People with early signs of multiple sclerosis who were treated with a vaccine used to prevent tuberculosis were less likely to get sick than patients who weren’t vaccinated, according to an early study.
Researchers recruited 73 people who had a first episode suggestive of multiple sclerosis, an autoimmune disease that can be difficult to diagnose. Five years later, almost 60 percent of those given the TB vaccine hadn’t developed multiple sclerosis compared with a third of the group that received a placebo instead, according to a study today in the journal Neurology.
The research supports the hygiene hypothesis, which suggests people have become so clean they suppress natural development of the immune system, leading to a surge in diseases in which these infection-fighting cells attack healthy tissue in the body, said Dennis Bourdette, who wrote an editorial accompanying the study. The tuberculosis vaccine may wake the regulatory arm of the immune system, helping to steer the body’s killer cells away from the neurons it attacks in MS.
“The interesting thing was that the single injection affected the course of the recipients for up to five years after they received it,” Bourdette, the chairman of neurology at Oregon Health and Science University in Portland, said in a telephone interview.
About 2.3 million people worldwide have multiple sclerosis, according to the National Multiple Sclerosis Society, a patient advocacy group. The disease destroys neurons when the immune system mistakenly attacks the protective coating on nerve fibers, disrupting the body’s communications. Eventually, this leads to blurred vision, poor balance and coordination, problems with speaking, tremors, fatigue and paralysis.
In the study, patients received either a Bacillus Calmette-Guérin vaccine or a placebo. Both groups were given interferon, a standard MS treatment, for 12 months. After 18 months, patients took disease-modifying therapies as prescribed by their doctors. Fewer people who received the vaccine were diagnosed with MS and more of them didn’t have to take disease-modifying drugs than those in the control group, said the researchers led by Giovanni Ristori, from the Center for Experimental Neurological Therapies at the University of Rome.
Though the approach looks promising, the BCG vaccine probably isn’t safe for widespread use, Bourdette said. It isn’t recommended for use against TB in the U.S. because the risk of TB infection is low. The vaccine contains live bovine tuberculosis bacteria, which can cause infections after an injection.
That’s particularly true for people whose immune system is suppressed, he wrote in the editorial published with the study. The typical treatment for multiple sclerosis involves suppressing the immune system, which means that MS patients on drugs may be more at risk for a TB infection.
BCG shouldn’t be used off-label to treat MS, since its safety is unknown, he wrote. It may be safer to use a vaccine with dead TB bacteria, or only duplicating parts of the bacteria for a new vaccine.
It’s not clear how the BCG vaccine works in multiple sclerosis, Bourdette said. It may awaken regulatory parts of the immune system, stopping rogue cells from attacking myelin. It may also lower inflammation, which can damage neurons, too.
Previous studies have shown that stimulating the immune system with parasites also had protective effects. A 2007 study in Argentina found that MS patients who were infected with schistosoma mansoni, a parasite found in poor countries, suffered fewer relapses that those who weren’t. A group of five MS patients who were dosed with pig whipworm eggs had fewer signs of MS while being treated, compared with before and after treatment, according to a 2011 study published in Multiple Sclerosis Journal.
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