Abstract
Recently, AAV2.retro, a new capsid variant capable of efficient retrograde transport in brain, was generated in mice using a directed evolution approach. However, it remains unclear to what degree transport will be recapitulated in the substantially larger and more complex nonhuman primate (NHP) brain. Here, we compared the biodistribution of AAV2.retro with its parent serotype, AAV2, in adult macaques following delivery into the caudate and putamen, brain regions which comprise the striatum. While AAV2 transduction was primarily limited to the injected brain regions, AAV2.retro transduced cells in the striatum and in dozens of cortical and subcortical regions with known striatal afferents. We then evaluated the capability of AAV2.retro to deliver disease-related gene cargo to biologically-relevant NHP brain circuits by packaging a fragment of human mutant HTT, the causative gene mutation in Huntington’s disease. Following intra-striatal delivery, pathological mHTT-positive protein aggregates were distributed widely among cognitive, motor, and limbic cortico-basal ganglia circuits. Together, these studies demonstrate strong retrograde transport of AAV2.retro in NHP brain, highlight its utility in developing novel NHP models of brain disease and suggest its potential for querying circuit function and delivering therapeutic genes in the brain, particularly where treating dysfunctional circuits, versus single brain regions, is warranted.
Highlights
AAV2.retro, a new capsid variant capable of efficient retrograde transport in brain, was generated in mice using a directed evolution approach
In order to investigate the retrograde transport capability of AAV2.retro in primate brain, naïve adult rhesus macaques were injected with AAV2.retro-eGFP bilaterally into the head of the caudate nucleus (80 μl at one injection site) and the putamen (150 μl over 2 injection sites spread apart by 4 mm). eGFP expression was driven from the human cytomegalovirus (CMV) promoter
Serum samples from all animals were tested for anti-AAV2 neutralizing antibodies prior to surgery, and animals were selected only if they had less than 50% inhibition of transduction when serum was diluted to 1:20
Summary
AAV2.retro, a new capsid variant capable of efficient retrograde transport in brain, was generated in mice using a directed evolution approach. AAVs have been used to create animal models of CNS disorders by delivering pathogenic constructs to brain regions of interest, such as the overexpression of α-synuclein in the striatum that results in progressive neurodegeneration and motor phenotypes characteristic of Parkinson’s disease (PD)[22,23,24], or of expanded glutamine-encoding CAG repeats to create a striatal degeneration model of Huntington’s disease (HD)[22,25,26], or of amyloid beta to reproduce features of Alzheimer’s disease (AD)[27,28] Despite these recent successes, intra-parenchymal applications of AAVs in the CNS remain largely confined to the injected tissue region, or sub-region, because of restricted spread and limited capacity for anterograde and/or retrograde transport. One way to achieve this is with an AAV capsid capable of strong synaptic transport
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