Visualization of the transgene distribution according to the administration route allows prediction of the transfection efficacy and validation of the results obtained

Comparative analysis of lentiviral vectors and modular protein nanovectors for traumatic brain injury gene therapy

Traumatic brain injury (TBI) remains as one of the leading causes of mortality and morbidity worldwide and there are no effective treatments currently available. Gene therapy applications have emerged as important alternatives for the treatment of diverse nervous system injuries. New strategies are evolving with the notion that each particular pathological condition may require a specific vector. Moreover, the lack of detailed comparative studies between different vectors under similar conditions hampers the selection of an ideal vector for a given pathological condition. The potential use of lentiviral vectors versus several modular protein-based nanovectors was compared using a controlled cortical impact model of TBI under the same gene therapy conditions. We show that variables such as protein/DNA ratio, incubation volume, and presence of serum or chloroquine in the transfection medium impact on both nanovector formation and transfection efficiency in vitro. While lentiviral vectors showed GFP protein 1 day after TBI and increased expression at 14 days, nanovectors showed stable and lower GFP transgene expression from 1 to 14 days. No toxicity after TBI by any of the vectors was observed as determined by resulting levels of IL-1β or using neurological sticky tape test. In fact, both vector types induced functional improvement per se.

Intrapulmonary delivery of XCL1-targeting small interfering RNA in mice chronically infected with Mycobacterium tuberculosis

Mice infected for 60 days with Mycobacterium tuberculosis were treated with aerosolized XCL1-targeting small interfering RNA (siRNA) to induce local and transient suppression of XCL1/lymphotactin (an important chemokine in tuberculoid granuloma formation). The local pulmonary siRNA therapy resulted in a 50% decrease in the total amount of xcl1 gene transcripts at 3 days, and 40 to 50% protein suppression 3 and 5 days after treatment. Reduced XCL1 expression in the lungs was associated with decreased numbers of T lymphocytes, reduction in the IFN-gamma response, disorganized granulomatous lesions, and higher fibrosis when compared with control mice treated with either PBS or nontargeting siRNA. This indicates that a transient but strong modulation of the production of XCL1 in the lungs has a significant effect on the influx of IFN-gamma-secreting T cells, as well as local pathology, but without significantly altering containment of the infection.

Superoxide dismutase expression attenuates cigarette smoke- or elastase-generated emphysema in mice

RATIONALE

Oxidants are believed to play a major role in the development of emphysema.

OBJECTIVES

This study aimed to determine if the expression of human copper-zinc superoxide dismutase (CuZnSOD) within the lungs of mice protects against the development of emphysema.

METHODS

Transgenic CuZnSOD and littermate mice were exposed to cigarette smoke (6 h/d, 5 d/wk, for 1 yr) and compared with nonexposed mice. A second group was treated with intratracheal elastase to induce emphysema.

MEASUREMENTS

Lung inflammation was measured by cell counts and myeloperoxidase levels. Oxidative damage was assessed by immunofluorescence for 3-nitrotyrosine and 8-hydroxydeoxyguanosine and lipid peroxidation levels. The development of emphysema was determined by measuring the mean linear intercept (Lm).

MAIN RESULTS

Smoke exposure caused a fourfold increase in neutrophilic inflammation and doubled lung myeloperoxidase activity. This inflammatory response did not occur in the smoke-exposed CuZnSOD mice. Similarly, CuZnSOD expression prevented the 58% increase in lung lipid peroxidation products that occurred after smoke exposure. Most important, CuZnSOD prevented the onset of emphysema in both the smoke-induced model (Lm, 68 exposed control vs. 58 exposed transgenic; p < 0.04) and elastase-generated model (Lm, 80 exposed control vs. 63 exposed transgenic; p < 0.03). These results demonstrate for the first time that antioxidants can prevent smoke-induced inflammation and can counteract the proteolytic cascade that leads to emphysema formation in two separate animal models of the disease.

CONCLUSIONS

These findings indicate that strategies aimed at enhancing or supplementing lung antioxidants could be effective for the prevention and treatment of this disease.

Molecular imaging of the lungs

An emerging suite of new imaging techniques offer the ability to monitor and quantify molecular and cellular processes in the lungs noninvasively. These techniques take advantage of dramatic advances in both imaging technology as well as molecular and cell biology. Molecular imaging is being used with increasing regularity in research protocols, and forms of molecular imaging have found their way into the patient care setting (eg, positron emission tomography imaging in cancer). Such techniques will afford the basic scientist as well as the clinician an unprecedented opportunity for in vivo study of the lung biology that drives normal pulmonary physiology as well as pathophysiology.

Molecular imaging of pulmonary gene expression with positron emission tomography

Gene expression imaging is one form of molecular imaging used to visualize, characterize, and quantify, spatially and temporally, normal as well as pathologic processes at cellular and subcellular levels within intact living organisms. Most studies to date have employed positron emission tomography as the imaging platform to detect, monitor, and quantify gene expression in the lungs. These studies have shown that imaging can be used to determine the onset and duration of transgene expression, the effectiveness of different gene delivery systems, and the linearity of vector dose-response relationships. This rapidly developing field can be expected to provide useful new tools with which to study gene expression in transgenic animals and in humans during gene therapy.

CFTR transgene expression in primary DeltaF508 epithelial cell cultures from human nasal polyps following gene transfer with cationic phosphonolipids

Cystic fibrosis (CF) is the most common autosomal lethal recessive disorder in the Caucasian population. The major cause of mortality is lung disease, owing to the failure of a functional protein from the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Today, even though the knowledge about the CFTR genomic is extensive, no efficient treatment has been developed yet. In this context, gene therapy represents a potential important advance on condition that it could develop efficient and safe transfection agents. Even though viral vectors have been used in most clinical trials owing to their high transfection efficiency, random integration and immunogenicity are still critical side effects. Consequently, all of these drawbacks brought forth the development of nonviral transfection systems. Although they engender few toxicity and immunogenicity problems, their low transfection efficiency is a hurdle that must be overcome. Over the past decade, we have developed an original family of monocationic lipids, cationic phosphonolipids, whose efficiency has been previously demonstrated both in vitro and in vivo. In this report, we observe that a new cationic phosphonolipid (KLN 30) can lead to the restoration of the CFTR protein following the ex vivo transfection of epithelial cells issuing from a F508 homozygous patient. The transgene expression and the cytotoxicity correlate with the charge ratio of the lipoplex. A kinetic study was performed, and a luminescent signal was detected until 35 d after transfection.

KLN-5: a safe monocationic lipophosphoramide to transfect efficiently haematopoietic cell lines and human CD34+ cells

The safe and efficient delivery of nucleic acids into haematopoietic stem cells (HSCs) has a wide range of therapeutic applications. Although viruses are being used in most clinical trials owing to their high transfection efficacy, recent results highlight many concerns about their use. Synthetic transfection reagents, in contrast, have the advantage of being safe and easy to manage while their low transfection efficiency remains a hurdle that needs to be addressed before they can be widely used. Using information on transfection mechanisms, a new family of monocationic lipids called lipophosphoramides was synthesized. Their efficiency to transfer genes into haematopoietic cell lines (K562, Jurkat and Daudi) and CD34+ cells was assessed. In this study, we report that one of these new compounds, KLN-5, leads to more efficient transfection activity than one of our previously most efficient reagents (EG-308) and the commercially available monocationic lipids (DC-CHOL and DOTAP/DOPE) (P<0.05). In addition, only a slight toxicity related to the chemical structure of the new compounds is observed. Moreover, we show that KLN-5 can successfully carry the transgene into haematopoietic progenitor cells (CD34+). These results demonstrate that synthetic transfection reagents represent a viable alternative to viruses and could have potential practical utility in a number of applications.

Non-viral vectors in cystic fibrosis gene therapy: progress and challenges

Although the viability of cystic fibrosis (CF) gene transfer to airway epithelium has been demonstrated in vitro and in animal models, so far none of the clinical investigations using adenovirus, adeno-associated virus, lentivirus, cationic lipids or polymers has shown a persistent correction of the ion transport defects that occur in CF. Despite disappointing results, these studies have shown that non-viral vectors could represent a viable alternative for gene therapy in CF airway epithelium. The transfer efficiency of non-viral vectors is currently low, however, and thus these systems are not clinically relevant as yet. Before clinical application, several limitations encountered by non-viral delivery systems must be addressed. Recent progress has been made towards overcoming these limitations and towards making non-viral gene therapy a more realistic option for CF.

A sensitive noninvasive method for monitoring successful liver-directed gene transfer of the low-density lipoprotein receptor in Watanabe hyperlipidemic rabbits in vivo

Noninvasive tools to quantitate transgene expression directly are a prerequisite for clinical gene therapy. We established a method to determine location, magnitude, and duration of low-density lipoprotein (LDL) receptor (LDLR) transgene expression after adenoviral gene transfer into LDLR-deficient Watanabe hypercholesterolemic rabbits by following tissue uptake of intravenously injected (111)In-labeled LDL using a scintillation camera. Liver-specific tracer uptake was calculated by normalizing the counts measured over the liver to counts measured over the heart that represent the circulating blood pool of the tracer (liver/heart (L/H) ratio). Our results indicate that the optimal time point for transgene imaging is 4 h after the tracer injection. Compared with control virus-injected rabbits, animals treated with the LDLR-expressing adenovirus showed seven-fold higher L/H ratios on day 6 after gene transfer, and had still 4.5-fold higher L/H ratios on day 30. This imaging method might be a useful strategy to obtain reliable data on functional transgene expression in clinical gene therapy trials of familial hypercholesterolemia.

Imaging the spatial distribution of transgene expression in the lungs with positron emission tomography

This study was designed to evaluate the utility of positron emission tomography (PET) to quantify the magnitude and spatial distribution of transgene expression after different methods of adenoviral vector delivery (with surfactant- and saline-based vehicles) within rat lungs. In all, 17 animals (eight in the surfactant group, nine in the saline group) were studied 3 days after intratracheal administration of a replication-incompetent adenovirus encoding a mutant Herpes simplex virus-1 thymidine kinase (mHSV1-TK)-enhanced green fluorescent protein fusion gene driven by a Cytomegalovirus promoter (Ad-CMV-mNLS-HSV1sr39tk-egfp). PET images were obtained 1 h after i.v. administration of 9-(4-[(18)F]-fluoro-3-hydroxymethylbutyl)guanine ([(18)F]-FHBG), an imaging substrate for mHSV1-TK. Overall, the average lung concentration of [(18)F]-FHBG was significantly greater in the surfactant group than in the saline group (0.24+/-0.06 versus 0.17+/-0.03% injected dose/ml lung, P< or =0.05). Lung [(18)F]-FHBG distribution was more peripheral and more homogeneous in the surfactant group than in the saline group (mean coefficient of variation=31+/-4 versus 36+/-3%, respectively, P< or =0.05). Regions of increased tracer concentration in the surfactant group compared to the saline group were evenly distributed throughout the lungs. We conclude that PET imaging provides useful and meaningful information about the effectiveness of different gene transfer delivery strategies within the lungs, and that surfactant-based vehicles may be a superior strategy for pulmonary gene transfer.

Biodistribution study of phosphonolipids: a class of non-viral vectors efficient in mice lung-directed gene transfer

BACKGROUND

A multitude of cationic lipids have been synthesized since they were first proposed for use in gene therapy. Cationic lipids are able to efficiently transfect cells both in vitro and in vivo. Whereas most research groups have focused their investigations on the toxicity of these molecules, and on the location of expression of the DNA transferred by these vectors, little has been done to determine their biodistribution and elimination pathways. Our group has developed a family of cationic lipids termed phosphonolipids. Following a large in vitro screening experiment, we have selected several molecules for in vivo testing, with some of these phosphonolipids forming lipoplexes efficient in transfecting mouse lungs. It was thus of interest to study their fate after intravenous injection.

METHODS

The respective biodistributions of both the GLB43 phosphonolipid and plasmid DNA were investigated and compared with DNA expression sites. Using the optimal conditions determined for phosphonolipids, we followed the gene transfer agent and plasmid DNA distributions versus time by radiolabeling them with (14)C and (32)P, respectively. Otherwise, we performed imaging by radiolabeling plasmid DNA with (99m)Tc.

RESULTS

The lipoplexes appear to be directly located in the lung after administration. Secondly, the plasmid is released mainly into the lungs and the phosphonolipid vector is rapidly degraded. The hydrophilic moiety of the phosphonolipid is eliminated in the urine, as is the free plasmid.

CONCLUSIONS

This study reveals that there are slight differences in the observed results depending on the technique used to label the DNA; secondly, results show that the residence time of phosphonolipids in the mouse body is related to the DNA binding time.