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In mice, liver-restricted expression of lysosomal enzymes from adeno-associated viral serotype 8 (AAV8) vectors results in reduced antibodies to the expressed proteins. To ask whether this result might translate to patients, nonhuman primates (NHPs) were injected systemically with AAV8 encoding α-galactosidase A (α-gal). As in mice, sustained expression in monkeys attenuated antibody responses to α-gal. However, this effect was not robust, and sustained α-gal levels were 1-2 logs lower than those achieved in male mice at the same vector dose. Because our mouse studies had shown that antibody levels were directly related to expression levels, several strategies were evaluated to increase expression in monkeys. Unlike mice, expression in monkeys did not respond to androgens. Local delivery to the liver, immune suppression, a self-complementary vector and pharmacologic approaches similarly failed to increase expression. While equivalent vector copies reached mouse and primate liver and there were no apparent differences in vector form, methylation or deamination, transgene expression was limited at the mRNA level in monkeys. These results suggest that compared to mice, transcription from an AAV8 vector in monkeys can be significantly reduced. They also suggest some current limits on achieving clinically useful antibody reduction and therapeutic benefit for lysosomal storage diseases using a systemic AAV8-based approach. [ABSTRACT FROM AUTHOR]

Abstract: The cationic lipid GL67A is one of the more efficient non-viral gene transfer agents (GTAs) for the lungs, and is currently being evaluated in an extensive clinical trial programme for cystic fibrosis gene therapy. Despite conferring significant expression of vector-specific mRNA following transfection of differentiated human airway cells cultured on air liquid interfaces (ALI) cultures and nebulisation into sheep lung in vivo we were unable to detect robust levels of the standard reporter gene Firefly luciferase (FLuc). Recently a novel secreted luciferase isolated from Gaussia princeps (GLuc) has been described. Here, we show that (1) GLuc is a more sensitive reporter gene and offers significant advantages over the traditionally used FLuc in pre-clinical models for lung gene transfer that are difficult to transfect, (2) GL67A-mediated gene transfection leads to significant production of recombinant protein in these models, (3) promoter activity in ALI cultures mimics published in vivo data and these cultures may, therefore, be suitable to characterise promoter activity in a human ex vivo airway model and (4) detection of GLuc in large animal broncho-alveolar lavage fluid and serum facilitates assessment of duration of gene expression after gene transfer to the lungs. In summary, we have shown here that GLuc is a sensitive reporter gene and is particularly useful for monitoring gene transfer in difficult to transfect models of the airway and lung. This has allowed us to validate that GL67A, which is currently in clinical use, can generate significant amounts of recombinant protein in fully differentiated human air liquid interface cultures and the ovine lung in vivo. [Copyright &y& Elsevier]

The efficacy of recombinant enzyme therapy for genetic diseases is limited in some patients by the generation of a humoral immune response to the therapeutic protein. Inducing immune tolerance to the protein prior to treatment has the potential to increase therapeutic efficacy. Using an AAV8 vector encoding human acid α-glucosidase (hGAA), we have evaluated direct intrathymic injection for inducing tolerance. We have also compared the final tolerogenic states achieved by intrathymic and intravenous injection. Intrathymic vector delivery induced tolerance equivalent to that generated by intravenous delivery, but at a 25-fold lower dose, the thymic hGAA expression level was 10,000-fold lower than the liver expression necessary for systemic tolerance induction. Splenic regulatory T cells (Tregs) were apparent after delivery by both routes, but with different phenotypes. Intrathymic delivery resulted in Tregs with higher FoxP3, TGFβ, and IL-10 mRNA levels. These differences may account for the differences noted in splenic T cells, where only intravenous delivery appeared to inhibit their activation. Our results imply that different mechanisms may be operating to generate immune tolerance by intrathymic and intravenous delivery of an AAV vector, and suggest that the intrathymic route may hold promise for decreasing the humoral immune response to therapeutic proteins in genetic disease indications. [ABSTRACT FROM AUTHOR]

Liver-directed gene therapy with adeno-associated virus (AAV) vectors effectively treats mouse models of lysosomal storage diseases (LSDs). We asked whether these results were likely to translate to patients. To understand to what extent preexisting anti-AAV8 antibodies could impede AAV8-mediated liver transduction in primates, commonly preexposed to AAV, we quantified the effects of preexisting antibodies on liver transduction and subsequent transgene expression in mouse and nonhuman primate (NHP) models. Using the highest viral dose previously reported in a clinical trial, passive transfer of NHP sera containing relatively low anti-AAV8 titers into mice blocked liver transduction, which could be partially overcome by increasing vector dose tenfold. Based on this and a survey of anti-AAV8 titers in 112 humans, we predict that high-dose systemic gene therapy would successfully transduce liver in >50% of human patients. However, although high-dose AAV8 administration to mice and monkeys with equivalent anti-AAV8 titers led to comparable liver vector copy numbers, the resulting transgene expression in primates was ~1.5-logs lower than mice. This suggests vector fate differs in these species and that strategies focused solely on overcoming preexisting vector-specific antibodies may be insufficient to achieve clinically meaningful expression levels of LSD genes using a liver-directed gene therapy approach in patients. [ABSTRACT FROM AUTHOR]

Due to the lack of acid α-glucosidase (GAA) activity, Pompe mice develop glycogen storage pathology and progressive skeletal muscle dysfunction with age. Applying either gene or enzyme therapy to reconstitute GAA levels in older, symptomatic Pompe mice effectively reduces glycogen storage in skeletal muscle but provides only modest improvements in motor function. As strategies to stimulate muscle hypertrophy, such as by myostatin inhibition, have been shown to improve muscle pathology and strength in mouse models of muscular dystrophy, we sought to determine whether these benefits might be similarly realized in Pompe mice. Administration of a recombinant adeno-associated virus serotype 8 vector encoding follistatin, an inhibitor of myostatin, increased muscle mass and strength but only in Pompe mice that were treated before 10 months of age. Younger Pompe mice showed significant muscle fiber hypertrophy in response to treatment with follistatin, but maximal gains in muscle strength were achieved only when concomitant GAA administration reduced glycogen storage in the affected muscles. Despite increased grip strength, follistatin treatment failed to improve rotarod performance. These findings highlight the importance of treating Pompe skeletal muscle before pathology becomes irreversible, and suggest that adjunctive therapies may not be effective without first clearing skeletal muscle glycogen storage with GAA. [ABSTRACT FROM AUTHOR]

Abstract: We have assessed whether viscoelastic gels known to inhibit mucociliary clearance can increase lipid-mediated gene transfer. Methylcellulose or carboxymethylcellulose (0.25–1.5%) was mixed with complexes of the cationic lipid GL67A and plasmids encoding luciferase and perfused onto the nasal epithelium of mice. Survival after perfusion with 1% CMC or 1% MC was 90 and 100%, respectively. In contrast 1.5% CMC was uniformly lethal likely due to the viscous solution blocking the airways. Perfusion with 0.5% CMC containing lipid/DNA complexes reproducibly increased gene expression by approximately 3-fold (n =16, p <0.05). Given this benefit, likely related to increased duration of contact, we also assessed the effect of prolonging contact time of the liposome/DNA complexes by delivering our standard 80μg DNA dose over either approximately 22 or 60min of perfusion. This independently increased gene transfer by 6-fold (n =8, p <0.05) and could be further enhanced by the addition of 0.5% CMC, leading to an overall 25-fold enhancement (n =8, p <0.001) in gene expression. As a result of these interventions CFTR transgene mRNA transgene levels were increased several logs above background. Interestingly, this did not lead to correction of the ion transport defects in the nasal epithelium of cystic fibrosis mice nor for immunohistochemical quantification of CFTR expression. To assess if 0.5% CMC also increased gene transfer in the mouse lung, we used whole body nebulisation chambers. CMC was nebulised for 1h immediately before, or simultaneously with GL67A/pCIKLux. The former did not increase gene transfer, whereas co-administration significantly increased gene transfer by 4-fold (p <0.0001, n =18). This study suggests that contact time of non-viral gene transfer agents is a key factor for gene delivery, and suggests two methods which may be translatable for use in man. [Copyright &y& Elsevier]

Abstract: Proteasome inhibitors have been shown to increase adeno-associated virus (AAV)-mediated transduction in vitro and in vivo. To assess if proteasome inhibitors also increase lipid-mediated gene transfer with relevance to cystic fibrosis (CF), we first assessed the effects of doxorubicin and N-acetyl-l-leucinyl-l-leucinal-l-norleucinal in non-CF (A549) and CF (CFTE29o-) airway epithelial cell lines. CFTE29o- cells did not show a response to Dox or LLnL; however, gene transfer in A549 cells increased in a dose-related fashion (p <0.05), up to approximately 20-fold respectively at the optimal dose (no treatment: 9.3×104 ±1.5×103, Dox: 1.6×106 ±2.6×105, LLnL: 1.9×106 ±3.2×105 RLU/mg protein). As Dox is used clinically in cancer chemotherapy we next assessed the effect of this drug on non-viral lung gene transfer in vivo. CF knockout mice were injected intraperitoneally (IP) with Dox (25–100mg/kg) immediately before nebulisation with plasmid DNA carrying a luciferase reporter gene under the control of a CMV promoter/enhancer (pCIKLux) complexed to the cationic lipid GL67A. Dox also significantly (p <0.05) increased expression of a plasmid regulated by an elongation factor 1α promoter (hCEFI) approximately 8-fold. Although administration of Dox before lung gene transfer may not be a clinically viable option, understanding how Dox increases lung gene expression may help to shed light on intracellular bottle-necks to gene transfer, and may help to identify other adjuncts that may be more appropriate for use in man. [Copyright &y& Elsevier]

Peripheral neuropathy is a particularly debilitating complication of both type 1 and type 2 diabetes characterized by sensory and motor neuron damage and decreased circulating levels of insulin-like growth factor 1 (IGF-1). Quite often, an early hyperalgesia is followed by hypoalgesia and muscle weakness. Hypoalgesia can lead to significant morbidity for which there is no current treatment. Hyperglycemic, streptozotocin (STZ)-induced rodent models reproduce these symptoms. We investigated whether increasing systemic IGF-1 could improve neuronal function in hyper- and hypoalgesic STZ-treated mice. Increased circulating levels of IGF-1 were achieved by delivering a plasmid or adeno-associated viral (AAV) vector bearing mouse IGF-1 to the liver. Treating mice in the hyperalgesia stage prevented later hypoalgesia. Treating mice in the hypoalgesia stage reversed existing hypoalgesia. This latter effect could be seen by merely restoring IGF-1 serum levels to normalcy, which was possible to achieve by IGF-1 gene therapy or insulin treatment. Sensory nerve functional correction was seen to be correlated with attenuated Schwann cell vacuolization and demyelination in peripheral sensory nerve fibers. A further increase in serum IGF-1 levels with gene therapy also improved motor function, consistent with the observed prevention of both muscle atrophy and peripheral motor nerve fiber demyelination. These results suggest that the restoration of systemic levels of IGF-1 may prove to be a highly effective therapeutic modality for treating diabetic peripheral neuropathy.Molecular Therapy (2008) 16 8, 1400–1408 doi:10.1038/mt.2008.115 [ABSTRACT FROM AUTHOR]

Abstract: Imaging of in vivo gene expression using luciferase expression in various organs has been used for several years. In contrast to other organs, in vivo imaging of the lung, particularly after non-viral gene transfer has not been extensively studied. The aim of this study was to address several questions: (1) Does in vivo light emission correlate with standard tissue homogenate-based luciferase detection in a dose-dependent manner? Recombinant Sendai virus (SeV) transduces airway epithelial cells very efficiently and was used to address this question, (2) Is the sensitivity of the assay sufficient to detect non-viral gene transfer? We treated mice with SeV-Lux vector using our standard “sniffing” protocol, a method that predominantly results in lung deposition. Dose-related in vivo light emission was visible in all animals. Importantly, there was a significant correlation (r >0.90, p <0.0001) between the in vivo and ex vivo assays in both the left and right lung. We next transfected the nasal epithelium via nasal perfusion or the lungs (“sniffing”) of mice with a luciferase plasmid (pCIKLux) complexed to the cationic lipid GL67 (n =25–27/group) and imaged luciferase expression in vivo 24h after transfection. Gene expression was detectable in both organs. Correlation between the in vivo and ex vivo assays was significant (r =0.52, p <0.005) in the left, but not the right lung. The correlation in the nose was weaker (r =0.45, p <0.05). To our knowledge these studies show for the first time that this non-invasive method of assessing pulmonary gene transfer is viable for evaluating non-viral gene transfer agents. [Copyright &y& Elsevier]

Classical late infantile neuronal ceroid lipofuscinosis (cLINCL) is a monogenic disorder caused by the loss of tripeptidyl peptidase 1 (TPP1) activity as a result of mutations in CLN2. Absence of TPP1 results in lysosomal storage with an accompanying axonal degeneration throughout the central nervous system (CNS), which leads to progressive neurodegeneration and early death. In this study, we compared the efficacies of pre- and post-symptomatic injections of recombinant adeno-associated virus (AAV) for treating the cellular and functional abnormalities of CLN2 mutant mice. Intracranial injection of AAV1-hCLN2 resulted in widespread human TPP1 (hTPP1) activity in the brain that was 10–100-fold above wild-type levels. Injections before disease onset prevented storage and spared neurons from axonal degeneration, reflected by the preservation of motor function. Furthermore, the majority of CLN2 mutant mice treated pre-symptomatically lived for at least 330 days, compared with a median survival of 151 days in untreated CLN2 mutant controls. In contrast, although injection after disease onset ameliorated lysosomal storage, there was evidence of axonal degeneration, motor function showed limited recovery, and the animals had a median lifespan of 216 days. These data illustrate the importance of early intervention for enhanced therapeutic benefit, which may provide guidance in designing novel treatment strategies for cLINCL patients.Molecular Therapy (2007) 15 10, 1782–1788. doi:10.1038/sj.mt.6300249 [ABSTRACT FROM AUTHOR]

Abstract: Antiviral antibodies within the human population remain a barrier to the effective clinical use of viral gene transfer vectors. We have asked whether local, balloon catheter-mediated delivery of a viral vector to the rabbit liver using a hepatic vein might mitigate the neutralizing effects of antiviral antibodies. We have compared directly the ability of adenovirus (Ad2) encoding nuclear-localized β-galactosidase to infect the rabbit liver after local and systemic delivery in both the presence and the absence of defined anti-Ad2 antibody titers. In naive rabbits, local delivery resulted in higher β-galactosidase expression compared to systemic delivery. In the presence of passively administered anti-Ad2 antibodies, local delivery resulted in expression levels that were comparable to those obtained in naive rabbits by systemic delivery. Local delivery also resulted in the majority of expression originating from hepatocytes, even in passively immunized animals, a result that could not be duplicated using the systemic approach. Since systemic delivery of adenovirus in naive animal models results in transgene expression levels often regarded as therapeutic, these results predict that local hepatic vein delivery of a viral vector is a clinically practical approach to mitigate neutralizing antiviral antibodies and generate therapeutic levels of transgene expression. [Copyright &y& Elsevier]

Abstract: Hepatocytes are an effective depot for protein production from gene therapy vectors. However, when gene transfer vectors or their delivery induces hepatic inflammation, adaptive immune responses against the transgene product can ensue. In BALB/c mice, hydrodynamic delivery of a CMV-driven plasmid DNA (pDNA) bearing human α-galactosidase A (αgal) to the liver generated antibodies against αgal. This humoral immune response was more robust in a transgenic knockout for αgal, the Fabry mouse. The antibody response could be attenuated in both mouse strains by using a promoter more restricted to hepatocytes. In an attempt to reduce further the humoral responses to αgal, expression from the transgene was attenuated by using siRNA during the period of initial delivery-associated liver inflammation. In both mouse models and with both promoters, codelivering an αgal siRNA resulted in a 2 log decrease in initial expression that then increased over the next few weeks to levels generated by the pDNA alone. This strategy led to both attenuated antibodies and an immune status approximating “tolerance” to αgal. Importantly, in the Fabry mouse, an αgal siRNA together with a hepatocyte-restricted promoter gave minimal anti-αgal antibodies and profound tolerance, suggesting that such an approach might have clinical utility for genetic diseases. [Copyright &y& Elsevier]

CpG-reduced, CMV-based plasmid DNA constructs encoding human α-galactosidase A and factor IX were injected into C57Bl/6, BALB/c, and CD1 mice using hydrodynamics-based delivery of plasmid DNA (pDNA), and gene expression was monitored for 6 months. Linearized and supercoiled pDNAs were compared for their abilities to support long-term expression and to generate immune responses to the transgene product. In all mouse strains supercoiled CpG-reduced pDNA encoding α-galactosidase A and factor IX generated higher and more sustained levels of circulating gene product than their supercoiled CpG-replete analogs. Linearizing supercoiled CpG-reduced pDNA did not significantly increase levels of circulating gene product beyond levels supercoiled CpG-reduced pDNA could achieve. Linearizing supercoiled CpG-replete pDNA vectors significantly increased expression compared to their supercoiled CpG-replete analogs, but the increase was short-lived or subtherapeutic. Regardless of vector, liver depot expression did not elicit significant antibody responses to human α-galactosidase A or factor IX. Taken together, these data suggest that a clinically acceptable hydrodynamics-based approach targeting the liver combined with CpG-reduced pDNA vectors may represent a viable option for individuals with hemophilia, a lysosomal storage disease, or other disease in which prolonged depot expression of a therapeutic protein from the liver is desirable. [Copyright &y& Elsevier]

Immunostimulatory CpG motifs have been implicated as a major contributor to the acute inflammatory response associated with nonviral vectors, most prominently seen after systemic delivery of cationic lipid–plasmid DNA (pDNA) complexes. We have shown previously that complexes containing pDNA vectors that have been largely depleted of CpG motifs have significantly reduced acute toxicity when delivered systemically. However, several CpGs remain in these vectors and the toxicity is not negligible, especially at higher doses of complex. To determine the maximal reduction in the acute toxic response that could be achieved by eliminating CpG signaling, we injected cationic lipid–pDNA complexes into transgenic mice that are deficient in Toll-like receptor 9 (TLR9), which is the receptor that recognizes immunostimulatory CpG motifs. We observed significantly decreased adverse hematological changes and liver damage in TLR9−/− mice compared to normal mice and increased survival at higher doses of complex. However, a pronounced loss of lymphocytes and platelets was still observed in the TLR9−/− mice at higher doses. We also measured the toxicity in normal mice of systemically delivered complexes containing non-CpG oligonucleotides. Although serum transaminase levels were reduced, a loss of lymphocytes and platelets akin to that seen in the TLR9−/− mice was observed. Taken together, these findings suggest that signaling through TLR9 contributes to the majority but not all of the toxic responses associated with systemic delivery of cationic lipid–pDNA complexes. [Copyright &y& Elsevier]

We have demonstrated recently that treatment of established peritoneal mesothelial tumors with complexes composed of cationic lipid and noncoding plasmid DNA (pNull) results in the inhibition of tumor growth accompanied by the induction of a tumor-specific cellular immune response. In this study, treatment of mice bearing intraperitoneal (i.p.) M3 melanoma tumors with i.p. injections of lipid/pNull complex was found to inhibit tumor growth and induce the development of a cytolytic response against several M3 melanoma-associated antigens. Depletion of CD8+ T cells, as opposed to natural killer (NK) or CD4+ T cells, essentially abrogated the therapeutic effect of lipid+pNull complex, thus supporting the involvement of cytotoxic CD8+ T cells in the antitumor response. The antitumor effect of lipid/pNull complex was maximal following delivery into a tumor-bearing compartment. For example, i.p. delivery of complex was more effective than intravenous (i.v.) or subcutaneous (s.c.) treatment of i.p. M3 tumors. In addition, i.v. injection of complex displayed therapeutic activity against lung metastases caused by i.v. injection of tumor cells, and intratumoral injection of complex into solid s.c. tumors caused regression in most animals. Importantly, the immune response induced by local treatment of tumors with complex also offered systemic protection against tumor cells at distal sites, as illustrated by the eradication of both peritoneal tumors and lung metastases in mice treated with complex delivered i.p. Treatment with lipid/pNull complex, therefore, represents an attractive immune-based treatment modality that could potentially be applied to many tumor types. [Copyright &y& Elsevier]

Systemic delivery of cationic lipid–plasmid DNA (pDNA) complexes induces an acute inflammatory response with adverse hematologic changes and liver damage. Immunostimulatory CpG motifs in the pDNA are known to contribute substantially to this response. Here we constructed a pDNA vector (pGZB) that has been depleted of 80% of the CpG motifs present in the original vector. Compared with the unmodified vector, systemic administration of pGZB induced considerably fewer changes in blood parameters, reduced levels of inflammatory cytokines, and decreased liver damage. Despite the extensive sequence modifications within pGZB, there were still robust levels of transgene expression. Furthermore, in contrast to the transient expression observed from the unmodified vector, we observed sustained or increasing expression for up to 49 days from pGZB in the lung and liver of immunocompetent BALB/c mice. Studies adding CpG motifs in trans or in cis indicate that the reduced CpG content of pGZB was the major determinant for its persistent expression. This combination of decreased toxicity and sustained expression suggests that CpG-depleted pDNA vectors can greatly improve the safety and efficacy of synthetic gene delivery systems. [Copyright &y& Elsevier]

An abstract of the article "Balloon Catheter-Mediated Hepatic Vein Delivery of a Viral Vector Mitigates Neutralization by Anti-Viral Antibodies and Results in Efficient Transduction of Rabbit Liver," by Bradley L. Hodgesand colleagues is presented.

Classical late infantile neuronal ceroid lipofuscinosis (cLINCL) is a neurodegenerative disorder that results from the loss of tripeptidyl peptidase I (TPP1) enzyme activity. Patients with cLINCL possess seizures that are frequently associated with blindness, exhibit cognitive and behavioral deficits that are progressive, and death by 7–20 years of age. Accumulation of autofluorescent storage material is a cardinal feature of the disease, as well as axonal degeneration and loss of cortical neurons. A recent study by our group in a knockout mouse model of cLINCL showed that recombinant AAV2 or AAV5 significantly reduced autofluorescent storage and curvilinear bodies in cells of the brain. Reversal of pathology was restricted to injected and nearby structures at a dose of 2.0 e11 genome copies (gc)/ml. To further evaluate AAV gene therapy, a codon-optimized synthetic human CLN2 cDNA was engineered, packaged into AAV1 capsids (AAV1-hCLN2), concentrated to a high titer (3.3 e12 gc/ml), and injected into the CLN2 (−/−) thalamus of one hemisphere. At 1 month post-injection, brain homogenates of the injection site contained TTP1 enzyme activity that was 15-fold higher than corresponding regions of untreated CLN2 (+/+) mice. TPP1 activity was also observed in the rostral and caudal regions of injected hemisphere, and in the contralateral hemisphere at levels 2-fold higher than CLN2 (+/+) controls. These data demonstrate that the AAV1 vector is capable of producing widespread and high levels of TPP1 activity in vivo. A cohort of 4-week old CLN2 (−/−) mice were then injected with AAV1-hCLN2 into multiple structures of the right (striatum, hippocampus, cerebellum) and left (motor cortex, thalamus, medulla) hemispheres to investigate global reversal of pathology, functional recovery, and extension of lifespan. The results of this experiment including behavioral testing and survival data will be presented.Molecular Therapy (2006) 13, S344–S344; doi: 10.1016/j.ymthe.2006.08.982 [ABSTRACT FROM AUTHOR]

In murine models of lysosomal storage diseases, sustained hepatocyte-restricted expression and secretion of the therapeutic enzyme is capable of correcting the peripheral pathology associated with the storage product. For example, systemic delivery of a recombinant AAV8 vector encoding human alpha-galactosidase A to Fabry mice resulted in complete clearance of the glycosphingolipid storage product in peripherally affected tissues when sustained serum alpha-galactosidase A levels were in excess of 1 ug/ml. In humans, transient blood levels of human FIX have been obtained after hepatocyte transduction with an AAV2 vector. The abbreviatedexpression was attributed to cytotoxic lymphocyte (CTL) recognition of viral capsid epitopes on the transduced cells. In view of these potential immune-based limitations on expression, we have asked whether we could generate prolonged circulating levels of human alpha-galactosidase A following delivery of an AAV2/8 vector encoding human alpha-galactosidase A under control of a hepatocyte-restricted promoter to immune suppressed rhesus macaques. We have compared systemic delivery using a peripheral vein approach and local delivery using a hepatic vein approach that was developed in a rabbit model. The hepatic vein approach uses a balloon catheter to isolate a lobe of the liver and block blood flow into the vena cava. We then flush the vasculature of the lobe retrograde to blood flow to reduce the concentration of any resident anti-viral antibodies and to allow the viral vector to “dwell” within the lobe for a defined period after delivery. A three month immune suppression regime was used to blunt any neutralizing immune responses to virally-transduced cells or human alpha-galactosidase A. After removing immune suppression, animals will be challenged with purified human alpha- galactosidase A to assess their degree of tolerance to this foreign protein. Although this experiment is not yet complete, we will present up-to-date expression and toxicity data comparing the two delivery techniques.Molecular Therapy (2006) 13, S84–S84; doi: 10.1016/j.ymthe.2006.08.242 [ABSTRACT FROM AUTHOR]

Recombinant Sendai-virus (SeV) vector transduces airway epithelium efficiently via the apical membrane and leads to high, but transient gene expression. The treatment of chronic diseases may require repeated administration of the virus. We have previously shown that three repeat administrations of recombinant Sendai virus (DF/SeV) did not lead to measurable luciferase (lux) expression after the third administration. However, as part of these experiments we noted that even after one administration, lux expression was lower than expected for a given virus dose. Sequence analysis revealed that the lux gene contained sequences that may be recognised by SeV as “stuttering” sequences and may interfere with gene expression.In an attempt to improve SeV-mediated lux expression we introduced several silent mutations to modify these putative stuttering sequences. SeV-mediated lux expression in the lung was increased 2.5-fold (n=10, p<0.005), when compared to the unmodified lux. We next repeated the re- administration experiment using both weekly and monthly dosing intervals [dose 1: SeV-GFP, dose 2: SeV-GFP, dose 3: SeV-lux, 108 pfu/mouse/dose (n=20/dose)]. Lux expression was measured two days after SeV-lux administration. Lux expression after three monthly administrations of SeV was significantly reduced compared to single administration, but remained significantly (p<0.005) higher than untransduced controls. Lux expression was similar to expression levels that can be achieved with the non-viral gene transfer agent GL67.To assess whether the expression pattern is similar in a host in which wild type SeV infection is of no apparent significance (as in men), we transduced sheep with DF/SeV-lacZ. We first determined the time-course of b-gal expression after aerosolisation of 2×1010 pfu/sheep (n=4) using a Trudell AeroProbe catheter. Bronchial biopsies (Bx, n=8/sheep/time-point) were collected 2-28 days after transduction and bgal expression compared to pre-treatment values. Similar to mice, gene expression in sheep was maximal 2 days after gene transfer (UT: 43.7±4.3; d2: 5705.7±3708.2 RLU/mg protein, p<0.05) and had returned to pre-treatment values 7 days after transduction. After monthly repeat administration (doses 1+2: DF/ SeV-empty, dose 3: DF/SeV-lacZ, n=4) we also detected low but significant (p<0.05) residual bgal expression (47.5±7.1 RLU/mg protein, n=20 bx/sheep) compared to sheep receiving 3 doses of DF/SeV-empty (29.5±1.1 RLU/mg protein, n=4). In conclusion, the expression pattern of SeV is similar in mice and sheep. Expression is transient, but after repeat administration of 3 doses, low but significant gene expression similar to levels seen with non-viral gene transfer agents can be detected.Molecular Therapy (2006) 13, S184–S184; doi: 10.1016/j.ymthe.2006.08.544 [ABSTRACT FROM AUTHOR]

We have previously shown that high-frequency (1 MHz) ultrasound (U/S) increases naked plasmid DNA (pDNA) gene transfer in the mouse lung and that this effect requires microbubbles (Optison) to be present in the formulation. Here, we assessed low-frequency (30–35 kHz) U/S, in an attempt to further increase non- viral gene delivery to the lung in vivo. The potential advantages of lowering U/S frequency include: a) increased cavitation, the mechanism responsible for the formation of transient pores on cell membranes and b) enhanced penetration of U/S energy into the lung, by reducing wave scattering and heat losses. Cationic lipid GL67 (GL67)/pDNA (80 μg/100 μl), polyethylenimine (PEI)/pDNA (20 μg/100 μl) and naked pDNA (100 μg/100 μl) were delivered to Balb/ c mice via intranasal instillation. Low-frequency U/S (30–35 kHz, 0.07 or 0.1 Mpa, 10 min) was then applied onto the chest and back. Sonoporation did not enhance GL67/pDNA and PEI/pDNA gene transfer. However, U/S exposure at 0.1 Mpa, but not at 0.07 Mpa, increased naked pDNA transfection approximately 4-fold (pDNA: 5.9±1.2 RLU/mg protein, pDNA + 0.1 Mpa: 22.6±3.8 RLU/mg protein, p<0.05, n=7–8). Importantly, low-frequency U/S increased lung gene transfer in the absence of microbubbles. Addition of Optison did not further enhance this effect, due to its inhibitory effects on non-viral lung gene transfer (pDNA + Optison: 0.4±0.1 RLU/mg protein, pDNA + Optison + 0.1 Mpa: 2.5±0.7 RLU/mg protein, n=7–8). Haemorrhage, a common U/S-induced side-effect, was also assessed and increased with pressure in a dose-dependent manner. Interestingly, haemorrhage occurred throughout the lung, indicating that U/S may penetrate deep into the tissue. We have, thus, established for the first time that low-frequency sonoporation can enhance non-viral gene delivery to the mouse lung in vivo.Molecular Therapy (2006) 13, S269–S269; doi: 10.1016/j.ymthe.2006.08.773 [ABSTRACT FROM AUTHOR]