Library selection and directed evolution approaches to engineering targeted viral vectors

Abstract

Gene therapy, to delivery of genetic material to a patient for therapeutic benefit, has significant promise for translating basic knowledge of disease mechanism into biomedical treatments. The clinical development of the field has been slowed, however, by the need for improvements in the properties and capabilities of gene delivery vehicles. Vehicles based on viruses offer the potential for efficient gene delivery, but because viruses did not evolve to serve human therapeutic needs, many of their properties require significant improvement, including their safety, efficiency, and capacity for targeted gene delivery. Since viruses are highly complex biological entities, engineering such properties at the molecular level can be challenging. However, there has been significant progress in developing approaches that mimic the mechanisms by which viruses arose in the first place. In particular, library-based selection, the generation of one diverse genetic library and selection for new properties, and directed evolution, based on the multiple rounds of library generation and selection for iterative improvement of function, have strong potential in engineering novel properties into these complex biomolecular assemblies. This review will discuss progress in the application of peptide display, library selection, and directed evolution technologies toward engineering vectors based on retrovirus, adeno-associated virus, and adenovirus that are capable of targeted delivery to specific cell types. In addition to creating biomedically useful products, these approaches have future potential to yield novel insights into viral structure-function relationships.

Electrospun nanofibers as versatile interfaces for efficient gene delivery

“…However, the direct administration of gene vectors in liquid formulations to humans, a representative delivery mode, can lead to systemic spread in the body, presumably resulting in risks arising from gene expression in off-target regions [ 14 ]. Importantly, direct exposure to viral vectors, which have typically been known to increase gene transfer efficiencies compared with non-viral vectors, might cause severe immune responses against the vectors or even its gene products [ 15 ]. Direct injection of gene vectors typically boosts the vector or gene expression dosages in the blood stream or target regions within a short time, possibly leading to cellular toxicities or a short duration of gene expression [ 7 ].…”

In Vitro and In Vivo Gene Therapy Vector Evolution via Multispecies Interbreeding and Retargeting of Adeno-Associated Viruses

“…A special type of chimeric capsids are those containing foreign proteins or peptides inserted into various positions of the virion shell. The methods and strategies used are widely diverse, and again, we refer to comprehensive reviews (12,35,41). Noteworthy here are approaches to fuse targeting ligands to the N termini of AAV capsid proteins (ideally, VP2 [45,83]), or more powerful, to insert short peptides (up to 14 amino acids [21], typically 7) into exposed regions of the assembled virion.…”

Directed Evolution of a Virus Exclusively Utilizing Human Epidermal Growth Factor Receptor as the Entry Receptor

“…Random mutagenesis has been used to modify the host range of influenza virus, retrovirus, and adeno-associated virus (41)(42)(43)(44). However, without coupling with rational design, random mutagenesis cannot effectively direct viral vectors toward any particular cellular receptor.…”