多発性硬化症(MS）は食中毒原因菌で腸内細菌でもあるウェルシュ菌が産生する毒素が引き金になる?@アメリカの研究

わたしたちの身体の神経繊維は、さまざまな刺激を電気的信号の形で伝達している。健康な神経繊維にはサヤ(髄鞘)が被さって保護しているもの(有髄線維)がある。有髄線維は、サヤのない神経線維に比べて、電気的信号の伝達が早い。ところが、この
　サヤが壊れてしまう病気
が
　多発性硬化症(MS)
だ。今のところは原因不明、日本では難病に指定されている。
サヤが破壊される場所によって症状はさまざまで、視力や運動に深刻な影響を与えたりする。
日本では稀な病気だが、欧米の白人の間では多い。自己免疫と関係しているのではないか、と考えられている。遺伝はしない。

この多発性硬化症が、
　ウェルシュ菌の産生する毒素が引き金になるのではないか
というワイル・コーネル医科大学のチームによる研究報告が、アメリカ微生物学会で先週23日に発表された。アメリカNBCのニュースより。

Foodborne toxin could trigger MS, studies suggest
JoNel Aleccia

Add another clue to the mystery of multiple sclerosis: Scientists say a poison produced by common foodborne germs could be a trigger for the debilitating autoimmune disorder that affects 400,000 Americans.

Researchers at Weill Cornell Medical College in New York have discovered that a toxin made by the bacterium Clostridium perfringens — responsible for a million cases of food poisoning in the U.S. each year — appears to attack the cells associated with MS.

“What we’ve shown is the toxins target the cells that are targeted in MS,” said Jennifer Linden, a Weill Cornell researcher who’s presenting findings Tuesday at a meeting of the American Society for Microbiology.

Her research also showed that about 13 percent of a small sample of food products harbored C. perfringens bacteria, and nearly 3 percent were positive for the toxin linked to MS.

It’s too early to suggest that MS is caused by food poisoning, but it does raise the possibility that the C. perfringens bacteria could be involved in activating the disease, said Bruce F. Bebo, associate vice president of discovery research for the National Multiple Sclerosis Society.

“To me, if you were going to design a trigger for this disease, this would really fit the mold really well,” Bebo said.

Specifically, it’s the epsilon toxin, one of 12 protein toxins produced by C. perfringens bacteria. Not only does the toxin attack the brain’s blood-brain barrier, it also kills the brain’s myelin-producing cells, the same cells that die in MS lesions, Linden said.

MS is a disease in which the fatty sheath around the nerves of the brain and spinal cord, called myelin, is destroyed, leading to a wide range of symptoms.
MS is thought to be caused by an environmental trigger, something scientists have sought for years, Bebo said. But the new theory from Weill Cornell’s team led by Dr. Timothy Vartanian, a professor of neurology and neuroscience, is particularly promising, Bebo said.
Most cases of C. perfringens food poisoning in people are caused by the A strain of the bacteria, one of five types. The B and D types, which produce the epsilon toxin, have rarely been seen in people. But last year, Weill Cornell researchers reported that they’d discovered the B strain in a 21-year-old MS patient, proving infection was possible.
They also examined banked blood and spinal fluid samples from MS patients and healthy controls and found that the MS patients were 10 times more likely to show evidence of antibodies signaling they’d previously been exposed to the epsilon toxin.

If the link with MS is proven, it’s possible that a vaccine or drug or probiotic treatment could be developed to destroy the C. perfringens B and D bacteria, which make the toxin, Vartanian has said.

まだ、
　ウェルシュ菌が犯人
とまでは言えないが、少なくとも
　ウェルシュ菌のつくる毒素が多発性硬化症を引き起こす可能性は高まった
ということになる。
ウェルシュ菌の食中毒というと、蛋白質の豊富な食品、特に食肉が汚染されて起きることが多い、という印象がある。なるほど
　欧米の肉食の盛んな地域での発生が多い
けれども
　日本では稀な病気
だ。これは
　食生活の違いが、発病率の違いに影響しているのか
と思うよね。

まだ、研究は始まったばかりだけど、多発性硬化症は実に厄介な病気、治療につながる発見ってことになるといいな。