Noninvasive Focal Transgene Delivery with Viral Neuronal Tracers in the Marmoset Monkey

We establish a reliable method for selectively delivering adeno-associated viral vectors (AAVs) across the blood -brain barrier (BBB) in the marmoset without the need for neurosurgical injection. We focally perturbed the BBB (-1 3 2 mm) in area 8aD of the frontal cortex in four adult marmoset monkeys using low -intensity transcranial focused ultrasound aided by microbubbles. Within an hour of opening the BBB, either AAV2 or AAV9 was delivered systemically via tail -vein injection. In all four marmosets, fluorescence -encoded neurons were observed at the site of BBB perturbation, with AAV2 showing a sparse distribution of transduced neurons when compared to AAV9. The results are compared to direct intracortical injections of anterograde tracers into area 8aD and similar (albeit sparser) long-range connectivity was observed. With evidence of transduced neurons specific to the region of BBB opening as well as long-distance tracing, we establish a framework for focal noninvasive transgene delivery to the marmoset brain.