Immune cells that target EBV may be driving MS

A type of immune cell that has received little attention in multiple sclerosis (MS) research may play an important role in how the condition develops.

A recent study found that some people living with MS had unusually high levels of virus-fighting CD8 T cells in the fluid surrounding the brain and spinal cord. Many of these cells appeared primed to recognise the Epstein Barr virus, known as EBV. The findings offer new insight into how this very common virus may be involved in MS.

MS is a condition in which the immune system mistakenly attacks healthy tissue in the brain and spinal cord. While the exact causes are still not fully understood, infection with EBV has emerged as one of the strongest known risk factors.

Most people are infected with EBV at some point in their lives. In many cases, it causes no serious illness and remains inactive in the body after the initial infection. However, a small number of people who have had EBV later go on to develop MS, and researchers are still working to understand why.

T cells are a type of immune cell that help the body fight infections. Each T cell carries a specific receptor that allows it to recognise a particular target, such as part of a virus. When the receptor binds to its target, the T cell becomes activated and multiplies, producing more cells with the same receptor to respond to the threat. When many T cells share the same receptor, it suggests the immune system is responding to something specific.

In this study, an international team of researchers analysed T cell receptors in blood samples and in cerebrospinal fluid, the fluid that surrounds the brain and spinal cord. The study involved 13 people with relapsing remitting MS or clinically isolated syndrome, which describes a first episode of MS-like symptoms, and five people who did not have MS.

The researchers looked for T cells that were more common in the cerebrospinal fluid than in the blood. This pattern suggests that these immune cells are actively responding within the brain and spinal cord. They identified more than two dozen groups of these expanded T cells. These were found in people with and without MS, but the specific targets recognised by the cells differed, suggesting that what they respond to may be important.

Most MS research has focused on CD4 T cells, which help coordinate immune responses. In this study, however, many of the expanded cells found in the cerebrospinal fluid were CD8 T cells. These cells directly destroy infected or abnormal cells and have been less studied in MS.

In several people living with MS, these expanded CD8 T cells carried receptors that specifically recognised EBV. Further analysis also showed increased activity of certain EBV related genes in these individuals, suggesting the virus may be active in the brain and spinal cord.

Taken together, the findings suggest that EBV may become active again in the brains of some people living with MS. This could prompt CD8 T cells to attack infected cells and potentially trigger inflammation.

If future research confirms this mechanism, it could help explain more clearly how EBV contributes to MS and support the development of treatments that target the virus. Several experimental therapies aimed at EBV are already being explored in MS research.

While more research is needed, this study adds to growing evidence that EBV plays a role in MS and highlights the importance of understanding how viral infections and the immune system interact.