Analysis of AAV Serotypes 1–9 Mediated Gene Expression and Tropism in Mice After Systemic Injection

Abstract

This study examines transgene expression and biodistribution of adeno-associated virus (AAV) pseudotyped 1-9 after tail vein (TV) injection in male mice. Using a cytomegalovirus (CMV)-luciferase transgene, the time-course of expression in each animal was tracked throughout the experiment. The animals were imaged at 7, 14, 29, 56, and 100 days after the TV injection. The total number of photons emitted from each animal was recorded, allowing examination of expression level and kinetics for each pseudotyped virus. The bioluminescence imaging revealed three expression levels (i) low-expression group, AAV2, 3, 4, and 5; (ii) moderate-expression group, AAV1, 6, and 8; and (iii) high-expression group, AAV7 and 9. In addition, imaging revealed two classes of kinetics (i) rapid-onset, for AAV1, 6, 7, 8, and 9; and (ii) slow-onset, for AAV2, 3, 4, and 5. We next evaluated protein expression and viral genome copy numbers in dissected tissues. AAV9 had the best viral genome distribution and highest protein levels. The AAV7 protein and genome copy numbers were comparable to those of AAV9 in the liver. Most surprisingly, AAV4 showed the greatest number of genome copies in lung and kidney, and a high copy number in the heart. AAV6 expression was observed in the heart, liver, and skeletal muscle, and the genome distribution corroborated these observations.

Heart-targeted adeno-associated viral vectors selected by in vivo biopanning of a random viral display peptide library

“…Although some earlier studies reported higher vg in the liver than in the heart with AAV9 vectors, 39,47,48 another publication found a better transduction of the heart than the liver of neonatal-injected animals. 45 These variations in biodistribution between different studies might be explained by different experimental conditions such as vector dose, mouse strain, gender of the mice and time point of tissue harvesting.…”

Cellular tropism and transduction properties of seven adeno-associated viral vector serotypes in adult retina after intravitreal injection

“…56,57 Use of appropriate AAV vectors may prevent or reduce such anomalous reorganizations within the inner nuclear layer, potentially enhancing the effectiveness of other therapies such as cellular or bionic implants. 57 Finally, new vector constructs, different modes of delivery, 24,25 and the isolation and modification of different serotypes 7,58-62 will lead to novel vectors that have greater packaging capacity 33,63 and cell specificity, and may even further minimize immunological sequelae following therapeutic application.…”

“…23 Variation in capsid structure affects viral tropism and expression kinetics in terms of the onset and expression levels of therapeutic genes, and the use of different serotypes may allow for a more cellspecific gene transfer. 3,6,8,12,24,25 Robust photoreceptor transduction has been reported after subretinal injection of many vector types; however, photoreceptors are only infrequently transduced after intravitreal injection of the serotypes tested to date. 3,4,[6][7][8]11,12,26 Intravitreal vector delivery is a less invasive technique compared with subretinal delivery.…”

“…Retinas were analyzed 10 weeks post-injection, a time point at which all vector types should maintain a strong gene expression. 6,8,12,24 For each serotype, the number, morphology and laminar distribution of GFP-positive ( + ) cells were quantified using confocal and fluorescence microscopy. Phenotype was also assessed by double immunolabelling with various markers for retinal cell types.…”

microRNA122-regulated transgene expression increases specificity of cardiac gene transfer upon intravenous delivery of AAV9 vectors

“…3,10,[12][13][14][15] However, AAV9 vectors exhibit a broad tissue tropism and allow also transduction of the liver upon intravascular administration. 3,[12][13][14]16,17 Reduction of AAV-mediated transgene expression in the liver, however, may be a desirable aim to reduce unwanted side effects in cardiac gene therapy. Transcriptional control of gene expression is a promising approach to overcome this limitation.…”