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Biomedical subjects

A Burny

Publications and source records attributed to A Burny.

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

[Vaccination against human papillomavirus and against the cellular proliferation that it induces: facts and expectations].

Vaccination against human papillomavirus (HPV) give promising results in animal models. Prophylactic vaccination uses essentially virus-like particles autoassembled from the L1 capsid protein in its native form. Protection is achieved: it is efficient, type-specific and humoral. Therapeutic vaccination is of cellular origin and raised against the E7 oncoprotein. Several vaccine preparations have been found to be efficient: they include virus-like particles formed with L1-E7 fusion protein, E7 encoding plasmidic DNA, dendritic cells pulsed with E7-derived peptides,.

Animals↗
PubMed1999

Bovine leukemia virus Gag particle assembly in insect cells: formation of chimeric particles by domain-switched leukemia/lentivirus Gag polyprotein.

A key stage in the life cycle of C-type retroviruses is the assembly of Gag precursor protein at the plasma membrane of infected cells. Here we report the assembly of bovine leukemia virus (BLV) gag gene product into virus-like particles (VLPs) using the baculovirus expression system. Expression of BLV Pr44(Gag) resulted in the assembly and release of VLPs, thereby confirming the ability of retroviral Gag polyprotein to assemble and bud from insect cells. Efficient particle formation required a myristoylation signal at the N-terminus of BLV Pr44(Gag). Recombinant baculoviruses expressing matrix (MA) or capsid-nucleocapsid (CA-NC) proteins of BLV were generated but neither of these domains was capable of assembling into particulate structures. To assess the compatibility of Gag domains between leukemia and lentivirus groups three different recombinant chimeras each expressing MA of one virus (e.g., simian immunodeficiency or BLV) and CA-NC of another (e.g., BLV or human T-cell leukemia virus type-I) were constructed. Each of the chimeric proteins assembled efficiently and budded as VLPs, suggesting that the MA and CA domains of these two evolutionary divergent retrovirus groups can be functionally exchanged without perturbation of Gag VLP formation. The lenti-leukemia chimeric Gag approach has potential for studying protein-protein interactions in other retroviruses.

Animals↗
PubMed1999

HIV-1 tat transcriptional activity is regulated by acetylation.

The human immunodeficiency virus (HIV) trans- activator protein, Tat, stimulates transcription from the viral long-terminal repeats (LTR) through an RNA hairpin element, trans-activation responsive region (TAR). We and others have shown that trans-activator protein (Tat)-associated histone acetyltransferases (TAHs), p300 and p300/CBP-associating factor (PCAF), assist functionally in the activation of chromosomally integrated HIV-1 LTR. Here, we show that p300 and PCAF also directly acetylate Tat. We defined two sites of acetylation located in different functional domains of Tat. p300 acetylated Lys50 in the TAR RNA binding domain, while PCAF acetylated Lys28 in the activation domain of Tat. In support of a functional role for acetylation in vivo, histone deacetylase inhibitor (trichostatin A) synergized with Tat in transcriptional activation of the HIV-1 LTR. Synergism was TAR-dependent and required the intact presence of both Lys28 and Lys50. Mechanistically, acetylation at Lys28 by PCAF enhanced Tat binding to the Tat-associated kinase, CDK9/P-TEFb, while acetylation by p300 at Lys50 of Tat promoted the dissociation of Tat from TAR RNA that occurs during early transcription elongation. These data suggest that acetylation of Tat regulates two discrete and functionally critical steps in transcription, binding to an RNAP II CTD-kinase and release of Tat from TAR RNA.

3T3 Cells↗
PubMed1999

Interleukin-12-secreting human papillomavirus type 16-transformed cells provide a potent cancer vaccine that generates E7-directed immunity.

The development of a vaccine that would be capable of preventing or curing the (pre)cancerous lesions induced by genital oncogenic human papillomaviruses (HPVs) is the focus of much research. Many studies are presently evaluating vaccines based on the viral E6 and E7 oncoproteins, both of which are continually expressed by tumor cells. The success of a cancer vaccine relies, in large part, on the induction of a tumor-specific Th1-type immunity. In this study, we have evaluated the ability of B7-related and/or interleukin-12 (IL-12)-expressing, non-immunogenic murine HPV16-transformed BMK-16/myc cells, to achieve this goal. BMK-16/myc cells engineered to express surface B7-1 or B7-2 molecules remain tumorigenic in syngeneic BALB/c mice, suggesting that expression of these molecules alone is not sufficient to induce tumor regression. In contrast, mice injected with tumor cells engineered to secrete IL-12 remained tumor-free, demonstrating that IL-12 expression is sufficient to induce tumor rejection. IL-12-secreting BMK-16/myc cells were further shown to induce potent and specific long-term tumor resistance, even after irradiation. B7-1 was found to slightly but systematically improve anti-tumor immunity elicited by IL-12-secreting BMK-16/myc cells. Injection of irradiated B7-1/IL-12+ BMK-16/myc cells generates long-lasting, Th1-type, BMK-16/myc-directed immunity in tumor-resistant mice. These mice display a memory-type, E7-specific, cell-mediated immune response, which is potentially significant for clinical applications.

Animals↗
PubMed1999

Active anti-interferon-alpha immunization: a European-Israeli, randomized, double-blind, placebo-controlled clinical trial in 242 HIV-1--infected patients (the EURIS study).

This randomized, double-blind, placebo-controlled, phase II/III study was designed to evaluate safety, immunogenicity, and efficacy of an active anti-interferon-alpha (anti-IFN-alpha) vaccine in asymptomatic HIV-1-infected patients. The active immunization was aimed at inducing anti-IFN-alpha antibodies to counteract IFN-alpha overproduction. In all, 242 patients, recruited between December 1995 and July 1996 in eight centers in Europe and Israel, with CD4+ counts from 100 to 634 cells/mm3 who were receiving or not receiving antiretroviral therapy (including protease inhibitors) were randomized to receive either anti-IFN-alpha vaccine or placebo. The anti-IFN-alpha immunization regimen consisted of three priming injections delivered intramuscularly at 1-month intervals in a water-in-oil emulsion of inactivated recombinant IFN-alpha-2b (i-IFN-alpha) followed by intramuscular booster injections of i-IFN-alpha adsorbed onto calcium phosphate every 3 months. Immunogenicity to vaccine was defined as an increase of anti-IFN-alpha antibody level of more than twofold the preimmunization value. Clinical progression, changes in antiretroviral treatment, and decrease of CD4+ counts to <200 cells/mm3 were considered endpoints for efficacy evaluation. Contrary to our previous experience, in which six to seven oil priming injections induced a >90% response rate, the three oil-adjuvanted injections in this trial were suboptimal because only 40 of 122 vaccinees (33%) had raised anti-IFN-alpha antibody following immunization. In vaccinees, both antibody responders (AbRV) and nonresponders (AbNRV), the tolerance to the vaccine was good and was without evidence of significant safety concerns. During the course of the trial, 62% of vaccine responders, 64% of nonresponders, and 63% of placebo patients elected to add protease inhibitor-containing regimens as new treatment guidelines were established, resulting in a marked decrease in clinical and laboratory progression such that the expected endpoints of the study could not be achieved and further follow-up was halted. Despite the unexpectedly low immunogenicity and fewer than expected endpoints, anti-IFN-alpha vaccine recipients, in comparison with placebo recipients, showed a lower rate of disease progression, nonelective treatment changes, and/or CD4+ count decrease to <200 cells/mm3, but the difference was not statistically significant. Nevertheless, the subgroup of patients immunized to IFN-alpha who experienced a rise in anti-IFN-alpha antibodies had a significantly lower rate of occurrence of HIV-1-related events and of any combination of the endpoints compared with those of either placebo patients or vaccinees who failed to develop anti-IFN-alpha antibodies, the latter two groups behaving similarly. Further studies of this approach are warranted because these data suggest a beneficial effect of this adjuvant approach.

AIDS Vaccines↗
PubMed1999

Tat toxoid as a component of a preventive vaccine in seronegative subjects.

Because administration of Tat protein, the HIV-1 toxin that induces immunosuppression and apoptosis, may be deleterious to the host immune system, a chemically inactivated but nonetheless immunogenic Tat preparation, Tat toxoid, was used to immunize seronegative individuals against Tat. In an open, controlled, phase I clinical trial, Tat toxoid turned out to be safe, well tolerated, and able to trigger a specific immune reaction. In particular, a threefold to more than 10-fold increase of circulating antibodies directed against the native Tat was observed after immunization in all of 5 immunized study subjects, together with a positive reaction to delayed-type hypersensitivity (DTH) skin test with Tat toxoid in vivo and increased lymphoproliferative response to native Tat in vitro. Persistent (> or =1 year) high levels of circulating anti-Tat antibodies could prevent the Tat-induced immune suppression and, following HIV-1 exposure, allow the anti-HIV-1 cellular immune response, with its early release of protective beta-chemokines, to occur leading to an increase of host resistance, that is, protection.

AIDS Vaccines↗
PubMed1999

Induction of cellular immunosuppression by the human papillomavirus type 16 E7 oncogenic protein.

The human papillomavirus type 16 (HPV-16) E7 oncogenic protein is found in the culture supernatant of SiHa cells, a cervical carcinoma cell line. Extracellular E7 protein, acting as a viral toxin in human immune cells, induces the overproduction of the immune suppressive IFN alpha cytokine by APCs, and inhibits the T-cell response to recall and allogenic antigens. These effects should be taken into account for the design of anti-human cervical carcinoma vaccines.

Animals↗
PubMed1999

Anti-IFN alpha immunization raises the IFN alpha-neutralizing capacity of serum--an adjuvant to antiretroviral tritherapy.

HAART (highly active antiretroviral therapy) suppresses but does not eradicate HIV-1 infection. However, since the antiretroviral agents used in HAART may also be toxic in the long-term, immunotherapies which correct HIV-1 immunosuppression or the cytokine dysregulation associated with it may be beneficial. In this respect, a double blind multicentric placebo-controlled phase II/III anti-IFN alpha vaccine trial has been carried out on 242 HIV-1 patients, the majority of whom were undergoing HAART treatment. In vaccinated patients (vaccinees) who responded to immunization by increased levels of IFN alpha Abs (whether under HAART or not) when compared to placebo or non-responder vaccinees, a strong correlation was found between an increased IFN alpha neutralizing capacity and the reduction of clinical manifestations.

AIDS Vaccines↗
PubMed1999

Lectin production by human T-lymphocytes.

Cultured human peripheral blood monocytes (PBMC) and the cell line H9 release a lectin. This lectin is not the previously described sarcolectin, since it does not specifically recognize the sugars lactose and sialic acid. The lectinic T-cell factor reduces the release by APCs of IFN alpha--a key cytokine known to inhibit the proliferation of activated T-lymphocytes.

Agglutination↗
PubMed1999

HPV-16 E7 but not E6 oncogenic protein triggers both cellular immunosuppression and angiogenic processes.

HPV-16 E6 and E7 oncoproteins impair the cell cycle in human uterine cervix carcinoma cells (HUCC) by acting on p53 and retinoblastoma proteins, respectively. We recently reported that E7 related into the extracellular compartment by HUCC SiHa cells could inhibit immune T-cell response to recall and alloantigens by a mechanism involving an overproduction of the immunosuppressive IFN alpha by antigen presenting cells (APCs). In this study, we found that besides E7, E6 protein and the vascular endothelium growth factor (VEGF) were released into the SiHa cell supernatants, and we further showed that extracellular E7 but not E6 oncoprotein 1) inhibits the immune cell response to recall and alloantigens, and 2) enhances the release of angiogenic cytokines, including TNF alpha, IL-1 beta and IL-6 by macrophages and/or dendritic cells. VEGF unexpectedly released by cancer cells could also contribute to angiogenesis. Thus in HUCC the same E7 oncoprotein which contributes to controlling the cancer cell cycle has the means in its extracellular configuration to contribute to microenvironmental immunosuppressive and angiogenic processes. Neutralizing anti-E7 antibodies either passively administered or induced by active immunization could represent a new immunotherapeutic endeavour to combat the immunosuppression and/or neoangiogenesis effects of extracellular E7 protein.

Cytokines↗
PubMed1999

Carbonic anhydrase IX antigen differentiates between preneoplastic malignant lesions in non-small cell lung carcinoma.

The MaTu interval (MN)/carbonic anhydrase (CA) IX tumour-associated antigen is a protein that is normally expressed in the gut and belongs to the carbonic anhydrase enzyme family (CA IX). It has been detected in tumour cell lines and in some solid tumours including cervical, oesophageal and clear cell renal carcinoma. This study determined MN/CA IX expression in 65 primary non-small cell lung cancer resected with curative intent and in 38 bronchial preneoplastic lesions, carcinoma in situ or microinvasive carcinoma as well as in normal bronchial tissue. The presence of MN/CA IX was detected using immunohistochemistry and Western blot analysis, whenever frozen material was available. Immunostaining was positive in 52/65 (80%) of the tumour samples. The staining was more often focal than diffuse. The percentage of stained cells in positive tumours was highly variable, ranging 1-85%. The pattern of immunostaining was predominantly cytoplasmic with a membranous reinforcement (87%). The intensity was mainly strong (69%). The presence of the protein in the tumour was confirmed by Western blot analysis in the eight samples tested. All the morphologically normal epithelia, except in close vicinity of tumours in some cases, as well as the preneoplastic bronchial lesions (basal cell hyperplasia, metaplasia and dysplasia) were immunonegative for MN/CA IX expression. In contrast, carcinoma in situ and microinvasive epithelioma showed the presence of MN-immunopositive tumoural cells in 5/7 and 4/5 of the samples, respectively. These data suggest that MN/CA IX is a useful marker for the differentiation between preneoplastic lesions and bronchial non-small cell lung cancer in the lung.

Adenocarcinoma↗
PubMed1999

Phosphorylation of the human T-cell leukemia virus type 1 transactivator tax on adjacent serine residues is critical for tax activation.

The Tax transactivator protein of human T-cell leukemia virus type 1 (HTLV-1) plays a central role in the activation of viral gene expression. In addition, Tax is capable of activating the expression of specific cellular genes and is involved in the transformation of T-lymphocytes resulting in the development of adult T-cell leukemia. Tax is a phosphoprotein that colocalizes in nuclear bodies with RNA polymerase II, splicing complexes, and specific transcription factors including members of the ATF/CREB and NF-kappaB families. In this study, we identified adjacent serine residues at positions 300 and 301 in the carboxy terminus of Tax as the major sites for phosphorylation. Phosphorylation of at least one of these serine residues is required for Tax localization in nuclear bodies and for Tax-mediated activation of gene expression via both the ATF/CREB and NF-kappaB pathways. Introduction of amino acid substitutions which are phosphoserine mimetics at positions 300 and 301 restored the ability of a phosphorylation-defective Tax mutant to form nuclear bodies and to activate gene expression. These studies define sites for regulatory phosphorylation events in Tax which are critical for its ability to activate gene transcription.

Animals↗
PubMed1999

In vivo rescue of a silent tax-deficient bovine leukemia virus from a tumor-derived ovine B-cell line by recombination with a retrovirally transduced wild-type tax gene.

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.

Animals↗
PubMed1999

Bovine leukemia virus-induced persistent lymphocytosis in cattle does not correlate with increased ex vivo survival of B lymphocytes.

Bovine leukemia virus (BLV) is an oncogenic retrovirus associated with B-cell lymphocytosis, leukemia, and lymphosarcoma in the ovine and bovine species. We have recently reported that in sheep, BLV protects the total population of peripheral blood mononuclear cells (PBMCs) from ex vivo spontaneous apoptosis. This global decrease in the apoptosis rates resulted from both direct and indirect mechanisms which allow extension of cell survival. Although sheep are not natural hosts for BLV, these animals are prone to develop virus-induced leukemia at very high frequencies. Most infected cattle, however, remain clinically healthy. This difference in the susceptibilities to development of leukemia in these two species might be related to alterations of the apoptotic processes. Therefore, we designed this study to unravel the mechanisms of programmed cell death in cattle. We have observed that PBMCs from persistently lymphocytotic BLV-infected cows were more susceptible to spontaneous ex vivo apoptosis than cells from uninfected or aleukemic animals. These higher apoptosis rates were the consequence of an increased proportion of B cells exhibiting lower survival abilities. About one-third of the BLV-expressing cells did not survive the ex vivo culture conditions, demonstrating that viral expression is not strictly associated with cell survival in cattle. Surprisingly, culture supernatants from persistently lymphocytotic cows exhibited efficient antiapoptotic properties on both uninfected bovine and uninfected ovine cells. It thus appears that indirect inhibition of cell death can occur even in the presence of high apoptosis rates. Together, these results demonstrate that the protection against spontaneous apoptosis associated with BLV is different in cattle and in sheep. The higher levels of ex vivo apoptosis occurring in cattle might indicate a decreased susceptibility to development of leukemia in vivo.

Animals↗
PubMed1998

Conservative mutations in the immunosuppressive region of the bovine leukemia virus transmembrane protein affect fusion but not infectivity in vivo.

Many retroviruses, including bovine leukemia virus (BLV), contain a highly conserved region located about 40 amino acids downstream from the fusion peptide within the sequence of the external domain of the transmembrane (TM) protein. This region is notably thought to be involved in the presentation of the NH2-terminal peptide to allow cell fusion. By using hydrophobic cluster analysis and by analogy with the influenza A hemagglutinin structures, the core of the TM structure including this particular region was predicted to consist, in the BLV and other retroviral envelope proteins, of an alpha-helix followed by a loop region, both docked against a subsequent alpha-helix that forms a triple-stranded coiled coil. The loop region could undergo, as in hemagglutinin, a major refolding into an alpha-helix integrating the coiled coil structure and putting the fusion peptide to one tip of the molecule. Based on this model, we have identified amino acids that may be essential to the BLV TM structure, and a series of mutations were introduced in the BLV env gene of an infectious molecular clone. A first series of mutations was designed to disturb the coiled coil structure (substitutions with proline residues), whereas others would maintain the general TM structure. When expressed by Semliki Forest virus recombinants, all the mutated envelope proteins were stable and efficiently synthesized in baby hamster kidney cells. Both proline-substituted and conservative mutants were strongly affected in their capacity to fuse to CC81 indicator cells. In addition, it appeared that the integrity of the TM coiled coil structure is essential for envelope protein multimerization, as analyzed by metrizamide gradient centrifugation. Finally, to gain insight into the role of this coiled coil in the infectious potential of BLV in vivo, the mutated TM genes were introduced in an infectious and pathogenic molecular clone and injected into sheep. It appeared that only the conservative mutations (A60V and A64S) allowed maintenance of viral infectivity in vivo. Since these mutations destroyed the ability to induce syncytia, we conclude that efficient fusion capacity of the recombinant envelopes is not a prerequisite for the infectious potential of BLV in vivo. Viral propagation of these mutants was strongly affected in some of the infected sheep. However, the proviral loads within half of the infected animals (2 out of 2 for A60V and 1 out of 4 for A64S) were close to the wild-type levels. In these sheep, it thus appears that the A60V and A64S mutants propagate efficiently despite being unable to induce syncytia in cell culture.

Amino Acid Sequence↗
PubMed1998

Phosphorylation of bovine leukemia virus Tax protein is required for in vitro transformation but not for transactivation.

The Tax proteins of the oncovirinae viruses are phosphorylated transcriptional activators that exhibit oncogenic potential. The role of phosphorylation in their functional activities remains unknown. As a model for the Human T-cell leukemia virus type I (HTLV-I), Bovine Leukemia Virus (BLV) permits the characterization of viral replication and leukemogenesis in vivo. Here, we show that the BLV Tax protein is phosphorylated on serine residues 106 and 293 both in insect and in mammalian cells. These sites can also be efficiently phosphorylated by the cdc2 and MAP kinases in vitro. Mutation of these residues does not affect the capacity of the Tax protein to function as a transactivator. Indeed, the Tax proteins mutated at one or both serines increase LTR-directed viral transcription at levels similar to those obtained with wild-type Tax in cell culture. Moreover, inhibition of Tax phosphorylation by W7, a calmodulin antagonist, does not alter its transactivation activity. Thus, phosphorylation on serines 106 and 293 is not required for transactivation by Tax. However, simultaneous substitution of both serines into alanine residues destroys the capacity of Tax to cooperate with the Ha-ras oncogene to transform primary rat embryo fibroblasts and induce tumors in nude mice. When the serines were replaced with aspartic acid residues, the oncogenic potential of Tax was maintained indicating that the negative charge rather than the phosphate group itself was required for Tax oncogenicity. Finally, to assess the role of the serine residues in vivo, recombinant viruses which express the Tax mutants were constructed and injected into sheep. It appeared that the mutated proviruses replicate at levels similar to the wild-type virus in vivo. We conclude that Tax phosphorylation is dispensable for transactivation and viral replication in vivo but is required for its oncogenic potential in vitro.

Animals↗
PubMed1998

Interferon alpha and Tat involvement in the immunosuppression of uninfected T cells and C-C chemokine decline in AIDS.

HIV type 1 (HIV-1) not only directly kills infected CD4(+) T cells but also induces immunosuppression of uninfected T cells. Two immunosuppressive proteins, interferon alpha (IFNalpha) and extracellular Tat, mediate this process because specific antibodies against these proteins prevent generation of suppressor cells in HIV-1-infected peripheral blood mononuclear cell cultures. Furthermore, the production of C-C chemokines in response to immune cell activation, initially enhanced by IFNalpha and Tat, ultimately is inhibited by these proteins in parallel with their induction of immunosuppression. The clinical corollary is the immunosuppression of uninfected T cells and the decline in C-C chemokine release found at advanced stages of HIV-1 infection paralleling rising levels of IFNalpha and extracellular Tat. We, therefore, suggest that IFNalpha and Tat may be critical targets for anti-AIDS strategies.

Acquired Immunodeficiency Syndrome↗