Intranasal versus intravenous AAV delivery: A comparative analysis of brain-targeting efficiency and peripheral exposure in mice

Adeno-associated viruses (AAVs) hold significant promise for gene therapy targeting the central nervous system (CNS). However, current delivery methods are either invasive or cause significant systemic exposure. Intranasal (IN) delivery presents a promising noninvasive alternative for direct CNS targeting, though its efficacy in delivering AAVs to the brain has seldom been explored. Here, we quantitatively assessed AAV transduction in the brain and peripheral organs of Swiss, BALB/c, and C57BL/6 J mice following IN administration, using intravenous (IV) injection as a benchmark for comparison. Our findings revealed that IN administration of the AAV9 vector achieved approximately 15% of the transduction efficiency and 9% of the gene expression levels observed with IV delivery. Importantly, IN delivery significantly reduced systemic exposure to most major peripheral organs by up to 1.34 × 10⁴-fold compared to IV injection. The ratios of gene transduction between the brain and various peripheral tissues were calculated, revealing that for key organs such as the liver, stomach, kidney, and spleen, IN delivery achieved higher brain-to-peripheral transduction ratios than IV delivery. These findings underscore the potential of IN delivery for noninvasive brain-targeted gene delivery with significant reductions in peripheral exposure.