Single-step, multiple retroviral transduction of human T cells

Background

Retroviral transduction of human peripheral blood T cells has considerable potential in the development of gene therapy strategies for immunological disorders. New vectors and experimental procedures have been developed for efficient transduction of several genes into human T cells.

Methods

Bicistronic retroviral vectors encoding distinct cell markers were used for the simultaneous multiple transduction of a human T‐cell line (MT‐2), as well as of human peripheral blood T cells from normal donors. Transduction efficiencies were evaluated by flow cytometry and double‐ and triple‐transduced cells were isolated by fluorescence cell sorting.

Results

Four new bicistronic retroviral vectors were developed that express different gene markers under the control of the internal ribosome entry site (IRES) of the encephalomyocarditis virus. These markers are, respectively, enhanced green fluorescent protein (EGFP), β‐galactosidase, and truncated versions of human nerve growth factor receptor (ΔNGFR) and human growth hormone receptor (ΔGHR). A single 1 h spinoculation infection, performed in the presence of polybrene and using transiently produced amphotropic retroviral particles, was sufficient to obtain transduction efficiencies consistently greater than 50% on human peripheral blood T lymphocytes which had been previously stimulated for 3 days with immobilized anti‐CD3. The transient production of viral particles encoding EGFP, ΔNGFR, and ΔGHR markers in the same viral supernatant has allowed up to three different genes to be introduced simultaneously into human T cells.

Conclusions

This study describes new experimental conditions for efficient single‐step multiple transduction of human primary T lymphocytes. The procedure could be of interest for the development of gene therapy approaches. Copyright © 2002 John Wiley & Sons, Ltd.

     

Feline immunodeficiency virus vectors. Gene transfer to mouse retina following intravitreal injection

Background

Transduction of the murine retinal pigmented epithelium (RPE) with adenovirus vectors requires technically difficult and invasive subretinal injections. This study tested the hypothesis that recombinant vectors based on feline immunodeficiency virus (FIV) could access the retina following intravitreal injection.

Methods

FIV vectors expressing E. coli β‐galactosidase (FIVβgal) were injected alone, or in combination with adenovirus vectors expressing eGFP, into the vitreous of normal mice and eyes evaluated for transgene expression. In further studies, the utility of FIV‐mediated gene transfer to correct lysosomal storage defects in the anterior and posterior chambers of eyes was tested using recombinant FIV vectors expressing β‐glucuronidase. FIVβgluc vectors were injected into β‐glucuronidase‐deficient mice, an animal model of mucopolysacharridoses type VII.

Results

The results of this study show that similar to adenovirus, both corneal endothelium and cells of the iris could be transduced following intravitreal injection of FIVβgal. However, in contrast to adenovirus, intravitreal injection of FIVβgal also resulted in transduction of the RPE. Immunohistochemistry following an intravitreal injection of an AdeGFP (adenovirus expressing green fluorescent protein) and FIVβgal mixture confirmed that both viruses mediated transduction of corneal endothelium and cells of the iris, while only FIVβgal transduced cells in the retina. Using the β‐glucuronidase‐deficient mouse, the therapeutic efficacy of intravitreal injection of FIVβgluc (FIV expressing β‐glucuronidase) was tested. Intravitreal injection of FIVβgluc to the eyes of β‐glucuronidase‐deficient mice resulted in rapid reduction (within 2 weeks) of the lysosomal storage defect within the RPE, corneal endothelium, and the non‐pigmented epithelium of the ciliary process. Transgene expression and correction of the lysosomal storage defect remained for at least 12 weeks, the latest time point tested.

Conclusion

These studies demonstrate that intravitreal injection of FIV‐based vectors can mediate efficient and lasting transduction of cells in the cornea, iris, and retina. Copyright © 2002 John Wiley & Sons, Ltd.

     

Development and characterization of a minimal inducible packaging cell line for simian immunodeficiency virus-based lentiviral vectors

Background

Lentiviral vectors allow gene transfer into non‐dividing cells. Further development of these vector systems requires stable packaging cell lines that enable adequate safety testing.

Methods

To generate a packaging cell line for vectors based on simian immunodeficiency virus (SIV), expression plasmids were constructed that contain the codon‐optimized gag‐pol gene of SIV and the gene for the G protein of vesicular stomatitis virus (VSV‐G) under the control of an ponasterone‐inducible promoter. Stable cell lines expressing these packaging constructs were established and characterized.

Results

The RT activity and vector titers of cell clones stably transfected with the inducible gag‐pol expession plasmid could be induced by ponasterone by more than a factor of 1000. One of these clones was subsequently transfected with the ponasterone‐inducible VSV‐G expression plasmid to generate packaging cells. Clones of the packaging cells were screened for vector production by infection with an SIV vector and subsequent induction by ponasterone. In the supernatant of selected ponasterone‐induced producer clones vector titers of more than 1×10⁵ transducing units/ml were obtained. Producer cell clones were stable for at least five months, as tested by vector production.

Conclusions

The packaging cells described should be suitable for most preclinical applications of SIV‐based vectors. By avoiding regions of high homology between the vector and the packaging constructs, the design of the SIV packaging cell line should reduce the risk of transfer of packaging genes to target cells and at the same time provide flexibility with respect to the SIV vector constructs that can be packaged. Copyright © 2002 John Wiley & Sons, Ltd.

     

Oncoretroviral gene transfer to NOD/SCID repopulating cells using three different viral envelopes

Background

The aim of this study was to investigate gene transfer to human umbilical cord blood (CB) CD34⁺/CD38^low and NOD/SCID repopulating cells using oncoretroviral vectors and to compare the transduction efficiency using three different viral envelopes.

Methods

CB cells were transduced on Retronectin using an MSCV‐based vector with the gene for GFP (MGIN), which was packaged into three different cell lines giving different envelopes: PG13‐MGIN (GALV), 293GPG‐MGIN (VSV‐G) or AM12‐MGIN (amphotropic).

Results

Sorted CD34⁺/CD38^low cells were efficiently transduced after 3 days of cytokine stimulation and the percentage of GFP‐positive cells was 61.8±6.6% (PG13‐MGIN), 26.9±3.5% (293GPG‐MGIN), and 39.3±4.8% (AM12‐MGIN). For transplantation experiments, CD34⁺ cells were pre‐stimulated for 2 days before transduction on Retronectin preloaded with vector and with the addition of 1/10th volume of viral supernatant on day 3. On day 4, the expanded equivalent of 2.5×10⁵ cells was injected into irradiated NOD/SCID mice. All three pseudotypes transduced NOD/SCID repopulating cells (SRCs) equally well in the presence of serum, but engraftment was reduced when compared with freshly thawed cells. Simultaneous transduction with all three vector pseudotypes increased the gene transfer efficiency to SRCs but engraftment was significantly impaired. There were difficulties in producing amphotropic vectors at high titers in serum‐free medium and transduction of CD34⁺ cells using VSV‐G‐pseudotyped vectors under serum‐free conditions was very inefficient. In contrast, transduction with PG13‐MGIN under serum‐free conditions resulted in the maintenance of SRCs during transduction, high levels of engraftment (29.3±6.6%), and efficient gene transfer to SRCs (46.2±4.8%).

Conclusions

The best conditions for transduction and engraftment of CB SRCs were obtained with GALV‐pseudotyped vectors using serum‐free conditions. Copyright © 2002 John Wiley & Sons, Ltd.

     

Rescue of retroviral envelope fusion deficiencies by cationic liposomes

Background

Retroviral particles that are inappropriately enveloped can transduce target cells if pre‐associated with cationic liposomes. This study optimises and addresses the mechanism of liposome‐enhanced gene delivery, and explores the potential for such agents to compensate for fusion deficiency associated with chimaeric envelope proteins.

Methods

Particles bearing wild‐type, chimaeric or no envelope proteins were complexed with DOTAP or DC‐Chol/DOPE cationic liposomes and added to target cells for various times. Particle binding was determined by detection of cell‐associated capsid protein and infectivity was measured histochemically.

Results

Stable association of cationic liposomes with retrovirus particles significantly enhanced their binding rate to target cells in proportion to the increase of transduction kinetics for infectious virus. Binding of virus was equivalent with or without envelope protein and/or virus receptor, indicating that a non‐specific interaction precedes receptor recognition. Non‐infectious combinations were rescued by the intrinsic fusogenicity of the cationic liposomes, which enabled entry of the viral core, but left subsequent events unaltered. The optimised transduction rate with non‐enveloped particles and DOTAP approached that of amphotropic‐enveloped virus in some cases, although the effect was target‐cell‐dependent. DC‐Chol/DOPE was less potent at direct fusion but was able to enhance 600‐fold the receptor‐dependent action of chimaeric envelopes that were deficient in fusion by virtue of the addition of targeting domains.

Conclusions

These data have implications for the development of retroviral vector targeting strategies from the perspectives of the specificity of target cell interaction and compensating for chimaeric envelope fusion deficiency. Copyright © 2002 John Wiley & Sons, Ltd.

     

The species–area relationship does not have an asymptote!

Aim

To attack a widespread myth.

Location

World‐wide.

Methods

Simple mathematical logical and empirical examples.

Results

As both species and area are finite and non‐negative, the species–area relationship is limited at both ends. The log species–log area relationship is normally effectively linear on scales from about 1 ha to 10⁷ km². There are no asymptotes. At the intercontinental scale it may get steeper; at small scales it may in different cases get steeper or shallower or maintain its slope.

Main conclusion

The species–area relationship does not have an asymptote.

     

Modification of pLL/DNA complexes with a multivalent hydrophilic polymer permits folate-mediated targeting in vitro and prolonged plasma circulation in vivo

Background

Gene delivery vectors based on poly(L ‐lysine) and DNA (pLL/DNA complexes) have limited use for targeted systemic application in vivo since they bind cells and proteins non‐specifically. In this study we have attempted to form folate‐targeted vectors with extended systemic circulation by surface modification of pLL/DNA complexes with hydrophilic polymers.

Methods

pLL/DNA complexes were stabilised by surface modification with a multivalent reactive polymer based on alternating segments of poly(ethylene glycol) and tripeptides bearing reactive ester groups. Folate moieties were incorporated into the vectors either by direct attachment of folate to the polymer or via intermediate poly(ethylene glycol) spacers of 800 and 3400 Da.

Results

Polymer‐coated complexes show similar morphology to uncoated complexes, their zeta potential is decreased towards zero, serum protein binding is inhibited and aqueous solubility is substantially increased. Intravenous (i.v.) administration to mice of coated complexes produced extended systemic circulation, with up to 2000‐fold more DNA measured in the bloodstream after 30 min compared with simple pLL/DNA complexes. In further contrast to simple pLL/DNA complexes, coated complexes do not bind blood cells in vivo. Folate receptor targeting is shown to mediate targeted association with HeLa cells in vitro, leading to increased transgene expression. We demonstrate for the first time that DNA uptake via the folate receptor is dependent on pEG spacer length, with the transgene expression relatively independent of the level of internalised DNA.

Conclusions

We show increased systemic circulation, decreased blood cell and protein binding, and folate‐targeted transgene expression using pLL/DNA complexes surface‐modified with a novel multireactive hydrophilic polymer. This work provides the basis for the development of plasma‐circulating targeted vectors for in vivo applications. Copyright © 2002 John Wiley & Sons, Ltd.

     

Preparation of dry powder dispersions for non-viral gene delivery by freeze-drying and spray-drying

Background

Dry powder dispersion devices offer potential for delivering therapeutic macromolecules to the pulmonary epithelia. Previously, freeze‐drying (lyophilisation) has been the accepted method for preparing dried formulations of proteins and non‐viral gene vectors despite the respirability of such powders being inadequate without further processing. In this study we compare the utility of freeze‐drying and spray‐drying, a one‐step process for producing dry and respirable powders, as methods for preparing non‐viral respiratory gene delivery systems.

Methods

Lipid:polycation:pDNA (LPD) vectors comprising 1,2‐dioleoyl‐3‐trimethylammoniumpropane (DOTAP), protamine sulphate and pEGFP‐N1 in 3% lactose solution were either snap‐frozen and lyophilised or spray‐dried. Lyophilised powder was used as recovered or following coarse grinding. Structural integrity of dehydrated pDNA was assessed by agarose gel electrophoresis and powder particle size determined by laser diffraction. The apparent structure of the systems was visualised by scanning and transmission electron microscopy with the biological functionality quantified in vitro (A549 human lung epithelial cell line) by Green Fluorescent Protein (GFP) associated fluorescence.

Results

Lyophilisation produced large, irregularly shaped particles prior to (mean diameter ～21 µm) and following (mean diameter ～18 µm) coarse grinding. Spray‐drying produced uniformly shaped spherical particles (mean diameter ～4 µm). All dehydrated formulations mediated reporter gene expression in A549 cells with the spray‐dried formulation generally proving superior even when compared with freshly prepared LPD complexes. Biological functionality of the LPD dry powders was not adversely affected following 3 months storage.

Conclusions

Spray‐drying has utility for producing stable, efficient and potentially respirable non‐viral dry powder systems for respiratory gene delivery. Copyright © 2002 John Wiley & Sons, Ltd.

     

Listeria monocytogenes mediated CFTR transgene transfer to mammalian cells

Background

Several approaches for gene therapy of cystic fibrosis using viral and non‐viral vectors are currently being undertaken. Nevertheless, the present data suggest that vectors currently being used will either have to be further modified or, alternatively, novel vector systems need to be developed. Recently, bacteria have been proven as suitable vehicles for DNA transfer to a wide variety of eukaryotic cells. In this study, we assessed the ability of the facultative intracellular pathogen Listeria monocytogenes to deliver a cDNA encoding the human cystic fibrosis transmembrane conductance regulator (CFTR) to CHO‐K1 cells, since these cells have been extensively used for heterologous CFTR expression.

Methods

An established in vitro gene transfer system based on antibiotic‐mediated lysis of intracellular L. monocytogenes was exploited to transfer eukaryotic expression plasmids. Transient as well as stable CFTR transgene expression was analyzed by microscopical and biochemical methods; functionality was tested by whole‐cell patch‐clamp recordings.

Results

L. monocytogenes mediated gene transfer to CHO‐K1 cells was facilitated by an improved transfection protocol. In addition, the use of the isogenic mutant L. monocytogenes hlyW491A, engineered to produce a hemolysin variant with low toxigenic activity, greatly enhanced the efficiency of gene transfer. This strain allowed the transfer of functional CFTR to CHO‐K1 cells.

Conclusions

This is the first demonstration of L. monoyctogenes mediated CFTR transgene transfer. The successful in vitro transfer suggests that L. monocytogenes might be a potential vector for cystic fibrosis gene therapy or alternative applications and deserves further investigation in vitro as well as in vivo. Copyright © 2002 John Wiley & Sons, Ltd.

     

Gutted adenoviral vector growth using E1/E2b/E3-deleted helper viruses

Background

Helper‐dependent, or gutted, adenoviruses (Ad) lack viral coding sequences, resulting in reduced immunotoxicity compared with conventional Ad vectors. Gutted Ad growth requires a conventional Ad to supply replication and packaging functions in trans. Methods that allow high‐titer growth of gutted vectors while reducing helper contamination, and which use safer helper viruses, will facilitate the use of gutted Ad vectors in vivo.

Methods

Replication‐defective helper viruses were generated that are deleted for Ad E1, E2b and E3 genes, but which contain loxP sites flanking the packaging signal. Complementing Ad packaging cell lines (C7‐cre cells) were also generated by transfecting 293 cells with the Ad E2b genes encoding DNA polymerase and pre‐terminal protein, and with a cre‐recombinase plasmid.

Results

We show that C7‐cre cells allow efficient production of gutted Ad using ΔE1 + ΔE2b + ΔE3 helper viruses whose growth can be limited by cre‐loxP‐mediated excision of the packaging signal. Gutted Ad vectors carrying ～28 kb cassettes expressing full‐length dystrophin were prepared at high titers, similar to those obtained with E2b+ helpers, with a resulting helper contamination of <1%.

Conclusions

These new packaging cell lines and helper viruses offer several significant advantages for gutted Ad vector production. They allow gutted virus amplification using a reduced number of passages, which should reduce the chances of selecting rearranged products. Furthermore, the residual helper contamination in gutted vector preparations should be less able to elicit immunological reactions upon delivery to tissues, since E2b‐deleted vectors display a profound reduction in viral gene expression. Copyright © 2002 John Wiley & Sons, Ltd.

     

Polyethyleneimine-based immunopolyplex for targeted gene transfer in human lymphoma cell lines

Background

Specific and efficient delivery of genes into targeted cells is a priority objective in non‐viral gene therapy. Polyethyleneimine‐based polyplexes have been reported to be good non‐viral transfection reagents. However, polyplex‐mediated DNA delivery occurs through a non‐specific mechanism. This article reports the construction of an immunopolyplex, a targeted non‐viral vector based on a polyplex backbone, and its application in gene transfer over human lymphoma cell lines.

Methods

Targeting elements (biotin‐labeled antibodies), which should recognize a specific element of the target cell membrane and promote nucleic acid entry into the cell, were attached to the polyplex backbone through a bridge protein (streptavidin). Immunopolyplex transfection activity was studied in several hematological cell lines [Jurkat (CD3+/CD19?), Granta 519 (CD3?/ CD19+), and J.RT3‐T3.5 (CD3?/CD19?)] using the EGFP gene as a reporter gene and anti‐CD3 and anti‐CD19 antibodies as targeting elements. Transfection activity was evaluated via green fluorescence per cell and the percentage of positive cells determined by flow cytometry.

Results

A significant selectivity of gene delivery was observed, since the anti‐CD3 immunopolyplex worked only in Jurkat cells while the anti‐CD19 immunopolyplex worked only in the Granta cell line. Moreover, transfection of a CD3+/CD3? cell mixture with anti‐CD3 immunopolyplexes showed up to 16‐fold more transfection in CD3+ than in CD3? cells. Several non‐specific transfection reagents showed poor or no transfection activity.

Conclusion

It is concluded that immunopolyplex is a good non‐viral vector for specific and selective nucleic acid delivery. Immunopolyplex design allows easy replacement of the targeting element (antibody) – the streptavidin–polyplex backbone remaining intact – thereby conferring high versatility. Copyright © 2002 John Wiley & Sons, Ltd.

     

Highly efficient gene transfer into antigen-specific primary mouse lymphocytes with replication-deficient retrovirus expressing the 10A1 envelope protein

Background

Introduction of recombinant genes in the genome of primary lymphocytes by virtue of a replication‐deficient retrovirus can be used in immunological studies and for cell‐based gene therapy.

Methods

Packaging cells GP+E86 producing replication‐deficient retrovirus incorporating the genes of enhanced green fluorescent protein (eGFP), C2γ or C2ξ, were generated by calcium phosphate‐mediated transfection. Clones with the highest titres of retrovirus vector were isolated from them and their supernatants were used for transduction of PT67 cells. Primary mouse lymphocytes and T‐cell hybridoma MD.45 were transduced by centrifugation with retroviral stock. The retroviral content of packaging cell supernatants was determined by dot blotting and hybridization with a DNA probe.

Results

PT67 cells produced ～50 times more retrovirus vector than the original GP+E86 clones. When retroviral stocks of PT67 and GP+E86 cells were used at 1/50 dilution and undiluted, respectively (to normalize them forretroviral RNA content), the transduction efficiency of mouse T‐cell hybridoma was 40% and 5%, respectively. Centrifugation of target cells with retroviral stock at 2000 g for 60 min increased the percentage of transduced cells two‐ to three‐fold. Within a population of cells isolated from the draining lymph nodes of an immunized mouse and reactivated with an antigen, up to 60% of CD4⁺ T cells and up to 80% of B cells could be transduced with a transgene in replication‐deficient retrovirus packaged by PT67 cells using the optimized gene transfer protocol.

Conclusions

This protocol allows for the generation of packaging cells producing high titres of retrovirus vector. The 10A1 envelope protein is superior to the ecotropic one for the transduction of mouse lymphocytes. Copyright © 2002 John Wiley & Sons, Ltd.

     

Lack of specificity of cell-surface protease targeting of a cytotoxic hyperfusogenic gibbon ape leukaemia virus envelope glycoprotein

Background

In a strategy termed “Protease Targeting”, retroviral vectors carrying an EGF infectivity‐blocking domain fused to the N‐terminus of the envelope SU via a MMP (matrix metalloproteinase)‐cleavable linker were successfully used to target gene delivery to EGF receptor‐(EGF‐R‐)positive tumour cells over‐expressing MMPs. In the current study, we aimed to investigate whether this strategy could be applied to (a) limit the cytotoxic activity of a hyperfusogenic GALV therapeutic gene, and (b) enhance the immune‐stimulatory properties of GALV via local, MMP‐mediated release human granulocyte‐macrophage colony stimulating factor (GM‐CSF).

Methods

We generated GALV envelope expression constructs displaying EGF or GM‐CSF blocking ligands at the N‐terminus of GALV envelope SU via a non‐cleavable, Factor Xa protease or MMP‐cleavable linker and investigated their cytotoxicity on MMP‐positive and negative cell lines.

Results

The unmodified hyperfusogenic GALV envelope was cytotoxic to all cell lines tested. The non‐cleavable linker GALV envelope constructs caused no cytotoxicity, demonstrating efficient inhibition by the displayed domains. Moderate activation of fusion of the protease‐cleavable linker constructs was observed in all cell lines, regardless of their level of MMP expression and of the specificity of the linker. High levels of the ‘blocking domain’ were detected in the cell supernatants due to dissociation of the surface unit (SU) from the transmembrane (TM) component of the GALV envelope glycoprotein TM.

Conclusions

Unlike protease targeting in the context of retroviral vectors, protease activation of the cytotoxicity of GALV envelope by cleavage of a fusion blocking ligand at the cell surface does not appear to be specifically mediated by cell‐surface MMPs. In addition, shedding of the SU‐fusion protein from the TM limits the general applicability of this strategy for cancer gene therapy. Specificity of cell‐cell fusion mediated by GALV envelope cannot be manipulated in the same fashion as virus‐cell fusion. Copyright © 2002 John Wiley & Sons, Ltd.

     

Neural crest and cardiovascular development: a 20-year perspective

Background

Twenty years ago this year was the first publication describing a region of neural crest cells necessary for normal cardiovascular development. Ablation of this region in chick resulted in persistent truncus arteriosus, mispatterning of the great vessels, outflow malalignments, and hypoplasia or aplasia of the pharyngeal glands.

Methods

We begin with a historical perspective and then review the progress that has been made in the ensuing 20 years in determining the direct and indirect contributions of the neural crest cells, now termed cardiac neural crest cells, in cardiovascular and pharyngeal arch development. Many of the molecular pathways that are now known to influence the specification, migration, patterning and final targeting of the cardiac neural crest cells are also reviewed.

Results

Although much knowledge has been gained by using many genetic manipulations to understand the cardiac neural crest cells' role in cardiovascular development, most models fail to explain the phenotypes seen in syndromic and non‐syndromic human congenital heart defects, such as the DiGeorge syndrome.

Conclusions

We propose that the cardiac neural crest exists as part of a larger cardiocraniofacial morphogenetic field and describe several human syndromes that result from abnormal development of this field. Birth Defects Research (Part C) 69:2–13, 2003. © 2003 Wiley‐Liss, Inc.

     

Polybrene and interleukin-4: two opposing factors for retroviral transduction of bone-marrow-derived dendritic cells

Background

Gene transfer using retroviral transduction offers the advantage of long‐term transgene expression in developing strategies that use dendritic cells (DCs) for immunotherapy. The goal of this study was to infect DCs in an immature state in order to take advantage of their proliferating and tolerogenic potential.

Methods

Immature DCs were generated from murine bone marrow (BM) using either GM‐CSF alone or GM‐CSF plus IL‐4. The cells were transduced directly with retroviral supernatants or by co‐culture with the GP + E‐86 retroviral packaging cell line in the presence of two different cationic polymers: polybrene and protamine sulfate. Phenotypic and functional characterization of the transduced cells were then performed.

Results

Our results show a low efficiency of retroviral infection of DCs in the presence of polybrene. This cationic polymer was found to be directly cytotoxic to murine DCs and thus favored the growth of contaminating macrophages. This effect was not observed using protamine sulfate. Furthermore, stimulation by IL‐4 early in the culture increased DC differentiation, proliferation and transduction. However, we found that DCs generated in GM‐CSF plus IL‐4 presented a more mature phenotype with an enhanced allogeneic stimulating activity. Finally, we showed that DCs themselves down‐regulated transgene expression in the co‐cultured packaging cell line in a promoter‐dependent manner.

Conclusions

We have defined optimal conditions to generate and transduce murine BM‐derived DCs. This included: the use of protamine sulfate during exposure to retroviral infectious supernatant and the addition of IL‐4 at an early stage of the culture. Nevertheless, this cytokine also induced DC maturation. These findings have potential implications in experimental gene therapy. Copyright © 2002 John Wiley & Sons, Ltd.

     

Effect of chitosan‐alginate nanoparticles and ultrasound on the efficiency of gene transfection of human cancer cells

Background

Gene therapy has been used to treat a variety of health problems, but transfection inefficiency and the lack of safe vectors have limited clinical progress. Fabrication of a vector that is safe and has high transfection efficiency is crucial for the development of successful gene therapy. The present study aimed to synthesize chitosan‐alginate nanoparticles that can be used as carriers of the pAcGFP1‐C1 plasmid and to use these nanoparticles with an ultrasound protocol to achieve high efficiency gene transfection.

Methods

Chitosan was complexed with alginate and the pAcGFP1‐C1 plasmid at different charge ratios to create chitosan‐alginate‐DNA nanoparticles (CADNs). The average particle size and loading efficiency were measured. Plasmid DNA retardation and integrity were analysed on 1% agarose gels. The effect of CADNs and ultrasound on the efficiency of transfection of cells and subcutaneous tumors was evaluated.

Results

In the CADNs, the average size of incorporated plasmid DNA was 600–650 nm and the loading efficiency was greater than 90%. On the basis of the results of the plasmid DNA protection test, CADNs could protect the transgene from DNase I degradation. The transgene product expression could be enhanced efficiently if cells or tumor tissues were first given CADNs and then treated with ultrasound.

Conclusions

The use of CADNs combined with an ultrasound regimen is a promising method for safe and effective gene therapy. Copyright © 2009 John Wiley & Sons, Ltd.