Supramolecular assembly of polycation/mRNA nanoparticles and in vivo monocyte programming.

Size-dependent phagocytosis is a well-characterized phenomenon in monocytes and macrophages. However, this size effect for preferential gene delivery to these important cell targets has not been fully exploited because commonly adopted stabilization methods for electrostatically complexed nucleic acid nanoparticles, such as PEGylation and charge repulsion, typically arrest the vehicle size below 200 nm. Here, we bridge the technical gap in scalable synthesis of larger submicron gene delivery vehicles by electrostatic self-assembly of charged nanoparticles, facilitated by a polymer structurally designed to modulate internanoparticle Coulombic and van der Waals forces. Specifically, our strategy permits controlled assembly of small poly(ß-amino ester)/messenger ribonucleic acid (mRNA) nanoparticles into particles with a size that is kinetically tunable between 200 and 1,000 nm with high colloidal stability in physiological media. We found that assembled particles with an average size of 400 nm safely and most efficiently transfect monocytes following intravenous administration and mediate their differentiation into macrophages in the periphery. When a CpG adjuvant is co-loaded into the particles with an antigen mRNA, the monocytes differentiate into inflammatory dendritic cells and prime adaptive anticancer immunity in the tumor-draining lymph node. This platform technology offers a unique ligand-independent, particle-size-mediated strategy for preferential mRNA delivery and enables therapeutic paradigms via monocyte programming.

Protospacer modification improves base editing of a canonical splice site variant and recovery of CFTR function in human airway epithelial cells.

Canonical splice site variants affecting the 5' GT and 3' AG nucleotides of introns result in severe missplicing and account for about 10% of disease-causing genomic alterations. Treatment of such variants has proven challenging due to the unstable mRNA or protein isoforms that typically result from disruption of these sites. Here, we investigate CRISPR-Cas9-mediated adenine base editing for such variants in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. We validate a CFTR expression minigene (EMG) system for testing base editing designs for two different targets. We then use the EMG system to test non-standard single-guide RNAs with either shortened or lengthened protospacers to correct the most common cystic fibrosis-causing variant in individuals of African descent (c.2988+1G>A). Varying the spacer region length allowed placement of the editing window in a more efficient context and enabled use of alternate protospacer adjacent motifs. Using these modifications, we restored clinically significant levels of CFTR function to human airway epithelial cells from two donors bearing the c.2988+1G>A variant.

Toward Gene Transfer Nanoparticles as Therapeutics.

Genetic medicine has great potential to treat the underlying causes of many human diseases with exquisite precision, but the field has historically been stymied by delivery as the central challenge. Nanoparticles, engineered constructs the size of natural viruses, are being designed to more closely mimic the delivery efficiency of viruses, while enabling the advantages of increased safety, cargo-carrying flexibility, specific targeting, and ease in manufacturing. The speed in which nonviral gene transfer nanoparticles are making progress in the clinic is accelerating, with clinical validation of multiple nonviral nucleic acid delivery nanoparticle formulations recently FDA approved for both expression and for silencing of genes. While much of this progress has been with lipid nanoparticle formulations, significant development is being made with other nanomaterials for gene transfer as well, with favorable attributes such as biodegradability, scalability, and cell targeting. This review highlights the state of the field, current challenges in delivery, and opportunities for engineered nanomaterials to meet these challenges, including enabling long-term therapeutic gene editing. Delivery technology utilizing different kinds of nanomaterials and varying cargos for gene transfer (DNA, mRNA, and ribonucleoproteins) are discussed. Clinical applications are presented, including for the treatment of genetic diseases such as cystic fibrosis.