Human Gene Therapy

Adeno-associated viruses (AAVs) have been employed successfully as gene therapy vectors in treating various genetic diseases for almost two decades. However, transgene packaging is usually imperfect, and developing a rapid and accurate method for measuring the proportion of DNA encapsidation is an important step for improving the downstream process of large scale vector production. In this study, we used two-dimensional class averages and three-dimensional classes, intermediate outputs in the single particle cryo-electron microscopy (cryo-EM) image reconstruction pipeline, to determine the proportion of DNA-packaged and empty capsid populations. Two different preparations of AAV3 were analyzed to estimate the minimum number of particles required to be sampled by cryo-EM in order for robust calculation of the proportion of the full versus empty capsids in any given sample. Cost analysis applied to the minimum amount of data required for a valid ratio suggests that cryo-EM is an effective approach to analyze vector preparations.

Synthetic engineering of viral vectors such as adeno-associated virus (AAV) is crucial to overcome host transduction barriers observed during clinical gene therapy. We reasoned that exploring the role of cellular ubiquitin-like modifiers (UBLs) such as Neddylation or SUMOylation during AAV transduction could be beneficial. Using a combination of in silico biochemical and molecular engineering strategies, we have studied the impact of these UBLs during AAV2 infection and further developed Neddylation or SUMOylation site–modified AAV vectors and validated them in multiple disease models in vitro and in vivo. Hepatic gene transfer of two novel vectors developed, K105Q (SUMOylation-site mutant) and K665Q (Neddylation-site mutant), demonstrated a significantly improved human coagulation factor (F) IX expression (up to two-fold) in a murine model of hemophilia B. Furthermore, subretinal gene transfer of AAV2-K105Q vector expressing RPE65 gene demonstrated visual correction in a murine model of a retinal degenerative disease (rd12 mice). These vectors did not have any adverse immunogenic events in vivo. Taken together, we demonstrate that gene delivery vectors specifically engineered at UBLs can improve the therapeutic outcome during AAV-mediated ocular or hepatic gene therapy.

Cell and gene therapies are finally becoming viable patient treatment options, with both T cell- and hematopoietic stem cell (HSC)-based therapies being approved to market in Europe. However, these therapies, which involve the use of viral vector to modify the target cells, are expensive and there is an urgent need to reduce manufacturing costs. One major cost factor is the viral vector production itself, therefore improving the gene modification efficiency could significantly reduce the amount of vector required per patient. This study describes the use of a transduction enhancing peptide, Vectofusin-1^®, to improve the transduction efficiency of primary target cells using lentiviral and gammaretroviral vectors (LV and RV) pseudotyped with a variety of envelope proteins. Using Vectofusin-1 in combination with LV pseudotyped with viral glycoproteins derived from baboon endogenous retrovirus, feline endogenous virus (RD114), and measles virus (MV), a strongly improved transduction of HSCs, B cells and T cells, even when cultivated under low stimulation conditions, could be observed. The formation of Vectofusin-1 complexes with MV-LV retargeted to CD20 did not alter the selectivity in mixed cell culture populations, emphasizing the precision of this targeting technology. Functional, ErbB2-specific chimeric antigen receptor-expressing T cells could be generated using a gibbon ape leukemia virus (GALV)-pseudotyped RV. Using a variety of viral vectors and target cells, Vectofusin-1 performed in a comparable manner to the traditionally used surface-bound recombinant fibronectin. As Vectofusin-1 is a soluble peptide, it was possible to easily transfer the T cell transduction method to an automated closed manufacturing platform, where proof of concept studies demonstrated efficient genetic modification of T cells with GALV-RV and RD114-RV and the subsequent expansion of mainly central memory T cells to a clinically relevant dose.

Wilson's disease (WD) is an autosomal recessive disorder of copper metabolism caused by mutations in the ATP7B gene encoding a liver active copper transport enzyme. Gene therapy with adeno-associated virus (AAV) carrying full-length ATP7B, which is about 4.4 kb, was shown to rescue copper metabolism disorder in WD mouse model. However, due to its relatively large size, the AAV vector containing full-length ATP7B could be oversized for its packaging capacity, which could lead to inefficient packaging. To this purpose, we engineered a truncated ATP7B mutant (tATP7B) that is about 3.3 kb in length and used for AAV gene therapy for WD mice. In vitro test showed that the excretion of copper outside the cells could be achieved with tATP7B as efficient as the full-length ATP7B. In vivo delivery of tATP7B to WD mice by AAV8 vectors corrected their copper metabolisms and significantly rescued copper accumulation-related syndromes, including reduced urinary copper excretion, increased serum ceruloplasmin, and improved liver damages. Thus, our study demonstrated that AAV gene therapy based on truncated ATP7B is a promising strategy in the treatment of WD.

Retinal ganglion cells (RGCs) play a key role in the pathogenesis and development of glaucoma. The present study aims to investigate the underlying mechanism of long noncoding RNA growth arrest-specific transcript 5 (GAS5) in glaucoma development through regulating the apoptosis of RGCs. Rat models of chronic glaucoma were successfully established by translimbal laser photocoagulation. Retinal tissues were collected to determine the density of RGCs through Toluidine blue staining. The overexpression vector or short hairpin RNA for GAS5 or enhancer of zeste homolog 2 (EZH2) was transfected into RGCs after in vitro pressurization culture to examine the function of GAS5 in RGC apoptosis. The involvement of EZH2 and ATP-binding cassette transporter A1 (ABCA1) was further identified. Cell apoptosis after laser treatment and transfection was assessed by flow cytometry. We found abundant GAS5 expression and a reduction in RGC density in the retinal tissues of glaucoma rats. Silencing of GAS5 led to increased EZH2 expression and decreased ABCA1 expression in RGCs. In addition, upregulation of EZH2 promoted trimethylation of lysine 27 on histone H3, thereby suppressing ABCA1 expression and eventually leading to the inhibition of RGC apoptosis. These findings provide further understanding of the function of GAS5 in RGC apoptosis. We conclude that downregulation of GAS5 could help relieve glaucoma symptoms. GAS5 is therefore a promising target for developing novel therapeutic approaches for treating patients with glaucoma.

Identifying early disease hallmarks in animal models with slow disease progression may expedite disease detection and assessment of treatment outcomes. Using optical coherence tomography, a widely applied noninvasive method for monitoring retinal structure changes, we analyzed retinal optical sections from six mouse lines with retinal degeneration caused by mutations in different disease-causing genes. While images from wild-type mice revealed four well-separated hyper-reflective bands in the outer retina (designated as outer retina reflective bands, ORRBs) at all ages, the second band (ORRB2) and the third band (ORRB3) were merged in retinas of five mutant mouse lines at early ages, suggesting the pathological nature of this alteration. This ORRB change appeared to be degenerating photoreceptor related, and occurred before obvious morphological changes that can be identified on both hematoxylin and eosin-stained sections and electron microscopic sections. Importantly, the merging of ORRB2 and ORRB3 was reversed by treatment with adeno-associated viral vector-mediated gene replacement therapies, and this restoration occurred much earlier than measurable functional or structural improvement. Our data suggest that the ORRB change could be a common hallmark of early retinal degeneration and its restoration could be used for rapid and noninvasive assessment of therapeutic effects following gene therapy or other treatment interventions.

Preclinical studies showed that tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) therapy is safe and effective to combat cancers, but clinical outcomes have been less than optimal due to short half-life of TRAIL protein, insufficient induction of apoptosis, and TRAIL resistance displayed in many tumors. In this study, we explored co-delivery of a TRAIL expressing plasmid (pTRAIL) and complementary small interfering RNAs (siRNAs) (silencing Bcl2-like 12 [BCL2L12] and superoxide dismutase 1 [SOD1]) to improve the response of breast cancer cells against TRAIL therapy. It is desirable to co-deliver the pDNA along with siRNA using a single delivery agent, but this is challenging given different structures of long/flexible pDNA and short/rigid siRNA. Toward this goal, we identified an aliphatic lipid-grafted low–molecular weight polyethylenimine (PEI) that accommodated both pDNA and siRNA in a single complex. The co-delivery of pTRAIL with BCL2L12- or SOD1-specific siRNAs resulted more significant cell death in different breast cancer cells compared with separate delivery without affecting nonmalignant cells viability. Ternary complexes of lipopolymer with pTRAIL and BCL2L12 siRNA significantly retarded the growth of breast cancer xenografts in mice. The enhanced anticancer activity was attributed to increased in situ secretion of TRAIL and sensitization of breast cancer cells against TRAIL by the co-delivered siRNAs. The lipid-grafted PEIs capable of co-delivering multiple types of nucleic acids can serve as powerful carriers for more effective complementary therapeutics.

There is an ongoing effort to increase the efficiency of gene delivery for the regulation of diseases-related genes. In this report, we demonstrate the efficiency of a DNA-based nanostructure to deliver morpholino antisense oligonucleotides for the upregulated genes in breast cancer as an alternative to the currently used delivery systems. A DNA-tile structure is constructed by embedding antisense oligonucleotides targeting the HER2 and ERα genes. Then, the sticky ends of the DNA-tile nanostructures are hybridized to gold nanoparticles (AuNPs) coated with the complementary oligonucleotides to enhance their cellular uptake. It is found that the morpholino antisense oligonucleotide embedded DNA-tile-AuNPs structure is 30% more effective than the liposome-based system to deliver morpholinos and induce gene silencing in breast cancer cells. The results of the study suggest that the prepared novel nanostructure is an effective and biocompatible carrier that can be used in in vitro gene silencing studies and can be further pursued in in vivo studies.

There are many kidney diseases that might be addressed by gene therapy. However, gene delivery to kidney cells is inefficient. This is due, in part, to the fact that the kidney excludes molecules above 50 kDa and that most gene delivery vectors are megaDaltons in mass. We compared the ability of adeno-associated virus (AAV), adenovirus (Ad), and lentiviral (LV) vectors to deliver genes to renal cells. When vectors were delivered by the intravenous (IV) route in mice, weak luciferase activity was observed in the kidney with substantially more in the liver. When gene delivery was observed in the kidney, expression was primarily in the glomerulus. To avoid these limitations, vectors were injected directly into the kidney by retrograde ureteral (RU) and subcapsular (SC) injections in mice. Small AAV vectors transduced the kidney, but also leaked from the organ and mediated higher levels of transduction in off-target tissues. Comparison of AAV2, 6.2, 8, and rh10 vectors by direct kidney injection demonstrated highest delivery by AAV6.2 and 8. Larger Ad and LV vectors transduced kidney cells and mediated less off-target tissue transduction. These data demonstrate the utility of direct kidney injections to circumvent the kidney size exclusion barrier. They also identify the effects of vector size on on-target and off-target transduction. This lays the foundation for the use of different vector platforms for gene therapy of diverse kidney diseases.