The Off-the-Shelf Nanoparticles Programming T Cells In Vivo to Halt Multiple Sclerosis

Scientists have engineered targeted lipid nanoparticles that program a patient’s own T cells inside the body, successfully wiping out the specific, virus-activated immune cells responsible for multiple sclerosis while leaving healthy immune defences intact.

The Giant Problem

The Epstein-Barr virus infects over 90% of adults worldwide, usually harmlessly. In some people, however, B cells carrying the virus begin producing antibodies against a viral protein called EBNA1. Because EBNA1 closely resembles proteins found on human brain tissue, these overactivated B cells cross into the central nervous system and spur T cells into attacking the body's own nerve sheaths. To stop this assault, doctors frequently prescribe monoclonal antibodies like ocrelizumab. These drugs carpet-bomb the immune system, destroying virtually every CD19 or CD20 B cell in sight. While this slows nerve damage, it strips away long-term immunological memory. Patients on continuous B-cell depletion face elevated risks of severe, potentially fatal bacterial and viral infections. Furthermore, conventional CAR-T therapy, which could theoretically target specific cells, requires extracting a patient’s blood, modifying T cells in a specialised lab over several weeks, and reinfusing them at enormous expense.

The Science

Instead of harvesting cells or wiping out an entire arm of the immune system, a team led by Xinyi Jiang at Shandong University packaged genetic instructions into tiny fat bubbles that seek out T cells inside the body. Think of these lipid nanoparticles as homing envelopes. On their outer surface, researchers attached antibodies that lock onto CD7, a marker uniquely present on circulating T cells. Inside, they packed circular RNA—a durable, loop-shaped genetic molecule—encoding a synthetic receptor engineered to spot EBNA1-reactive B cells. Once injected into the bloodstream, the nanoparticles bind to T cells and drop off their circular RNA cargo. The T cells temporarily express this new receptor on their outer membrane, turning them into precision interceptors. Because the instructions are carried on circular RNA rather than DNA integrated into the genome, the CAR receptor expression peaks within two days and naturally clears over two weeks, preventing long-term, uncontrolled T-cell proliferation. In dish experiments, these in situ CAR-T cells destroyed anti-EBNA1 B cells extracted from diseased mice with zero activity against healthy B cells. When tested in living mice, a single IV infusion reprogrammed roughly 4.7% of circulating T cells at peak levels, effectively clearing pathogenic B cells from both the bloodstream and the spinal cord.

How They Did It

The researchers used microfluidic mixing to assemble lipid nanoparticles composed of ionizable lipids, cholesterol, and helper lipids encapsulating the circular RNA. They then chemically conjugated anti-CD7 antibodies to the nanoparticle surface to ensure high-affinity targeting of T lymphocytes.

Why You Should Care

This strategy proves that CAR-T cells can be generated directly inside a living organism to treat autoimmune conditions, completely skipping the multi-week, high-cost manufacturing pipeline of traditional cell therapy. Because the treatment preserves healthy B cells, treated mice maintained normal antibody production and easily survived high-dose Staphylococcus aureus bacterial challenges that killed half of the mice receiving broad B-cell depletion therapy. If translated to humans, this platform could offer an off-the-shelf IV injection for multiple sclerosis that restores neurological function without forcing patients into lifetime isolation to avoid standard infections. Clinical trials remain necessary before human testing can begin.