June 25, 2014
Italian researchers explore tuberculosis vaccine as potential treatment approach to preventing or treating MS
Immune systems are designed to protect the body against foreign invaders, such as viruses and bacteria. An autoimmune disease is a condition in which the immune system recognizes tissues in the body as foreign invaders and attacks them in the same way they would the viruses and bacteria. This can lead to a variety of symptoms depending on the tissues that are being harmed.
In MS, the target of errant immune cells is myelin - a substance which coats the nerve cells in the brain, spinal cord, and optic nerve. Without myelin, nerves are not properly insulated and can no longer communicate with one other efficiently. Ultimately this leads to mobility impairment, speech problems, blurred vision and fatigue among other physical challenges.
MS often begins with an initial neurological episode called “clinically isolated syndrome” or CIS. Many people with CIS go on to develop full-blown MS or “clinically definitive MS”, while approximately 10% of individuals with CIS remain disease free. Many studies are currently underway to determine whether treatment of CIS can prevent or delay the onset of MS. A research team from Italy recently published one approach in the journal Neurology, which involves the use of a tuberculosis (TB) vaccine called Bacille Calmette-Guérin (BCG) to curb the effects of the immune system in people displaying early signs of MS.
Dr. Giovanni Ristori and colleagues recruited 73 people aged 18-50 who displayed a first clinical episode suggestive of MS. They randomly assigned some of the people to the treatment group, and the others to the control group. The treatment group received the BCG vaccine, while the control group received a sham injection (no vaccine). All participants underwent MRI scans for 6 months after the administration of the vaccine, after which they began treatment with interferon beta-1a for one year. After treatment with interferon beta-1a, participants followed their usual treatment regimen prescribed by their neurologists, and were analyzed after 5 years. The study was conducted in a double-blinded fashion. This means that neither the study participants nor the investigators knew who received the vaccine and who received a sham injection.
Compared with placebo, treatment with BCG vaccine reduced the number of active brain lesions as shown on the monthly MRI scans, suggesting a decrease in disease activity. After 5 years, those who had received the vaccine experienced less relapses and a lower risk of converting to clinically definite MS, than those who received the sham injection. More people who received the vaccine did not have to continue taking disease-modifying therapies than those who received a sham injection. The procedure also appeared to be safe with no serious adverse events reported except for an injection site reaction in three vaccinated people.
“BCG vaccination appears to have early beneficial effects and possible long-term effectiveness in people with CIS, supporting previous observations in people with MS” - Dr. Ristori
The exact mechanism behind the effects of BCG vaccination in MS is unclear at this stage, but researchers propose one idea that involves the diversion of harmful immune cells away from the brain. This study also provides interesting support for the Hygiene Hypothesis, which states that ‘Western habits’ have created an ultra-clean environment that suppresses natural development of the immune system. Thus treatments like the BCG vaccine may wake up the immune system, preventing it from attacking the body’s own tissues.
In an accompanying editorial, Drs. Dennis Bourdette and Robert Naismith note that the safety of repeated administration of this vaccine is uncertain, and that clinicians should not use BCG to treat CIS or MS at this time. Other considerations include the fact that this vaccine is not widely available in developed countries, and contains a live bovine (cow) tuberculosis bacteria which can cause infection. Full evaluation of the long-term effects, safety profile, and appropriate dosage of the BCG vaccine in MS will require additional, larger clinical trials.
RISTORI G. et coll. « Effects of Bacille Calmette-Guérin after the first demyelinating event in the CNS », Neurology, 2014 Jan; 82(1):41-8.