JAWS II) by a Nonviral Transfection Reagent Fection, on the Other Hand, Is Successful but Requires a Fairly High Multiplicity Shanjana Awasthi and Rebecca A
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DRUG DISCOVERY AND GENOMIC TECHNOLOGIES cies varying from less than 1% to 20% Transfection of murine dendritic cell line (15–17). Adenoviral-mediated trans- (JAWS II) by a nonviral transfection reagent fection, on the other hand, is successful but requires a fairly high multiplicity Shanjana Awasthi and Rebecca A. Cox of infection (100–1000) (18,19), and the utility of this approach is limited University of Texas Health Science Center at San Antonio, San Antonio, TX, USA by the finding that cellular immune BioTechniques 35:600-604 (September 2003) responses are elicited against viral pro- teins as well (20,21), resulting in mild activation of the phenotype of dendritic Dendritic cells are the most potent antigen-presenting cells that initiate and modulate the cells (22–24). Here we describe an im- host immune system. Based on their immunostimulatory activity, a variety of strategies have proved transfection protocol, using the been developed to use dendritic cells as vaccines and immunotherapeutic agents against nonviral nonliposomal lipid polymer, infection and cancer. Genetically modified dendritic cells are useful for immunotherapeutic TransIT-TKO® transfection reagent purposes because of their sustained activity in vivo. However, transfection of dendritic cells (Mirus, Madison, WI, USA), for trans- with plasmid DNA has been very difficult. While the viral transfection is associated with fecting murine dendritic cells with the nonspecific activation of dendritic cells, commonly used nonviral transfection reagents have gene that encodes Coccidioides immitis a low efficiency of transfection. Here we describe an improved, simple, less time-consuming ® antigen 2 (Ag2). Experimental studies transfection protocol using the nonviral nonliposomal lipid polymer, TransIT-TKO trans- in a murine model have established that fection reagent, for transfecting murine dendritic cells (JAWS II) with the gene that encodes C. immitis Ag2 DNA, a cell wall gly- Coccidioides immitis antigen 2 (Ag2). The JAWS II cells were cotransfected with pHYG- coprotein, induces protective immunity enhanced green fluorescent protein (EGFP) and pVR1012-C. immitis Ag2 plasmid DNAs against lethal challenge (25). using TransIT-TKO reagent. We reproducibly obtained 30%–50% transfection efficiency. The transfected cells maintained their immature phenotype and were functionally active. In addi- tion, the flexibility of this agent for expressing multiple antigens (GFP and C. immitis Ag2) MATERIALS AND METHODS offers an advantage of delivering multiple immunogens. In the present study, murine den- dritic cells (JAWS II) (ATCC, Manas- sas, VA, USA) were transfected with INTRODUCTION cells with viable (7–11) or killed infec- pHYG-enhanced green fluorescent pro- tious agents or tumor cells and derived tein (EGFP) (BD Biosciences Clontech, Dendritic cells are unique antigen- antigens (11,12). It has been noted that Palo Alto, CA, USA) and C. immitis presenting immune cells that play an genetic transfection is a highly effec- Ag2 cDNA ligated to pVR1012 (Vi- important role in regulating the host tive means for induction of immature cal, San Diego, CA, USA). The JAWS immune responses (1,2). Immature dendritic cells with sustained immuno- II dendritic cells were derived from the dendritic cells have a unique capabil- modulatory activity (13,14). However, bone marrow of C57/BL6 mice and ity of sensing the maturation signals of transfection of dendritic cells with express an immature phenotype. The infection or inflammation and inducing plasmid DNA using nonviral reagents plasmid DNA was prepared using an primary immune responses (3). These has been very difficult, with efficien- EndoFree® Plasmid Maxi kit (Qiagen, cells can internalize and process bacte- rial, fungal, viral, and other particulate antigens for major histocompatibility complex (MHC) classes I and II anti- gen presentation to T cells. Following an encounter with an antigen, dendritic cells mature into antigen-presenting cells, up-regulate their chemokine and co-stimulatory receptors, and migrate to secondary lymphoid organs where they can prime naive T cells and naive and memory B cells and activate natural killer cells to induce specific immune responses (4–6). Because of these unique characteristics, dendritic cells have gained considerable interest in the field of vaccine development Figure 1. Fluorescent micrographs of (A) nontransfected and (B) pHYG-enhanced green fluores- and immunotherapy. Ex vivo activa- cent protein (EGFP) and pVR1012-Coccidioides immitis antigen 2 (Ag2) plasmid DNA-cotrans- tion and maturation of dendritic cells fected JAWS II cells. The green fluorescence shows expression of GFP. These results are representative have been achieved by incubating the of three different experiments. These photographs were taken after a 48-h transfection. 600 BioTechniques Vol. 35, No. 3 (2003) Vol. 35, No. 3 (2003) BioTechniques 601 Valencia, CA, USA). The JAWS II cells DNA) to the TransIT-TKO reagent (in were maintained in complete α-mini- 150 µL DMEM). The mixture was kept mum essential medium containing ribo- at room temperature for at least 5 min nucleosides and deoxyribonucleosides before adding it to the cells. The cells (Sigma, St. Louis, MO, USA), 20% were incubated at 37°C in a 5% CO2 fetal bovine serum (Invitrogen, Carls- incubator. After a 4-h incubation, an bad, CA, USA), 4 mM L-glutamine, 5 additional 250 µL of complete medium ng/mL recombinant mouse granulocyte were added. The percent transfection macrophage colony-stimulating factor efficiency was evaluated by visual (GM-CSF) (Peprotech, Rocky Hill, enumeration of the green fluorescence- NJ, USA), penicillin-streptomycin transfected cells versus the total number (100 µg/mL penicillin and 100 U/mL of cells using a fluorescent microscope streptomycin; Invitrogen), and 50 with the appropriate filter (Olympus µg/mL gentamycin (Invitrogen). The Optical Co. Ltd., Tokyo, Japan). After cells were allowed to grow overnight a 24-h transfection, both the transfected to 50%–60% monolayer confluency in and nontransfected JAWS II cells were 24-well plates. The cells were washed stained with propidium iodide to con- with serum-free Dulbecco’s minimum firm the viability. essential medium (DMEM; Invitrogen) The expression of the C. immitis before transfection. The transfection Ag2 protein was detected by dot-blot reagent/DNA complex (4 µL:2 µg immunoblotting. Briefly, the cells each plasmid DNA) was prepared in were washed once with Dulbecco’s serum-free DMEM by adding plas- phosphate-buffered saline (Invitrogen), mid DNAs (2 µg pHYG-EGFP and 2 and the cell lysates were prepared in µg pVR1012-C. immitis Ag2 plasmid homogenization buffer containing 1% Igepal CA-630, 0.1% sodium dodecyl sulfate, protease inhibitors (1.1 µM leupeptin, 1 µM pepstatin, and 0.2 mM phenylmethylsulfonyl fluoride), and 1 mM EDTA (all from Sigma). Various amounts of cell lysate protein were loaded on prewetted nitrocellulose pa- per (Schleicher & Schuell, Keene, NH, USA) in Tris-buffered saline (TBS; 20 mM Tris-HCl, pH 7.5, 150 mM NaCl). The nonspecific sites were blocked by incubating with 5% bovine serum albumin in TBST (TBS containing 0.05% Tween® 20). The nitrocellulose sheet was then incubated with goat anti-Ag2 antibody (1:1000) followed by incubation with secondary alkaline phosphatase-labeled rabbit anti-goat immunoglobulin G (IgG) antibody (1: 10,000; Sigma). The immunocomplex was detected by an AP Conjugate Substrate kit (Bio-Rad Laboratories, Hercules, CA, USA). We also confirmed the pheno- type and stimulatory capacity of the pVR1012-C. immitis Ag2 plasmid DNA-transfected JAWS II cells. The cells were transfected with pVR1012 or Figure 2. Flow cytometry analysis of (A) prop- pVR1012-C. immitis Ag2 plasmid DNA idium iodide-stained nontransfected and (B) according to the method described here pHYG-enhanced green fluorescent protein using TransIT-TKO reagent. After a 24- (EGFP) and pVR1012-Coccidioides immitis antigen 2 (Ag2) plasmid DNA-cotransfected h transfection, cells were incubated with JAWS II cells. Numbers in the upper right indi- Escherichia coli O111:B4 lipopolysac- cate the percentage of viable cells. charide (LPS) (final concentration 100 600 BioTechniques Vol. 35, No. 3 (2003) Vol. 35, No. 3 (2003) BioTechniques 601 DRUG DISCOVERY AND GENOMIC TECHNOLOGIES ng/mL; Sigma) for another 24 h. The pression of cell surface markers in either tervention using transfected dendritic cells were stained with fluorochrome- the pVR1012 vector or the pVR1012-C. cells could provide an alternative or labeled anti-mouse CD14, CD11c, immitis Ag2 plasmid DNA-transfected adjunctive means for reducing the mor- CD86, MHC class II (IA/E), CD80, JAWS II cells, as compared to the non- tality associated with this disease. and CD40 antibodies, according to transfected JAWS II cells, except for the method described by the manufac- CD80 and CD86 (Figure 4A). However, turer (BD Pharmingen, San Diego, CA, after LPS treatment, nontransfected and ACKNOWLEDGMENTS USA), and fluorescence analysis was pVR1012- or pVR1012-C. immitis Ag2 performed using a FACSCalibur flow plasmid DNA-transfected JAWS II cells This work was supported by the cytometer and CellQuest V3.1 soft- showed up-regulation of MHC class II, California HealthCare Foundation, ware (both from BD Biosciences, San CD86, CD80, and CD40 (Figure 4B), the Department of Health Services of Jose, CA, USA). The mean fluorescent and cytokines [tumor necrosis factor α the State of California, and California index above background was obtained