Tailored transgene expression to specific cell types in the central nervous system after peripheral injection with...

The capacity of certain adeno-associated virus (AAV) vectors to cross the blood-brain barrier after intravenous delivery offers a unique opportunity for noninvasive brain delivery. However, without a well-tailored system, the use of a peripheral route injection may lead to undesirable transgene expression in nontarget cells or organs. To refine this approach, the present study characterizes the transduction profiles of new self-complementary AAV9 (scAAV9) expressing the green fluorescent protein (GFP) either under an astrocyte (glial fibrillary acidic (GFA) protein) or neuronal (Synapsin (Syn)) promoter, after intravenous injection of adult mice (2 × 10¹³ vg/kg). ScAAV9-GFA-GFP and scAAV9-Syn-GFP robustly transduce astrocytes (11%) and neurons (17%), respectively, without aberrant expression leakage. Interestingly, while the percentages of GFP-positive astrocytes with scAAV9-GFA-GFP are similar to the performances observed with scAAV9-CBA-GFP (broadly active promoter), significant higher percentages of neurons express GFP with scAAV9-Syn-GFP. GFP-positive excitatory as well as inhibitory neurons are observed, as well as motor neurons in the spinal cord. Additionally, both activated (GFAP-positive) and resting astrocytes (GFAP-negative) express the reporter gene after scAAV9-GFA-GFP injection. These data thoroughly characterize the gene expression specificity of AAVs fitted with neuronal and astrocyte-selective promoters after intravenous delivery, which will prove useful for central nervous system (CNS) gene therapy approaches in which peripheral expression of transgene is a concern.