A new study suggests a cancer therapy that uses genetically altered immune cells to home in on cancer cells and destroy them can be used to eliminate unwanted cells that cause autoimmune diseases such as multiple sclerosis. The findings extend the powerful tool of immunotherapy to a class of diseases that are often debilitating and difficult to treat.

At the heart of the cancer therapy, known as CAR-T, are the immune system’s T cells. T cells respond to threats such as bacteria, viruses, and cancerous cells by coordinating an immune assault and killing foreign organisms and infected or cancerous cells. But every once in a while, T cells mistake healthy cells for infected cells and turn their weapons on the body’s own cells and tissues, triggering an autoimmune disease. 

MS is marked by rogue T cells that trigger the destruction of myelin, the protective covering over nerves. Immunosuppressive drugs can quash the self-destructive activity of rogue T cells, but such drugs also suppress helpful T cells and put people at risk of severe infections.

In CAR-T therapies, doctors take a patient’s own T cells, modify them to recognize and vigorously attack his or her specific cancer, and then put them back in the body on a seek-and-destroy mission. Inspired by this approach, the researchers at Washington University School of Medicine in St. Louis set out to create CAR-T cells equipped to seek out and destroy the rogue T cells that cause MS.

First, the researchers made some bait. They designed a molecule that combined a fragment of a protein found in myelin with a protein that activates T cells. Only T cells that target myelin would respond to this hybrid molecule. Then, they loaded the bait molecule onto a kind of T cell known as killer T cells. Any rogue T cells that took the bait would be eliminated by the killer T cells.

To test the idea, the researchers turned to mice with an MS-like condition. Treating such mice with the engineered CAR-T cells prevented disease in those that had yet to develop problems, and reduced signs of disease in those that were already showing neurological effects.

The core of the CAR-T approach is that by swapping out the protein fragment in the bait molecule, killer T cells can be redirected toward different rogue immune cells to treat different diseases. However, the results of mouse model studies sometimes do not translate to humans and may be years away from being a marketable treatment.

The findings were published in the journal Science Immunology.