Trial hints that a vaccine used to prevent tuberculosis may open a new treatment approach to preventing or treating MS
Researchers in Italy provide preliminary evidence that a vaccine used in some parts of the world to prevent tuberculosis, called Bacille Calmette-Guérin (BCG), may help people who exhibit early signs of possible MS from developing full-blown, definite MS. Additional, larger trials would be needed to determine the safety and effectiveness of this approach. Dr. Giovanni Ristori and colleagues at the University of Rome and other institutions recently reported their results in Neurology. The study was funded by the Italian Ministry of Health, the Italian MS Foundation, and other agencies.
Background: MS often begins with an initial neurological attack called “clinically isolated syndrome” (CIS). Many with CIS experience additional attacks and are eventually diagnosed with clinically defined MS. Dr. Ristori and colleagues conducted a small clinical study to see if the BCG vaccine could prevent people with CIS from developing clinically definite MS. BCG is a vaccine that is prepared from a strain of weakened bovine (cow) tuberculosis bacteria, and while commonly used in developing countries, is not approved for preventing tuberculosis in the United States.
The study: The investigators performed a double-blind, placebo-controlled clinical trial in which 73 participants with CIS received either the BCG vaccine or a sham injection (no vaccine), then after 6 months all participants received one year of interferon beta-1a, which was followed by whatever disease-modifying therapy recommended by their physicians. Participants and researchers were unaware of the assignment to a particular group. All told, 33 people received a single injection of the vaccine and 40 received the sham injection.
At six months after the injection, those who received the real vaccine had fewer active brain MRI lesions (an average of 3.1 lesions) consistent with MS, compared to those who had received the sham injections (an average of 6.6 lesions), suggesting a decrease in disease activity. Five years after completing the study, those who had been vaccinated were less likely to have experienced relapses, and the diagnosis of clinically definite MS, than those who received the sham injection: 58% of vaccinated participants were free of relapses compared to 30% of sham-injected participants. No adverse events were seen except an injection site reaction in three vaccinated people. No major adverse events were noted.
How BCG vaccination helped to prevent MS relapses in this study is not known. One idea is that vaccination alters the function of the immune system to decrease the ability of the immune system to attack the brain. In this study, the contribution of disease-modifying therapies in the results is unclear.
Comment: This small study provides intriguing evidence for a potentially beneficial effect of BCG vaccination in curbing MS. In an accompanying editorial, Drs. Dennis Bourdette (Oregon Health & Science University) and Robert Naismith (Washington University) note that the safety of repeated administration of this live vaccine is unclear, and that clinicians should not use BCG to treat CIS or MS at this time. Larger trials of this or a similar approach and additional research into the reasons for the vaccination’s impact may lead to the development of a new strategy for preventing or treating MS.