of CD40-activated B cells to respond to multiple gammac-common cytokines was analyzed with individual PP B cell clones. All B cell clones displayed similar proliferative responses to IL-2 but quantitatively different responses to IL-4, IL-7 and IL-15. The biological significance of B cell responsiveness to multiple gammac-common cytokines is discussed.
International Immunology 08/1999; 11(7):1139-47. · 3.41 Impact Factor
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ABSTRACT: T cells are central players in the immune response to infectious disease, with the specificity of their responses controlled by the T-cell receptor (TCR)/CD3 complex on the cell surface. Impairment of TCR/CD3-directed CD4(+) T-cell immune responses is frequently observed in individuals infected with human immunodeficiency virus types 1 and 2 (HIV-1 and HIV-2). Virus replication is also regulated by T-cell activation factors, with HIV-1 and HIV-2 responding to different TCR/CD3-directed cellular pathways. We previously demonstrated that HIV-1 infection of the human interleukin-2-dependent CD4(+) T-cell line WE17/10 abrogates TCR/CD3 function and surface expression by a specific loss of CD3-gamma gene transcripts. In this study, we show that HIV-2 provokes the same molecular defect in CD3-gamma gene transcripts, resulting in a similar but delayed progressive loss of TCR/CD3 surface expression after infection.
Journal of Virology 07/1999; 73(6):5207-13. · 5.40 Impact Factor
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ABSTRACT: The lack of bovine leukemia virus (BLV) expression is a consistent finding in freshly isolated ovine tumor cells and in the B-cell lines derived from these tumors. In order to gain further insight into the mechanisms of BLV silencing in these tumors, we have used the YR2 B-cell line, which was derived from the leukemic cells of a BLV-infected sheep. This cell line contains a single, monoclonally integrated, silent provirus, which cannot be reactivated either by stimulation in vitro or by in vivo injection of the tumor cells or cloned proviral DNA in sheep. Sequence analysis of the tax gene from the YR2 cell line identified two G-to-A transitions (G7924 to A7924 and G8149 to A8149) that result in E-to-K amino acid changes at positions 228 and 303 in the Tax protein. Following retroviral vector-mediated transfer of a wild-type tax gene into YR2 cells, we showed that BLV mRNA, viral proteins, and virions were produced, demonstrating that the cellular factors required for virus expression were present in the original YR2 cell line. Injection of this transduced YR2 cell line in sheep led to the rescue of replication-competent BLV proviruses. The integrated competent proviruses exhibited unique chimeric tax genes, which arose from homologous recombination between the transduced wild-type tax and the YR2-derived tax sequences. Furthermore, in one of these functional recombinant proviruses, only the A8149-to-G8149 reversion was present, providing clear evidence that the defect underlying the silent phenotype in YR2 cells results from a single C-terminal E303-to-K303 amino acid substitution in the BLV Tax protein. Our observations suggest that a single strategically located mutation in tax provides a mechanism for BLV inactivation in B-cell tumors.
Journal of Virology 03/1999; 73(2):1054-65. · 5.40 Impact Factor
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V Kiermer,
F Dequiedt,
R Masengo,
Y Cleuter,
D Briclet,
M Ciesiolka, A Van den Broeke,
L Willems,
R Kettmann,
A Burny,
L Droogmans
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ABSTRACT: We report the cloning of an ovine c-myc cDNA. The clone was isolated from a bovine leukemia virus-infected cell line (YR2) cDNA library cloned in the lambda gt10 vector. The clone encodes the full length c-Myc protein made of 439 amino-acids with 93, 96, 92 and 93% similarity with human, feline, murine and rat c-Myc proteins, respectively.
DNA Sequence 02/1997; 7(3-4):235-8. · 0.75 Impact Factor
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Developments in biological standardization 02/1990; 72:77-80.
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Haematology and blood transfusion 02/1989; 32:428-32.
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ABSTRACT: To investigate the role of proviral integration and expression in cellular transformation induced by bovine leukemia virus (BLV), three BLV-induced tumors harboring a single proviral copy were selected upon restriction and hybridization analysis. Tumors 344 and 395 were shown to contain a full-size proviral copy, whereas in tumor 1345 the provirus appeared to be heavily deleted. RNA gel blot hybridization with an antisense RNA probe showed no transcription of the viral sequences in the fresh tumors or in sheep tumor cells growing in vitro. The proviruses were cloned and transfected in mammalian cell lines. Transient-expression experiments revealed that the complete proviruses were still able to express the trans-activating protein (Tat) as well as structural proteins, demonstrating that the nonexpression of a provirus in a tumor cell does not necessarily imply a structural alteration of the viral information. In contrast, sequence analysis of the provirus with a large deletion and transient-expression assays proved that this truncated provirus, isolated from a tumor, was unable to code for viral proteins. These data indicate that expression of viral genes, including tat, is not required for the maintenance of the transformed state.
Proceedings of the National Academy of Sciences 01/1989; 85(23):9263-7. · 9.68 Impact Factor
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ABSTRACT: Bovine leukemia virus is the etiological agent of a chronic lymphatic leukemia/lymphoma in cows, sheep, and goats. Infection without neoplastic transformation also was obtained in pigs, rhesus monkeys, chimpanzees, and rabbits, and was observed in capybaras and water buffaloes. Structurally and functionally, BLV is a relative of the human T lymphotropic viruses (HTLV-I and HTLV-II). HTLV-I induces in humans a T cell leukemia, and its type II counterpart has been found in dermatopathic lymphadenopathy, hairy T cell leukemia and prolymphocytic leukemia cases. At variance with HTLV-I, BLV has not been associated with neurological diseases of the degenerative type. BLV, HTLV-I, and HTLV-II show clearcut sequence homologies. The pathology of the BLV-induced disease, most notably, the absence of chronic viremia, a long latency period, and a lack of preferred proviral integration sites in tumors, is similar to that of adult T cell leukemia/lymphoma induced by HTLV-I. The most striking feature of the three naturally transmitted leukemia viruses is the X region located between the env gene and the LTR sequence. The X region contains several overlapping long open reading frames. One of them designated XBL-I encodes a trans-activator function capable of increasing the level of gene expression directed by BLV-LTR and most probably involved in "genetic instability" of BLV-infected cells of the B cell lineage. The genetic instability puts the cell into a context of fragility and ready to move along a number of stages towards full malignancy. Little is known about these events and their causes; we have presented some theoretical possibilities. BLV infection has a worldwide distribution. In temperate climates the virus spreads mostly via iatrogenic transfer of infected lymphocytes. In warm climates and in areas heavily populated by hematophageous insects, there are indications of insect-born propagation of the virus.
Advances in Veterinary Medicine 02/1988; 32:149-70.
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Bulletin et memoires de l'Academie royale de medecine de Belgique 02/1987; 142(6-7):357-63.
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ABSTRACT: Bovine leukaemia virus (BLV) is the aetiological agent of a chronic lymphatic leukaemia/lymphoma in cows, sheep and goats. Infection without neoplastic transformation has also been demonstrated in pigs, rhesus monkeys, chimpanzees and rabbits and observed in capybaras and water buffaloes. Structurally and functionally, BLV is a relative of human T lymphotropic viruses 1 and 2 (HTLV-I and HTLV-II) since all three viruses show clear-cut sequence homologies. The pathology of the BLV-induced disease, most notably the absence of chronic viraemia, a long latency period and lack of preferred proviral integration sites in tumours, is similar to that of adult T-cell leukaemia/lymphoma induced by HTLV-I. The most striking feature of the three naturally transmitted leukaemia viruses is the X region located between the env gene and the long terminal repeat (LTR) sequence. The X region contains several overlapping long open reading frames, one of which, designated XBL-1, encodes a trans-activator function capable of increasing the level of gene expression directed by BLV-LTR and is most probably involved in genetic instability of BLV-infected cells of the B-cell lineage. The 'genetic instability' may put the cell into a state of fragility, ready to move along a number of stages towards full malignancy. Little is known about these events and their causes and we present some theoretical possibilities. BLV infection has a worldwide distribution. In temperate climates the virus spreads mostly through iatrogenic transfer of infected lymphocytes. In warm climates and in areas heavily populated by haematophagous insects, there are indications of insect-borne propagation of the virus.
Cancer surveys 02/1987; 6(1):139-59.
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ABSTRACT: Relative transduction efficiency with retroviral vector-producing clones was assayed by cocultivating TF-1, a human CD34+ hematopoietic cell line and YR-2, a sheep B-lymphoid cell line, with LacZ containing vector-producing cells, and then by scoring the percentage of X-Gal+ cells. At the same time, viral titer was estimated by titration assay with murine fibroblasts. Results clearly demonstrated a lack of correlation between viral titer and efficiency of transduction into hematopoietic cells, which depends neither on the type of packaging cell line, PG-13 and GP-envAM12 in this study, nor on the type of LacZ containing retroviral vector. These results strongly favor consideration of interactions between producers and target cells of the study for the screening of producing cell lines.
Cancer Gene Therapy 4(1):5-8. · 2.80 Impact Factor
