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Yu FH, Wang CT. HIV-1 protease with leucine zipper fused at N-terminus exhibits enhanced linker amino acid-dependent activity. Retrovirology 2018; 15:32. [PMID: 29655366 PMCID: PMC5899837 DOI: 10.1186/s12977-018-0413-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 04/05/2018] [Indexed: 01/24/2023] Open
Abstract
Background HIV-1 protease (PR) activation is triggered by Gag-Pol dimerization. Premature PR activation results in reduced virion yields due to enhanced Gag cleavage. A p6* transframe peptide located directly upstream of protease is believed to play a modulating role in PR activation. Previous reports indicate that the C-terminal p6* tetra-peptide prevents premature PR activation triggered by a leucine zipper (LZ) dimerization motif inserted in the deleted p6* region. To clarify the involvement of C-terminal p6* residues in mitigating enhanced LZ-incurred Gag processing, we engineered constructs containing C-terminal p6* residue substitutions with and without a mutation blocking the p6*/PR cleavage site, and created other Gag or p6* domain-removing constructs. The capabilities of these constructs to mediate virus maturation were assessed by Western blotting and single-cycle infection assays. Results p6*-PR cleavage blocking did not significantly reduce the LZ enhancement effect on Gag cleavage when only four amino acid residues were present between the p6* and PR. This suggests that the potent LZ dimerization motif may enhance PR activation by facilitating PR dimer formation, and that PR precursors may trigger sufficient enzymatic activity without breaking off from the PR N-terminus. Enhanced LZ-induced activation of PR embedded in Gag-Pol was found to be independent of the Gag assembly domain. In contrast, the LZ enhancement effect was markedly reduced when six amino acids were present at the p6*-PR junction, in part due to impaired PR maturation by substitution mutations. We also observed that a proline substitution at the P3 position eliminated the ability of p6*-deleted Gag-Pol to mediate virus maturation, thus emphasizing the importance of C-terminal p6* residues to modulating PR activation. Conclusions The ability of HIV-1 C-terminal p6* amino acid residues to modulate PR activation contributes, at least in part, to their ability to counteract enhanced Gag cleavage induced by a leucine zipper substituted for a deleted p6*. Changes in C-terminal p6* residues between LZ and PR may affect PR-mediated virus maturation, thus providing a possible method for assessing HIV-1 protease precursor activation in the context of virus assembly.
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Affiliation(s)
- Fu-Hsien Yu
- Department of Medical Research, Taipei Veterans General Hospital and Institute of Clinical Medicine, National Yang-Ming University School of Medicine, 201, Sec. 2, Shih-Pai Road, Taipei, 11217, Taiwan
| | - Chin-Tien Wang
- Department of Medical Research, Taipei Veterans General Hospital and Institute of Clinical Medicine, National Yang-Ming University School of Medicine, 201, Sec. 2, Shih-Pai Road, Taipei, 11217, Taiwan.
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Huang SW, Wang SF, Lin YT, Yen CH, Lee CH, Wong WW, Tsai HC, Yang CJ, Hu BS, Lin YH, Wang CT, Wang JJ, Hu Z, Kuritzkes DR, Chen YH, Chen YMA. Patients infected with CRF07_BC have significantly lower viral loads than patients with HIV-1 subtype B: mechanism and impact on disease progression. PLoS One 2014; 9:e114441. [PMID: 25502811 PMCID: PMC4263662 DOI: 10.1371/journal.pone.0114441] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Accepted: 11/07/2014] [Indexed: 11/21/2022] Open
Abstract
The circulating recombinant form (CRF) 07_BC is the most prevalent HIV-1 strain among injection drug users (IDUs) in Taiwan. It contains a 7 amino-acid deletion in its p6gag. We conducted a cohort study to compare viral loads and CD4 cell count changes between patients infected with subtype B and CRF07_BC and to elucidate its mechanism. Twenty-one patients infected with CRF07_BC and 59 patients with subtype B were selected from a cohort of 667 HIV-1/AIDS patients whom have been followed up for 3 years. Generalized estimated equation was used to analyze their clinical data and the results showed that patients infected with CRF07_BC had significantly lower viral loads (about 58,000 copies per ml less) than patients with subtype B infection (p = 0.002). The replicative capacity of nine CRF07_BC and four subtype B isolates were compared and the results showed that the former had significantly lower replicative capacity than the latter although all of them were CCR5- tropic and non-syncytium inducing viruses. An HIV-1-NL4-3 mutant virus which contains a 7 amino-acid deletion in p6gag (designated as 7d virus) was generated and its live cycle was investigated. The results showed that 7d virus had significantly lower replication capacity, poorer protease-mediated processing and viral proteins production. Electron microscopic examination of cells infected with wild-type or 7d virus demonstrated that the 7d virus had poorer and slower viral maturation processes: more viruses attached to the cell membrane and higher proportion of immature virions outside the cells. The interaction between p6gag and Alix protein was less efficient in cells infected with 7d virus. In conclusion, patients infected with CRF07_BC had significantly lower viral loads than patients infected with subtype B and it may due to the deletion of 7 amino acids which overlaps with Alix protein-binding domain of the p6gag.
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Affiliation(s)
- Szu-Wei Huang
- Center for Infectious Disease and Cancer Research (CICAR), Kaohsiung Medical University, Kaohsiung, Taiwan
- Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan
| | - Sheng-Fan Wang
- Center for Infectious Disease and Cancer Research (CICAR), Kaohsiung Medical University, Kaohsiung, Taiwan
- Department of Medical Laboratory Science and Biotechnology, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Yu-Ting Lin
- Center for Infectious Disease and Cancer Research (CICAR), Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Chia-Hung Yen
- Center for Infectious Disease and Cancer Research (CICAR), Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Chih-Hao Lee
- Center for Infectious Disease and Cancer Research (CICAR), Kaohsiung Medical University, Kaohsiung, Taiwan
- Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan
| | - Wing-Wai Wong
- Section of Infectious Diseases, Department of Internal Medicine, Taipei Veterans' General Hospital, Taipei, Taiwan
| | - Hung-Chin Tsai
- Section of Infectious Diseases, Department of Internal Medicine, Kaohsiung Veterans' General Hospital, Kaohsiung, Taiwan
| | - Chia-Jui Yang
- Section of Infectious Diseases, Department of Internal Medicine, Far Eastern Memorial Hospital, New Taipei City, Taiwan
| | - Bor-Shen Hu
- Section of Infectious Diseases, Department of Internal Medicine, Taipei City Hospital, Taipei, Taiwan
| | - Yu-Huei Lin
- Section of Infectious Diseases, Department of Internal Medicine, Taichung Veterans' General Hospital, Taichung, Taiwan
| | - Chin-Tien Wang
- Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Jaang-Jiun Wang
- Department of Pediatrics, Children's Healthcare of Atlanta and Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Zixin Hu
- Division of Infectious Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Daniel R. Kuritzkes
- Division of Infectious Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Yen-Hsu Chen
- School of Medicine, Graduate Institute of Medicine, Sepsis Research Center, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
- Division of Infectious Diseases, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
| | - Yi-Ming Arthur Chen
- Center for Infectious Disease and Cancer Research (CICAR), Kaohsiung Medical University, Kaohsiung, Taiwan
- Department of Microbiology, Institute of Medical Research and Institute of Clinical Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
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Garrod TJ, Gargett T, Yu W, Major L, Burrell CJ, Wesselingh S, Suhrbier A, Grubor-Bauk B, Gowans EJ. Loss of long term protection with the inclusion of HIV pol to a DNA vaccine encoding gag. Virus Res 2014; 192:25-33. [PMID: 25152448 DOI: 10.1016/j.virusres.2014.08.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Revised: 08/11/2014] [Accepted: 08/14/2014] [Indexed: 11/29/2022]
Abstract
Traditional vaccine strategies that induce antibody responses have failed to protect against HIV infection in clinical trials, and thus cell-mediated immunity is now an additional criterion. Recent clinical trials that aimed to induce strong T cell responses failed to do so. Therefore, to enhance induction of protective T cell responses, it is crucial that the optimum antigen combination is chosen. Limited research has been performed into the number of antigens selected for an HIV vaccine. This study aimed to compare DNA vaccines encoding either a single HIV antigen or a combination of two antigens, using intradermal vaccination of C57BL/6 mice. Immune assays were performed on splenocytes, and in vivo protection was examined by challenge with a chimeric virus, EcoHIV, able to infect mouse but not human leukocytes, at 10 days (short term) and 60 days (long term) post final vaccination. At 60 days there was significantly lower frequency of induced antigen-specific CD8(+) T cells in the spleens of pCMVgag-pol-vaccinated mice compared with mice which received pCMVgag only. Most importantly, short term viral control of EcoHIV was similar for pCMVgag and pCMVgag-pol-vaccinated mice at day 10, but only the pCMVgag-vaccinated significantly controlled EcoHIV at day 60 compared with pCMV-vaccinated mice, showing that control was reduced with the inclusion of the HIV pol gene.
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Affiliation(s)
- Tamsin J Garrod
- Virology Laboratory, Basil Hetzel Institute, Department of Surgery, University of Adelaide, Adelaide, Australia.
| | - Tessa Gargett
- Virology Laboratory, Basil Hetzel Institute, Department of Surgery, University of Adelaide, Adelaide, Australia
| | - Wenbo Yu
- Virology Laboratory, Basil Hetzel Institute, Department of Surgery, University of Adelaide, Adelaide, Australia
| | - Lee Major
- Inflammation Biology Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | | | - Steven Wesselingh
- South Australian Health and Medical Research Institute, Adelaide, Australia
| | - Andreas Suhrbier
- Inflammation Biology Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - Branka Grubor-Bauk
- Virology Laboratory, Basil Hetzel Institute, Department of Surgery, University of Adelaide, Adelaide, Australia
| | - Eric J Gowans
- Virology Laboratory, Basil Hetzel Institute, Department of Surgery, University of Adelaide, Adelaide, Australia
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Pan YY, Wang SM, Huang KJ, Chiang CC, Wang CT. Placement of leucine zipper motifs at the carboxyl terminus of HIV-1 protease significantly reduces virion production. PLoS One 2012; 7:e32845. [PMID: 22396796 PMCID: PMC3291649 DOI: 10.1371/journal.pone.0032845] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Accepted: 01/31/2012] [Indexed: 11/19/2022] Open
Abstract
Natural HIV-1 protease (PR) is homodimeric. Some researchers believe that interactions between HIV-1 Gag-Pol molecules trigger the activation of embedded PR (which mediates Gag and Gag-Pol cleavage), and that Gag-Pol assembly domains outside of PR may contribute to PR activation by influencing PR dimer interaction in a Gag-Pol context. To determine if the enhancement of PR dimer interaction facilitates PR activation, we placed single or tandem repeat leucine zippers (LZ) at the PR C-terminus, and looked for a correlation between enhanced Gag processing efficiency and increased Gag-PR-LZ multimerization capacity. We found significant reductions in virus-like particles (VLPs) produced by HIV-1 mutants, with LZ fused to the end of PR as a result of enhanced Gag cleavage efficiency. Since VLP production can be restored to wt levels following PR activity inhibition, this assembly defect is considered PR activity-dependent. We also found a correlation between the LZ enhancement effect on Gag cleavage and enhanced Gag-PR multimerization. The results suggest that PR dimer interactions facilitated by forced Gag-PR multimerization lead to premature Gag cleavage, likely a result of premature PR activation. Our conclusion is that placement of a heterologous dimerization domain downstream of PR enhances PR-mediated Gag cleavage efficiency, implying that structural conformation, rather than the primary sequence outside of PR, is a major determinant of HIV-1 PR activation.
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Affiliation(s)
- Yen-Yu Pan
- Department of Medical Research and Education, Taipei Veterans General Hospital, Taipei, Taiwan
- Institute of Clinical Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Shiu-Mei Wang
- Institute of Clinical Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Kuo-Jung Huang
- Department of Medical Research and Education, Taipei Veterans General Hospital, Taipei, Taiwan
| | - Chien-Cheng Chiang
- Institute of Clinical Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Chin-Tien Wang
- Department of Medical Research and Education, Taipei Veterans General Hospital, Taipei, Taiwan
- Institute of Clinical Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan
- * E-mail:
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Chiang CC, Tseng YT, Huang KJ, Pan YY, Wang CT. Mutations in the HIV-1 reverse transcriptase tryptophan repeat motif affect virion maturation and Gag-Pol packaging. Virology 2011; 422:278-87. [PMID: 22104208 DOI: 10.1016/j.virol.2011.11.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Revised: 08/30/2011] [Accepted: 11/01/2011] [Indexed: 11/29/2022]
Abstract
Our goal was to determine the contribution of HIV-1 reverse transcriptase tryptophan repeat motif residues to virion maturation. With the exception of W402A, we found none of the single substitution mutations exerted major impacts on virus assembly or processing. However, all mutants except for W410A exhibited significant decreases in virus-associated RT, presumably a result of unstable RT mutant degradation. Mutations W398A, W401A and W406A decreased the enhancement effect of efavirenz on PR-mediated Gag processing efficiency, which is in agreement with their destabilizing RT effects. Furthermore, combined double or triple W398, W401 and W406 mutations significantly affected virus processing and Gag-Pol packaging. Further analyses suggest that inefficient PR-mediated Gag cleavage partly accounts for the virion processing defect. Our results support the idea that in addition to playing a role in RT heterodimer stabilization, the RT Trp repeat motif in the Gag-Pol context is also involved in PR activation via Gag-Pol/Gag-Pol interaction.
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Affiliation(s)
- Chien-Cheng Chiang
- Department of Medical Research and Education, Taipei Veterans General Hospital and Institute of Clinical Medicine, National Yang-Ming University School of Medicine, Taipei, Taiwan
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Mutations at human immunodeficiency virus type 1 reverse transcriptase tryptophan repeat motif attenuate the inhibitory effect of efavirenz on virus production. Virology 2008; 383:261-70. [PMID: 19019404 DOI: 10.1016/j.virol.2008.10.027] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2008] [Revised: 08/15/2008] [Accepted: 10/18/2008] [Indexed: 11/22/2022]
Abstract
HIV-1 virus particle processing is mediated by protease (PR), with enzymatic activation triggered by Gag-Pol/Gag-Pol interaction. We previously reported that truncation mutations at the reverse transcriptase (RT) connection subdomain markedly impair virus particle processing, suggesting an important role for the RT subdomain in PR-mediated virus processing. A highly conserved tryptophan (Trp) repeat motif of the HIV-1 RT connection subdomain is involved in RT dimerization. Our goal in this study was to determine whether mutations at the Trp repeat motif have any effect on PR-mediated virus processing. Our results indicate that even though alanine substitutions at W401 (W401A) or at both W401 and W402 (W401A/W402A) have no major effect on steady-state virus processing, the combined W401A/W402A mutations partially negate and the W401A mutation almost completely negates an efavirenz (EFV)-imposed barrier to virus production. The combination of RT instability and poor enzymatic activity reflects a RT dimerization defect incurred by the mutations. We also found that an artificial p66RT carrying the W401A or W401A/W402A mutations was packaged into virions more efficiently than wild-type p66RT, and that the viral incorporation of p66RT is significantly reduced by EFV, implying a novel effect of EFV on RT-Gag interaction. Our results suggest that the Trp repeat motif may play a role in the Gag-Pol/Gag-Pol interaction that contributes to subsequent PR activation.
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Lau TS, Li Y, Kameoka M, Ng TB, Wan DCC. Suppression of HIV replication using RNA interference against HIV-1 integrase. FEBS Lett 2007; 581:3253-9. [PMID: 17592732 DOI: 10.1016/j.febslet.2007.06.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2007] [Revised: 05/04/2007] [Accepted: 06/01/2007] [Indexed: 11/22/2022]
Abstract
RNA interference (RNAi) has become one of the most powerful and popular approach on gene silencing in clinical research study especially in virology due to the gene-specific suppression property of small interfering RNA (siRNA). In this report, we demonstrate that expression of vector-mediated small hairpin RNA (shRNA) against human immunodeficiency virus type 1 (HIV-1) integrase (IN), one of the three important enzymes in HIV infection by controlling the integration of viral RNA to host DNA, could suppress the protein synthesis of EGFP-tagged IN in HeLa cell model efficiently. Furthermore, we show that IN shRNA can successfully reduce the HIV particles production in 293T cells at the level similar to the positive control of HIV-1 tat shRNA. These results provide the therapeutic possibility of HIV replication using RNAi against HIV-1 integrase.
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Affiliation(s)
- Tat San Lau
- Department of Biochemistry, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, China
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Bukrinskaya A. HIV-1 matrix protein: a mysterious regulator of the viral life cycle. Virus Res 2007; 124:1-11. [PMID: 17210199 DOI: 10.1016/j.virusres.2006.07.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2006] [Revised: 06/30/2006] [Accepted: 07/05/2006] [Indexed: 01/17/2023]
Abstract
Significant progress has been achieved in the last few years concerning the human immunodeficiency virus (HIV-1) life cycle, mostly in the fields of cellular receptors for the virus, virus assembly and budding of virus particles from the cell surface. Meanwhile, some aspects, such as postentry events, virus maturation and the regulatory role of individual viral proteins remain poorly defined. This review summarizes some recent findings concerning the role of Gag Pr55 and its proteolytic processing in the HIV-1 life cycle with particular emphasis on the functions of matrix protein p17 (MA), the protein which plays a key role in regulation of the early and late steps of viral morphogenesis. Based on our recent observations, the possibility is discussed that two subsets of MA exist, one cleaved from the Gag precursor in the host cell (cMA), and the other cleaved in the virions (vMA). It is suggested that two MA fractions possess diverse functions and are involved in different stages of virus morphogenesis as key regulators of the viral life cycle.
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Affiliation(s)
- Alissa Bukrinskaya
- D.I.Ivanovsky Institute of Virology, Russian Academy of Medical Sciences, Moscow 123098, RF, Russia.
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Chiu HC, Wang FD, Chen YMA, Wang CT. Effects of human immunodeficiency virus type 1 transframe protein p6* mutations on viral protease-mediated Gag processing. J Gen Virol 2006; 87:2041-2046. [PMID: 16760407 DOI: 10.1099/vir.0.81601-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The proteolytic processing of human immunodeficiency virus (HIV) particles mediated by the viral pol-encoded protease (PR) is essential for viral infectivity. The pol coding sequence partially overlaps with the gag coding sequence and is translated as a Gag-Pol polyprotein precursor. Within Gag-Pol, the C-terminal p6(gag) domain is replaced by a transframe peptide referred to as p6*, which separates the Gag nucleocapsid domain from PR. Several previous in vitro studies have ascribed a PR-suppression regulatory function to p6*. Here, it was demonstrated that an HIV-1 Gag-Pol lacking p6* is efficiently incorporated into virions when coexpressed with HIV-1 Gag precursor. However, the released virions are not processed appropriately and show a greatly reduced viral infectivity. This suggests that the p6* is indispensable during the process of PR-mediated virus particle maturation.
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Affiliation(s)
- Hsu-Chen Chiu
- Institute of Public Health, National Yang-Ming University, Taipei, Taiwan
- Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Fu-Der Wang
- Department of Internal Medicine, Division of Infectious Disease, Taipei Veterans General Hospital, 201 Section 2 Shih-Pai Road, Taipei 11217, Taiwan
- Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Yi-Ming Arthur Chen
- AIDS Prevention and Research Center, National Yang-Ming University, Taipei, Taiwan
- Institute of Public Health, National Yang-Ming University, Taipei, Taiwan
| | - Chin-Tien Wang
- Department of Medical Research and Education, Taipei Veterans General Hospital, 201 Section 2 Shih-Pai Road, Taipei 11217, Taiwan
- Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan
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Cockrell AS, Ma H, Fu K, McCown TJ, Kafri T. A trans-lentiviral packaging cell line for high-titer conditional self-inactivating HIV-1 vectors. Mol Ther 2006; 14:276-84. [PMID: 16516556 DOI: 10.1016/j.ymthe.2005.12.015] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2005] [Revised: 12/06/2005] [Accepted: 12/19/2005] [Indexed: 11/29/2022] Open
Abstract
Lentiviral vector safety has been the impetus underlying the progress in packaging cell line development. The prospects of generating replication-competent lentiviruses (RCLs) and the potential for vector mobilization continue to be the driving force for the advancement of packaging cell lines. We have exploited the trans-lentiviral packaging system to develop the SODk3 packaging cell line for the generation of conditional self-inactivating (cSIN) vectors. Separating the gag-pol genome into two distinct expression cassettes (gag-pro and vpr-RT-IN) may reduce the potential for RCL formation, while concurrently employing cSIN vectors supports retention of the SIN phenotype in target cells and alleviates technical constraints associated with generating producer cell lines. Through development of the SODk3 packaging cell line we determined that the ratio of Gag/Pol in vector particles may be used as an indicator for packaging cell clones that yield high vector titers. Conditional SIN vector titers (1 x 10(7) TU/ml) were augmented through clonal selection. Distinct producer cell clones revealed a parallel between vector titer and transgene expression levels. We exploited this observation to demonstrate that incorporation of an internal ribosome entry site between the GFP marker and a relevant transgene affords efficient selection of high-titer producer cell lines. Furthermore, cSIN vectors generated from SODk3 packaging cells imparted efficient transduction of primary human fibroblasts, an indication of the future applicability of the SODk3 packaging cell line.
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Affiliation(s)
- Adam S Cockrell
- Gene Therapy Center, University of North Carolina at Chapel Hill, 7119 Thurston Bowles, CB 7352, 27599-7352, USA
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Liao WH, Wang CT. Characterization of human immunodeficiency virus type 1 Pr160 gag-pol mutants with truncations downstream of the protease domain. Virology 2004; 329:180-8. [PMID: 15476885 DOI: 10.1016/j.virol.2004.08.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2004] [Revised: 07/09/2004] [Accepted: 08/12/2004] [Indexed: 11/20/2022]
Abstract
We have constructed a series of HIV-1 Gag-pol mutants by progressive deletion of the pol sequence downstream of the viral protease (PR) domain. Effects of the truncation mutations on virus particle production and Gag particle processing were analyzed. Analysis indicated that removal of the integrase (IN) domain had no major effect on the efficiency of particle processing, but resulted in a marked reduction in virus particle budding. Deletion of both the IN and RNase H domains, however, restored the production of virus particles to wild-type level. The proteolytic processing of virus particle was significantly impaired when the p51RT domain was truncated. All of the truncated Gag-pol proteins could be incorporated into virus particles and demonstrated an immunofluorescence staining pattern similar to that of the wild type (wt). Our data are consistent with the proposal that signals for directing the Gag-pol transport and particle incorporation are determined by its N-terminal Gag domain. Truncated Gag-pol retaining an intact p51RT was able to complement a PR-defective mutant to produce infectious pseudotyped virions, with a virus titer 20-70% of that of wt. Pseudotyped virions produced by the Gag-pol lacking an intact p51RT were noninfectious or poorly infectious. This suggests that an intact p51RT domain is required for the Gag-pol to mediate production of mature infectious virus particles in trans.
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Affiliation(s)
- Wei-Hao Liao
- Institute of Clinical Medicine, National Yang-Ming University School of Medicine, and Department of Medical Research and Education, Taipei Veterans General Hospital, 201 Sec. 2 Shih-Pai Road, Taipei 11217, Taiwan
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Liao WH, Chiu HC, Wang CT. Effects of mutations in an HIV-1gag gene containing a 107-codon tandem repeat in the matrix region on assembly and processing of the protein product. J Med Virol 2004; 74:528-35. [PMID: 15484268 DOI: 10.1002/jmv.20209] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
It has been demonstrated previously that a human immunodeficiency virus (HIV) type 1 Gag mutant (MA2) with a tandem repeat of 107-matrix codons in the matrix domain could direct virus particle assembly and budding [Wang et al. (2000c): J Med Virol 61:423-432]. Since the regions involved functionally in HIV Gag assembly and transport have been mapped to the matrix domain, it was interesting to test the effects of the duplicated matrix-coding sequence on Gag assembly, transport, and virus processing of some assembly-defective HIV matrix mutants. In this study, a number of HIV matrix mutations were introduced into either the proximal or distal copy of the duplicated matrix-coding sequence. Assembly, release, processing, and subcellular localization of the Gag mutants were analyzed by transient expression in 293T cells. The result indicates that the budding defect of HIV matrix mutants could be moderately or significantly reversed when the additional 107-matrix codons were present; however, these matrix double mutations affected significantly the virus particle processing. Mislocalized matrix mutants could also be redistributed to a certain degree in the presence of the duplicated matrix copy. Although the subcellular distribution patterns of the matrix mutants did not correlate completely with the budding efficiency, the data suggest that the budding defect caused by the matrix mutations could be masked to some extent by the duplicated matrix coding sequence.
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Affiliation(s)
- Wei-Hao Liao
- Institute of Clinical Medicine, National Yang-Ming University School of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
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