Recombinant Adeno-Associated Virus: Efficient Transduction of the Rat VMH and Clearance from Blood

Abstract

To promote the efficient and safe application of adeno-associated virus (AAV) vectors as a gene transfer tool in the central nervous system (CNS), transduction efficiency and clearance were studied for serotypes commonly used to transfect distinct areas of the brain. As AAV2 was shown to transduce only small volumes in several brain regions, this study compares the transduction efficiency of three AAV pseudotyped vectors, namely AAV2/1, AAV2/5 and AAV2/8, in the ventromedial nucleus of the hypothalamus (VMH). No difference was found between AAV2/1 and AAV2/5 in transduction efficiency. Both AAV2/1 and AAV2/5 achieved a higher transduction rate than AAV2/8. One hour after virus administration to the brain, no viral particles could be traced in blood, indicating that no or negligible numbers of virions crossed the blood-brain barrier. In order to investigate survival of AAV in blood, clearance was determined following systemic AAV administration. The half-life of AAV2/1, AAV2/2, AAV2/5 and AAV2/8 was calculated by determining virus clearance rates from blood after systemic injection. The half-life of AAV2/2 was 4.2 minutes, which was significantly lower than the half-lives of AAV2/1, AAV2/5 and AAV2/8. With a half-life of more than 11 hours, AAV2/8 particles remained detectable in blood significantly longer than AAV2/5. We conclude that application of AAV in the CNS is relatively safe as no AAV particles are detectable in blood after injection into the brain. With a half-life of 1.67 hours of AAV2/5, a systemic injection with 1×109 genomic copies of AAV would be fully cleared from blood after 2 days.

Bidirectional Control of Anxiety-Related Behaviors in Mice: Role of Inputs Arising from the Ventral Hippocampus to the Lateral Septum and Medial Prefrontal Cortex

“…The use of CAV2-Cre in combination with the Creresponsive AAV vectors allowed us to activate (by hM3D) or inhibit (by hM4D) vHPC cells that project to the LS or the mPFC (van Gestel et al, 2014). It should be noted, however, that retrogradely-targeted vHPC cells send axon collaterals to multiple target structures.…”

CRISPR/Cas9 Epigenome Editing Potential for Rare Imprinting Diseases: A Review

“…Their affinity to specific tissues may be controlled through modification or removal of surface receptors [93]. A possible disadvantage of EVs is a short lifetime in vivo (up to 6 h) compared to AAV-mediated delivery (up to 2 days) [94,95]. It has been shown that cell-derived EVs enable efficient drug or gene delivery with minimal immune response.…”

Gene Delivery Strategies to Promote Spinal Cord Repair

“…Furthermore, researchers have exploited highly evolved mechanisms that viruses have developed to cross the blood–brain barrier and target specific cell types. 36 , 97 , 98 Viral vectors commonly investigated for gene therapies include herpes simplex virus (HSV), retrovirus, lentivirus, adenovirus, and adeno-associated virus (AAV).…”

“… 97 , 102 , 132 Notably, some AAV pseudotypes have been shown to effectively cross the blood–brain barrier and transduce cells in the spinal cord when injected systemically. 97 , 98 , 102 , 107 Many viral vectors, including HSV, 143 AAV, 107 , 109 , 110 lentivirus, 108 , 113 and adenovirus, 144 , 145 can be delivered into the CNS via retrograde transport from axons at peripheral neuromuscular junctions. Although this process is more complicated and invasive than intravenous administration, it is still a safer and more efficient alternative than direct injection into the spinal cord or brain.…”

“… 175 , 195 After delivery, the majority of virus or complexed plasmid is inactivated and cleared by a maximum of 72 hours. 98 This relatively short period of activity dictates that those cells that are able to physically encounter the vectors during this time will become transfected/transduced. 62 , 195 , 203 Therapies capable of fully restoring functional tissue after SCI will likely require combinations of factors to be delivered, where each factor addresses a specific barrier to regeneration.…”