Systemic gene delivery following intravenous administration of AAV9 to fetal and neonatal mice and late-gestation nonhuman primates.

Several acute monogenic diseases affect multiple body systems, causing death in childhood. The development of novel therapies for such conditions is challenging. However, improvements in gene delivery technology mean that gene therapy has the potential to treat such disorders. We evaluated the ability of the AAV9 vector to mediate systemic gene delivery after intravenous administration to perinatal mice and late-gestation nonhuman primates (NHPs). Titer-matched single-stranded (ss) and self-complementary (sc) AAV9 carrying the green fluorescent protein (GFP) reporter gene were intravenously administered to fetal and neonatal mice, with noninjected age-matched mice used as the control. Extensive GFP expression was observed in organs throughout the body, with the epithelial and muscle cells being particularly well transduced. ssAAV9 carrying the WPRE sequence mediated significantly more gene expression than its sc counterpart, which lacked the woodchuck hepatitis virus posttranscriptional regulatory element (WPRE) sequence. To examine a realistic scale-up to larger models or potentially patients for such an approach, AAV9 was intravenously administered to late-gestation NHPs by using a clinically relevant protocol. Widespread systemic gene expression was measured throughout the body, with cellular tropisms similar to those observed in the mouse studies and no observable adverse events. This study confirms that AAV9 can safely mediate systemic gene delivery in small and large animal models and supports its potential use in clinical systemic gene therapy protocols.

Intravenous administration of AAV2/9 to the fetal and neonatal mouse leads to differential targeting of CNS cell types and extensive transduction of the nervous system.

Several diseases of the nervous system are characterized by neurodegeneration and death in childhood. Conventional medicine is ineffective, but fetal or neonatal gene therapy may provide an alternative route to treatment. We evaluated the ability of single-stranded and self-complementary adeno-associated virus pseudotype 2/9 (AAV2/9) to transduce the nervous system and target gene expression to specific neural cell types following intravenous injection into fetal and neonatal mice, using control uninjected age-matched mice. Fetal and neonatal administration produced global delivery to the central (brain, spinal cord, and all layers of the retina) and peripheral (myenteric plexus and innervating nerves) nervous system but with different expression profiles within the brain; fetal and neonatal administration resulted in expression in neurons and protoplasmic astrocytes, respectively. Neither single-stranded nor self-complementary AAV2/9 triggered a microglia-mediated immune response following either administration. In summary, intravenous AAV2/9 targets gene expression to specific neural cell types dependent on developmental stage. This represents a powerful tool for studying nervous system development and disease. Furthermore, it may provide a therapeutic strategy for treatment of early lethal genetic diseases, such as Gaucher disease, and for disabling neuropathies, such as preterm brain injury.