AAV Capsid-Promoter Interactions in the Brain Translate from Rat to the Non-Human Primate.

Recently, we established an AAV9 capsid-promoter interaction that directly determined cell-specific gene expression across two synthetic promoters, Cbh and CBA, in the rat striatum. The present studies not only expand this capsid-promoter interaction to include another promoter in the rat striatum, but also establishes AAV capsid-promoter interactions in the non-human primate brain. When AAV9 vectors were injected into the rat striatum, the minimal synthetic promoter JetI drove GFP gene expression predominantly in oligodendrocytes. However, similar to our previous findings, the insertion of 6 alanines into VP1/VP2 of the AAV9 capsid (AAV9AU) significantly shifted JetI-driven GFP gene expression to neurons. In addition, previous retrograde tracing studies in the non-human primate brain also revealed the existence of a capsid-promoter interaction. When rAAV2-Retro vectors were infused into the frontal eye field (FEF) of rhesus macaques, local gene expression was prominent using either the hybrid chicken beta actin (CAG) or human synapsin (hSyn) promoters. However, only the CAG promoter, not the hSyn promoter, led to gene expression in the ipsilateral claustrum and contralateral FEF. Conversely, infusion of rAAV2-retro-hSyn vectors, but not rAAV2-retro-CAG, into the macaque superior colliculus led to differential and selective retrograde gene expression in cerebellotectal afferent cells. Clearly, this differential promoter/capsid expression profile could not be attributed to promoter inactivation from retrograde transport of the rAAV2-Retro vector. In summary, we document the potential for AAV capsid/promoter interactions to impact cell specific gene expression across species, experimental manipulations and engineered capsids, independent of capsid permissivity.