Download or read book Study of the Regulation of the Human T Cell Leukemia Virus Type 1 HTLV 1 Promoter Formatted in the Context of Chromatin in T Cells and Monocytes written by Devanshi Pandya and published by . This book was released on 2007 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Molecular Analysis of Human T cell Leukemia Virus Regulatory and Accessory Proteins written by Ihab H. Younis and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Human T-cell leukemia virus type 1 (HTLV-1) and type 2 (HTLV-2) are closely related pathogenic human retroviruses. Although, they both transform human primary T cells in vitro, in humans, HTLV-1 is the causative agent for ATLL and HAM/TSP, whereas HTLV-2 disease association is less clear. In this dissertation, we report molecular studies regarding the regulation of HTLV replication and its impact on viral persistence in vivo. In Chapter 2, we generate a novel HTLV-1 clone (H1IT) in which the two regulatory proteins, Tax and Rex, have been separated in an attempt to provide a better reagent to study mutants of these proteins in the context of the provirus and analyze their contribution to HTLV-mediated transformation. In vitro data indicates that H1IT is replication competent and is capable of cellular transformation of primary human T-cells. However, H1IT was unable to persist in vivo, emphasizing the importance of temporal and quantitative regulation of Tax RNA to viral replication. In Chapter 3, we report that both HTLV-1 and HTLV-2 have evolved accessory genes whose products are able to restrict viral replication at a post-transcriptional level. The HTLV-1 p30 and the related HTLV-2 p28 proteins inhibit both Tax and Rex by binding to and retaining tax/rex mRNA in the nucleus, thereby inhibiting virion production. In Chapter 4, we show that p28 is recruited to the viral promoter in a Tax-dependent manner. After recruitment to the promoter, p28 or p30 travels with the transcription elongation machinery until its target mRNA is synthesized. Since the above data is consistent with a critical role of these accessory proteins in viral persistence in vivo, in Chapter 5, we used an animal model of HTLV infection to study the specific contribution of p28 on HTLV-2 survival. In this study, all wtHTLV-2 infected rabbits showed persistent infection, whereas those infected with HTLV-2[delta]p28 were able to eliminate the virus as early as 2 weeks, indicating that p28 is critical for early viral infectivity, spread and/or persistence in rabbits. Collectively, data presented within this dissertation support the conclusion that the regulation of HTLV gene expression a complicated but a tightly controlled process.
Download or read book The Role of Chromatin in the Transcriptional Regulation of the Human T cell Leukemia Virus Type 1 written by Nicole Ann Siddon and published by . This book was released on 2000 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Human T cell leukemia virus 1 HTLV 1 infection associated pathology and response of the host written by Roberto S. Accolla and published by Frontiers Media SA. This book was released on 2023-06-30 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Human T Cell Leukemia Virus written by P.K. Vogt and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: characteristic features in common with the genome of other retroviruses: long terminal repeats (L TR), and coding regions for internal proteins (gag), for re verse transcriptase (pol), and for glycosylated virion surface proteins (env) , ar ranged in the sequence gag, pol, env from the 5' to the 3' end of the genome. However, the HTL V genome also contains some specific features not shared with all other retroviruses: the LTR regions are unusually long (745 base pairs, with 298 base pairs constituting the R region), but unlike the long L TRs of mouse mammary tumor viruses, they do not contain open reading frames. A stretch of noncoding sequences separates the gag and the pol genes. Most interestingly, the HTLV genome contains a region between the 3' end of the env gene and the L TR, called the pX region, that encompasses four open reading frames. Leukemic T cells freshly obtained from patients contain the HTL V provirus but usually do not express it. However, once established in culture, these cells produce viral proteins and release type C particles. Likewise, T cells infected and transformed by HTL V in vitro synthesize virus. Such producing cell lines have been widely used in seroepidemiological surveys and continue to be of importance for detailed studies of viral proteins and nucleic acids.
Download or read book Molecular Analysis of Human T cell Leukemia Virus Type 2 Accessory Protein written by Brenda Michiyo Yamamoto and published by . This book was released on 2009 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The human T-cell leukemia virus type 1 (HTLV-1) and type 2 (HTLV-2) are two pathogenic retroviruses. Although both viruses share a common genome organization and amino acid homology in common viral proteins, the incidence of disease with infection is distinct. Infection with HTLV-1 may result in the development of adult T-cell leukemia/lymphoma (ATL), an aggressive neoplastic disease, or a variety of immune-mediated/inflammatory disorders such as HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP), whereas HTLV-2 is less pathogenic. Our studies focused on the open reading frame II encoded p28 protein of HTLV-2, which has been shown to negatively regulate viral expression by the nuclear retention of the tax/rex mRNA. A similar post-transcriptional regulatory function has been observed with HTLV-1 ORF-II p30. However, p28 contrasts p30 in that there appears to be no significant transcriptional effects. In Chapter 2, we examined the functional significance of p28 in HTLV-2 infection, proliferation, and immortalization of primary T-cells in culture, and viral infection and survival in a rabbit model of HTLV infection. We generated a novel HTLV-2 p28 termination clone (HTLV2Deltap28) in which a stop codon had been introduced into the p28 sequence without altering the amino acid sequence of the overlapping regulatory proteins, Tax and Rex. In short-term proliferation and long-term immortalization coculture assays, HTLV2Deltap28 infected and immortalized primary human T-cells, similar to wtHTLV-2. However, HTLV2Deltap28 had a lower capacity to establish persistent infection in rabbits, indicating the in vivo importance of HTLV-2 p28. These results are consistent with the hypothesis that p28 repression of Tax and Rex-mediated viral gene expression allows infected cells to avoid immune recognition and elimination, or acts to enhance early viral spread by enhancing the survival of HTLV-2 infected cells. In Chapter 3, we generated and characterized various dual-promoter and single-promoter lentiviral expression vectors. Post-transduction, p28 protein was readily detected with the dual-promoter vectors in 293T cells but not in Jurkat T-cells. The differential p28 protein expression was found to be due to cell-type specific translation mechanisms. To circumvent this problem we utilized a single-promoter lentiviral vector that expresses p28 via the murine stem cell virus (MSCV)-promoter, which resulted in efficient p28 protein expression in both T-cell lines and primary human CD8+ T-lymphocytes. In Chapter 4, the capacity of p28 to modify cellular gene expression was examined. In transient transfection studies, low doses of p28 modulated CRE- and NF[kappa]B-driven reporter constructs in 293T cells, suggesting the ability of p28 in modulating cellular gene expression. Interestingly, transduction of Jurkat T-cells with the lentiviral p28 expression vector had no significant effect on cellular proliferation. Additionally, initial analysis of global cellular gene expression by microarray analysis suggests that p28 results in nominal alterations in cellular gene expression. Collectively, data presented in this thesis indicates that p28 is critical for the establishment and survival of HTLV-2, compatible with the conclusion that the regulation of HTLV gene expression is a tightly controlled and complex process. Ultimately, while minimal, the impact of p28 upon cellular genes likely contributes to HTLV-2 establishment of infection in vivo.
Download or read book Regulation of the P21WAF1 Promoter by Human T Cell Leukemia Virus Type I HTLV I Tax written by Julie Christine Watt and published by . This book was released on 2005 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Regulation of Human T cell Leukemia Virus Type 1 Infection and Replication written by Gunjan Choudhary and published by . This book was released on 2010 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: Retroviruses have evolved complex mechanisms to regulate their cellular tropism and gene expression. It is generally accepted that productive infections proceed via interactions between viral envelope molecules and specific receptors on the host cell surface. Currently, there is no known receptor for HTLV-1, though a number of factors that enhance entry have been identified. In an effort to identify a cellular receptor or attachment factor for HTLV-1, we carried out a retroviral cDNA library screen, in which cDNA from permissive HeLa S3 cells was introduced into poorly susceptible NIH 3T3 cells. These cells were selected after infection with HTLV-1 envelope pseudotyped viral particles expressing a drug resistance gene. We isolated approximately 460 cDNAs, of which 20 were prioritized as potential candidates. These candidates are being tested to determine if they participate in viral entry. In addition to encoding the structural and enzymatic genes common to all retroviruses, HTLV-1 also encodes several accessory genes which contribute to viral replication and the maintenance of gene expression. A newly identified viral gene, HTLV-1 bZIP factor or hbz, has been shown to have pleiotropic effects as it functions differently in its protein and mRNA forms. In an effort to elucidate its role in HTLV-1 replication, we identified a novel function. Mutations that abrogated the hbz mRNA or disrupted a stem-loop in hbz mRNA, or mutations that eliminated or truncated the HBZ protein were introduced in a functional molecular clone of HTLV-1. The protein and stem-loop mutants had no effect on viral gene expression. However, the mutant that disrupted hbz mRNA expressed lower levels of tax mRNA, suggesting that hbz promotes tax expression. We found that this effect of hbz was indirect, as hbz represses another accessory gene, p30II, which is known to sequester tax mRNA in the nucleus. These results provide new insights into the regulation of HTLV-1 infection, specifically viral entry and gene expression.
Download or read book Kinetic Analysis of Human T cell Leukemia Virus Type 1 Gene Expression written by Min Li and published by . This book was released on 2008 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Human T-cell leukemia virus type 1 (HTLV-1) and type 2 (HTLV-2) are closely related human retroviruses that transform T lymphocytes in cell culture and persist in infected individuals. HTLV-1 infection is clearly associated with leukemia/lymphoma and neurological disease, whereas HTLV-2 disease association is less compelling. HTLV replication and survival requires the expression of multiple gene products from an unspliced and a series of highly related alternatively spliced mRNA species. To date, the levels of viral gene expression throughout the process of infection, cellular transformation, and pathogenesis have not been experimentally assessed. We posit that having a concise viral gene expression profile will provide important insight into the function of specific viral genes and their role in the biology and pathogenesis of HTLV-1.
Download or read book Human T Cell Leukemia Virus Type I Basic Leucine Zipper Factor HBZ Modulates Cellular DNA Damage Repair and Antioxidant Responses to Promote Host Cell Survival and Leukemogenesis written by Amanda W Rushing and published by . This book was released on 2018 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: Approximately twenty million people worldwide are infected with Human T-cell Leukemia Virus type 1 (HTLV-1). HTLV-1 establishes a life-long, chronic infection which can result in the development of severe HTLV-1 associated diseases: Adult T-cell Leukemia (ATL) or HTLV-1-associated myelopathy/ tropical spastic paraparesis (HAM/TSP). ATL is a fatally-aggressive lymphoproliferative disorder of HTLV-1-infected CD4+ T-cells. HAM/TSP is a debilitating neurodegenerative disorder that greatly reduces quality of life. There exists a distinct lack of effective vaccine and therapeutic options for both ATL and HAM/TSP patients. Though the mechanisms that drive HTLV-1 pathogenesis remain poorly understood, extensive study of the virus has revealed the importance of two viral regulatory proteins in disease progression: Tax and HBZ. Tax is a transcriptional regulator which is important for establishing initial infection; however, Tax is highly immunogenic and stimulates a robust antiviral immune response. To evade immune detection, HTLV-1 host cells often silence Tax expression through the transcriptionally repressive activity of the basic leucine zipper factor HBZ. HBZ is expressed throughout all phases of infection and plays important roles in maintaining host cell survival and clonal expansion. HBZ expression is sufficient to induce ATL-like disease progression in in vivo models, supporting its contribution to leukemogenesis in patients. Here, we report novel functions of HBZ that may promote the long-term survival of infected lymphocytes, including the direct upregulation of antioxidant response gene expression, the detoxification of reactive oxygen species, and the prevention of oxidative stress-induced cell death. We also evaluated the contribution of HBZ to the accumulation of genetic abnormalities which may promote leukemogenesis. Here, we report that HBZ contributes to genetic instability by affecting the double-stranded DNA damage repair system non-homologous end joining (NHEJ), possibly through specific interactions with DNA repair proteins. These findings support the role of HBZ in promoting leukemogenesis through the accumulation of chromosomal abnormalities which arise from double-stranded DNA breaks. Together, the data presented here indicate that HBZ is an important driving force in the prolonged survival and transformation of HTLV-1-infected lymphocytes.
Download or read book Transformation Studies of Human T cell Leukemia Virus with Emphasis on the Role of Tax and Rex written by Jianxin Je and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: HTLV-1 and HTLV-2 both transform human primary T cells but the precise transformation mechanism remains to be elucidated. We studied two HTLV regulatory proteins, Tax and Rex, and their role in HTLV-mediated cellular transformation. HTLV-1 has a preferential transformation tropism of CD4+ T cells, whereas HTLV-2 transforms primarily CD8+ T cells. Since Tax is critical for cellular transformation and differences have been identified between Tax-1 and Tax-2, we hypothesize that the viral determinant of transformation tropism is encoded by Tax. Using molecular clones of HTLV-1 (Ach) and HTLV-2 (pH6neo) we constructed recombinants in which Tax and overlapping Rex genes of the two viruses were exchanged. p19 Gag expression from proviral clones transfected into 293T cells indicated that both recombinants contained functional Tax and Rex but with significantly altered activity as compared to the wild-type clones. Stable transfectants expressing recombinant viruses were established, irradiated, and cocultured with peripheral blood mononuclear cells (PBMC). Both recombinants were competent to transform T-lymphocytes with efficiency similar to the parental viruses. Flow cytometry analysis indicated that HTLV-1 and HTLV-1/TR2 had a preferential tropism for CD4+ T cells and HTLV-2 and HTLV-2/TR1 had a preferential tropism for CD8+ T cells. Our results indicate that tax/rex in different genetic backgrounds display altered functional activity but ultimately do not contribute to the different in vitro transformation tropism. We also studied the contribution of Rex in HTLV-1-mediated immortalization of primary T-cells in vitro and viral survival in a rabbit animal model. Our results provide the first direct evidence that Rex and its function to modulate viral gene expression and virion production is not required for in vitro immortalization by HTLV-1. However, Rex is critical for efficient infection of cells and persistence in vivo. Efficient HTLV replication requires Rex/RxRE regulation of incompletely spliced viral mRNAs that encode the viral enzymatic and structural proteins. Overall, our results indicate that post-transcriptional control elements identified in other viruses have a partial capacity to substitute for HTLV Rex/RxRE function, although the low activities of these elements are insufficient to maintain viral replication and virus spread in culture. Together this work provides important information on the role of Tax and Rex on HTLV replication and cellular transformation and further insight into the biological differences between HTLV-1 and HTLV-2.
Download or read book Subcellular Localization of Human T cell Leukemia Virus Type 1 Tax Oncoprotein written by Kimberly Anne Fryrear and published by . This book was released on 2008 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Molecular Mechanisms of Monocyte Depletion and CD4 T cell Persistence During Human T cell Leukemia Virus Infection written by Alexandre Sze and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Human T-cell Leukemia Virus type 1 (HTLV-1) was the first human retrovirus discovered in 1980. It is the causal agent of two well characterized human diseases, Adult T-cell Leukemia (ATL) and HTLV-1-Associated Myelopathy/Tropical Spastic Paraparesis (HAM/TSP). Few treatment options have been developed for ATL and HAM/TSP; the median survival times for ATL remains under a year, and treatment options of HAM/TSP remain palliative in nature. Thankfully the incidence of disease in HTLV-1 infected patients is relatively low, with only approximately 5% of individuals developing ATL and 2% HAM/TSP. One major obstacle in the development of effective therapies is a lack of understanding regarding the factors that determine HTLV-1 associated pathology. The route of transmission, contaminated breast milk and blood, almost exclusively lead to ATL or HAM/TSP development respectively, but it is unclear as to why. This suggests that the early events of HTLV-1 infection may be key in discerning pathological outcomes. Unfortunately this time point is understudied, in part due to the fact that de novo infection is asymptomatic. The activity of cytotoxic T-cell lymphocytes seems to be vital in controlling viral replication, and is likely a key determinant in disease progression. We thus set out to study the early events of HTLV-1 infection in two important immunologically relevant peripheral blood mononuclear cell populations, monocytes and CD4+ T-cells. HTLV-1 infection of primary human monocytes resulted in the depletion of this cell type. This was not mediated by viral accessory proteins, as host restriction factor SAMHD1 prevented the completion of reverse transcription. The DNA by-products of this inhibition induced a potent STING-mediated immunological response, that triggered Bax and IRF3 activation and complex formation that led to apoptosis. Infection of activated CD4+ T-cells on the other hand, resulted in persistent cellular survival. This was mediated by the viral accessory protein Tax, known to have oncogenic properties. Tax expression activated the AKT pathway, which resulted in the inactivation of the pro-apoptotic FOXO3a transcription factor. This led to the long-term survival of an activated CD4+ T-cell population that was capable of viral transmission. Overall this work has demonstrated the molecular consequences of HTLV-1 infection in two important cell types, monocytes and CD4+ T-cells. These events likely shape the subsequent immunological events that control viral replication and likely influence HTLV-1 disease pathology." --
Download or read book Studies with the Human T cell Leukemia Virus Tax and Rex Positive Trans regulatory Proteins written by Matthew David Anderson and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Retroviruses have highly organized genomes that encode a large number of proteins from a relatively short nucleic acid sequence. They utilize a variety of methods to achieve this, including the use of overlapping reading frames and the production of multiple RNAs through alternative splicing. In order to efficiently express RNAs encoding structural and enzymatic proteins, complex retroviruses like human T-cell leukemia virus (HTLV) must first express a doubly spliced RNA encoding both the Tax and Rex positive transregulatory proteins in separate but partially overlapping reading frames. As a result, functional studies of each of these proteins in the context of replicating virus, particularly mutational studies, present unique challenges. This dissertation both describes and utilizes experimental systems for the study of Tax and Rex that model in vivo in the context of replicating virus in human T cells, the natural target of HTLV infection. As a whole, the work described in this dissertation uses methods for the study of the HTLV regulatory proteins Tax-1 and Rex-2 that closely approximate conditions that occur in in vivo HTLV infections. Ideally this is an infection of primary human T-lymphocytes. This approach provides highly relevant insight into the molecular mechanisms utilized by these proteins, validates previous results obtained from in vitro studies as well as extends and refines our understanding of the way these proteins function in natural infection.
Download or read book Effects of Chromatin Insulator CTCF and HTLV 1 Hbz MRNA on HTLV 1 Biology and Pathogenesis written by Michael P. Martinez and published by . This book was released on 2020 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: Human T-cell leukemia virus type 1 (HTLV-1) is deltaretrovirus with an estimated 5-10 million individuals infected worldwide. HTLV-1 is the etiologic agent of a non- Hodgkin’s peripheral T-cell malignancy called adult T-cell leukemia/lymphoma (ATL) and a demyelinating lymphocytic meningomyelitis termed HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Approximately 10% of infected individuals will develop ATL or HAM/TSP and there are limited treatment options. Examining the viral and cellular determinants that modulate early infection is vital to our understanding HTLV-1 pathobiology. Recently a binding site for the multifunctional DNA-binding protein CTCF was identified at a sharp border of epigenetic modification within the HTLV-1 provirus.
Download or read book Role of Human T lymphotropic Virus Type 1 P30 II and Surface Envelope as Determinants of in Vivo Pathogenesis written by Lee Silverman and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Human T-cell leukemia virus type 1 (HTVL-1) is the first identified human retrovirus. In addition to gag, pol, and env genes, HTLV-1 contains four open reading frames (ORF) within its pX region. ORF II encodes p30II and p13II. Herein, we determine the in vivo significance of p30II by inoculating rabbits with cell lines expressing either a wild-type clone of HTLV-1 (ACH. 1) or a p30II mutant clone (ACH. 30.1). Compared to ACH. 1 rabbits, ACH. 30.1 rabbits had lower antibody titers, a smaller percentage of seropositive animals, a smaller percentage of animals with provirus in peripheral blood mononuclear cells (PBMC), and lower proviral loads. Sequencing revealed that provirus in ACH. 30.1 provirus positive rabbits had reverted to wild-type sequence. We conclude that there is strong selective pressure for expression of p30II in vivo. We next sought to determine if p30II modulates cellular apoptosis. A greater percentage of ACH. 30.1 cells were induced into apoptosis compared to ACH. 1 cells following treatment with camptothecin (specific for S-phase of cell cycle). There was no difference in apoptosis induction between ACH. 30.1 and ACH. 1 cells following treatment with etoposide (intrinsic pathway) or TRAIL (extrinsic pathway). p30II did not modulate susceptibility to apoptosis when expressed in 293T cells or in Jurkat T cells. Expression of p30II in Jurkat T cells reduced cell proliferation by delaying onset of division. Although p30II does not modulate susceptibility to apoptosis, it does reduce cell proliferation. HTLV-1 Env Ser75Ile, Asn95Asp, and Asn195Asp mutants are able to immortalize lymphocytes in vitro. Herein, we examine the effects of these mutations in rabbits via inoculations with ACH. 75, ACH. 95, ACH. 195, and ACH. 1 cell lines. All mutations were maintained in vivo. ACH. 75 and ACH. 95 rabbits had decreased antibody responses to Gag and Env. One ACH. 195 rabbit had an antibody response to HTLV-1 proteins and HTLV-2 Env. Another ACH. 195 rabbit had provirus in PBMC but no serologic response. ACH. 195 rabbits had a diminished antibody response to Env surface (SU) protein. PBMC proviral loads did not correlate with antibody response to SU. These mutations in HTLV-1 Env SU alter proviral loads and antibody responses against Env but do not prevent virus replication in vivo.
Download or read book Characterization of Human T cell Leukemia Virus 1 Reverse Transcriptase written by Pinky Gundayao Agbuya and published by . This book was released on 2000 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt:
