A vaccine normally used to thwart the respiratory illness tuberculosis also
might help prevent the development of multiple sclerosis, a disease of the
central nervous system, a new study suggests.
In people who had a first episode of symptoms that indicated they might
develop multiple sclerosis (MS), an injection of the tuberculosis vaccine lowered
the odds of developing MS, Italian researchers report.
"It is possible that a safe, handy and cheap approach will be available
immediately following the first [episode of symptoms suggesting MS]," said
study lead author Dr Giovanni Ristori, of the Centre for Experimental
Neurological Therapies at Sant'Andrea Hospital in Rome.
But, the study authors cautioned that much more research is needed before
the tuberculosis vaccine could possibly be used against multiple sclerosis.
In people with MS, the immune system attacks healthy cells in the central
nervous system, which includes the brain and spinal cord.
First signs of MS
One of the first signs of MS is what's known as "clinically isolated
syndrome". Symptoms include numbing and problems with vision, hearing and
balance. About half of people who experience clinically isolated syndrome
develop MS within two years, Ristori said.
The study, published online in the journal Neurology, included 73
people who'd had clinically isolated syndrome. Thirty-three received the
tuberculosis vaccine and the remaining 40 were given a placebo, or dummy,
injection. The tuberculosis vaccine is a live vaccine called the Bacille
Calmette-Guerin vaccine, which isn't widely used in the United States. The same
vaccine also is being studied as a treatment for type 1 diabetes.
The participants had monthly MRI scans of their brains for the first six
months of the study to look for lesions associated with multiple sclerosis. For
the next year, they received a drug (interferon beta-1a) given to people with
MS. After that, they received the treatment recommended by their own
neurologist. After five years, the participants were re-examined to see if they
had developed MS.
After the first six months, the researchers found an average of about eight
brain lesions (a potential sign of MS) in people who received a placebo,
compared to an average of three lesions in those who received the vaccine.
After five years, 70% of those who received the placebo had developed MS,
compared to 42% of those given the vaccine, the researchers said. No major side
effects were reported during the study.
Ristori said it's not clear how the vaccine is protecting against multiple
sclerosis. "There seems to be complex, multiple effects on brain
inflammation," he said.
Because lesions were reduced in people who received the vaccine, Ristori
said, it might also be helpful for people who already have MS.
The authors of an accompanying journal editorial said this study's findings
lend support to the "hygiene hypothesis". This theory suggests that a
lack of infections during childhood may affect the development of the immune
system, and that vaccinating with a live vaccine may help induce a
"protective immunity" against MS.
Nicholas LaRocca, vice president of health care delivery and policy research
for the National Multiple Sclerosis Society, said this is the latest in a
number of studies that have looked at what environmental factors contribute to
the development of MS.
"What we're learning is that the immune system isn't a self-contained
entity, but that it has a lot of interactions with other things in the
body," LaRocca said.
"This study adds to what we know about MS," he said. "But
it's just one piece of a big puzzle."
For now, the editorial authors recommend against using the vaccine to treat
clinically isolated syndrome or full-blown MS because the long-term safety and
effectiveness of the treatment is unknown.
The tuberculosis vaccine often is given to infants and small children in
countries where the disease is common. US health officials recommend it only
when tuberculosis is likely.
Learn more about MS from the National Multiple Sclerosis Society.