Takis Athanasopoulos

Adenovirus vector vaccination induces expansion of memory CD4 T cells with a mucosal homing phenotype that are readily susceptible to HIV-1

In the recently halted HIV type 1 (HIV-1) vaccine STEP trial, individuals that were seropositive for adenovirus serotype 5 (Ad5) showed increased rates of HIV-1 infection on vaccination with an Ad5 vaccine. We propose that this was due to activation and expansion of Ad5-specific mucosal-homing memory CD4 T cells. To test this hypothesis, Ad5 and Ad11 antibody titers were measured in 20 healthy volunteers. Dendritic cells (DCs) from these individuals were pulsed with replication defective Ad5 or Ad11 and co-cultured with autologous lymphocytes. Cytokine profiles, proliferative capacity, mucosal migration potential, and susceptibility to HIV infection of the adenovirus-stimulated memory CD4 T cells were measured. Stimulation of T cells from healthy Ad5-seropositive but Ad11-seronegative individuals with Ad5, or serologically distinct Ad11 vectors induced preferential expansion of adenovirus memory CD4 T cells expressing α4β7 integrins and CCR9, indicating a mucosal-homing phenotype. CD4 T-cell proliferation and IFN-γ production in response to Ad stimulation correlated with Ad5 antibody titers. However, Ad5 serostatus did not correlate with total cytokine production upon challenge with Ad5 or Ad11. Expanded Ad5 and Ad11 memory CD4 T cells showed an increase in CCR5 expression and higher susceptibility to infection by R5 tropic HIV-1. This suggests that adenoviral-based vaccination against HIV-1 in individuals with preexisting immunity against Ad5 results in preferential expansion of HIV-susceptible activated CD4 T cells that home to mucosal tissues, increases the number of virus targets, and leads to a higher susceptibility to HIV acquisition.

Codon and mRNA sequence optimization of microdystrophin transgenes improves expression and physiological outcome in dystrophic mdx mice following AAV2/8 gene transfer

Duchenne muscular dystrophy is a fatal muscle-wasting disorder. Lack of dystrophin compromises the integrity of the sarcolemma and results in myofibers that are highly prone to contraction-induced injury. Recombinant adeno-associated virus (rAAV)-mediated dystrophin gene transfer strategies to muscle for the treatment of Duchenne muscular dystrophy (DMD) have been limited by the small cloning capacity of rAAV vectors and high titers necessary to achieve efficient systemic gene transfer. In this study, we assess the impact of codon optimization on microdystrophin (DeltaAB/R3-R18/DeltaCT) expression and function in the mdx mouse and compare the function of two different configurations of codon-optimized microdystrophin genes (DeltaAB/R3-R18/DeltaCT and DeltaR4-R23/DeltaCT) under the control of a muscle-restrictive promoter (Spc5-12). Codon optimization of microdystrophin significantly increases levels of microdystrophin mRNA and protein after intramuscular and systemic administration of plasmid DNA or rAAV2/8. Physiological assessment demonstrates that codon optimization of DeltaAB/R3-R18/DeltaCT results in significant improvement in specific force, but does not improve resistance to eccentric contractions compared with noncodon-optimized DeltaAB/R3-R18/DeltaCT. However, codon-optimized microdystrophin DeltaR4-R23/DeltaCT completely restored specific force generation and provided substantial protection from contraction-induced injury. These results demonstrate that codon optimization of microdystrophin under the control of a muscle-specific promoter can significantly improve expression levels such that reduced titers of rAAV vectors will be required for efficient systemic administration.

β-catenin as a potential key target for tumor suppression.

β‐catenin is a multifunctional protein identified to be pivotal in embryonic patterning, organogenesis and adult homeostasis. It plays a critical structural role in mediating cadherin junctions and is also an essential transcriptional co‐activator in the canonical Wnt pathway. Evidence has been documented that both the canonical Wnt pathway and cadherin junctions are deregulated or impaired in a plethora of human malignancies. In the light of this, there has been a recent surge in elucidating the mechanisms underlying the etiology of cancer development from the perspective of β‐catenin. Here, we focus on the emerging roles of β‐catenin in the process of tumorigenesis by discussing novel functions of old players and new proteins, mechanisms identified to mediate or interact with β‐catenin and the most recently unraveled clinical implications of β‐catenin regulatory pathways toward tumor suppression.

Gene therapy for muscular dystrophy: current progress and future prospects

Muscular dystrophies refer to a group of inherited disorders characterized by progressive muscle weakness, wasting and degeneration. So far, there is no effective treatment but new gene-based therapies are currently being developed with particular noted advances in using conventional gene replacement strategies, RNA-based approaches, or cell-based gene therapy with a main focus on Duchenne muscular dystrophy (DMD). DMD is the most common and severe form of muscular dystrophy and current treatments are far from adequate. However, genetic and cell-based therapies, in particular exon skipping induced by antisense strategies, and corrective gene therapy via functionally engineered dystrophin genes hold great promise, with several clinical trials ongoing. Proof-of-concept of exon skipping has been obtained in animal models, and most recently in clinical trials; this approach represents a promising therapy for a subset of patients. In addition, gene-delivery-based strategies exist both for antisense-induced reading frame restoration, and for highly efficient delivery of functional dystrophin mini- and micro-genes to muscle fibres in vivo and muscle stem cells ex-vivo. In particular, AAV-based vectors show efficient systemic gene delivery to skeletal muscle directly in vivo, and lentivirus-based vectors show promise of combining ex vivo gene modification strategies with cell-mediated therapies.

Langerin negative dendritic cells promote potent CD8+ T-cell priming by skin delivery of live adenovirus vaccine microneedle arrays

Stabilization of virus protein structure and nucleic acid integrity is challenging yet essential to preserve the transcriptional competence of live recombinant viral vaccine vectors in the absence of a cold chain. When coupled with needle-free skin delivery, such a platform would address an unmet need in global vaccine coverage against HIV and other global pathogens. Herein, we show that a simple dissolvable microneedle array (MA) delivery system preserves the immunogenicity of vaccines encoded by live recombinant human adenovirus type 5 (rAdHu5). Specifically, dried rAdHu5 MA immunization induced CD8+ T-cell expansion and multifunctional cytokine responses equipotent with conventional injectable routes of immunization. Intravital imaging demonstrated MA cargo distributed both in the epidermis and dermis, with acquisition by CD11c+ dendritic cells (DCs) in the dermis. The MA immunizing properties were attributable to CD11c+ MHCIIhi CD8αneg epithelial cell adhesion molecule (EpCAMneg) CD11b+ langerin (Lang; CD207)neg DCs, but neither Langerhans cells nor Lang+ DCs were required for CD8+ T-cell priming. This study demonstrates an important technical advance for viral vaccine vectors progressing to the clinic and provides insights into the mechanism of CD8+ T-cell priming by live rAdHu5 MAs.

Long-term functional adeno-associated virus-microdystrophin expression in the dystrophic CXMDj dog.

Duchenne muscular dystrophy (DMD) is a severe, inherited, muscle‐wasting disorder caused by mutations in the dystrophin gene. Preclinical studies of adeno‐associated virus gene therapy for DMD have been described in mouse and dog models of this disease. However, low and transient expression of microdystrophin in dystrophic dogs and a lack of long‐term microdystrophin expression associated with a CD8+ T‐cell response in DMD patients suggests that the development of improved microdystrophin genes and delivery strategies is essential for successful clinical trials in DMD patients.

Delivery of AAV2/9-Microdystrophin Genes Incorporating Helix 1 of the Coiled-Coil Motif in the C-Terminal Domain of Dystrophin Improves Muscle Pathology and Restores the Level of α1-Syntrophin and α-Dystrobrevin in Skeletal Muscles of mdx Mice

Duchenne muscular dystrophy is a severe X-linked inherited muscle wasting disorder caused by mutations in the dystrophin gene. Adeno-associated virus (AAV) vectors have been extensively used to deliver genes efficiently for dystrophin expression in skeletal muscles. To overcome limited packaging capacity of AAV vectors (<5 kb), truncated recombinant microdystrophin genes with deletions of most of rod and carboxyl-terminal (CT) domains of dystrophin have been developed. We have previously shown the efficiency of mRNA sequence-optimized microdystrophin (ΔR4-23/ΔCT, called MD1) with deletion of spectrin-like repeat domain 4 to 23 and CT domain in ameliorating the pathology of dystrophic mdx mice. However, the CT domain of dystrophin is thought to recruit part of the dystrophin-associated protein complex, which acts as a mediator of signaling between extracellular matrix and cytoskeleton in muscle fibers. In this study, we extended the ΔR4-23/ΔCT microdystrophin by incorporating helix 1 of the coiled-coil motif in the CT domain of dystrophin (MD2), which contains the α1-syntrophin and α-dystrobrevin binding sites. Intramuscular injection of AAV2/9 expressing CT domain-extended microdystrophin showed efficient dystrophin expression in tibialis anterior muscles of mdx mice. The presence of the CT domain of dystrophin in MD2 increased the recruitment of α1-syntrophin and α-dystrobrevin at the sarcolemma and significantly improved the muscle resistance to lengthening contraction-induced muscle damage in the mdx mice compared with MD1. These results suggest that the incorporation of helix 1 of the coiled-coil motif in the CT domain of dystrophin to the microdystrophins will substantially improve their efficiency in restoring muscle function in patients with Duchenne muscular dystrophy.

Inhibition of atherosclerosis in apolipoprotein-E-deficient mice following muscle transduction with adeno-associated virus vectors encoding human apolipoprotein-E.

Apolipoprotein E (apoE) is a multifunctional plasma glycoprotein involved in lipoprotein metabolism and a range of cell signalling phenomena. ApoE-deficient (apoE-/-) mice exhibit severe hypercholesterolaemia and are an excellent model of human atherosclerosis. ApoE somatic gene transfer and bone marrow transplantation in apoE-/- mice results in reversal of hypercholesterolaemia, inhibition of atherogenesis and regression of atherosclerotic plaque density. Replication defective adeno-associated virus vectors (rAAVs) are an attractive system currently in clinical trial for muscle-based heterologous gene therapy to express secreted recombinant plasma proteins. Here we have applied rAAV transduction of skeletal muscle to express wild-type (ɛ3) and a defective receptor-binding mutant (ɛ2) human apoE transgene in apoE-/- mice. In treated animals, apoE mRNA was present in transduced muscles and, although plasma levels of recombinant apoE fell below the detection levels of our ELISA (ie <10 ng/ml), circulating antibodies to human apoE and rAAV were induced. Up to 3 months after a single administration of rAAV/apoE3, a significant reduction in atherosclerotic plaque density in aortas of treated animals was observed (approximately 30%), indicating that low-level rAAV-mediated apoE3 expression from skeletal muscle can retard atherosclerotic progression in this well-defined genetic model.

Abnormal splicing switch of DMD's penultimate exon compromises muscle fibre maintenance in myotonic dystrophy

Myotonic Dystrophy type 1 (DM1) is a dominant neuromuscular disease caused by nuclear-retained RNAs containing expanded CUG repeats. These toxic RNAs alter the activities of RNA splicing factors resulting in alternative splicing misregulation and muscular dysfunction. Here we show that the abnormal splicing of DMD exon 78 found in dystrophic muscles of DM1 patients is due to the functional loss of MBNL1 and leads to the re-expression of an embryonic dystrophin in place of the adult isoform. Forced expression of embryonic dystrophin in zebrafish using an exon-skipping approach severely impairs the mobility and muscle architecture. Moreover, reproducing Dmd exon 78 missplicing switch in mice induces muscle fibre remodelling and ultrastructural abnormalities including ringed fibres, sarcoplasmic masses or Z-band disorganization, which are characteristic features of dystrophic DM1 skeletal muscles. Thus, we propose that splicing misregulation of DMD exon 78 compromises muscle fibre maintenance and contributes to the progressive dystrophic process in DM1.

RNAi-mediated knockdown of dystrophin expression in adult mice does not lead to overt muscular dystrophy pathology

Duchenne muscular dystrophy (DMD) is a fatal muscle wasting disorder caused by mutations in the dystrophin gene. DMD has a complex and as yet incompletely defined molecular pathophysiology. The peak of the pathology attributed to dystrophin deficiency happens between 3 and 8 weeks of age in mdx mice, the animal model of DMD. Accordingly, we hypothesized that the pathology observed with dystrophin deficiency may be developmentally regulated. Initially, we demonstrated that profound small interfering RNA-mediated dystrophin knockdown could be achieved in mouse primary muscle cultures. The use of adeno-associated virus vectors to express short-hairpin RNAs targeting dystrophin in skeletal muscle in vivo yielded a potent and specific dystrophin knockdown, but only after approximately 5 months, indicating the very long half-life of dystrophin. Interestingly, and in contrast to what is observed in congenital dystrophin deficiency, long-term ( approximately 1 year) dystrophin knockdown in adult mice did not result, per se, in overt dystrophic pathology or upregulation of utrophin. This supports our hypothesis and suggests new pathophysiology of the disease. Furthermore, taking into account the rather long half-life of dystrophin, and the notion that the development of pathology is age-dependent, it indicates that a single gene therapy approach before the onset of pathology might convey a long-term cure for DMD.