The authors would like to acknowledge Michael Chou, Bingbing Dai, and Liang Xiao for contributing data for this manuscript. We also acknowledge Dr. John Gray for the generous gifts of reagents used in this study. P.B. is supported by a postdoctoral fellowship from the National Cancer Center. This research was supported by grants from the National Institute of Health (R01AI68978, P01CA132681 and RCA170820A), a grant from the Bill and Melinda Gates Foundation, a translational acceleration grant from the Joint Center for Translational Medicine and a grant from the California HIV/AIDS Research Program.

DC-LV stable producer cells are constructed based on the GPR packaging cell line 11 that contains the necessary lentiviral components gagpol, rev and the tet-off system. First, retroviral transduction is used to generate a GPRS packaging cell line that encodes a tet-dependent SVGmu glycoprotein. Then, concatemer array transfection is used to transfect the GPRS cell line with a lentiviral vector transgene such as GFP. This stable producer cell line, designated as LV-MGFP, can be tested in vitro</em...

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The authors declare that they have no competing financial interests.

Here, we have outlined a method for producing large quantities of lentiviral vectors using 293T cells stably transduced with all lentiviral components under the tet off regulatory system. To date, most protocols to produce lentiviral vectors rely on standard calcium phosphate transient transfection (see 18, for example). This approach has been successful on a clinical scale, but it may suffer from some limitations not likely to be present in scaling up production from stable cell lines. For example, co-transfe...

Many vector systems have been developed for gene delivery. Vectors based on lentiviruses have been among the most commonly studied viral system. These vectors are advantageous because they can efficiently transduce both dividing and non-dividing cells 1, achieve long-term expression due to integration into the host genome, exhibit low natural anti-vector immunity in most human populations 2, and have a low potential for genotoxicity from insertional mutagenesis 3,4.
Production of lentiviruses has always been colored by safety concerns. Lentiviral vectors are generally derived from HIV-1, the etiological agent of AIDS. Transient transfection of individual components of the lentivector (transfer, envelope, and packaging plasmids) is a common and flexible means of delivering genetic material in laboratory settings. However, scaling-up transient transfections for clinical applications is cumbersome and may lead to the development of replication-competent lentivirus 5,6. To overcome these hurdles, several stable packaging and producer cell lines have been developed 6-11. One of these lines, the GPR packaging line 11, has the attractive advantage of being regulated by tetracycline. In this paper, we demonstrate how to adapt this system to produce self-inactivating lentiviral vectors that are specifically targeted toward dendritic cells (DC-LVs) 12.
Dendritic cells (DCs) are the most robust antigen presenting cells of the immune system. They have been the subject of great interest in cancer vaccine development because they directly initiate, program, and regulate tumor-specific immune responses 13. Incorporating a vaccination protocol to include DCs has the potential to elicit a stronger antitumor immune response than peptide or DNA vaccines. Recently, we have developed a lentiviral vector that specifically targets dendritic cells through a modified sindbis virus glycoprotein, SVGmu 14. These vectors are unique in that they show high specificity to dendritic cells and generate stronger immune responses than nonspecific, VSVg-pseudotyped vectors.
Here, we report a method for producing large quantities of these DC-targeted lentiviral vectors. We demonstrate that these DC-LVs can infect DCs and generate strong CD8+ T cell immune responses. All procedures involving animals were performed humanely, under the approval of the USC Intitutional Animal Care and Use Committee. In order to perform in vivo and clinical experiments, it is critical to create a cell line that can produce virus at a high titer. Performing the transduction and transfection steps exactly as described will maximize the chances of generating such a clone.

<table border="1">
		<tbody>
		 <tr>
			<td>Name of Reagent/Material</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		 </tr>
		 <tr>
			<td>DMEM</td>
			<td>Mediatech Inc.</td>
			<td>10-013-CV</td>
			<td></td>
		 </tr>
		 <tr>
			<td>FBS</td>
			<td>Sigma-Aldrich</td>
			<td>F2442</td>
			<td></td>
		 </tr>
		 <tr>
			<td>Glutamine</td>
			<td>Mediatech Inc.</td>
			<td>25-005-Cl</td>
			<td></td>
		 </tr>
		 <tr>
			<td>Doxycycline</td>
			<td>Clontech Laboratories, Inc.</td>
			<td>631311</td>
			<td></td>
		 </tr>
		 <tr>
			<td>Zeocin</td>
			<td>Invitrogen</td>
			<td>R250-01</td>
			<td>Toxic</td>
		 </tr>
		 <tr>
			<td>Puromycin</td>
			<td>Sigma-Aldrich</td>
			<td>P8833</td>
			<td></td>
		 </tr>
		 <tr>
			<td>T4 DNA Ligase</td>
			<td>NEB</td>
			<td>M0202S</td>
			<td></td>
		 </tr>
		 <tr>
			<td>DNeasy Blood &amp; Tissue Kit</td>
			<td>Qiagen</td>
			<td>69506</td>
			<td></td>
		 </tr>
		</tbody>
 </table>

a tetracycline-regulated cell line produces high-titer lentiviral vectors that specifically target dendritic cells

Lentiviral vectors (LVs) are a powerful means of delivering genetic material to many types of cells. Because of safety concerns associated with these HIV-1 derived vectors, producing large quantities of LVs is challenging. In this paper, we report a method for producing high titers of self-inactivating LVs. We retrovirally transduce the tet-off stable producer cell line GPR to generate a cell line, GPRS, which can express all the viral components, including a dendritic cell-specific glycoprotein, SVGmu. Then, we use concatemeric DNA transfection to transfect the LV transfer plasmid encoding a reporter gene GFP in combination with a selectable marker. Several of the resulting clones can produce LV at a titer 10-fold greater than what we achieve with transient transfection. Plus, these viruses efficiently transduce dendritic cells in vitro and generate a strong T cell immune response to our reporter antigen. This method may be a good option for producing strong LV-based vaccines for clinical studies of cancer or infectious diseases.

The stable cell line described in this method can produce large quantities of lentiviral vectors that are specifically targeted to dendritic cells. As shown in Figure 1B, isolation of individual clones yielded stable cell lines of varying quality 12. Among 26 clones tested, 8 produced lentiviral particles at a titer of greater than 106 transduction units per ml (TU/ml), which is a typical benchmark for SVG-pseudotyped lentiviral vectors produced by transient transfection. At the sam...

Watch this Scientific Journal Video about A Tetracycline-regulated Cell Line Produces High-titer Lentiviral Vectors that Specifically Target Dendritic Cells at JoVE.com

A Tetracycline-regulated Cell Line Produces High-titer Lentiviral Vectors that Specifically Target Dendritic Cells

Here, we use retroviral transduction and concatemeric transfection to create a cell line that can express the components of a lentiviral vector (LV) in the absence of tetracycline. This LV encodes GFP and is pseudotyped with a glycoprotein, SVGmu, which is specific for a receptor on dendritic cells.

Lentiviral  vectors (LVs) are a powerful means of delivering genetic material to many types  of cells. Because of safety concerns associated with these ...

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Immunology and Infection

14.4K visualizações.  University of Southern California, Los Angeles. Aqui, nós utilizamos a transdução retroviral e transfecção concatemeric para criar uma linha celular que possa expressar os componentes de um vector lentiviral (LV) na ausência de tetraciclina. Este LV codifica GFP e é pseudotipado com glicoproteína, SVGmu, que é específico para um receptor em células dendríticas.