A vaccine that’s typically used to prevent tuberculosis outside of the United States could also prevent multiple sclerosis (MS) in people who are in the beginning stages of the disease, a study reported in Neurology.

Researchers looked at 73 patients who showed early signs of MS, which include numbness, vision problems and imbalance along with MRI scans indicating early neurological damage caused by the disease. According to the authors, half of all patients at this early stage of MS, known as the clinically isolated syndrome, usually develop a “clinically definite” form within two years of diagnosis while 10 percent remain unchanged. Importantly, they add, this first episode is still “generally reversible.”

The opportunity to treat MS at this early stage led researchers to test the Bacille Calmette-Guérin (BCG) vaccine. MRI scans hinted at its potential to treat patients with MS symptoms that come and go, and it was proven to be safe. At the onset of the study, 33 participants received one injection of the vaccine while the rest got a placebo. After six months of brain scans, all the participants received another MS drug called interferon beta-1a for one year, followed by whatever MS drug their neurologist prescribed. The patients were evaluated for definite MS for five years, starting at the vaccine (or placebo) injection.

Six months into the study, patients who received the vaccine — a weakened strain of bacteria — had a lower-than-average number of brain lesions (three) that are indicative of MS compared with the placebo group (seven). No major differences in side effects were noticed between the two groups by the end of the study. Altogether, 58 percent of the vaccinated group hadn’t developed MS, which was almost twice that of the placebo groups (30 percent).

"These results are promising, but much more research needs to be done to learn more about the safety and long-term effects of this live vaccine," explained study author Giovanni Ristori, of Sapienza University of Rome, in a press relese. "Doctors should not start using this vaccine to treat MS or clinically isolated syndrome." Still, the findings “demonstrate the feasibility and possible benefit of safe, inexpensive, and handy approaches immediately after the first demyelinating episode [of the disease],” the authors conclude in their study.

MS is an inflammatory disease that damages the insulating sheath — myelin — which wraps around nerve cells in the brain and spinal cord. Ristori and colleagues were uncertain as to how BCG is able to quell the autoimmune response from which MS patients suffer. One possibility they considered was the “hygiene hypothesis,” which blames “Western habits” for facilitating the development of immune disorders by restricting exposure early in life. In the case of MS, the BCG bacteria’s positive impact might indicate that the more immunologically challenging environment of our less industrialized past might have kept our immune cells too busy to commit friendly fire.

In an accompanying editorial, Dennis Bourdette and Robert Naismith elaborated on how hygiene might play a role in the incidence of MS: “[B]etter sanitation and common use of disinfectants and antibiotics may account in part for the increased prevalence of MS and other autoimmune diseases in North America and much of Europe, compared with Africa, South America, and parts of Asia,” they write. “If true, might we harness this natural phenomenon to develop new treatments for MS?”

Source: Ristori et al. Effects of Bacille Calmette-Guérin after the first demyelinating events in the CNS. Neurolgy. Published ahead of print Dec. 4, 2013