Enhancement of recombinant adeno-associated virus type 2-mediated transgene expression in a lung epithelial cell line by inhibition of the epidermal growth factor receptor

Gene Therapy for Osteoarthritis: Pharmacokinetics of Intra-Articular Self-Complementary Adeno-Associated Virus Interleukin-1 Receptor Antagonist Delivery in an Equine Model

Toward the treatment of osteoarthritis (OA), the authors have been investigating self-complementary adeno-associated virus (scAAV) for intra-articular delivery of therapeutic gene products. As OA frequently affects weight-bearing joints, pharmacokinetic studies of scAAV gene delivery were performed in the joints of the equine forelimb to identify parameters relevant to clinical translation in humans. Using interleukin-1 receptor antagonist (IL-1Ra) as a secreted therapeutic reporter, scAAV vector plasmids containing codon-optimized cDNA for equine IL-1Ra (eqIL-1Ra) were generated, which produced eqIL-1Ra at levels 30- to 50-fold higher than the native sequence. The most efficient cDNA was packaged in AAV2.5 capsid, and following characterization in vitro, the virus was injected into the carpal and metacarpophalangeal joints of horses over a 100-fold dose range. A putative ceiling dose of 5 × 10¹² viral genomes was identified that elevated the steady-state eqIL-1Ra in the synovial fluids of injected joints by >40-fold over endogenous levels and was sustained for at least 6 months. No adverse effects were seen, and eqIL-1Ra in serum and urine remained at background levels throughout. Using the 5 × 10¹² viral genome dose of scAAV, and green fluorescent protein as a cytologic marker, the local and systemic distribution of vector and transduced cells following intra-articular injection scAAV.GFP were compared in healthy equine joints and in those with late-stage, naturally occurring OA. In both cases, 99.7% of the vector remained within the injected joint. Strikingly, the pathologies characteristic of OA (synovitis, osteophyte formation, and cartilage erosion) were associated with a substantial increase in transgenic expression relative to tissues in healthy joints. This was most notable in regions of articular cartilage with visible damage, where foci of brilliantly fluorescent chondrocytes were observed. Overall, these data suggest that AAV-mediated gene transfer can provide relatively safe, sustained protein drug delivery to joints of human proportions.

Adeno-Associated Virus Serotype 2 Vector-Mediated Reintroduction of microRNA-19b Attenuates Hepatic Fibrosis

Fibrotic liver injury is a significant healthcare burden in the United States. It represents a major cause of morbidity and mortality for which there are no effective Food and Drug Administration-approved treatment strategies. Fibrosis is considered a disruption of the normal wound healing responses mediated by fibroblastic cells, which are triggered and sustained by pro-fibrotic cytokines such as transforming growth factor beta 1 (TGF-β1). TGF-β1-mediated trans-differentiation of hepatic stellate cells (HSCs) from quiescent to activated myofibroblasts is a pivotal event in the development of fibrosis. Activation is accompanied by global changes in microRNA (miR) expression. It has been previously reported that miR19b is decreased in activated HSCs and contributes to increased expression of TGF-β receptor II and connective tissue growth factor, both confirmed targets of miR19b. An adeno-associated virus serotype 2 vector (AAV2) with a miR19b transgene downstream of enhanced green fluorescent protein under the murine collage alpha 1(I) promoter was developed specifically to target HSCs. Male Sprague Dawley rats (250 g) underwent sham or bile-duct ligation (BDL) surgery. Directly after BDL, rats received AAV2-miR19b, AAV2-control, or vehicle normal saline (NS) by portal-vein injection. After 2 weeks, the animals were euthanized, and blood was collected for alanine and aspartate aminotransferase, total and direct bilirubin, and alkaline phosphatase. Tissue was collected for RNA and protein extraction and histology. Fibrosis and measures of hepatic injury were significantly reduced in AAV2-miR19b-treated rats in combination with significant improvements in total and direct bilirubin. Histological analysis of collagen by PicroSirius Red staining revealed a ∼50% reduction compared to AAV2-control or NS-injected animals. Pro-fibrotic markers, smooth-muscle alpha-actin, TGF-β receptor II, and collagen alpha 2(I) mRNA and protein were significantly decreased compared to AAV2-control and NS groups. AAV2-mediated reintroduction of miR-19b, specifically expressed in HSCs, improved liver function, inhibited fibrosis, and improved measures of hepatic injury in a BDL model.

Adeno-associated virus infection of murine fibroblasts with help provided by mouse adenovirus

Adeno-associated virus (AAV-2) replicates to high titers when host cells are coinfected with a helper virus. Here we analyzed the coinfection of AAV-2 and mouse adenovirus (MAV-1) in murine fibroblasts. We observed that AAV-2/MAV-1 coinfected NIH 3T3 cells produced approximately 10-40-fold less AAV-2 DNAse resistant particles than Hela cells. Levels of AAV-2 DNA replication were approximately 30-fold less in 3T3 cells as compared to Hela cells coinfected with human adenovirus (Ad-5). A study of these lower levels of infection in 3T3 cells compared to Hela cells revealed that receptor binding and internalization of AAV-2 in 3T3 and Hela cells was comparable. However, AAV-2 did not enter into the nucleus of mouse cells as efficiently as it does in human cells. Furthermore, viral DNA replication levels of AAV-2 DNA were found to be lower in mouse cells than human cells, indicating limitations in the murine nucleus for viral replication.

The use of recombinant adeno-associated virus for skeletal gene therapy

OBJECTIVES

To provide a comprehensive literature review describing recent developments of the recombinant adeno-associated virus (rAAV) vector and exploring the therapeutic application of rAAV for bone defects, cartilage lesions and rheumatoid arthritis.

DESIGN

Narrative review.

RESULT

The review outlines the serotypes and genome of AAV, integration and life cycle of the rAAV vectors, the immune response and regulating system for AAV gene therapy. Furthermore, the advancements of rAAV gene therapy for bone growth together with cartilage repair are summarized.

CONCLUSION

Recombinant adeno-associated virus vector is perceived to be one of the most promising vector systems for bone and cartilage gene therapy approaches and further investigations need to be carried out for craniofacial research.

Adeno-associated virus induces apoptosis during coinfection with adenovirus

Adeno-associated virus (AAV) is a nonpathogenic parvovirus that efficiently replicates in the presence of adenovirus (Ad). Exogenous expression of the AAV replication proteins induces caspase-dependent apoptosis, but determining if AAV infection causes apoptosis during viral infection is complicated by Ad-mediated programmed cell death. To eliminate Ad-induced cytolysis, we used an E3 adenoviral death protein (ADP) mutant, pm534. AAV and pm534-coinfected cells exhibited increased cell killing compared to pm534 alone. Relative to cells infected with Ad alone, AAV and wild-type Ad-infected cells displayed decreased ADP expression, increased cytolysis until the third day of the infection, and decreased cytolysis thereafter. Biochemical and morphological characteristics of apoptosis were observed during coinfections with AAV and pm534 or Ad, including a moderate degree of caspase activation that was not present during infections with pm534 or Ad alone. AAV coinfection also increased extracellular pH. These studies suggest that AAV induces caspase-dependent and caspase-independent apoptosis.

Effects of adeno-associated virus on adenovirus replication and gene expression during coinfection

Adeno-associated virus (AAV) is a nonpathogenic parvovirus that requires adenovirus (Ad) or another helper virus for a fully permissive infection. AAV-mediated inhibition of Ad is well documented, yet many details of this interaction remain unclear. In this study, we observed a maximum 50-fold decrease in infectious virus production and a 10- to 40-fold reduction in Ad DNA synthesis during coinfections with AAV. With the exception of the E3 gene, AAV decreased all steady-state Ad mRNA levels at 24 h postinfection (hpi) in a dose-dependent manner. However, not all transcription units were affected equally. E4 and late transcription were the most strongly inhibited, and E1A and E2A were the least affected. The temporal effects of AAV on Ad mRNA transcript levels also varied among the Ad genes. Ad protein expression paralleled mRNA levels at 24 hpi, suggesting that coinfecting AAV does not exert substantial effects on translation. In plasmid transfection assays, Rep78 protein most effectively limited Ad amplification, while Rep40 had no effect. Since E2a and E4 proteins are essential for efficient Ad DNA amplification, we examined the relationship between reduced E2A and E4 expression and decreased DNA amplification. Transfected Rep78 did not reduce E2A and E4 transcript levels prior to DNA replication. Also, AAV-induced inhibition of E2A and E4 mRNA production did not occur in the presence of hydroxyurea. It is therefore unlikely that decreased early gene expression is solely responsible for AAV's suppression of Ad DNA replication. Our results suggest that AAV amplification and/or Rep gene expression inhibits Ad DNA synthesis.

Mechanisms of AAV transduction in glaucoma-associated human trabecular meshwork cells

BACKGROUND

Glaucoma is a chronic eye disease which leads to irreversible blindness. The trabecular meshwork tissue controls intraocular pressure (IOP), which is the major risk factor for glaucoma. Gene therapy treatment of chronic diseases requires the use of long-term expression, low toxicity and lack of immune response vectors. Adeno-associated viruses (AAV) possess these characteristics but have been unable to transduce the trabecular meshwork. Because of the importance of regulating elevated IOP by long-term gene therapy, we investigated mechanisms of AAV transduction to the human trabecular meshwork (TM).

METHODS

Primary human trabecular meshwork cells (HTM) and perfused organ cultures were infected with rAAV2-GFP, RGD-pseudotyped rAAV2-GFP alone, or combined with recombinant DeltaE1/E3 adenoviruses. Intracellular rAAV2 DNA and RNA were measured by relative quantitative and real-time TaqMan polymerase chain reaction (PCR). Host transcriptome was analyzed using high-density oligonucleotide microarrays. One transduction mechanism was tested using self-complementary AAV (scAAV).

RESULTS

The dramatic transduction enhancement obtained upon co-infection of rAAV2 with DeltaE1/E3 adenoviruses provides insights into transduction mechanisms in the HTM. Even if not transduced, rAAV2 enters TM cells. GeneChip analysis showed significant changes in host genes involved in cell cycle and DNA replication. Consequently, scAAV-GFP transduction was highly efficient. Other transduction-enhancement genes included coxsackie adenovirus receptor (CAR) and genes relevant to trabecular meshwork function.

CONCLUSIONS

The rate-limiting step of AAV transduction was not viral entry failure but, at least in part, host downregulation of DNA replication. Additional specific host genes might be involved. Our study revealed genes and mechanisms which led for the first time to efficient AAV transduction of the HTM.

Novel approaches to augment adeno-associated virus type-2 endocytosis and transduction

Recombinant adeno-associated virus (rAAV) receptor binding, endocytosis, nuclear trafficking and second strand gene conversion have been described as potential rate-limiting steps in rAAV type-2 (rAAV-2) transduction. Several strategies have been developed to enhance rAAV-2 intracellular trafficking and gene conversion in an attempt to increase the efficiency of this virus as a gene therapy vector. To this end, the current study has investigated novel methods for augmenting rAAV transduction by enhancing endocytosis of rAAV-2. A selective trypsinization assay demonstrated that the abundance of internalized rAAV ssDNA was increased only in cells treated with both pyrrolidinedithiocarbonate (PDTC) and a genotoxic agent. Treating cells with each of these agents alone had no effect on rAAV endocytosis in comparison to controls. To investigate the mechanisms of this synergistic effect on rAAV transduction, the involvement of Rac1 protein was evaluated. Inhibition of the Rac1 pathway by expression of a dominant negative mutant of Rac1 (N17Rac1) decreased rAAV transduction. In contrast, expression of a dominant active form of Rac1 (V12Rac1) alone mimicked the up-regulated response seen in the presence of PDTC and genotoxic agents. These studies provide potential insights into the importance of the Rac1 pathway to enhance uptake of rAAV-2.