MS is a chronic disease of the central nervous system (CNS) that disrupts nerve signals between the brain and the rest of the body.
While nearly 1 million people in the United States over the age of 18 years live with a diagnosis of MS, and 2.3 million people globally have the condition, its causes remain a mystery. Women are two to three times more likely than men to receive an MS diagnosis, and most people with MS are 20–50 years old.
The symptoms, which may come and go or worsen, include weakness, blurred vision, lack of coordination, imbalance, pain, memory lapses, mood changes, and — less commonly — paralysis, tremor, and blindness.
The flightiness of MS and the nonspecific nature of its symptoms make it difficult to diagnose, and there is currently no hope of a cure. However, there are certain drugs, commonly known as anti-B cell drugs, which help moderate attacks and delay the progression of disability.
Now, a new study by the University of Montreal Hospital Research Centre (CRCHUM) in Canada has shown a way of decelerating the progression of MS and possibly overcoming some of the health risks associated with traditional B cell treatments. The findings appear in Science Translational Medicine.
“B cell-directed therapies are effective in MS, but they deplete all B cells, and some patients develop cancers and opportunistic infections,” said Dr. Alexandre Prat, a researcher at CRCHUM, a professor at the University of Montreal, and holder of the Canada Research Chair in MS.
Experts believe MS to result from the immune system attacking healthy tissue in the CNS, causing damage that interferes with the body’s nerve signaling system.
Ordinarily, the blood-brain barrier shields the brain from elements that could damage it. So, for example, it keeps the immune system’s B lymphocytes, or B cells, from entering the brain.
However, in people with MS, this defense system no longer serves as a barrier, allowing large numbers of lymphocytes to invade the brain and attack the myelin sheath. The sheath normally serves to protect and insulate the nerve axons, or fibers, that enable the transmission of nerve signals.
The presence of B lymphocytes in cerebrospinal fluid is a classic marker of MS, and it is these cells that give MS its progressive nature.
“Keeping B cells outside of the brain by blocking their migration but retaining them in the blood could reduce MS symptoms and progression — without the infectious side effects because they are not depleted from the rest of the body.”
Dr. Alexandre Prat
A molecule that can alter the course of MS
Prat and fellow researchers at CRCHUM set out to show that by blocking a molecule called ALCAM (Activated Leukocyte Cell Adhesion Molecule), they could reduce the flow of B cells into the brain and, thereby, slow the progression of MS.
Working with mice and human cells in vitro, the study revealed for the first time that ALCAM, which B cells express at higher levels in people with MS, is what enables B cells to invade the brain via blood vessels.
The study showed that blocking ALCAM in mice lessens the flow of B cells to the brain and slows the progression of MS.
“We provide the proof of principle that B cell entry in the brain can be selectively targeted by ALCAM and that this leads to a reduced burden of disease in animal models of MS.”
Dr. Alexandre Prat
The researchers hope that by showing that the blocking of ALCAM is an effective way to tackle the flow of B cells to the brain and CNS, they have paved the way for a new generation of therapies to treat MS.
The average life expectancy of people living with MS is currently 7 years less than that of the general population, an improvement on the past thanks to treatment developments, better healthcare, and more healthful lifestyles.
So, what is next for the team? “To develop safe anti-ALCAM targeting medication for use in human MS,” Dr. Prat told Medical News Today.