For decades, gene therapy for neurological disease has been constrained by two problems: getting therapeutic genes into the brain and ensuring they reach the cells that matter. The blood-brain barrier excludes most treatments delivered through the bloodstream, while viral vectors that do enter the central nervous system often lack the precision needed to selectively target disease-relevant cell populations.
Researchers at the University of Rochester have now published a strategy that tackles both challenges simultaneously. The team developed engineered adeno-associated virus (AAV) vectors designed to preferentially infect human glial cells and paired them with a delivery approach that exploits the brain's own glymphatic transport system. This technique enabled widespread gene delivery throughout the brain while minimizing exposure to peripheral organs, potentially opening new therapeutic avenues for disorders including progressive multiple sclerosis, Huntington's disease, and inherited white matter diseases.
"You need a way to get therapies into the brain selectively and efficiently, and you need vectors that can deliver those therapies to the right cells once they get there," said Steve Goldman, study lead and neuroscientist at the University of Rochester Medicine Center for Translational Neuromedicine, in the press release. "This work addresses both challenges simultaneously."
Shifting the focus from neurons to glia
Many neurological diseases have historically been viewed primarily as disorders of neurons. However, growing evidence suggests that dysfunction in glial cells also plays a central role in disease progression.
Among the most important of these cells are glial progenitor cells, which can generate oligodendrocytes and astrocytes throughout life. In healthy brains, these progenitors help maintain white matter by replacing damaged oligodendrocytes that produce myelin. But in diseases including progressive multiple sclerosis, Huntington's disease, cerebral palsy-associated white matter injury, and some psychiatric disorders, these progenitor cells fail to mature into functional myelin-producing cells.
That failure leaves damaged white matter unable to repair itself, contributing to progressive neurological decline despite the presence of cells theoretically capable of regeneration.
"Over the last decade, we've learned that many neurological disorders involve glial dysfunction as a major driver of disease," Goldman said. "That realization has created an urgent need for tools that can safely and efficiently deliver therapies to these cells throughout the brain."
Engineering vectors for human glial cells
The researchers first addressed the challenge of cellular targeting by engineering a library of modified AAV5 vectors. Each contained small changes to its outer protein shell, or capsid, which determines the types of cells a virus can infect.
Rather than screening these vectors using conventional cell culture systems, the team evaluated them in mice whose brains had been transplanted with human glial progenitor cells. This allowed the researchers to identify viral variants under conditions that more closely reflected the biology of the human brain.
"Human cells display different molecular signatures than mouse cells, and cells behave differently in the brain than they do in a dish," Goldman said. "By selecting vectors under biologically relevant conditions, we were able to identify candidates with a strong preference for human glia."
The optimized vectors showed preferential infection of human glial progenitor cells and their differentiated descendants, including astrocytes and oligodendrocytes, while exhibiting relatively little transduction of peripheral tissues.
Turning the glymphatic system into a delivery route
Designing a glia-targeting vector solved only part of the problem. Therapeutic genes still needed to be distributed broadly throughout the brain.
Instead of attempting to force viral vectors across the blood-brain barrier through the circulation, the researchers took advantage of the glymphatic system, a network of cerebrospinal fluid channels that naturally circulates fluid through brain tissue and clears metabolic waste.
The team injected the engineered vectors into the cisterna magna, a cerebrospinal fluid-filled cavity at the base of the brain, and used a hypertonic treatment to enhance fluid movement through glymphatic pathways. This enabled the vectors to spread extensively throughout brain tissue while largely bypassing the blood-brain barrier.
Because the vectors remained concentrated within the central nervous system, the strategy also substantially reduced delivery to peripheral organs such as the liver, which is frequently associated with dose-limiting toxicity in systemic AAV gene therapy.
Broad potential across neurological disorders
The platform could have broad applications across neurological diseases driven by glial dysfunction or white matter degeneration. Among the most immediate opportunities are pediatric lysosomal storage disorders and other inherited diseases in which glial cells lack essential enzymes. In these conditions, widespread gene replacement throughout the brain could potentially alter disease progression.
"These are diseases where the biological target is well defined," Goldman said. "If you can deliver the corrective gene broadly throughout the brain, there is a real opportunity to change the course of disease."
Beyond this specific platform, the study also establishes a workflow for developing future CNS-targeted vectors. Goldman and colleagues are now exploring AI approaches to design viral capsids with tailored cell-targeting properties, potentially accelerating the creation of next-generation gene therapies for specific neurological diseases.
"We envision a future in which vectors can be designed for specific diseases and specific cell populations," Goldman said. "This study shows that by combining targeted vector engineering with glymphatic delivery, we can begin to build that future."
