Engineered Viruses as Genome Editing Devices

Abstract

Genome editing based on sequence-specific designer nucleases, also known as programmable nucleases, seeks to modify in a targeted and precise manner the genetic information content of living cells. Delivering into cells designer nucleases alone or together with donor DNA templates, which serve as surrogate homologous recombination (HR) substrates, can result in gene knockouts or gene knock-ins, respectively. As engineered replication-defective viruses, viral vectors are having an increasingly important role as delivery vehicles for donor DNA templates and designer nucleases, namely, zinc-finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs) and clustered, regularly interspaced, short palindromic repeats (CRISPR)-associated Cas9 (CRISPR−Cas9) nucleases, also known as RNA-guided nucleases (RGNs). We review this dual role played by engineered viral particles on genome editing while focusing on their main scaffolds, consisting of lentiviruses, adeno-associated viruses, and adenoviruses. In addition, the coverage of the growing body of research on the repurposing of viral vectors as delivery systems for genome editing tools is complemented with information regarding their main characteristics, pros, and cons. Finally, this information is framed by a concise description of the chief principles, tools, and applications of the genome editing field as a whole.

From the Immune Response to the Genome Design; CRISPR-Cas9 System: Review

“…Tur ki ye Kli nik le ri J Med Sci 2017;37 (1) 44,47 Bu vektörler genoma entegre olmadan transdüksi-yon sağladıkları için, hızlı çoğalan hücrelere kazandırdıkları geçici Cas9 ekspresyonu sayesinde güvenlik açısından avantajlı olarak tanımlanmak-tadır. Ancak yavaş çoğalan hücrelerde Cas9 ekspresyonu kalıcı olabilir ve bu da hedef dışı kesimin daha yüksek olması gibi dezavantajlar ortaya çıka-rabilir.…”

“…Fakat virülans kazanarak hastalık etmenine dönüşme ihtimallerinin olması ve immün reaksiyonlara sebep olabilmeleri bakımın-dan viral vektörlerin klinik uygulanabilirlikleri hala tartışma konusudur. 44,49,53,54 Bu bakımdan plazmit vektörler daha güvenilir görünmektedir.…”

“…51,60,61 Genel olarak viral ve viral olmayan vektörler karşılaştırılacak olursa Tablo 2'deki gibi bir durum ortaya çıkmaktadır. 44,59,62,63 Buna göre viral vektör-ler yüksek verimle CRISPR-Cas9 sisteminin taşın-masında kullanılma potansiyeline sahiptir. Ancak bunun yanında mutajenite ve immunojenite riski taşımalarından dolayı viral olmayan transfeksiyon ve gen taşıma yöntemlerinin önemi ortaya çık-maktadır.…”

Gene Editing for Treatment of Neurological Infections

“…There are various available means of delivery and these include viral transduction with adenovirus, adeno-associated virus (AAV) or lentiviruses [64][65][66], as well as physical methods [67]. Adenovirus vectors are useful but restricted in application because they are immunogenic [64].…”

“…However, lentiviral vectors, which are frequently derived from HIV-1, are capable of effecting permanent genetic alterations to their DNA targets but are limited by off-target events if the presence of the transduced nuclease is not transient. Therefore, integrase-defective lentiviruses or self-inactivating replication-incompetent lentiviruses are preferable because they give transient expression and have the ability to transduce both dividing and nondividing cells [65,66]. The feasibility of lentiviral CRISPR/Cas9 delivery vectors is illustrated by many studies, including the eradication of latent infection by HIV-1 and JCV [11,12].…”