Sonoselective delivery using ultrasound and microbubbles combined with intravenous rAAV9 CLDN5-GFP does not increase endothelial gene expression

Transcranial ultrasound combined with intravenous microbubbles can be used to increase blood-brain barrier permeability or, at lower pressures, to mediate sonoselective gene delivery to endothelial cells. Previously, sonoselective gene delivery with plasmid-coated microbubbles as gene carriers resulted in transient transgene expression in the brain endothelium. We investigated the potential of recombinant adeno-associated virus 9 (rAAV9), a serotype known for its efficient transduction and long-term transgene expression, for sonoselective gene delivery to endothelial cells of the brain. We found that rAAV9 led to gene delivery to brain endothelial cells following intravenous administration at a dosage of 1 × 1011 GC/g. However, the sonoselective gene delivery approach with intravenous rAAV9, using the same parameters as previously used for plasmid delivery, did not increase transgene expression in brain endothelial cells targeted. These results suggest that intravenous rAAV9 are using mechanisms of entry into the cerebrovasculature that are not significantly influenced by sonoselective treatments known to facilitate endothelial cell entry of plasmids coated onto microbubbles.

Delivery Approaches for Therapeutic Genome Editing and Challenges

Impressive therapeutic advances have been possible through the advent of zinc-finger nucleases and transcription activator-like effector nucleases. However, discovery of the more efficient and highly tailorable clustered regularly interspaced short palindromic repeats (CRISPR) and associated proteins (Cas9) has provided unprecedented gene-editing capabilities for treatment of various inherited and acquired diseases. Despite recent clinical trials, a major barrier for therapeutic gene editing is the absence of safe and effective methods for local and systemic delivery of gene-editing reagents. In this review, we elaborate on the challenges and provide practical considerations for improving gene editing. Specifically, we highlight issues associated with delivery of gene-editing tools into clinically relevant cells.

GMP-Compliant Adenoviral Vectors for Gene Therapy

Recently, gene therapy as one of the most promising treatments can apply genes for incurable diseases treatment. In this context, vectors as gene delivery systems play a pivotal role in gene therapy procedure. Hereupon, viral vectors have been increasingly introduced as a hyper-efficient tools for gene therapy. Adenoviral vectors as one of the most common groups which are used in gene therapy have a high ability for humans. Indeed, they are not integrated into host genome. In other words, they can be adapted for direct transduction of recombinant proteins into targeted cells. Moreover, they have large packaging capacity and high levels of efficiency and expression. In accordance with translational pathways from the basic to the clinic, recombinant adenoviral vectors packaging must be managed under good manufacturing practice (GMP) principles before applying in clinical trials. Therein, in this chapter standard methods for manufacturing of GMP-compliant Adenoviral vectors for gene therapy have been introduced.

The Impact of Alkyl-Chain Purity on Lipid-Based Nucleic Acid Delivery Systems - Is the Utilization of Lipid Components with Technical Grade Justified?

The physicochemical properties and transfection efficacies of two samples of a cationic lipid have been investigated and compared in 2D (monolayers at the air/liquid interface) and 3D (aqueous bulk dispersions) model systems using different techniques. The samples differ only in their chain composition due to the purity of the oleylamine (chain precursor). Lipid 8 (using the oleylamine of technical grade for cost-efficient synthesis) shows lateral phase separation in the Langmuir layers. However, the amount of attached DNA, determined by IRRAS, is for both samples the same. In 3D systems, lipid 8 p forms cubic phases, which disappear after addition of DNA. At physiological temperatures, both lipids (alone and in mixture with cholesterol) assemble to lamellar aggregates and exhibit comparable DNA delivery efficiency. This study demonstrates that non-lamellar structures are not compulsory for high transfection rates. The results legitimate the utilization of oleyl chains of technical grade in the synthesis of cationic transfection lipids.

A Critical Review of Electroporation as A Plasmid Delivery System in Mouse Skeletal Muscle

The gene delivery to skeletal muscles is a promising strategy for the treatment of both muscular disorders (by silencing or overexpression of specific gene) and systemic secretion of therapeutic proteins. The use of a physical method like electroporation with plate or needle electrodes facilitates long-lasting gene silencing in situ. It has been reported that electroporation enhances the expression of the naked DNA gene in the skeletal muscle up to 100 times and decreases the changeability of the intramuscular expression. Coelectransfer of reporter genes such as green fluorescent protein (GFP), luciferase or beta-galactosidase allows the observation of correctly performed silencing in the muscles. Appropriate selection of plasmid injection volume and concentration, as well as electrotransfer parameters, such as the voltage, the length and the number of electrical pulses do not cause long-term damage to myocytes. In this review, we summarized the electroporation methodology as well as the procedure of electrotransfer to the gastrocnemius, tibialis, soleus and foot muscles and compare their advantages and disadvantages.

Evaluation of AAV-mediated delivery of shRNA to target basal-like breast cancer genetic vulnerabilities

Adeno-associated viral vectors (AAV) for gene therapy applications are gaining momentum, with more therapies moving into later stages of clinical development and towards market approval, namely for cancer therapy. The development of cytotoxic vectors is often hampered by side effects arising when non-target cells are infected, and their production can be hindered by toxic effects of the transgene on the producing cell lines. In this study, we evaluated the potential of rAAV-mediated delivery of short hairpin RNAs (shRNA) to target basal-like breast cancer genetic vulnerabilities. Our results show that by optimizing the stoichiometry of the plasmids upon transfection and time of harvest, it is possible to increase the viral titers and quality. All rAAV-shRNA vectors obtained efficiently transduced the BLBC cell lines MDA-MB-468 and HCC1954. In MDA-MB-468, transduction with rAAV-shRNA vector targeting PSMA2 was associated with significant decrease in cell viability and apoptosis induction. Importantly, rAAV2-PSMA2 also slowed tumor growth in a BLBC mouse xenograft model, thus potentially representing a therapeutic strategy against this type of cancer.

Pharmaceutical Development of AAV-Based Gene Therapy Products for the Eye

A resurgence of interest and investment in the field of gene therapy, driven in large part by advances in viral vector technology, has recently culminated in United States Food and Drug Administration approval of the first gene therapy product targeting a disease caused by mutations in a single gene. This product, LUXTURNA™ (voretigene neparvovec-rzyl; Spark Therapeutics, Inc., Philadelphia, PA), delivers a normal copy of the RPE65 gene to retinal cells for the treatment of biallelic RPE65 mutation–associated retinal dystrophy, a blinding disease. Many additional gene therapy programs targeting both inherited retinal diseases and other ocular diseases are in development, owing to an improved understanding of the genetic basis of ocular disease and the unique properties of the ocular compartment that make it amenable to local gene therapy. Here we review the growing body of literature that describes both the design and development of ocular gene therapy products, with a particular emphasis on target and vector selection, and chemistry, manufacturing, and controls.

Synthesis, characterization and evaluation of transfection efficiency of dexamethasone conjugated poly(propyleneimine) nanocarriers for gene delivery#. Pharm Biol 2018;56:519-527. [PMID: 30270694 PMCID: PMC6171438 DOI: 10.1080/13880209.2018.1517183]

CONTEXT

Polypropylenimine (PPI), a cationic dendrimer with defined structure and positive surface charge, is a potent non-viral vector. Dexamethasone (Dexa) conveys to the nucleus through interaction with its intracellular receptor.

OBJECTIVE

This study develops efficient and non-toxic gene carriers through conjugation of Dexa at various percentages (5, 10 and 20%) to the fourth and the fifth generation PPIs (PPIG4s and PPIG5s).

MATERIALS AND METHODS

The 21-OH group of Dexa (0.536 mmol) was modified with methanesulfonyl chloride (0.644 mmol) to activate it (Dexa-mesylate), and then it was conjugated to PPIs using Traut's reagent. After dialysis (48 h) and lyophilization, the physicochemical characteristics of products (PPI-Dexa) including zeta potential, size, buffering capacity and DNA condensing capability were investigated and compared with unmodified PPIs. Moreover, the cytotoxicity and transfection activity of the Dexa-modified PPIs were assessed using Neuro2A cells.

RESULTS

Transfection of PPIG4 was close to PEI 25 kDa. Although the addition of Dexa to PPIG4s did not improve their transfection, their cytotoxicity was improved; especially in the carrier to DNA weight ratios (C/P) of one and two. The Dexa conjugation to PPIG5s enhanced their transfection at C/P ratio of one in both 5% (1.3-fold) and 10% (1.6-fold) Dexa grafting, of which the best result was observed in PPIG5-Dexa 10% at C/P ratio of one.

DISCUSSION AND CONCLUSIONS

The modification of PPIs with Dexa is a promising approach to improve their cytotoxicity and transfection. The higher optimization of physicochemical characteristics, the better cell transfection and toxicity will be achieved.

Synthetic biology and occupational risk

Synthetic biology is an emerging interdisciplinary field of biotechnology that involves applying the principles of engineering and chemical design to biological systems. Biosafety professionals have done an excellent job in addressing research laboratory safety as synthetic biology and gene editing have emerged from the larger field of biotechnology. Despite these efforts, risks posed by synthetic biology are of increasing concern as research procedures scale up to industrial processes in the larger bioeconomy. A greater number and variety of workers will be exposed to commercial synthetic biology risks in the future, including risks to a variety of workers from the use of lentiviral vectors as gene transfer devices. There is a need to review and enhance current protection measures in the field of synthetic biology, whether in experimental laboratories where new advances are being researched, in health care settings where treatments using viral vectors as gene delivery systems are increasingly being used, or in the industrial bioeconomy. Enhanced worker protection measures should include increased injury and illness surveillance of the synthetic biology workforce; proactive risk assessment and management of synthetic biology products; research on the relative effectiveness of extrinsic and intrinsic biocontainment methods; specific safety guidance for synthetic biology industrial processes; determination of appropriate medical mitigation measures for lentiviral vector exposure incidents; and greater awareness and involvement in synthetic biology safety by the general occupational safety and health community as well as by government occupational safety and health research and regulatory agencies.

Spectral study of interaction between poly(L-lysine)-poly(ethylene glycol)-poly(L-lysine) and nucleic acids

Polymer-DNA interactions have attracted considerable interests due to their important application in DNA transfection and cellular drug delivery technologies. In this work, a new detection assay for DNA is proposed with a tri-block copolymer poly(L-lysine)-poly(ethylene glycol)-poly(L-lysine) by resonance light scattering technique with the linear ranges from 0.0656 to 6.56 μg ml⁻¹. The detection limit for DNA is 0.42 ng ml⁻¹. Most coexisting substances do not interfere in the detection. UV-spectra and FTIR-spectra were employed to demonstrate the mechanisms of the interaction that the conformation of the DNA changes because the microenvironment of DNA changes.

Best practice procedures for the establishment of a C(4) cycle in transgenic C(3) plants

C(4) plants established a mechanism for the concentration of CO(2) in the vicinity of ribulose-1,5-bisphosphate carboxylase/oxygenase in order to saturate the enzyme with substrate and substantially to reduce the alternative fixation of O(2) that results in energy losses. Transfer of the C(4) mechanism to C(3) plants has been repeatedly tested, but none of the approaches so far resulted in transgenic plants with enhanced photosynthesis or growth. Instead, often deleterious effects were observed. A true C(4) cycle requires the co-ordinated activity of multiple enzymes in different cell types and in response to diverse environmental and metabolic stimuli. This review summarizes our current knowledge about the most appropriate regulatory elements and coding sequences for the establishment of C(4) protein activities in C(3) plants. In addition, technological breakthroughs for the efficient transfer of the numerous genes probably required to transform a C(3) plant into a C(4) plant will be discussed.

Quantitative evaluation of siRNA delivery in vivo

Effective small interfering RNA (siRNA)-mediated therapeutics require the siRNA to be delivered into the cellular RNA-induced silencing complex (RISC). Quantitative information of this essential delivery step is currently inferred from the efficacy of gene silencing and siRNA uptake in the tissue. Here we report an approach to directly quantify siRNA in the RISC in rodents and monkey. This is achieved by specific immunoprecipitation of the RISC from tissue lysates and quantification of small RNAs in the immunoprecipitates by stem-loop PCR. The method, expected to be independent of delivery vehicle and target, is label-free, and the throughput is acceptable for preclinical animal studies. We characterized a lipid-formulated siRNA by integrating these approaches and obtained a quantitative perspective on siRNA tissue accumulation, RISC loading, and gene silencing. The described methodologies have utility for the study of silencing mechanism, the development of siRNA therapeutics, and clinical trial design.

Transient non-viral cutaneous gene delivery in burn wounds

BACKGROUND

Gene transfer to burn wounds could present an alternative to conventional and often insufficient topical and systemic application of therapeutic agents to aid in wound healing. The goals of this study were to assess and optimize the potential of transient non-viral gene delivery to burn wounds.

METHODS

HaCaT cells were transfected with luciferase or beta-galactosidase transgene using either pure plasmid DNA (pDNA) or complexed with Lipofectamine 2000, FuGENE6, or DOTAP-Chol. Expression was determined by bioluminescence and fluorescence. Forty male Sprague-Dawley rats received naked pDNA, lipoplexes, or carrier control intradermally into either unburned skin, superficial, partial, or full-thickness scald burn. Animals were sacrificed after 24 h, 48 h, or 7 days, and transgene expression was assessed.

RESULTS

Gene transfer to HaCaT cells showed the overall highest expression for DOTAP/Chol (77.85 ng luciferase/mg protein), followed by Lipofectamine 2000 (33.14 ng luciferase/mg protein). pDNA-derived gene transfer to superficial burn wounds showed the highest expression among burn groups (0.77 ng luciferase/mg protein). However, lipoplex-derived gene transfer to superficial burns and unburned skin failed to show higher expression.

CONCLUSIONS

Lipofectamine 2000 and DOTAP/Chol lipoplex showed significantly enhanced gene transfer, whereas no transfection was detectable for naked DNA in vitro. In contrast to the in vitro study, naked DNA was the only agent with which gene delivery was successful in experimental burn wounds. These findings highlight the limited predictability of in vitro analysis for gene delivery as a therapeutic approach.

Reverse genetics in ecological research

By precisely manipulating the expression of individual genetic elements thought to be important for ecological performance, reverse genetics has the potential to revolutionize plant ecology. However, untested concerns about possible side-effects of the transformation technique, caused by Agrobacterium infection and tissue culture, on plant performance have stymied research by requiring onerous sample sizes. We compare 5 independently transformed Nicotiana attenuata lines harboring empty vector control (EVC) T-DNA lacking silencing information with isogenic wild types (WT), and measured a battery of ecologically relevant traits, known to be important in plant-herbivore interactions: phytohormones, secondary metabolites, growth and fitness parameters under stringent competitive conditions, and transcriptional regulation with microarrays. As a positive control, we included a line silenced in trypsin proteinase inhibitor gene (TPI) expression, a potent anti-herbivore defense known to exact fitness costs in its expression, in the analysis. The experiment was conducted twice, with 10 and 20 biological replicates per genotype. For all parameters, we detected no difference between any EVC and WT lines, but could readily detect a fitness benefit of silencing TPI production. A statistical power analyses revealed that the minimum sample sizes required for detecting significant fitness differences between EVC and WT was 2-3 orders of magnitude larger than the 10 replicates required to detect a fitness effect of TPI silencing. We conclude that possible side-effects of transformation are far too low to obfuscate the study of ecologically relevant phenotypes.

Future developments in neurovascular ultrasound

Significant new developments in neurovascular ultrasound include molecular approaches to diagnostics and therapy. Addition of targeted ligands to microbubbles, has opened new avenues for the identification of vascular injury. This is because the molecular signatures of overexpressed adhesion molecules such as the integrin alphavbeta3, ICAM-1, and fibrinogen receptor GPIIb/II can be used to localize contrast agents through the use of complementary receptor ligands. Recent experiments have demonstrated the feasibility of microbubble-ultrasound-enhanced gene therapy to the brain. This new technology holds the promise of delivering genes more selectively than other methods and less invasively than direct injection. Microbubbles may also be employed as carriers of gene agents. The ability to focus ultrasound and cause local cavitation with these carriers may provide a new tool for gene therapy. Fortuitously, the intact blood-brain barrier (BBB), a major limitation in using genes for therapy of brain disease, can be opened with ultrasound. This localized, transient, and reversible opening of the BBB with ultrasound can provide an anatomically selective and targeted gene delivery. Future developments in neurovascular ultrasound will include improvements in technologies for ligand attachment to microbubbles, better methods for imaging targeted ultrasound agents in the brain, and optimization of ultrasound-mediated gene delivery.

Lentiviral vector-mediated genetic modification of human neural progenitor cells for ex vivo gene therapy

Human neural progenitor cells (hNPC) hold great potential as an ex vivo system for delivery of therapeutic proteins to the central nervous system. When cultured as aggregates, termed neurospheres, hNPC are capable of significant in vitro expansion. In the current study, we present a robust method for lentiviral vector-mediated gene delivery into hNPC that maintains the differentiation and proliferative properties of neurosphere cultures while minimizing the amount of viral vector used and controlling the number of insertion sites per population. This method results in long-term, stable expression even after differentiation of the hNPC to neurons and astrocytes and allows for generation of equivalent transgenic populations of hNPC. In addition, the in vitro analysis presented predicts the behavior of transgenic lines in vivo when transplanted into a rodent model of Parkinson's disease. The methods presented provide a powerful tool for assessing the impact of factors such as promoter systems or different transgenes on the therapeutic utility of these cells.

Clinical trial design issues raised during recombinant DNA advisory committee review of gene transfer protocols

Gene transfer clinical trial protocols are reviewed by the Recombinant DNA Advisory Committee (RAC). Identifying the design concerns and suggestions commonly raised during RAC review may help investigators and sponsors shorten the process of protocol development and improve the quality of gene transfer trials. We therefore examined 53 full public reviews of gene transfer clinical trial protocols performed by the RAC between December 2000 and June 2004 to determine what trial design concerns or suggestions RAC members raised during written review or public discussion or in the formal letter to investigators after the review was completed. We also determined how frequently these concerns were raised. We found that RAC members raised issues regarding selection of subjects in 89% of reviews, dose escalation in 77%, selection of safety end points in 76%, biological activity measures in 66%, and overall design in 60% of reviews. The most common issue raised by RAC reviewers was the need to exclude subjects at increased risk for adverse events. Furthermore, in 89% of reviews, at least one design issue pertaining to safety of participants was raised. In 91% of reviews, at least one design concern was presented as a written RAC recommendation or concern to the investigator after the public review. When submitting protocols for RAC review, investigators and sponsors might devote more attention to issues that RAC reviewers commonly raise. Such attention might help strengthen clinical trial protocols, shorten the protocol development process, and enhance the protection of research participants.

Adeno-associated viral vectors for clinical gene transfer studies

Recombinant adeno-associated viral (rAAV) vectors can mediate the safe and long-term correction of genetic diseases in animal models following a single administration. These pre-clinical studies are the basis of human trials that have shown rAAV vector persistence and safety in humans following delivery to lung, sinus, skeletal muscle, brain and liver. Transient disease correction has also been demonstrated in humans treated for hemophilia B and cystic fibrosis using AAV2 vectors. The physiochemical properties of rAAV vector virions are amenable to industry accepted manufacturing methodologies, long-term storage and direct in vivo administration. Recombinant adeno-associated virus vectors are manufactured in compliance with current Good Manufacturing Practices (cGMPs) as outlined in the Code of Federal Regulations (21CFR). To meet these requirements, manufacturing controls and quality systems are established, including 1) adequate facilities and equipment, 2) personnel who have relevant education or experience and are trained for specific assigned duties, 3) raw materials that are qualified for use and 4) a process (including production, purification, formulation, filling, storage and shipping) that is controlled, aseptic, reliable and consistent. Quality systems including Quality Control (QC) and Quality Assurance (QA) are also implemented. These manufacturing procedures and quality systems are designed so the product meets its release specifications to ensure that patients receive a safe, pure, potent and stable investigational drug.

Gene transfer for neurologic disease

Advances in molecular biology have contributed to a growing interest in gene therapy as a form of management for neurologic diseases. However, implementation requires knowledge of the regulatory policies governing this field of research, especially in view of the greater stringency imposed by the serious adverse events affecting some patients participating in gene therapy protocols. Educational resources for neurologists, or any clinicians, who hope to serve as potential principal investigators for a gene therapy protocol are not available through any single source, requiring considerable effort to discover appropriate guidance. Summarized here are the regulatory agencies and their requirements, the phases of clinical development with emphasis on a Phase I study, and specific steps leading to an Investigational New Drug application for a biologic product to be used in a gene therapy clinical trial. The links provided to all appropriate Web sites will facilitate the process for the clinician investigator.

Liposome-mediated adenomatous polyposis coli gene therapy: a novel anti-adenoma strategy in multiple intestinal neoplasia mouse model

PURPOSE

Familial adenomatous polyposis is a highly penetrant, autosomal dominant disease resulting from a germline mutation of the adenomatous polyposis coli gene. Besides colorectal polyps and cancer, more than 90 percent of familial adenomatous polyposis patients also develop duodenal polyposis with an approximately 5 percent lifetime risk of malignant transformation. Because adenomatous polyposis coli protein has a "gatekeeper role" in the adenoma-carcinoma sequence, replacing its function may reduce polyp formation. We studied the functional outcome of per-oral, liposome-mediated adenomatous polyposis coli gene replacement therapy in a multiple intestinal neoplasia mouse model.

METHODS

Twenty multiple intestinal neoplasia mice, heterozygous for the human homologue adenomatous polyposis coli gene, were randomly assigned to three groups: no treatment (n = 8); control plasmid containing green fluorescence protein reporter gene (n = 6); and plasmid containing the full-length adenomatous polyposis coli gene (n = 6). For the adenomatous polyposis coli-treated and green fluorescence protein reporter gene-treated groups, each mouse received the appropriate plasmid complexed with liposome, administered twice per week by oral gavage regime. Treatment lasted four weeks and all animals were killed at the end of treatment period with harvesting of intestinal tissue for polyp number estimation.

RESULTS

There was a statistically significant 25 percent reduction in the total number of polyps in the adenomatous polyposis coli-treated (73.1 +/- 1.4) group compared with untreated control (97.8 +/- 5.3, P < 0.01, Tukey test) and multiple intestinal neoplasia mice treated with control green fluorescence protein gene (103.3 +/- 1.7, P < 0.01, Tukey test).

CONCLUSION

Adenomatous polyposis coli gene dysfunction underlies tumorigenesis in familial adenomatous polyposis patients and multiple intestinal neoplasia mice. This in vivo study provides evidence to support a novel anti-adenoma strategy using enteral adenomatous polyposis coli gene replacement therapy.

RNA-based gene transfer for adult stem cells and T cells

Electroporation of mRNA has become an established method for gene transfer into dendritic cells for immunotherapeutic purposes. However, many more cell types and applications might benefit from an efficient mRNA-based gene transfer method. In this study, we investigated the potential of mRNA-based gene transfer to induce short-term transgene expression in adult stem cells and activated T cells, based on electroporation with mRNA encoding the enhanced green fluorescent protein. The results show efficient transgene expression in CD34-positive hematopoietic progenitor cells (35%), in in vitro cultured mesenchymal cells (90%) and in PHA-stimulated T cells (50%). Next to presentation of gene transfer results, potential applications of mRNA-based gene transfer in stem cells and T cells are discussed.

PET reporter genes for noninvasive imaging of gene therapy, cell tracking and transgenic analysis

Positron-emission tomography (PET) has been used extensively in the clinic for cancer diagnosis, for staging and for monitoring of therapeutic efficacy. PET has not, however, been used extensively in contemporary animal cancer models. Until recently, appropriate instrumentation was not available and the expertise and knowledge necessary to perform PET analyses in murine models has not been widespread. The fabrication of microPET instruments with appropriate resolution for murine experiments has lead to the establishment of non-invasive techniques for functional imaging. The development of "PET reporter genes" whose activity can be monitored in living animals, based on the reporter gene-dependent sequestration of positron-emitting "PET reporter probes," has lead to innovative analyses of gene expression in transgenic animals, to methods to monitor the location, magnitude and duration of expression for gene therapy vectors and to the ability to non-invasively track the targeting, viability and expansion of cellular therapeutics.

Gene transfer: regulatory issues and their impact on the clinical investigator and the good manufacturing production facility

The first human gene-transfer study was submitted to the Recombinant DNA Advisory Committee (RAC) in 1988, thus initiating a new era in clinical research. As per the RAC Website (last updated 22nd November 2002), almost 550 human gene-transfer studies have been submitted to the RAC. However, there are currently no licensed gene-therapy products available in the USA. The natural evolution of the review process to accommodate these novel protocols, as well as the death of Jesse Gelsinger in 1999, have led to significant changes in the initial and ongoing review of gene-transfer studies. However, the basic framework of the review process remains unchanged.Gene-transfer protocols require oversight by the Food and Drug Administration (FDA), the Recombinant DNA Advisory Committee (RAC), the Institutional Biosafety Committee (IBC), and the Institutional Review Board (IRB). Such oversight includes both initial review of the protocol and ongoing review of the study through the review of annual reports, adverse events, and proposed amendments to the study. In addition to such review of the protocol, the product itself is required by the FDA to be prepared under current good manufacturing practices (cGMP). This article discusses both regulatory oversight and current GMP issues in depth.

Predictable and efficient retroviral gene transfer into murine bone marrow repopulating cells using a defined vector dose

OBJECTIVE

Current protocols of retroviral gene transfer into murine hematopoietic stem cells (HSC) result in variable gene transfer efficiency and involve various procedures that are not clinically applicable. We developed and evaluated a reliable transduction protocol that is more related to clinical methods.

MATERIALS AND METHODS

HSC were enriched from steady-state bone marrow by magnetic cell sorting (lineage depletion) and cultured in defined serum-free medium containing an improved growth factor cocktail (Flt3-ligand, stem cell factor, interleukin-3, interleukin-11). Cell-free ecotropic retroviral vector particles, generated by transient transfection of human 293T-based packaging cells, were preloaded at defined titers on CH296-coated tissue culture plates, thus largely avoiding serum contamination. These conditions were evaluated in 17 experiments involving 29 transduction cultures and 185 recipient mice.

RESULTS

After two rounds of infection, the gene marking rates in cultured mononuclear cells and stem/progenitor cells (Lin(-)c-Kit(+)) were 15 to 85% (53.7%+/-21.7%, n=23) and 30 to 95% (69.8%+/-20.4%, n=17), respectively. Even after one round of infection, gene transfer was efficient (31.2%+/-15.1%, n=12). Using identical conditions, gene transfer rates were highly reproducible. Average transgene expression in reconstituted animals correlated well with pretransplant data. Using a moderate multiplicity of infection, the majority of transduced cells carried less than three transgene copies. In addition, coinfection was possible to establish two different vectors in single cells.

CONCLUSION

The protocol described here achieves efficient retroviral transduction of murine bone marrow repopulating cells with a defined gene dosage, largely avoiding procedures that decrease stem cell output and repopulating capacity. This protocol may help to improve the predictive value of preclinical efficiency/toxicity studies for gene therapeutic interventions and basic research.

Optimized, highly efficient transfer of foreign genes into newborn mouse hearts in vivo

Expression of foreign genes in vivo is a standard method to disclose functions of specific genes and to alter physiological conditions in distinct cell types and tissues. Virus-mediated gene transfer has proved to be a valuable tool for directed gene expression in vivo complementary to transgenic approaches. However, several problems associated with routes of application, endurance of gene expression, and efficiency of infections still have to be solved. We have optimized a gene transfer protocol into hearts of newborn mice to achieve widespread long-lasting expression using adenoviral vectors. Intrathoracic injection of high-titer adenoviral preparations (10(8)pfu) led to expression of foreign genes in >71+/-8% of all heart cells for >50 days after infection without any morphological signs of cardiac malfunction, inflammation, or immune response. This approach might be adapted to long-term cellular studies in vivo since 5 months after infection up to 20% of all cardiac cells still expressed virally encoded genes. Successful and efficient expression of other gene of interest can be easily controlled by co-injection of low titers of a reporter vector encoding EGFP (10(6)pfu).

Effect of chemical features and stability of polyplexes on their gene transfer efficiency

Chemically modified poly-L-lysine (PL) derivatives with two essential features, which we have recently reported on, have been used to study key factors affecting transgene expression efficiency. PL derivatives having both of N epsilon-trimethyl lysine residue and 25 mole % serine residue showed enhanced transfection efficiency. When PL was modified in either way, no marked enhancement in gene expression was observed. These PL derivatives were found to be able to deliver plasmid DNA into nucleus of the transfected cells with a similar amount. Judging from the loss of EtBr fluorescence intercalating to DNA, the condensing tendency of the DNA were greatly affected by the sequence of the polypeptides used. This loose compaction seems to enhance the transgene expression because of an easy disassembly of the formed complexes or recognition of the DNA molecules in the complexes.

Fish can be first--advances in fish transgenesis for commercial applications

Over the past 15 years researchers have generated stable lines of several species of transgenic fish important for aquaculture. 'All-fish' growth hormone (GH) gene constructs and antifreeze protein (AFP) genes have been successfully introduced into the fish genome resulting in a significant acceleration of growth rate and an increase in cold and freeze tolerance. However, neither gene modification is completely understood; there are still questions to be resolved. Expression rates are still low, producing variable growth enhancement rates and less than desired levels of freeze resistance. Transgene strategies are also being developed to provide improved pathogen resistance and modified metabolism for better utilization of the diet. Additional challenges are to tailor the genetically modified fish strains to prevent release of the modified genes into the environment.

Humoral immune response in mice against a circulating antigen induced by adenoviral transfer is strictly dependent on expression in antigen-presenting cells

Adenoviral transfer of human apo A-I in Balb/c mice induces a strong humoral immune response against the transgene product when expression is driven from the ubiquitously active CMV promoter but induces no immune response when driven by the hepatocyte-specific 256-base pair apo A-I promoter. Here the hypothesis was tested, which is that the humoral immune response against the circulating transgene product correlates with its expression in antigen-presenting cells. No humoral immune response was observed after adenoviral transfer of vectors with human apo A-I expression driven by the hepatocyte-specific apo C-II or 1.5-kilobase (kb) human alpha(1)-antitrypsin promoter, but antibodies were induced after transfer with vectors driven by the ubiquitously active U1b promoter and the murine MHCII E beta promoter. A strict correlation was observed between antigen expression in the spleen and the occurrence of an immune response. Coinjection of the 1.5-kb human alpha(1)-antitrypsin and the murine MHCII E beta promoter-driven vectors resulted in a very short-lived humoral immune response against human apo A-I, suggesting that the time course of human apo A-I expression is a critical determinant of the development of tolerance for human apo A-I. High titers of antibodies against human apo A-I after subcutaneous gene transfer with the MHCII E beta promoter-driven vector underscore the potential of this promoter for vaccination purposes. In conclusion, humoral immune response in mice against a circulating antigen induced by adenoviral transfer is strictly dependent on expression in antigen-presenting cells.

[Gene transfer systems and gene therapy]

One of the most important developments in medicine is gene therapy. But before it can be accepted to be used widely, certain technical problems should be overcome, especially the methods of gene delivery. In order to modify a specific cell type or tissue, the therapeutic gene must be efficiently delivered to the cell, in such a way that the gene can be expressed at the appropriate level and for a sufficient duration. There are currently availible two gene delivery vehicles. The first consists of viral vectors, which take advantage of a variety of naturally occurring viruses to shuttle the foreign cargo to be integrated permanently into the host's chromosome. The second is non-viral vectors, which rely on direct delivery of either naked DNA or mixture of genes with cationic lipids (liposome). There have been over 600 clinical trials of gene therapy protocols. The majority of clinical trials of gene therapy have been involved in the treatment of cancer and most of them have been at phase I clinical trials. Phase II stage of gene therapy had started of the end of 1996.

Influence of ex vivo expansion and retrovirus-mediated gene transfer on primary T lymphocyte phenotype and functions

To modulate alloreactivity after hematopoietic stem cell (HSC) transplantation, suicide gene-expressing donor T cells can be administered with an allogeneic T cell-depleted HSC graft. Immune competence of such cells is a critical issue. We have examined the impact of our ex vivo gene transfer protocol (12-day culture period including CD3/IL-2 activation, retrovirus-mediated gene transfer, and G418-based selection) on the phenotype and functional properties of gene-modified cells (GMC). GMC were compared with control cells that had been cultured in parallel with GMC, but nontransduced and nonselected, as well as with peripheral blood mononuclear cells (PBMC). Our data show that phenotypical modifications are similar in control cells and GMC, demonstrating that alterations result from the 12-day culture rather than from the transduction and/or selection process itself. Such modifications include a reversal of CD4/CD8 ratio, activated phenotype (increased expression of CD45RO, CD95, and HLA-DR), and acquisition or increased expression of co-stimulatory molecules (CD80, CD86, and CD40). This led to an enhanced allostimulating potential of GMC, as compared with resting T cells, when used as stimulating cells in mixed lymphocyte reactions. Conversely, when using them as responder cells in mixed lymphocyte reactions, GMC exhibited a rapid loss of alloreactivity that resulted both from culture-dependent and from transduction and/or selection-dependent events. In conclusion, the retrovirus-mediated gene transfer can be associated with major phenotypical and functional alterations that could have strong clinical implications (increased immunogenicity, reduced anti-leukemic effect). Thus, future T cell expansion protocols should try to improve not only cell expansion or gene transfer efficiency, but also T cell functions.

Repeated cationic multilamellar liposome-mediated gene transfer enhanced transduction efficiency against murine melanoma cell lines

We investigated whether repeated cationic multilamellar liposome-mediated gene transfers enhanced the transduction efficiency against murine melanoma cell lines and experimental subcutaneous melanoma. In the former, the murine melanoma cell line, B16F10, was transfected by our original cationic multilamellar liposomes containing pVLacZ, which express beta-galactosidase in eukaryotic cells. Cells were exposed to the liposomes in a single, double, or triple procedure during the cell logarithmic proliferative period. We then evaluated the transduction efficiency by X-gal staining and beta-galactosidase assay. The number of positive cells and level of beta-galactosidase activity were significantly increased by repeated exposures compared with a single one. Cells transfected by the fluorescently labeled cationic liposome containing pEGFP-C1 showed both an increased uptake of liposomes and an increased number of EGFP expression cells following repeated exposures. In the latter, murine subcutaneous melanomas, which were made by transplantation of B16F10 in C57BL6 mice, were transfected by same liposomes. Subcutaneous melanomas were exposed to the liposomes in a single, double, or triple procedure. We then evaluated the transduction efficiency by the beta-galactosidase assay. The level of beta-galactosidase activity was significantly increased by repeated exposures compared with a single one. The results indicate that repeated exposures to the liposomes enhanced the transduction efficiency toward murine melanoma cells and experimental subcutaneous melanoma, and may provide a basis for the repeated-exposure protocol for human trials.

High efficiency gene transfer to human CD34+ cells

We have previously reported the development of improved MLV-based retroviral vectors whose prototype is entitled MT (Kim et al, J. Virol. 72:994-1044; Yu et al, Gene Therapy 7:797-804). The MT vector does not contain any viral coding sequences, and thus the possibility of homologous recombination between the vector and the packaging genome is virtually nil. Indeed, in a shotgun RCR detection assay, an MT-based vector did not produce any RCR. On the contrary, the MFG vector, containing parts of all three viral coding sequences (gag, pol, and env), generated a significant number of RCR. In addition to being safe, MT-based vectors produce levels of gene expression and viral titer comparable to or higher than other vectors currently available within the community. Based on this vector, we have constructed a number of retroviral vectors that can be used for the treatment of a variety of human diseases. Our major target diseases are those that can be treated with or the status of which can be significantly improved with bone marrow transplantation. To obtain the most significant therapeutic effects, it is necessary to achieve the highest possible gene delivery efficiency, drive the highest level of gene expression, and prevent expression of the inserted therapeutic gene from being negatively influenced by the genome environment. To these ends, we compared various LTRs for their effects on the level of gene expression, tested the effect of cis-acting elements that may influence chromatin structure or position effect of the inserted gene, and studied different transduction conditions for their gene delivery efficiency. Data recently obtained from these experiments will be presented.

Suicide gene therapy of hepatocellular carcinoma and delivery procedure and route of therapeutic gene in vivo

OBJECTIVE

To study the induction of sensitivity to ganciclovir (GCV) or acyclovir (ACV) in human hepatocellular carcinoma (HCC) cell line transferred by an Epstein-Barr virus (EBV)-based replicon expression vector carrying the herpes simplex virus thymidine kinase (HSV-tk) gene, including killing and "bystander" effect, and also the gene delivery procedure and route of gene therapy in vivo for HCC.

METHODS

Liposome-entrapped plasmid pDR2/tk was transferred into HCC cells, and then different concentrations of GCV or ACV were added. The transferred cells were mixed with untransferred HCC cells in different proportion and 200 micromol/L GCV was then added into each well. After 72 hours, all samples were measured by MTT colorimetric assay. An EBV-based plasmid eukarotic expression vector carrying IL-2 cDNA was used. Three models of gene direct injection in the local liver, injection through the portal vein, and injection through the embolized hepatic artery were established in closed Wister rats. For each model, two subgroups, injected either naked plasmid DNA or lipofectin-plasmid complex were included. The expression of the IL-2 gene was regularly examined immunohistochemically.

RESULTS

GCV or ACV could apparently kill the transferred HCC cells at a concentration of 0.2 micromol/L. The inhibition rate was changed with different drug concentrations. The "bystander" effect was obviously induced at a transferred to untransferred HCC cells ratio of 1:5. IL-2 gene expression was observed in liver cells of all animals on day 3, which reached peak within 3-7 days, and declined after day 7. Injection of naked plasmid DNA through the hepatic artery plus embolization obtained a best expression.

CONCLUSIONS

EBV-based vector is suitable for carrying suicide gene therapy for hepatocellular carcinoma. Gene direct delivery in vivo combined with interventional surgery can be used to treat hepatocellular carcinoma.

Action of nonviral gene delivery vectors on human complement system: low anticomplementary activity of lipoplexes based on lacZ plasmid and phospholipid/oligocation liposomes

A simple test-system has been developed for the first time in order to detect the ability of effectors (lipoplexes) to activate the complement system in an antibody-independent manner to serve as acceptors of nascent C4b and to inhibit formation of the key enzyme of complement, C3-convertase. The effect of plasmid DNA (pCMV-SPORT-LacZ), negatively charged cardiolipin (CL), neutral phosphatidylcholine (PC) vesicles and their lipoplexes, on the complement system was studied using the method developed. It was revealed that PC vesicles did not affect the complement system, while CL vesicles manifested low activation. The influence of plasmid DNA and its lipoplex based on PC liposomes as well on the complement system was very low. PC/LacZ lipoplex (143 microg/ml) acted on the complement system like 5.36 microg/ml heat aggregated IgG (agg) (the level of no pathological ruptures), whereas CL/LacZ lipoplex (143 microg/ml) acted similar to 10.7 microg/ml IgG (agg). Thus, weak activation of the complement system with CL lipoplex, and even weaker for the PC lipoplex testified to the use of neutral and positively charged lipoplexes preferably in gene therapy protocols. The technique can also be used for testing the influence of injectable gene therapy vectors on the complement system.

Lipofection of rabbit chondrocytes and long lasting expression of a lacZ reporter system in alginate beads

OBJECTIVE

Our aim was to investigate the maintenance of the transfection status of non-viral transfected chondrocytes in an alginate culture system.

DESIGN

Chondrocytes harvested from rabbit knees were isolated by sequential digestion and cultivated in monolayer culture. At 60-70% cell density, chondrocytes were transfected with different transfection systems (FuGENE6, CaCl2, Lipofectin). A lac Z expression vector (pcDNA 3.1/Myc-His+ lacZ) was used as a reporter system. In order to improve transfection rates, hyaluronidase (4 U/ml) was used prior and during the transfection procedure. Thereafter, transfected cells were either kept in monolayer culture or embedded in alginate beads and kept in culture for up to the next 30 weeks.

RESULTS

Transfection efficiency was maximal using FuGENE6TM/DNA at a ratio of 3:2 and hyaluronidase (4 U/ml). Transfection efficiency reached up to 40.8% (+/- 3.2%) after 36 h. In alginate beads lac Z positive cells declined to 8.5% +/- 3.3% after 4 weeks and to 4.6% +/- 3.2% after 12 weeks of culturing. After 30 weeks 3% of chondrocytes still expressed lac Z. In contrast, during culturing in monolayer, no lac Z expression was detectable after 4 weeks. Differentiation status of the chondrocytes was confirmed by histology and immunohistochemistry methods.

CONCLUSIONS

After successful gene transfer to rabbit chondrocytes the alginate system made it possible to culture lipofected chondrocytes phenotypically stable. Genetically engineered chondrocytes express the lac Z reporter gene over a period of at least 30 weeks. This transfection and culture system provides a promising tool to further investigate the over-expression of growth factors and enzyme inhibitors.

Virally mediated gene transfer to the vasculature

Gene transfer technology provides valuable tools for the study of vascular biology. By using gene transfer, effects of specific gene products can be evaluated in a highly selective manner. In recent years, techniques used for gene transfer have been adapted for applications to blood vessels, including microvessels, both in vitro and in vivo. The purpose of this review is to provide a survey of published work in this field of investigation and to discuss advantages and limitations of current methods used for gene transfer to the vasculature.

Nonviral gene transfer strategies for the vasculature

Major attention has been focused on the development of gene therapy approaches for the treatment of vascular diseases. In this review, we focus on an alternative use of gene therapy: the use of genetic means to study vascular cell biology and physiology. Both viral and nonviral gene transfer strategies have limitations, but because of the overwhelming inflammatory responses associated with the use of viral vectors, nonviral gene transfer methods are likely to be used more abundantly for future applications in the vasculature. Researchers have made great strides in the advancement of gene delivery to the vasculature in vivo. However, the efficiency of gene transfer seen with most nonviral approaches has been exceedingly low. We discuss how to circumvent and take advantage of a number of the barriers that limit efficient gene delivery to the vasculature to achieve high-level gene expression in appropriate cell types within the vessel wall. With such levels of expression, gene transfer offers the ability to alter pathways at the molecular level by genetically modulating the activity of a gene product, thus obviating the need to rely on pharmacological agents and their foreseen and unforeseen side effects. This genetic ability to alter distinct gene products within a signaling or biosynthetic pathway or to alter structural interactions within and between cells is extremely useful and technologically possible today. Hopefully, with the availability of these tools, new advances in cardiovascular physiology will emerge.

Water-soluble lipopolymer for gene delivery

The use of biocompatible polymeric gene carriers may overcome the current problems associated with viral vectors in safety, immunogenicity, and mutagenesis. Nontoxic water-soluble lipopolymer (WSLP), poly(ethylenimine)-co-[N-(2-aminoethyl) ethyleneimin]-co-N-(N-cholesteryloxycarbonyl-(2-aminoethyl)ethylenimine) was synthesized using branched poly(ethylenimine) (PEI, mw 1800) and cholesteryl chloroformate. Following synthesis and purification, the structure and molecular weight of WSLP were confirmed by (1)H NMR and MADI-TOF mass spectrometry, respectively. The percentage of cholesterol conjugated to PEI was about 47%, and the average molecular weight of WSLP was approximately 2000 Da. WSLP/pDNA complexes were prepared at different N/P (nitrogen atoms of WSLP/phosphate of plasmid DNA) ratios and characterized in terms of particle size, zeta potential, osmolarity, surface morphology, and cytotoxicity. WSLP condensed plasmid DNA when N/P ratio reached 2.5/1 and no free DNA was detected at N/P ratio of 5/1 and above, as determined by agarose gel electrophoresis. The mean particle size was in the range of 25.9 to 148.5 nm and was dependent on N/P ratios. Atomic force microscopy (AFM) showed complete condensation of plasmid DNA with spherical particles of approximately 50 nm in diameter. WSLP/pDNA complexes or WSLP itself were nontoxic to CT-26 colon adenocarcinoma and 293 T human embryonic kidney transformed cells when formulated at the N/P ratio of 10/1 and below as determined by MTT assay. In contrast, PEI25000/pDNA complexes were toxic to these cells. Erythrocytes aggregated when incubated with PEI25000/pCMV-Luc complexes at high DNA concentrations, but there was little aggregation with WSLP/pCMV-Luc complexes. WSLP/pCMV-Luc complexes demonstrated higher transfection efficiency in both CT-26 and 293 T cells compared to PEI25000- or PEI1800-based formulations. WSLP/pCMV-Luc complexes are nontoxic and showed enhanced in vitro transfection. Thus, WSLP will be a suitable carrier for in vivo gene delivery.

Rapid generation of a tetracycline-inducible BCR-ABL defective retrovirus using a single autoregulatory retroviral cassette

The development of chronic myelogenous leukemia (CML) models in mice using an inducible BCR-ABL gene has been hampered by the requirement of sequential expression of tTA (Tet repressor-VP16 fusion protein) and Tet-OP sequences in the same cells after separate transfection. This double transfection strategy is time consuming as it requires screening of many hundreds of individual clones and cannot be applied to primary hematopoietic cells. To generate a tetracycline-inducible BCR-ABL retrovirus, we have subcloned BCR-ABL p210 cDNA in the SIN-Retro-TET vector, which allows regulated expression of a gene of interest in a single autoregulatory cassette, containing both tTA and Tet OP sequences. Retroviral particles were obtained by transfecting the SIN-BCR-ABL p210 construct into the 293 cells and by VSVG pseudotyping. To determine the functionality of the retrovirus, the IL-3-dependent murine Ba/F3 cell line was retrovirally transduced and clones were grown in the absence of both IL-3 (to select for transformed cells) and a tetracycline analog, doxycycline (to induce BCR-ABL expression). Using this technique, polyclonal Ba/F3 cells and several growth factor-independent Ba/F3 clones expressing BCR-ABL were obtained within 2-3 weeks. A single dose of doxycycline added to the medium (1 microg/ml), induced in different clones, a reduction of BCR-ABL protein levels by 60-90% at 24 h, leading to cell death in the absence of IL-3. In several individual clones, BCR-ABL expression was further reduced to become almost undetectable at 48 h. The doxycycline-regulated BCR-ABL expression was stable, as many clones maintained in culture for >8 months showed a persistent inhibitory response to doxycycline addition in the medium. In in vivo experiments, subcutaneous injection of 2 x 10(6) Ba/F3-SIN p210 cells in nude mice induced visible tumors in 2 weeks and all established tumors completely regressed upon addition of doxycycline in the drinking water (200 microg/ml). To determine the functionality of the inducible BCR-ABL retrovirus in vivo, primary Lin- bone marrow cells were transduced with SIN-p210 and transplanted in lethally irradiated mice. All transplanted mice had successful hematopoietic reconstitution and BCR-ABL integration was found in the peripheral blood of seven out of 14 mice available for long-term analysis (>6 months). However, despite evidence of retrovirus-mediated gene transfer, there was no evidence of leukemia, due either to low viral titers or to the relative inefficiency of the minimal CMV promoter in primary hematopoietic cells. Thus, these results demonstrate for the first time, to our knowledge, the feasibility to generate an inducible BCR-ABL retrovirus in a single step, in the context of an immortalized cell line. Our data suggest that with further improvements of the retrovirus-mediated gene transfer technology, it might be possible to generate inducible leukemia models in mice by the use of single retroviral constructs.

Highly efficient gene delivery by mRNA electroporation in human hematopoietic cells: superiority to lipofection and passive pulsing of mRNA and to electroporation of plasmid cDNA for tumor antigen loading of dendritic cells

Designing effective strategies to load human dendritic cells (DCs) with tumor antigens is a challenging approach for DC-based tumor vaccines. Here, a cytoplasmic expression system based on mRNA electroporation to efficiently introduce tumor antigens into DCs is described. Preliminary experiments in K562 cells using an enhanced green fluorescent protein (EGFP) reporter gene revealed that mRNA electroporation as compared with plasmid DNA electroporation showed a markedly improved transfection efficiency (89% versus 40% EGFP(+) cells, respectively) and induced a strikingly lower cell toxicity (15% death rate with mRNA versus 51% with plasmid DNA). Next, mRNA electroporation was applied for nonviral transfection of different types of human DCs, including monocyte-derived DCs (Mo-DCs), CD34(+) progenitor-derived DCs (34-DCs) and Langerhans cells (34-LCs). High-level transgene expression by mRNA electroporation was obtained in more than 50% of all DC types. mRNA-electroporated DCs retained their phenotype and maturational potential. Importantly, DCs electroporated with mRNA-encoding Melan-A strongly activated a Melan-A-specific cytotoxic T lymphocyte (CTL) clone in an HLA-restricted manner and were superior to mRNA-lipofected or -pulsed DCs. Optimal stimulation of the CTL occurred when Mo-DCs underwent maturation following mRNA transfection. Strikingly, a nonspecific stimulation of CTL was observed when DCs were transfected with plasmid DNA. The data clearly demonstrate that Mo-DCs electroporated with mRNA efficiently present functional antigenic peptides to cytotoxic T cells. Therefore, electroporation of mRNA-encoding tumor antigens is a powerful technique to charge human dendritic cells with tumor antigens and could serve applications in future DC-based tumor vaccines.

The evolution of public review and oversight mechanisms in human gene transfer research: joint roles of the FDA and NIH

The federal government is critically examining its responsibilities and opportunities for bringing the new field of gene therapy to fruition and for assuring public confidence in this new area of biomedicine. The evolving mechanisms for review and regulation in human gene transfer studies in the United States are being enhanced by increasingly effective interactions between the Food and Drug Administration and the National Institutes of Health.