Researchers Develop a Novel AAV Platform for Efficient, Specific, and Durable Microglial Gene Manipulation

Targeting microglia with adeno-associated viruses (AAVs) has long posed significant challenges due to low transduction efficiency, off-target expression, and inconsistent payload performance.

Recently, a research team led by Minmin Luo at the Chinese Institute for Brain Research (CIBR), Beijing, published an online research article in Neuron titled "A cross-species AAV platform for precise microglial interrogation." The study presents an integrated, Cre-independent AAV platform that achieves efficient, specific, and durable genetic manipulation of microglia.

By combining a microglia-specific regulatory element (MSRE), a high-yield AAV2/9.m capsid, a microRNA-mediated neuronal detargeting strategy, and a microglia-tailored codon optimization approach, this platform establishes a versatile, cross-species toolkit for microglial research.

Microglia serve as the resident immune cells of the central nervous system (CNS), playing pivotal roles in maintaining brain homeostasis and modulating the progression of neurological disorders. In the healthy brain, microglia constantly survey the parenchyma and support neural circuit function through synaptic pruning, clearance of cellular debris, and trophic support. In response to injury or disease, microglia adopt activated states that promote pathogen elimination, tissue repair, and neuroinflammatory signaling.

While beneficial in acute contexts, sustained or dysregulated microglial activation fuels chronic neuroinflammation and drives neurodegeneration, brain tumors, and other neurological conditions. Consequently, tools enabling precise and reliable genetic access to microglia are essential for dissecting their functional biology and developing targeted therapeutic interventions.

Figure 1. Schematic diagram of the mechanism. (Yu F, et al., 2026)

To address these hurdles, the researchers engineered an integrated, Cre-independent AAV platform incorporating:

• A compact, 446-bp microglia-specific regulatory element (MSRE)
• A high-yield AAV2/9.m capsid
• MicroRNA-mediated neuronal detargeting
• A microglia-tailored codon optimization framework

Following direct intracranial delivery, the optimized vectors achieved robust, long-term transgene expression with over 90% microglial specificity across multiple brain regions in mice, including Alzheimer's disease models.

Furthermore, facilitated by doxorubicin-assisted delivery, the platform enabled highly efficient and selective microglial targeting in rats, rhesus macaques, and ex vivo human brain slices. Codon optimization allowed the expression of historically challenging functional payloads—enabling calcium imaging, chemogenetic modulation, and CRISPR-Cas9-mediated genome editing. This cross-species toolkit provides a powerful, versatile resource for interrogating microglial biology and developing targeted therapeutic strategies.