Rescue of a familial dysautonomia mouse model by AAV9-Exon-specific U1 snRNA.

Familial dysautonomia (FD) is a currently untreatable, neurodegenerative disease caused by a splicing mutation (c.2204+6T>C) that causes skipping of exon 20 of the elongator complex protein 1 (ELP1) pre-mRNA. Here, we used adeno-associated virus serotype 9 (AAV9-U1-FD) to deliver an exon-specific U1 (ExSpeU1) small nuclear RNA, designed to cause inclusion of ELP1 exon 20 only in those cells expressing the target pre-mRNA, in a phenotypic mouse model of FD. Postnatal systemic and intracerebral ventricular treatment in these mice increased the inclusion of ELP1 exon 20. This also augmented the production of functional protein in several tissues including brain, dorsal root, and trigeminal ganglia. Crucially, the treatment rescued most of the FD mouse mortality before one month of age (89% vs 52%). There were notable improvements in ataxic gait as well as renal (serum creatinine) and cardiac (ejection fraction) functions. RNA-seq analyses of dorsal root ganglia from treated mice and human cells overexpressing FD-ExSpeU1 revealed only minimal global changes in gene expression and splicing. Overall then, our data prove that AAV9-U1-FD is highly specific and will likely be a safe and effective therapeutic strategy for this debilitating disease.

Harnessing the power of RNA therapeutics in treating ischemic heart failure: the TRAIN-HEART story.

Ischemic heart disease (IHD) is one of the world's foremost killers, accounting for 16% of all deaths worldwide. IHD is the main cause of heart failure (HF), as it leads to pathological changes in the heart, improper pumping function and eventual death. Therapeutic interventions usually follow a systemic general strategy for all heart failure subtypes due to the lack of a deep understanding of the disease mechanisms. Hence, HF and IHD therapeutics need groundbreaking concepts to guide the development of a new therapeutics class that tackles the disease at a molecular level. The TRAIN-HEART consortium, a Marie Sklodowska-Curie Actions Innovative Training Network (MSCA-ITN) funded by the European Commission, was established with the goal of filling that gap and developing RNA-based cardiovascular therapeutics. Created in the context of the Horizon 2020 research and innovation program, TRAIN-HEART comprises three key work packages (WPs) focusing on the pathogenesis of heart disease (WP1), the therapeutic potential of RNA therapeutics (WP2), and the development of new efficient delivery systems (WP3). Fifteen international early stage researchers (ESRs) from multiple complementary scientific disciplines were recruited to collaborate with a network of PIs from nine academic and eight non-academic partners in various disciplines to fully harness their collective potential for the betterment of HF treatment. This article provides an overview of the benefits of being part of an MSCA-ITN, with its different training and networking opportunities, maximizing ESRs' potential and broadening collaborative research possibilities. Finally, it describes what was like to do a PhD during the COVID-19 pandemic, with all the uncertainty and concern attached to it. Luckily, TRAIN-HEART stood out as a proactive network, finding new initiatives and alternatives to promote scientific and personal development. By bringing together leading academic teams, (biotech) companies, and highly motivated researchers, TRAIN-HEART is expanding scientific horizons and accelerating future development of effective RNA-based therapies to treat IHD.

AAV Gene Transfer with Tandem Promoter Design Prevents Anti-transgene Immunity and Provides Persistent Efficacy in Neonate Pompe Mice.

Hepatocyte-restricted, AAV-mediated gene transfer is being used to provide sustained, tolerogenic transgene expression in gene therapy. However, given the episomal status of the AAV genome, this approach cannot be applied to pediatric disorders when hepatocyte proliferation may result in significant loss of therapeutic efficacy over time. In addition, many multi-systemic diseases require widespread expression of the therapeutic transgene that, when provided with ubiquitous or tissue-specific non-hepatic promoters, often results in anti-transgene immunity. Here we have developed tandem promoter monocistronic expression cassettes that, packaged in a single AAV, provide combined hepatic and extra-hepatic tissue-specific transgene expression and prevent anti-transgene immunity. We validated our approach in infantile Pompe disease, a prototype disease caused by lack of the ubiquitous enzyme acid-alpha-glucosidase (GAA), presenting multi-systemic manifestations and detrimental anti-GAA immunity. We showed that the use of efficient tandem promoters prevents immune responses to GAA following systemic AAV gene transfer in immunocompetent Gaa-/- mice. Then we demonstrated that neonatal gene therapy with either AAV8 or AAV9 in Gaa-/- mice resulted in persistent therapeutic efficacy when using a tandem liver-muscle promoter (LiMP) that provided high and persistent transgene expression in non-dividing extra-hepatic tissues. In conclusion, the tandem promoter design overcomes important limitations of AAV-mediated gene transfer and can be beneficial when treating pediatric conditions requiring persistent multi-systemic transgene expression and prevention of anti-transgene immunity.