AAV5-Syn-FLPo

AAV integrates into a specific site, AAVS1, on chromosome 19 of the human genome, which makes AAV genome insertion more predictable than other viral vectors. Random integration into the host cell genome does occur, but at a much lower frequency compared to other vectors. However, the ability of AAV to integrate can be blocked by removing Rep and Cap from the AAV genome. To construct an AAV transfer plasmid, the promoter and transgene are placed between two ITRs, and Rep and Cap are provided in trans for vector production. For AAV replication to occur, an adenovirus, herpes simplex virus, or a helper plasmid containing adenoviral genes is also required to mediate AAV replication.

Of the types of viruses commonly used in neuroscience, AAV can infect quiescent, non-dividing cells (e.g., neurons) as well as dividing cells like lentiviruses, whereas retroviruses can only infect dividing cells. Furthermore, by removing the Rep and Cap genes from the plasmid, AAV integration into the host genome can be prevented. When recombinant AAV fails to integrate into AAVS1, the virus is processed into a double-stranded circular episome that is maintained extrachromosomally and can survive for years in non-dividing cells, allowing long-term transgene expression in non-dividing cells. This property makes them prime candidates for neuroscience research because they are non-pathogenic, elicit less immune reactivity during and after transduction than other viral vectors, can be targeted to neurons without helper viruses or capsids, and have less impact on basal cellular function than other viral vectors.