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Quach ABV, Little SR, Shih SCC. Viral Generation, Packaging, and Transduction on a Digital Microfluidic Platform. Anal Chem 2022; 94:4039-4047. [PMID: 35192339 DOI: 10.1021/acs.analchem.1c05227] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Viral-based systems are a popular delivery method for introducing exogenous genetic material into mammalian cells. Unfortunately, the preparation of lentiviruses containing the machinery to edit the cells is labor-intensive, with steps requiring optimization and sensitive handling. To mitigate these challenges, we introduce the first microfluidic method that integrates lentiviral generation, packaging, and transduction. The new method allows the production of viral titers between 106 and 107 (similar to macroscale production) and high transduction efficiency for hard-to-transfect cell lines. We extend the technique for gene editing applications and show how this technique can be used to knock out and knock down estrogen receptor gene─a gene prominently responsible for 70% of breast cancer cases. This new technique is automated with multiplexing capabilities, which have the potential to standardize the methods for viral-based genome engineering.
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Affiliation(s)
- Angela B V Quach
- Department of Biology, Concordia University, 7141 Sherbrooke Street West, Montréal, Québec H4B 1R6, Canada.,Centre for Applied Synthetic Biology, Concordia University, 7141 Sherbrooke Street West, Montréal, Québec H4B 1R6, Canada
| | - Samuel R Little
- Centre for Applied Synthetic Biology, Concordia University, 7141 Sherbrooke Street West, Montréal, Québec H4B 1R6, Canada.,Department of Electrical and Computer Engineering, Concordia University, 1455 de Maisonneuve Blvd. West, Montréal, Québec H3G 1M8, Canada
| | - Steve C C Shih
- Department of Biology, Concordia University, 7141 Sherbrooke Street West, Montréal, Québec H4B 1R6, Canada.,Centre for Applied Synthetic Biology, Concordia University, 7141 Sherbrooke Street West, Montréal, Québec H4B 1R6, Canada.,Department of Electrical and Computer Engineering, Concordia University, 1455 de Maisonneuve Blvd. West, Montréal, Québec H3G 1M8, Canada
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Gardner TJ, Bourne CM, Dacek MM, Kurtz K, Malviya M, Peraro L, Silberman PC, Vogt KC, Unti MJ, Brentjens R, Scheinberg D. Targeted Cellular Micropharmacies: Cells Engineered for Localized Drug Delivery. Cancers (Basel) 2020; 12:E2175. [PMID: 32764348 PMCID: PMC7465970 DOI: 10.3390/cancers12082175] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 07/31/2020] [Accepted: 08/02/2020] [Indexed: 12/19/2022] Open
Abstract
The recent emergence of engineered cellular therapies, such as Chimeric antigen receptor (CAR) CAR T and T cell receptor (TCR) engineered T cells, has shown great promise in the treatment of various cancers. These agents aggregate and expand exponentially at the tumor site, resulting in potent immune activation and tumor clearance. Moreover, the ability to elaborate these cells with therapeutic agents, such as antibodies, enzymes, and immunostimulatory molecules, presents an unprecedented opportunity to specifically modulate the tumor microenvironment through cell-mediated drug delivery. This unique pharmacology, combined with significant advances in synthetic biology and cell engineering, has established a new paradigm for cells as vectors for drug delivery. Targeted cellular micropharmacies (TCMs) are a revolutionary new class of living drugs, which we envision will play an important role in cancer medicine and beyond. Here, we review important advances and considerations underway in developing this promising advancement in biological therapeutics.
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Affiliation(s)
- Thomas J. Gardner
- Molecular Pharmacology Program, Sloan Kettering Institute, New York, NY 10065, USA; (T.J.G.); (C.M.B.); (M.M.D.); (K.K.); (M.M.); (L.P.); (P.C.S.); (K.C.V.)
| | - Christopher M. Bourne
- Molecular Pharmacology Program, Sloan Kettering Institute, New York, NY 10065, USA; (T.J.G.); (C.M.B.); (M.M.D.); (K.K.); (M.M.); (L.P.); (P.C.S.); (K.C.V.)
- Immunology Program, Weill Cornell Graduate School of Medical Sciences, New York, NY 10065, USA
| | - Megan M. Dacek
- Molecular Pharmacology Program, Sloan Kettering Institute, New York, NY 10065, USA; (T.J.G.); (C.M.B.); (M.M.D.); (K.K.); (M.M.); (L.P.); (P.C.S.); (K.C.V.)
- Pharmacology Program, Weill Cornell Graduate School of Medical Sciences, New York, NY 10065, USA;
| | - Keifer Kurtz
- Molecular Pharmacology Program, Sloan Kettering Institute, New York, NY 10065, USA; (T.J.G.); (C.M.B.); (M.M.D.); (K.K.); (M.M.); (L.P.); (P.C.S.); (K.C.V.)
- Pharmacology Program, Weill Cornell Graduate School of Medical Sciences, New York, NY 10065, USA;
| | - Manish Malviya
- Molecular Pharmacology Program, Sloan Kettering Institute, New York, NY 10065, USA; (T.J.G.); (C.M.B.); (M.M.D.); (K.K.); (M.M.); (L.P.); (P.C.S.); (K.C.V.)
| | - Leila Peraro
- Molecular Pharmacology Program, Sloan Kettering Institute, New York, NY 10065, USA; (T.J.G.); (C.M.B.); (M.M.D.); (K.K.); (M.M.); (L.P.); (P.C.S.); (K.C.V.)
| | - Pedro C. Silberman
- Molecular Pharmacology Program, Sloan Kettering Institute, New York, NY 10065, USA; (T.J.G.); (C.M.B.); (M.M.D.); (K.K.); (M.M.); (L.P.); (P.C.S.); (K.C.V.)
- Pharmacology Program, Weill Cornell Graduate School of Medical Sciences, New York, NY 10065, USA;
| | - Kristen C. Vogt
- Molecular Pharmacology Program, Sloan Kettering Institute, New York, NY 10065, USA; (T.J.G.); (C.M.B.); (M.M.D.); (K.K.); (M.M.); (L.P.); (P.C.S.); (K.C.V.)
- Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Mildred J. Unti
- Pharmacology Program, Weill Cornell Graduate School of Medical Sciences, New York, NY 10065, USA;
| | - Renier Brentjens
- Department of Medicine, Memorial Hospital, New York, NY 10065, USA;
| | - David Scheinberg
- Molecular Pharmacology Program, Sloan Kettering Institute, New York, NY 10065, USA; (T.J.G.); (C.M.B.); (M.M.D.); (K.K.); (M.M.); (L.P.); (P.C.S.); (K.C.V.)
- Pharmacology Program, Weill Cornell Graduate School of Medical Sciences, New York, NY 10065, USA;
- Department of Medicine, Memorial Hospital, New York, NY 10065, USA;
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Namdari H, Rezaei F, Teymoori-Rad M, Mortezagholi S, Sadeghi A, Akbari A. CAR T cells: Living HIV drugs. Rev Med Virol 2020; 30:1-14. [PMID: 32713110 DOI: 10.1002/rmv.2139] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 06/04/2020] [Accepted: 06/09/2020] [Indexed: 12/29/2022]
Abstract
Human immunodeficiency virus type 1 (HIV-1), the virus that causes AIDS (acquired immunodeficiency syndrome), is a major global public health issue. Although the advent of combined antiretroviral therapy (ART) has made significant progress in inhibiting HIV replication in patients, HIV-infected cells remain the principal cellular reservoir of HIV, this allows HIV to rebound immediately upon stopping ART, which is considered the major obstacle to curing HIV infection. Chimeric antigen receptor (CAR) cell therapy has provided new opportunities for HIV treatment. Engineering T cells or hematopoietic stem cells (HSCs) to generate CAR T cells is a rapidly growing approach to develop an efficient immune cell to fight HIV. Herein, we review preclinical and clinical data available for the development of CAR T cells. Further, the advantages and disadvantages of clinical application of anti-HIV CAR T cells will be discussed.
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Affiliation(s)
- Haideh Namdari
- Iranian Tissue Bank Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Farhad Rezaei
- Department of Virology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - Majid Teymoori-Rad
- Department of Virology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - Sahar Mortezagholi
- Department of Immunology, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Ahmadreza Sadeghi
- Iranian Tissue Bank Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Abolfazl Akbari
- Colorectal Research Center, Iran University of Medical Sciences, Tehran, Iran
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Aznan AN, Abdul Karim N, Wan Ngah WZ, Jubri Z. Critical factors for lentivirus-mediated PRDX4 gene transfer in the HepG2 cell line. Oncol Lett 2018; 16:73-82. [PMID: 29930713 PMCID: PMC6006497 DOI: 10.3892/ol.2018.8650] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 12/04/2017] [Indexed: 12/19/2022] Open
Abstract
Optimization of critical factors affects transduction efficiency and is able to reduce reagent consumption. The present study aimed to determine the optimum transduction conditions of small hairpin (sh)RNA against peroxiredoxin 4 (PRDX4) in the HepG2 cell line. Cell viability assays were conducted based on serum condition, incubation time, polybrene concentration and antibiotic dose selection. Non-targeting control shRNA was transduced into HepG2 cells in a 5-fold serial dilution, and colonies positive for green fluorescent protein were counted using ImageJ software. Reverse transcription-quantitative polymerase chain reaction and western blot analysis were performed to validate PRDX4 expression. The optimum cell density for transduction was 5.0×103 cells/well in 96-well plates to achieve 40 to 50% confluency the following day. The transduction media consisted of 10% fetal bovine serum (FBS) and 12 µg/ml polybrene, and was used to dilute lentiviral particles at a functional titer of 4.9×105 TU/ml for multiplicity of infection (MOI) of 20, 15 and 10, for 24 h of incubation. Selection with 7 µg/ml puromycin was performed in transduced cells. shRNA 3 was revealed to inhibit PRDX4 mRNA and protein expression. In conclusion, PRDX4 was successfully silenced in 5.0×103 HepG2 cells cultured with 10% FBS and 12 µg/ml polybrene, at a 4.9×105 TU/ml functional titer for MOI of 20, 15 and 10.
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Affiliation(s)
- Afiah Nasuha Aznan
- Department of Biochemistry, National University of Malaysia Medical Centre, Kuala Lumpur 56000, Malaysia
| | - Norwahidah Abdul Karim
- Department of Biochemistry, National University of Malaysia Medical Centre, Kuala Lumpur 56000, Malaysia
| | - Wan Zurinah Wan Ngah
- Department of Biochemistry, National University of Malaysia Medical Centre, Kuala Lumpur 56000, Malaysia
| | - Zakiah Jubri
- Department of Biochemistry, National University of Malaysia Medical Centre, Kuala Lumpur 56000, Malaysia
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5
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Roychoudhury P, De Silva Feelixge HS, Pietz HL, Stone D, Jerome KR, Schiffer JT. Pharmacodynamics of anti-HIV gene therapy using viral vectors and targeted endonucleases. J Antimicrob Chemother 2016; 71:2089-99. [PMID: 27090632 DOI: 10.1093/jac/dkw104] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Accepted: 02/29/2016] [Indexed: 12/14/2022] Open
Abstract
OBJECTIVES A promising curative approach for HIV is to use designer endonucleases that bind and cleave specific target sequences within latent genomes, resulting in mutations that render the virus replication incompetent. We developed a mathematical model to describe the expression and activity of endonucleases delivered to HIV-infected cells using engineered viral vectors in order to guide dose selection and predict therapeutic outcomes. METHODS We developed a mechanistic model that predicts the number of transgene copies expressed at a given dose in individual target cells from fluorescence of a reporter gene. We fitted the model to flow cytometry datasets to determine the optimal vector serotype, promoter and dose required to achieve maximum expression. RESULTS We showed that our model provides a more accurate measure of transduction efficiency compared with gating-based methods, which underestimate the percentage of cells expressing reporter genes. We identified that gene expression follows a sigmoid dose-response relationship and that the level of gene expression saturation depends on vector serotype and promoter. We also demonstrated that significant bottlenecks exist at the level of viral uptake and gene expression: only ∼1 in 220 added vectors enter a cell and, of these, depending on the dose and promoter used, between 1 in 15 and 1 in 1500 express transgene. CONCLUSIONS Our model provides a quantitative method of dose selection and optimization that can be readily applied to a wide range of other gene therapy applications. Reducing bottlenecks in delivery will be key to reducing the number of doses required for a functional cure.
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Affiliation(s)
- Pavitra Roychoudhury
- Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | | | - Harlan L Pietz
- Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA Department of Microbiology, University of Washington, Seattle, WA, USA Department of Biochemistry, University of Washington, Seattle, WA, USA
| | - Daniel Stone
- Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Keith R Jerome
- Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA Department of Microbiology, University of Washington, Seattle, WA, USA Department of Laboratory Medicine, University of Washington, Seattle, WA, USA
| | - Joshua T Schiffer
- Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA Department of Medicine, University of Washington, Seattle, WA, USA
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Zakas PM, Spencer HT, Doering CB. Engineered Hematopoietic Stem Cells as Therapeutics for Hemophilia A. ACTA ACUST UNITED AC 2012; 1. [PMID: 25383239 DOI: 10.4172/2157-7412.s1-003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Philip M Zakas
- Graduate Program in Molecular and Systems Pharmacology, Graduate Division of Biological and Biomedical Sciences, Emory University
| | - H Trent Spencer
- Aflac Cancer Center and Blood Disorders Service, Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia
| | - Christopher B Doering
- Aflac Cancer Center and Blood Disorders Service, Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia
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Doering CB, Archer D, Spencer HT. Delivery of nucleic acid therapeutics by genetically engineered hematopoietic stem cells. Adv Drug Deliv Rev 2010; 62:1204-12. [PMID: 20869414 PMCID: PMC2991563 DOI: 10.1016/j.addr.2010.09.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Revised: 08/17/2010] [Accepted: 09/08/2010] [Indexed: 01/02/2023]
Abstract
Several populations of adult human stem cells have been identified, but only a few of these are in routine clinical use. The hematopoietic stem cell (HSC) is arguably the most well characterized and the most routinely transplanted adult stem cell. Although details regarding several aspects of this cell's phenotype are not well understood, transplant of HSCs has advanced to become the standard of care for the treatment of a range of monogenic diseases and several types of cancer. It has also proven to be an excellent target for genetic manipulation, and clinical trials have already demonstrated the usefulness of targeting this cell as a means of delivering nucleic acid therapeutics for the treatment of several previously incurable diseases. It is anticipated that additional clinical trials will soon follow, such as genetically engineering HSCs with vectors to treat monogenic diseases such as hemophilia A. In addition to the direct targeting of HSCs, induced pluripotent stem (iPS) cells have the potential to replace virtually any engineered stem cell therapeutic, including HSCs. We now know that for the broad use of genetically modified HSCs for the treatment of non-lethal diseases, e.g. hemophilia A, we must be able to regulate the introduction of nucleic acid sequences into these target cells. We can begin to refine transduction protocols to provide safer approaches to genetically manipulate HSCs and strategies are being developed to improve the overall safety of gene transfer. This review focuses on recent advances in the systemic delivery of nucleic acid therapeutics using genetically modified stem cells, specifically focusing on i) the use of retroviral vectors to genetically modify HSCs, ii) the expression of fVIII from hematopoietic stem cells for the treatment of hemophilia A, and iii) the use of genetically engineered hematopoietic cells generated from iPS cells as treatment for disorders of hematopoiesis.
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Affiliation(s)
- Christopher B Doering
- Aflac Cancer Center and Blood Disorders Service, Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, USA
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Wu Y, Melton DW, Zhang Y, Hornsby PJ. Improved coinfection with amphotropic pseudotyped retroviral vectors. J Biomed Biotechnol 2009; 2009:901079. [PMID: 19478961 PMCID: PMC2686103 DOI: 10.1155/2009/901079] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2008] [Revised: 02/08/2009] [Accepted: 03/11/2009] [Indexed: 11/18/2022] Open
Abstract
Amphotropic pseudotyped retroviral vectors have typically been used to infect target cells without prior concentration. Although this can yield high rates of infection, higher rates may be needed where highly efficient coinfection of two or more vectors is needed. In this investigation we used amphotropic retroviral vectors produced by the Plat-A cell line and studied coinfection rates using green and red fluorescent proteins (EGFP and dsRed2). Target cells were primary human fibroblasts (PHF) and 3T3 cells. Unconcentrated vector preparations produced a coinfection rate of approximately 4% (defined as cells that are both red and green as a percentage of all cells infected). Optimized spinoculation, comprising centrifugation at 1200 g for 2 hours at 15 degrees C, increased the coinfection rate to approximately 10%. Concentration by centrifugation at 10,000 g or by flocculation using Polybrene increased the coinfection rate to approximately 25%. Combining the two processes, concentration by Polybrene flocculation and optimized spinoculation, increased the coinfection rate to 35% (3T3) or >50% (PHF). Improved coinfection should be valuable in protocols that require high transduction by combinations of two or more retroviral vectors.
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Affiliation(s)
- Yuehong Wu
- Institute of Biotechnology, Northwest A&F University, Yangling, Shaanxi 712100, China
- Department of Physiology and Sam and Ann Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center, San Antonio, TX 78245, USA
| | - David W. Melton
- Department of Physiology and Sam and Ann Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center, San Antonio, TX 78245, USA
| | - Yong Zhang
- Institute of Biotechnology, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Peter J. Hornsby
- Department of Physiology and Sam and Ann Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center, San Antonio, TX 78245, USA
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Krishna D, Le Doux JM. Murine leukemia virus particles activate Rac1 in HeLa cells. Biochem Biophys Res Commun 2006; 345:1184-93. [PMID: 16716260 DOI: 10.1016/j.bbrc.2006.05.027] [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] [Received: 04/13/2006] [Accepted: 05/05/2006] [Indexed: 12/19/2022]
Abstract
A number of viruses, when they bind to cells, activate intracellular signals that facilitate post-binding steps of infection. To determine if retroviruses activate intracellular signaling, we transduced HeLa cells with amphotropic retroviruses produced by TelCeB6 cells and examined cell lysates for activated Rac1. We found that retroviruses activate Rac1. Rac1 activation was blocked when cells were depleted of cholesterol, cultured in suspension, or incubated with an anti-beta(1) integrin antibody, and when viruses were treated with heparinase III. Retrovirus activation of Rac1 did not require the amphotropic envelope protein. Gene transfer was reduced 2.4-fold when viruses were treated with heparinase III, but did not change when cells were transduced in the presence of function-blocking anti-beta(1) integrin antibodies. The implications of these findings with respect to retrovirus-cell interactions are discussed.
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Affiliation(s)
- Delfi Krishna
- The School of Chemical and Biomolecular Engineering, Atlanta, GA 30332-0535, USA
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Chen Y, Miller WM, Aiyar A. Transduction efficiency of pantropic retroviral vectors is controlled by the envelope plasmid to vector plasmid ratio. Biotechnol Prog 2005; 21:274-82. [PMID: 15903266 PMCID: PMC2913131 DOI: 10.1021/bp049865x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Pantropic retroviral vectors pseudotyped with vesicular stomatitis virus envelope G protein (VSV-G) are typically produced by transient transfection of the VSV-G expression plasmid because constitutive expression of VSV-G is cytotoxic. To produce pantropic vectors, the VSV-G expression plasmid and the vector plasmid are cotransfected into a packaging cell line, such as 293-gag-pol. Typically, the ratio of VSV-G plasmid to the vector plasmid ranges from 0.33 to 1.0. However, it is not clear that this range is optimal for vector production. In this study we have systematically examined the effect of the ratio of VSV-G plasmid (pVSV-G) to vector plasmid on vector production. For this, 293-gag-pol stable packaging cells were cotransfected with pVSV-G and an enhanced green fluorescent protein- (EGFP-) expressing retroviral vector plasmid (pLTR-EGFP) by use of lipofectamine. Vector was collected following transfection and used to transduce three target cell lines, namely, 3T3 fibroblasts, telomerase-immortalized human diploid fibroblasts (HDF), and the human hepatoma cell line HuH7. Transduction efficiency was evaluated for vectors produced at different pVSV-G:pLTR-EGFP ratios such that the total amount of plasmid transfected into 293-gag-pol cells was kept constant. Our results indicate that transduction efficiency is greatest when the pVSV-G:pLTR-EGFP ratio is substantially below 1.0. For 3T3 and HDF cells, the maximum transduction efficiency was obtained when a ratio of pVSV-G:pLTR-EGFP ranging from 0.053 to 0.2 was used for transfection. The relative magnitude of this effect was greater for lower transduction efficiencies in control cultures. For HuH7 cells, the beneficial effects were smaller than those observed when HDF or 3T3 cells were used. The difference in transduction efficiency for vector produced under various pVSV-G:pLTR-EGFP ratios was not due to differences in the proliferation of packaging cells or target cells. Further characterization showed that the amount of vector RNA relative to p30gag decreased as the ratio of pVSV-G:pLTR-EGFP increased. These results indicate that transduction efficiency increases with increasing levels of vector RNA as long as a minimally sufficient level of pantropic envelope protein is expressed.
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Affiliation(s)
| | | | - Ashok Aiyar
- To whom correspondence should be addressed. W.M.M. . A.A.
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