MRI-Guided Focused Ultrasound for Targeted Delivery of rAAV to the Brain

Recombinant adeno-associated viral (rAAV) vectors are a promising tool for therapeutic gene delivery to the brain. However, the delivery of rAAVs across the blood-brain barrier (BBB) and entry into the brain remains a major challenge for rAAV-based gene therapy. To circumvent this limitation, transcranial MRI-guided focused ultrasound (MRIgFUS) combined with intravenously injected microbubbles has been used to transiently and reversibly increase BBB permeability in targeted brain regions. Systemic administration of rAAVs at the time of sonication with focused ultrasound (FUS) facilitates the passage of rAAVs through the BBB and into the brain parenchyma. We and others have demonstrated that FUS-mediated rAAV delivery to the brain results in efficient transduction and transgene expression in vivo. Using this approach, the dose of intravenously injected rAAV variants that can cross the BBB can be reduced by 100 times, achieving significant transgene expression in the brain parenchyma with reduced peripheral transduction. Moreover, this strategy can be used to deliver rAAV variants that do not cross the BBB from the blood to selected brain regions. Here, we provide a detailed protocol for FUS-induced BBB permeability for targeted rAAV delivery to the brain of adult mice and rats.

An overview: CRISPR/Cas-based gene editing for viral vaccine development

INTRODUCTION

: Gene-editing technology revolutionized vaccine manufacturing and offers a variety of benefits over traditional vaccinations, such as improved immune response, higher production rate, stability, precise immunogenic activity, and fewer adverse effects. The more recently discovered Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/associated protein 9 (Cas9) system has become the most widely utilized technology based on its efficiency, utility, flexibility, versatility, ease of use, and cheaper compared to other gene-editing techniques. Considering its wider scope for genomic modification, CRISPR/Cas9-based technology's potential is explored for vaccine development.

AREAS COVERED

: In this review, we will address the recent advances in the CRISPR/Cas system for the development of vaccines and viral vectors for delivery. In addition, we will discuss strategies for the development of the vaccine, as well as the limitations and future prospects of the CRISPR/Cas system.

EXPERT OPINION

: Human and animal viruses have been exposed to antiviral CRISPR/Cas9-based engineering to prevent infection, which uses knockout, knock-in, gene activation/deactivation, RNA targeting, and editing cell lines strategies for gene editing of viruses. Because of that CRISPR/Cas system is used to boost the vaccine production yield by removing unwanted genes that cause disease or are required for viral infection.

Delivery of gene editing therapeutics

For the past decades, gene editing demonstrated the potential to attenuate each of the root causes of genetic, infectious, immune, cancerous, and degenerative disorders. More recently, Clustered Regularly Interspaced Short Palindromic Repeats-CRISPR-associated protein 9 (CRISPR-Cas9) editing proved effective for editing genomic, cancerous, or microbial DNA to limit disease onset or spread. However, the strategies to deliver CRISPR-Cas9 cargos and elicit protective immune responses requires safe delivery to disease targeted cells and tissues. While viral vector-based systems and viral particles demonstrate high efficiency and stable transgene expression, each are limited in their packaging capacities and secondary untoward immune responses. In contrast, the nonviral vector lipid nanoparticles were successfully used for as vaccine and therapeutic deliverables. Herein, we highlight each available gene delivery systems for treating and preventing a broad range of infectious, inflammatory, genetic, and degenerative diseases. STATEMENT OF SIGNIFICANCE: CRISPR-Cas9 gene editing for disease treatment and prevention is an emerging field that can change the outcome of many chronic debilitating disorders.