New research presented at a scientific meeting adds to a growing body of evidence that a toxin produced by a common food bug may trigger multiple sclerosis, an inflammatory disease of the central nervous system.
Dr. Jennifer Linden, a microbiologist at Weill Cornell Medical College in New York, presented the research at the 2014 ASM Biodefense and Emerging Diseases Research Meeting that is taking place in Washington, D.C., this week.
Multiple sclerosis (MS) is an inflammatory disease, where the body's own immune system attacks and destroys healthy tissue in the central nervous system. The disease gradually disrupts the blood brain barrier (BBB) and destroys myelin, the protein that insulates the nerves in the spinal cord, brain and optic nerve and stops the electrical signals they convey from leaking out.
As the disease progresses, patients experience symptoms ranging from mild numbness in the arms and legs to paralysis and blindness.
According to the National Multiple Sclerosis Society, MS affects around 400,000 Americans, and with the exception of trauma, it is thought to be the most frequent cause of neurological disability that starts before old age.
Epsilon toxin may be a trigger for MS
MS is thought to result when genetically susceptible individuals are exposed to one or more environmental triggers. But while we have not yet firmly identified the triggers, there is increasing evidence, like this latest research, that a toxin called epsilon produced by certain strains of food bacteria is one of them, as Dr. Linden explains:
"We provide evidence that supports epsilon toxin's ability to cause BBB permeability and show that epsilon toxin kills the brain's myelin producing cells, oligodendrocytes; the same cells that die in MS lesions."
She and her colleagues also found that epsilon toxin targets other types of cells associated with MS inflammation, found in other parts of the central nervous system.
"Epsilon toxin may be responsible for triggering MS," concludes Dr. Linden.
Epsilon toxin produced by certain strains of food bug C. perfringens
Epsilon toxin is produced by certain strains of Clostridium perfringens, a bacterium that commonly causes foodborne illness in the United States.
According to the US Centers for Disease Control and Prevention (CDC), strains of C. perfringens that do not produce epsilon toxin cause nearly a million cases of foodborne illness each year.
C. perfringens is found in soil and contaminated undercooked meats, and previous studies have suggested the bacterium, and epsilon toxin, may play a role in triggering MS.
For instance, in October 2013, Dr. Linden and colleagues reported in the journal PLOS ONE that the soil bacterium might be a trigger for MS when they found C. perfringens type B - a strain that produces epsilon toxin - in a 21-year-old patient suffering from MS.
They further tested their hypothesis by studying the toxin in mice, to see which particular cells it targeted. They found that it targeted not only brain cells, but also cells in other parts of the central nervous system, producing effects only seen in MS patients, as Dr. Linden explains:
"Originally, we only thought that epsilon toxin would target the brain endothelium cells and oligodendrocytes; we just happened to notice that it also bound to and killed meningeal cells. This was exciting because it provides a possible explanation for meningeal inflammation and subpial cortical lesions exclusively observed in MS patients, but not fully understood."
When they tested 37 local food samples, the researchers found 13.5% of them contained C. perfringens and 2.7% contained the epsilon toxin gene.
If further studies confirm these findings, Dr. Linden says it suggests a vaccine that neutralizes the ability of epsilon toxin to trigger MS could stop the disease progressing, or perhaps even prevent it.
Written by Catharine Paddock PhD