Systemic AAV6-synapsin-GFP administration results in lower liver biodistribution, compared to AAV1&2 and AAV9, with neuronal expression following ultrasound-mediated brain delivery

Abstract

Non-surgical gene delivery to the brain can be achieved following intravenous injection of viral vectors coupled with transcranial MRI-guided focused ultrasound (MRIgFUS) to temporarily and locally permeabilize the blood–brain barrier. Vector and promoter selection can provide neuronal expression in the brain, while limiting biodistribution and expression in peripheral organs. To date, the biodistribution of adeno-associated viruses (AAVs) within peripheral organs had not been quantified following intravenous injection and MRIgFUS delivery to the brain. We evaluated the quantity of viral DNA from the serotypes AAV9, AAV6, and a mosaic AAV1&2, expressing green fluorescent protein (GFP) under the neuron-specific synapsin promoter (syn). AAVs were administered intravenously during MRIgFUS targeting to the striatum and hippocampus in mice. The syn promoter led to undetectable levels of GFP expression in peripheral organs. In the liver, the biodistribution of AAV9 and AAV1&2 was 12.9- and 4.4-fold higher, respectively, compared to AAV6. The percentage of GFP-positive neurons in the FUS-targeted areas of the brain was comparable for AAV6-syn-GFP and AAV1&2-syn-GFP. In summary, MRIgFUS-mediated gene delivery with AAV6-syn-GFP had lower off-target biodistribution in the liver compared to AAV9 and AAV1&2, while providing neuronal GFP expression in the striatum and hippocampus.

Incisionless targeted adeno-associated viral vector delivery to the brain by focused ultrasound-mediated intranasal administration

“…Indeed, the ddPCR quantification showed that FUS-BBBD increased the EGFP DNA concentration by 5-fold compared to the IN only ( Figure 2 f). Previous studies of FUS-BBBD delivery of AAVs demonstrated successful gene expression by immunofluorescence staining to amplify the fluorescence signal 32 , 48 , 49 or by utilizing AAV9 vectors 14 , 15 , 48 which are known to be BBB permeable. 16 , 32 FUS-BBBD broadened previous options for systemic AAV delivery to the brain to include serotypes that cannot innately cross the BBB.…”

“…Previous studies of FUS-BBBD delivery of AAVs demonstrated successful gene expression by immunofluorescence staining to amplify the fluorescence signal 32 , 48 , 49 or by utilizing AAV9 vectors 14 , 15 , 48 which are known to be BBB permeable. 16 , 32 FUS-BBBD broadened previous options for systemic AAV delivery to the brain to include serotypes that cannot innately cross the BBB. To achieve effective gene transduction, FUS-BBBD requires either the use of ultrasound parameters that are close to the limits that damage tissues 50 , 51 , 52 or overdosed AAV injection.…”

“…The experimental procedure for FUS-BBBD delivery of AAVs was the same as in FUSIN delivery, with the only difference being that the AAV5-hSyn-EGFP was administered by IV injection following a similar protocol used by others for FUS-BBBD delivery of AAVs. 32 , 33 In brief, the AAV5-hSyn-EGFP was injected into the mouse, followed by microbubble injection and then FUS sonication targeting at the cortex. The microbubble dose and FUS parameter were kept the same as those used in FUSIN delivery.…”

Non-invasive optogenetics with ultrasound-mediated gene delivery and red-light excitation

“…To facilitate viral transduction and gene expression, new generations of AAV serotypes are being designed, in an effort to enhance FUS-mediated delivery across the BBB and neuronal tropism, while limiting non-specific transduction [37]. Out of the natural AAV serotypes, AAV6 has been shown to result in lower liver biodistribution compared to a mosaic AAV1&2 and AAV9 vectors following intravenous administration [38]. A limited number of studies have established viral transduction in larger animal models, like non-human primates (NHPs), using capsid mutants such as AAV-PHP.…”

Transgene distribution and immune response after ultrasound delivery of rAAV9 and PHP.B to the brain in a mouse model of amyloidosis

“… 51 A neuron-specific promoter, such as the synapsin promoter, could therefore be used to specifically favor transgene expression in neurons and thereby reduce the potential of an immune response and ensure long-term transgene expression upon gene delivery to the brain either using PHP.B or rAAV delivered by MRIgFUS. 14 , 52 , 53 , 54 , 55 …”