The Experts below are selected from a list of 732 Experts worldwide ranked by ideXlab platform
Salomon Amar - One of the best experts on this subject based on the ideXlab platform.
-
p53 short peptide (p53pep164) regulates lipopolysaccharide-induced tumor necrosis factor-alpha factor/cytokine expression. Cancer Res
2016Co-Authors: Xiaoren Tang, Manuel Molina, Salomon AmarAbstract:The p53 protein is a sequence-specific DNA-binding factor that can induce apoptosis or activate genes whose dysregula-tion is involved in cancer. By using serial analysis of gene expression technique, p53-induced genes (PIGs) have been identified, one of which was lipopolysaccharide (LPS)– induced tumor necrosis factor-A (TNF-A) factor (LITAF/ PIG7). LITAF regulates the transcription of cytokines such as TNF-A. To further elucidate the role of p53 in LITAF expression, LITAF promoter activity was carefully dissected. In this study, we found that the element required for transcriptional activity is mainly located in the region from 990 to 500 of the LITAF promoter; the specific site required for p53 protein-DNA binding is located between 550 and 500. We also found that transient transfection of either a p53 short DNA sequence, called p53LFB12, or its corresponding 7-amino-acid synthetic peptide from amino acids 164 to 170 (K164Q165S166Q167H168M169T170), named p53pep164, sig-nificantly reduced LITAF promoter activity to 15 % in p53-null H1299 cells. Transfection of p53pep164 into H1299 cells significantly down-regulated LPS-induced LITAF expression as well. Furthermore, transfection of p53pep164 into human monocytes resulted in down-regulation of nine proinflam-matory cytokines, including TNF-A. We also found that the LPS-activated p53 is a short-lived protein, and that p53-orchestrated apoptosis occurs shortly after the initiation stage following LPS stimulation and lasts a short time. Once p53 levels return to baseline, the p53-mediated inhibition of LITAF is released, and LITAF-mediated cytokine production can proceed. The present finding proposes a novel link between p53 and the inflammatory processes and highlights potential interventional approaches to control p53-associated inflam-matory processes. [Cancer Res 2007;67(3):1308–16
-
kavain involvement in lps induced signaling pathways
Journal of Cellular Biochemistry, 2016Co-Authors: Xiaoren Tang, Salomon AmarAbstract:: Kavain, a compound extracted from the Kava plant, Piper methysticum, is found to be involved in TNF-α expression in human and mouse cells via regulation of transcriptional factors such as NF-kB and LITAF. LITAF is known to activate the transcription of more than 20 cytokines that are involved in a variety of cellular processes and is associated with many inflammatory diseases, including angiogenesis, cancer, arthritis, and more. The modulation of LITAF is expected to positively affect cytokine-mediated diseases. Thus, intensive efforts have been deployed in search of LITAF inhibitors. In this work, we found that, in vitro, Kavain reduced LPS- induced TNF-α secretion in mouse macrophages, mouse bone marrow macrophages (BMM), and human peripheral blood mononuclear cells (HPBMC). We also found that Kavain treatment in RAW264.7 cells deactivated MyD88 and Akt, inhibited LITAF, and reduced the production of TNF-α, IL-27, and MIG in response to LPS. Similarly, it had a significant in vivo anti-inflammatory effect on wild-type (WT) mice that developed Collagen Antibody Induced Arthritis (CAIA). Overall, MyD88 was found to be an important mediator of the LPS-induced inflammatory response that can be distinguished from the NF-κB pathway. We also found that MyD88 is involved in the pathway linking LPS/LITAF to TNF-α. Therefore, given that Kavain modulates LPS-induced signaling pathways leading to cytokine expression, therapeutic interventions involving Kavain in inflammatory diseases are warranted. J. Cell. Biochem. 117: 2272-2280, 2016. © 2016 Wiley Periodicals, Inc.
-
LITAF Mediation of Increased TNF-a Secretion from Inflamed
2016Co-Authors: Colonic Lamina Propria Macrophages, Kristen N. Bushell, Susan E. Leeman, Earl Gillespie, Adam C. Gower, Karen L. Reed, James M. Becker, Arthur F, Salomon AmarAbstract:Dysregulation of TNF-a in lamina propria macrophages (LPM) is a feature of inflammatory bowel diseases (IBD). LPS-Induced-TNF-Alpha-Factor (LITAF) is a transcription factor that mediates TNF-a expression. To determine whether LITAF participates in the mediation of TNF-a expression in acutely inflamed colonic tissues, we first established the TNBS-induced colonic inflammation model in C57BL/6 mice. LPM were harvested from non-inflamed and inflamed colonic tissue and inflammatory parameters TNF-a and LITAF mRNA and protein levels were measured ex-vivo. LPM from TNBS-treated mice secreted significantly more TNF-a at basal state and in response to LPS than LPM from untreated mice (p,0.05). LITAF mRNA and protein levels were elevated in LPM from TNBS compared with untreated animals and LPS further increased LITAF protein levels in LPM from inflamed tissue (P,0.05). To further confirm the role of LITAF in acutely inflamed colonic tissues, TNBS-induced colonic inflammation was produced in LITAF macrophage specific knockout mice (LITAF mac-/- mice) and compared to wild type (WT) C57BL/6. Twenty four hours following TNBS administration, colonic tissue from LITAF mac-/-mice had less MPO activity and reduced colonic TNF-amRNA then WT C57BL/6 mice (p,0.05). LPM harvested from LITAF mac-/- secreted significantly less TNF-a in response to LPS than wild type (WT) C57BL/6 (p,0.05). This study provides evidence that LITAF contributes to the regulation of TNF-a in LPM harvested following acute inflammation or LPS treatment paving the wa
-
kavain inhibition of lps induced tnf α via erk LITAF
Toxicology Research, 2016Co-Authors: Xiaoren Tang, Salomon AmarAbstract:Kavain, an extract from the shrub Piper methysticum, was recently reported to modulate TNF-α expression in both human and mouse cells via regulation of LPS-Induced TNF-Alpha Factor (LITAF). The purpose of the present study was to define the molecular pathway(s) associated with Kavain′s effects on TNF modulation. In vitro studies using WT mouse primary macrophages showed that Kavain significantly reduced E. coli LPS-induced TNF-α production but this effect was almost abrogated in LITAF−/− and ERK2−/− cells. Therefore we reintroduced the ERK2 gene in ERK2−/− cells and partially restored E. coli LPS-induced LITAF-mediated TNF-α production. The translocation of LITAF into to nucleus was found to be dependent on ERK2 S206 residue. Kavain inhibits LITAF/TNF-α expression via dephosphorylation of ERK2 in response to E. coli LPS. Finally, in vivo, Kavain had a significant anti-inflammatory effect on wild type mice that developed Collagen Antibody Induced Arthritis (CAIA), but only a minor effect in ERK2−/− mice also affected by CAIA. Based on these findings, we concluded that ERK2 may be the kinase upstream for LITAF being a crucial factor for Kavain-mediated regulation of LPS-induced TNF-α.
-
kavain inhibition of lps induced tnf α via erk LITAF
Toxicology Research, 2016Co-Authors: Xiaoren Tang, Salomon AmarAbstract:Kavain, an extract from the shrub Piper Methysticum, was recently reported to modulate TNF-α expression in both human and mouse cells via regulation of LPS-Induced TNF-Alpha Factor (LITAF). The purpose of the present study was to define the molecular pathway(s) associated with Kavain effects on TNF modulation. In vitro studies using WT mouse primary macrophages showed that Kavain significantly reduced E.coli LPS-induced TNF-α production but this effect was almost abrogated in LITAF-/- and ERK2-/- cells. Therefore we reintroduced the ERK2 gene in ERK2-/- cells and partially restored E.coli LPS-induced LITAF-mediated TNF-α production. The translocation of LITAF into to nucleus was found to be dependent on ERK2 S206 residue. Kavain inhibits LITAF/TNF-α expression via dephosphorylation of ERK2 in response to E.coli LPS. Finally, in vivo, Kavain had a significant anti-inflammatory effect on wild type mice that developed Collagen Antibody Induced Arthritis (CAIA), but only a minor effect in ERK2-/- mice also affected by CAIA. Based on these findings, we concluded that ERK2 may be the kinase upstream of LITAF with its Serine residue 206 being crucial for the regulation of LPS-induced TNF-α.
Xiaoren Tang - One of the best experts on this subject based on the ideXlab platform.
-
p53 short peptide (p53pep164) regulates lipopolysaccharide-induced tumor necrosis factor-alpha factor/cytokine expression. Cancer Res
2016Co-Authors: Xiaoren Tang, Manuel Molina, Salomon AmarAbstract:The p53 protein is a sequence-specific DNA-binding factor that can induce apoptosis or activate genes whose dysregula-tion is involved in cancer. By using serial analysis of gene expression technique, p53-induced genes (PIGs) have been identified, one of which was lipopolysaccharide (LPS)– induced tumor necrosis factor-A (TNF-A) factor (LITAF/ PIG7). LITAF regulates the transcription of cytokines such as TNF-A. To further elucidate the role of p53 in LITAF expression, LITAF promoter activity was carefully dissected. In this study, we found that the element required for transcriptional activity is mainly located in the region from 990 to 500 of the LITAF promoter; the specific site required for p53 protein-DNA binding is located between 550 and 500. We also found that transient transfection of either a p53 short DNA sequence, called p53LFB12, or its corresponding 7-amino-acid synthetic peptide from amino acids 164 to 170 (K164Q165S166Q167H168M169T170), named p53pep164, sig-nificantly reduced LITAF promoter activity to 15 % in p53-null H1299 cells. Transfection of p53pep164 into H1299 cells significantly down-regulated LPS-induced LITAF expression as well. Furthermore, transfection of p53pep164 into human monocytes resulted in down-regulation of nine proinflam-matory cytokines, including TNF-A. We also found that the LPS-activated p53 is a short-lived protein, and that p53-orchestrated apoptosis occurs shortly after the initiation stage following LPS stimulation and lasts a short time. Once p53 levels return to baseline, the p53-mediated inhibition of LITAF is released, and LITAF-mediated cytokine production can proceed. The present finding proposes a novel link between p53 and the inflammatory processes and highlights potential interventional approaches to control p53-associated inflam-matory processes. [Cancer Res 2007;67(3):1308–16
-
kavain involvement in lps induced signaling pathways
Journal of Cellular Biochemistry, 2016Co-Authors: Xiaoren Tang, Salomon AmarAbstract:: Kavain, a compound extracted from the Kava plant, Piper methysticum, is found to be involved in TNF-α expression in human and mouse cells via regulation of transcriptional factors such as NF-kB and LITAF. LITAF is known to activate the transcription of more than 20 cytokines that are involved in a variety of cellular processes and is associated with many inflammatory diseases, including angiogenesis, cancer, arthritis, and more. The modulation of LITAF is expected to positively affect cytokine-mediated diseases. Thus, intensive efforts have been deployed in search of LITAF inhibitors. In this work, we found that, in vitro, Kavain reduced LPS- induced TNF-α secretion in mouse macrophages, mouse bone marrow macrophages (BMM), and human peripheral blood mononuclear cells (HPBMC). We also found that Kavain treatment in RAW264.7 cells deactivated MyD88 and Akt, inhibited LITAF, and reduced the production of TNF-α, IL-27, and MIG in response to LPS. Similarly, it had a significant in vivo anti-inflammatory effect on wild-type (WT) mice that developed Collagen Antibody Induced Arthritis (CAIA). Overall, MyD88 was found to be an important mediator of the LPS-induced inflammatory response that can be distinguished from the NF-κB pathway. We also found that MyD88 is involved in the pathway linking LPS/LITAF to TNF-α. Therefore, given that Kavain modulates LPS-induced signaling pathways leading to cytokine expression, therapeutic interventions involving Kavain in inflammatory diseases are warranted. J. Cell. Biochem. 117: 2272-2280, 2016. © 2016 Wiley Periodicals, Inc.
-
kavain inhibition of lps induced tnf α via erk LITAF
Toxicology Research, 2016Co-Authors: Xiaoren Tang, Salomon AmarAbstract:Kavain, an extract from the shrub Piper methysticum, was recently reported to modulate TNF-α expression in both human and mouse cells via regulation of LPS-Induced TNF-Alpha Factor (LITAF). The purpose of the present study was to define the molecular pathway(s) associated with Kavain′s effects on TNF modulation. In vitro studies using WT mouse primary macrophages showed that Kavain significantly reduced E. coli LPS-induced TNF-α production but this effect was almost abrogated in LITAF−/− and ERK2−/− cells. Therefore we reintroduced the ERK2 gene in ERK2−/− cells and partially restored E. coli LPS-induced LITAF-mediated TNF-α production. The translocation of LITAF into to nucleus was found to be dependent on ERK2 S206 residue. Kavain inhibits LITAF/TNF-α expression via dephosphorylation of ERK2 in response to E. coli LPS. Finally, in vivo, Kavain had a significant anti-inflammatory effect on wild type mice that developed Collagen Antibody Induced Arthritis (CAIA), but only a minor effect in ERK2−/− mice also affected by CAIA. Based on these findings, we concluded that ERK2 may be the kinase upstream for LITAF being a crucial factor for Kavain-mediated regulation of LPS-induced TNF-α.
-
kavain inhibition of lps induced tnf α via erk LITAF
Toxicology Research, 2016Co-Authors: Xiaoren Tang, Salomon AmarAbstract:Kavain, an extract from the shrub Piper Methysticum, was recently reported to modulate TNF-α expression in both human and mouse cells via regulation of LPS-Induced TNF-Alpha Factor (LITAF). The purpose of the present study was to define the molecular pathway(s) associated with Kavain effects on TNF modulation. In vitro studies using WT mouse primary macrophages showed that Kavain significantly reduced E.coli LPS-induced TNF-α production but this effect was almost abrogated in LITAF-/- and ERK2-/- cells. Therefore we reintroduced the ERK2 gene in ERK2-/- cells and partially restored E.coli LPS-induced LITAF-mediated TNF-α production. The translocation of LITAF into to nucleus was found to be dependent on ERK2 S206 residue. Kavain inhibits LITAF/TNF-α expression via dephosphorylation of ERK2 in response to E.coli LPS. Finally, in vivo, Kavain had a significant anti-inflammatory effect on wild type mice that developed Collagen Antibody Induced Arthritis (CAIA), but only a minor effect in ERK2-/- mice also affected by CAIA. Based on these findings, we concluded that ERK2 may be the kinase upstream of LITAF with its Serine residue 206 being crucial for the regulation of LPS-induced TNF-α.
-
novel regulation of ccl2 gene expression by murine LITAF and stat6b
PLOS ONE, 2011Co-Authors: Xiaoren Tang, Yu Yang, Salomon AmarAbstract:Inflammation is a multifaceted process: beneficial as a defense mechanism but also detrimental depending on its severity and duration. At the site of injury, inflammatory cells are activated by a cascade of mediators, one of which is LITAF, a transcription regulator known to upregulate TNF-α. We previously showed that human LITAF forms a complex with human STAT6B, which translocates into the nucleus to upregulate cytokine transcription. To dissect the molecular implications of this complex, a murine model was developed and interactions between mouse STAT6B (mSTAT6B) and mouse LITAF (mLITAF) were analyzed. Both mLITAF and mSTAT6B expression were MyD88- and TLR ligand-dependent. Furthermore, mLITAF was found to mediate LPS-induced CCL2 gene transcription with the cooperation of mSTAT6B leading to CCL2 protein expression. In LITAF-deficient mice, mLITAF-mediated CCL2 production in macrophages was significantly reduced compared to the wild-type control animals. Mice knockdown for mSTAT6B by 6BsiRNA1 tail vein injection resulted in a decrease in serum TNF-α and CCL2 production. mLITAF/mSTAT6B complex is proposed to play a role in LPS-induced CCL2 expression and possibly other cytokines.
Veerle Lejon - One of the best experts on this subject based on the ideXlab platform.
-
a litat 1 5 variant surface glycoprotein derived peptide with diagnostic potential for trypanosoma brucei gambiense
Tropical Medicine & International Health, 2013Co-Authors: Liesbeth Van Nieuwenhove, Fatima Balharbi, Michael Humbert, Yves Guisez, Philippe Buscher, Veerle LejonAbstract:objective To evaluate the accuracy of a peptide, corresponding to the variant surface glycoprotein (VSG) LiTat 1.5 amino acid (AA) sequence 268–281 and identified through alignment of monoclonal antibody selected mimotopes, for diagnosis of Trypanosoma brucei gambiense sleeping sickness. methods A synthetic biotinylated peptide (peptide 1.5/268–281), native VSG LiTat 1.3 and VSG LiTat 1.5 were tested in an indirect ELISA with 102 sera from patients with HAT and 102 endemic HAT-negative controls. results The area under the curve (AUC) of peptide 1.5/268–281 was 0.954 (95% confidence interval 0.918–0.980), indicating diagnostic potential. The areas under the curve of VSG LiTat 1.3 and LiTat 1.5 were 1.000 (0.982–1.000) and 0.997 (0.973–1.000), respectively, and significantly higher than the AUC of peptide 1.5/268–281. On a model of VSG LiTat 1.5, peptide 1.5/268–281 was mapped near the top of the VSG. conclusions A biotinylated peptide corresponding to AA 268–281 of VSG LiTat 1.5 may replace the native VSG in serodiagnostic tests, but the diagnostic accuracy is lower than for the full-length native VSG LiTat 1.3 and VSG LiTat 1.5.
-
Identification of mimotopes with diagnostic potential for trypanosoma brucei gambiense variant surface glycoproteins using human antibody fractions
PLoS Neglected Tropical Diseases, 2012Co-Authors: Liesbeth Van Nieuwenhove, Fatima Balharbi, Tessa Dieltjens, Michael Humbert, Yves Guisez, Philippe Buscher, Veerle LejonAbstract:BACKGROUND: At present, screening of the population at risk for gambiense human African trypanosomiasis (HAT) is based on detection of antibodies against native variant surface glycoproteins (VSGs) of Trypanosoma brucei (T.b.) gambiense. Drawbacks of these native VSGs include culture of infective T.b. gambiense trypanosomes in laboratory rodents, necessary for production, and the exposure of non-specific epitopes that may cause cross-reactions. We therefore aimed at identifying peptides that mimic epitopes, hence called "mimotopes," specific to T.b. gambiense VSGs and that may replace the native proteins in antibody detection tests.\n\nMETHODOLOGY/PRINCIPAL FINDINGS: A Ph.D.-12 peptide phage display library was screened with polyclonal antibodies from patient sera, previously affinity purified on VSG LiTat 1.3 or LiTat 1.5. The peptide sequences were derived from the DNA sequence of the selected phages and synthesised as biotinylated peptides. Respectively, eighteen and twenty different mimotopes were identified for VSG LiTat 1.3 and LiTat 1.5, of which six and five were retained for assessment of their diagnostic performance. Based on alignment of the peptide sequences on the original protein sequence of VSG LiTat 1.3 and 1.5, three additional peptides were synthesised. We evaluated the diagnostic performance of the synthetic peptides in indirect ELISA with 102 sera from HAT patients and 102 endemic negative controls. All mimotopes had areas under the curve (AUCs) of ≥0.85, indicating their diagnostic potential. One peptide corresponding to the VSG LiTat 1.3 protein sequence also had an AUC of ≥0.85, while the peptide based on the sequence of VSG LiTat 1.5 had an AUC of only 0.79.\n\nCONCLUSIONS/SIGNIFICANCE: We delivered the proof of principle that mimotopes for T.b. gambiense VSGs, with diagnostic potential, can be selected by phage display using polyclonal human antibodies.
-
identification of peptide mimotopes of trypanosoma brucei gambiense variant surface glycoproteins
PLOS Neglected Tropical Diseases, 2011Co-Authors: Liesbeth Van Nieuwenhove, Fatima Balharbi, Tessa Dieltjens, Yves Guisez, Philippe Buscher, Stijn Roge, Thierry Laurent, Veerle LejonAbstract:BACKGROUND: The current antibody detection tests for the diagnosis of gambiense human African trypanosomiasis (HAT) are based on native variant surface glycoproteins (VSGs) of Trypanosoma brucei (T.b.) gambiense. These native VSGs are difficult to produce, and contain non-specific epitopes that may cause cross-reactions. We aimed to identify mimotopic peptides for epitopes of T.b. gambiense VSGs that, when produced synthetically, can replace the native proteins in antibody detection tests. METHODOLOGY/PRINCIPAL FINDINGS: PhD.-12 and PhD.-C7C phage display peptide libraries were screened with mouse monoclonal antibodies against the predominant VSGs LiTat 1.3 and LiTat 1.5 of T.b. gambiense. Thirty seven different peptide sequences corresponding to a linear LiTat 1.5 VSG epitope and 17 sequences corresponding to a discontinuous LiTat 1.3 VSG epitope were identified. Seventeen of 22 synthetic peptides inhibited the binding of their homologous monoclonal to VSG LiTat 1.5 or LiTat 1.3. Binding of these monoclonal antibodies to respectively six and three synthetic mimotopic peptides of LiTat 1.5 and LiTat 1.3 was significantly inhibited by HAT sera (p<0.05). CONCLUSIONS/SIGNIFICANCE: We successfully identified peptides that mimic epitopes on the native trypanosomal VSGs LiTat 1.5 and LiTat 1.3. These mimotopes might have potential for the diagnosis of human African trypanosomiasis but require further evaluation and testing with a large panel of HAT positive and negative sera.
Qiwei Qin - One of the best experts on this subject based on the ideXlab platform.
-
mir homohsv of singapore grouper iridovirus sgiv inhibits expression of the sgiv pro apoptotic factor LITAF and attenuates cell death
PLOS ONE, 2013Co-Authors: Chuanyu Guo, Xiaohong Huang, Yang Yan, Huachun Cui, Qiwei QinAbstract:Growing evidence demonstrates that various large DNA viruses could encode microRNAs (miRNAs) that regulate host and viral genes to achieve immune evasion. In this study, we report that miR-homoHSV, an miRNA encoded by Singapore grouper iridovirus (SGIV), can attenuate SGIV-induced cell death. Mechanistically, SGIV miR-homoHSV targets SGIV ORF136R, a viral gene that encodes the pro-apoptotic lipopolysaccharide-induced TNF-α (LITAF)-like factor. miR-homoHSV suppressed exogenous and endogenous SGIV LITAF expression, and thus inhibited SGIV LITAF-induced apoptosis. Meanwhile, miR-homoHSV expression was able to attenuate cell death induced by viral infection, presumably facilitating viral replication through the down-regulation of the pro-apoptotic gene SGIV LITAF. Together, our data suggest miR-homoHSV may serve as a feedback regulator of cell death during viral infection. The findings of this study provide a better understanding of SGIV replication and pathogenesis.
-
characterization of lps induced tnfα factor LITAF from orange spotted grouper epinephelus coioides
Fish & Shellfish Immunology, 2013Co-Authors: Jia Cai, Youhua Huang, Shina Wei, Zhengliang Ouyang, Xiaohong Huang, Qiwei QinAbstract:Lipopolysaccharide-induced TNF alpha factor (LITAF) is an important transcription factor that mediates cell apoptosis and inflammatory response. In the present study, we cloned and characterized a LITAF gene from orange-spotted grouper (Epinephelus coioides) (Ec-LITAF). Ec-LITAF encoded a predicted 142 amino acid protein which shared 74% identity to sablefish (Anoplopoma fimbria) LITAF homolog. Multiple amino acid alignment showed that Ec-LITAF contained a typical LITAF domain with two CXXC motifs. Phylogenetic analysis indicated that Ec-LITAF was closely related to that of sablefish. Ec-LITAF mRNA was widely expressed in different tissues and its expression level in spleen was up-regulated after Singapore grouper iridovirus (SGIV) infection. Subcellular localization analysis revealed that the distribution of Ec-LITAF showed diffuse and aggregated patterns in cytoplasm. Interestingly, the distribution of Ec-LITAF overlayed with a viral LITAF homolog (vLITAF) encoded by SGIV. Overexpression of Ec-LITAF in vitro up-regulated the expression of tumor necrosis factors (TNF1 and TNF2) and TNF receptors (TNFR1 and TNFR2), and the expression of itself initiated apoptosis in fish cells. In addition, overexpression of Ec-LITAF not only accelerated SGIV infection induced CPE and cell death, but also increased viral gene transcription. Taken together, our data suggested that Ec-LITAF might play crucial roles during SGIV replication. (C) 2013 Elsevier Ltd. All rights reserved.
-
identification and characterization of a putative lipopolysaccharide induced tnf α factor LITAF homolog from singapore grouper iridovirus
Biochemical and Biophysical Research Communications, 2008Co-Authors: Xiaohong Huang, Youhua Huang, Jie Gong, Yang Yan, Qiwei QinAbstract:Lipopolysaccharide-induced TNF-alpha factor (LITAF), a transcription factor, can regulate tumor necrosis factor alpha (TNF-alpha) transcription. Here, a novel LITAF homolog encoded by Singapore grouper iridovirus (SGIV LITAF) was identified and characterized. The putative SGIV LITAF encoded a protein of 104 amino acids (aa) with a predicted molecular mass of 11.6 kDa. Reverse transcription-PCR (RT-PCR) and Western blot analyses of SGIV-infected cells revealed that SGIV LITAF was an early viral gene. Subcellular localization and immunofluorescence assay revealed that SGIV LITAF expression was distributed predominantly in the cytoplasm, associated with mitochondria. Overexpression of SGIV LITAF induced apoptosis, as shown by increased apoptotic bodies, depolarization of mitochondrial membrane potential (DeltaPsi(m)) and activation of caspase-3. Furthermore, NF-kappaB and NFAT activities were increased in cells expressing SGIV LITAF. This is the first report of the identification and characterization of a viral LITAF homolog involved in virus-host interaction.
Liesbeth Van Nieuwenhove - One of the best experts on this subject based on the ideXlab platform.
-
a litat 1 5 variant surface glycoprotein derived peptide with diagnostic potential for trypanosoma brucei gambiense
Tropical Medicine & International Health, 2013Co-Authors: Liesbeth Van Nieuwenhove, Fatima Balharbi, Michael Humbert, Yves Guisez, Philippe Buscher, Veerle LejonAbstract:objective To evaluate the accuracy of a peptide, corresponding to the variant surface glycoprotein (VSG) LiTat 1.5 amino acid (AA) sequence 268–281 and identified through alignment of monoclonal antibody selected mimotopes, for diagnosis of Trypanosoma brucei gambiense sleeping sickness. methods A synthetic biotinylated peptide (peptide 1.5/268–281), native VSG LiTat 1.3 and VSG LiTat 1.5 were tested in an indirect ELISA with 102 sera from patients with HAT and 102 endemic HAT-negative controls. results The area under the curve (AUC) of peptide 1.5/268–281 was 0.954 (95% confidence interval 0.918–0.980), indicating diagnostic potential. The areas under the curve of VSG LiTat 1.3 and LiTat 1.5 were 1.000 (0.982–1.000) and 0.997 (0.973–1.000), respectively, and significantly higher than the AUC of peptide 1.5/268–281. On a model of VSG LiTat 1.5, peptide 1.5/268–281 was mapped near the top of the VSG. conclusions A biotinylated peptide corresponding to AA 268–281 of VSG LiTat 1.5 may replace the native VSG in serodiagnostic tests, but the diagnostic accuracy is lower than for the full-length native VSG LiTat 1.3 and VSG LiTat 1.5.
-
Identification of mimotopes with diagnostic potential for trypanosoma brucei gambiense variant surface glycoproteins using human antibody fractions
PLoS Neglected Tropical Diseases, 2012Co-Authors: Liesbeth Van Nieuwenhove, Fatima Balharbi, Tessa Dieltjens, Michael Humbert, Yves Guisez, Philippe Buscher, Veerle LejonAbstract:BACKGROUND: At present, screening of the population at risk for gambiense human African trypanosomiasis (HAT) is based on detection of antibodies against native variant surface glycoproteins (VSGs) of Trypanosoma brucei (T.b.) gambiense. Drawbacks of these native VSGs include culture of infective T.b. gambiense trypanosomes in laboratory rodents, necessary for production, and the exposure of non-specific epitopes that may cause cross-reactions. We therefore aimed at identifying peptides that mimic epitopes, hence called "mimotopes," specific to T.b. gambiense VSGs and that may replace the native proteins in antibody detection tests.\n\nMETHODOLOGY/PRINCIPAL FINDINGS: A Ph.D.-12 peptide phage display library was screened with polyclonal antibodies from patient sera, previously affinity purified on VSG LiTat 1.3 or LiTat 1.5. The peptide sequences were derived from the DNA sequence of the selected phages and synthesised as biotinylated peptides. Respectively, eighteen and twenty different mimotopes were identified for VSG LiTat 1.3 and LiTat 1.5, of which six and five were retained for assessment of their diagnostic performance. Based on alignment of the peptide sequences on the original protein sequence of VSG LiTat 1.3 and 1.5, three additional peptides were synthesised. We evaluated the diagnostic performance of the synthetic peptides in indirect ELISA with 102 sera from HAT patients and 102 endemic negative controls. All mimotopes had areas under the curve (AUCs) of ≥0.85, indicating their diagnostic potential. One peptide corresponding to the VSG LiTat 1.3 protein sequence also had an AUC of ≥0.85, while the peptide based on the sequence of VSG LiTat 1.5 had an AUC of only 0.79.\n\nCONCLUSIONS/SIGNIFICANCE: We delivered the proof of principle that mimotopes for T.b. gambiense VSGs, with diagnostic potential, can be selected by phage display using polyclonal human antibodies.
-
identification of peptide mimotopes of trypanosoma brucei gambiense variant surface glycoproteins
PLOS Neglected Tropical Diseases, 2011Co-Authors: Liesbeth Van Nieuwenhove, Fatima Balharbi, Tessa Dieltjens, Yves Guisez, Philippe Buscher, Stijn Roge, Thierry Laurent, Veerle LejonAbstract:BACKGROUND: The current antibody detection tests for the diagnosis of gambiense human African trypanosomiasis (HAT) are based on native variant surface glycoproteins (VSGs) of Trypanosoma brucei (T.b.) gambiense. These native VSGs are difficult to produce, and contain non-specific epitopes that may cause cross-reactions. We aimed to identify mimotopic peptides for epitopes of T.b. gambiense VSGs that, when produced synthetically, can replace the native proteins in antibody detection tests. METHODOLOGY/PRINCIPAL FINDINGS: PhD.-12 and PhD.-C7C phage display peptide libraries were screened with mouse monoclonal antibodies against the predominant VSGs LiTat 1.3 and LiTat 1.5 of T.b. gambiense. Thirty seven different peptide sequences corresponding to a linear LiTat 1.5 VSG epitope and 17 sequences corresponding to a discontinuous LiTat 1.3 VSG epitope were identified. Seventeen of 22 synthetic peptides inhibited the binding of their homologous monoclonal to VSG LiTat 1.5 or LiTat 1.3. Binding of these monoclonal antibodies to respectively six and three synthetic mimotopic peptides of LiTat 1.5 and LiTat 1.3 was significantly inhibited by HAT sera (p<0.05). CONCLUSIONS/SIGNIFICANCE: We successfully identified peptides that mimic epitopes on the native trypanosomal VSGs LiTat 1.5 and LiTat 1.3. These mimotopes might have potential for the diagnosis of human African trypanosomiasis but require further evaluation and testing with a large panel of HAT positive and negative sera.