December 4, 1999
By Barbara Turnbull
Toronto Star Staff Reporter
A team of Montreal scientists has regenerated injured spinal cords in mice with a new vaccine treatment.
Fifty-five per cent of the mice given the ``vaccine therapy'' recovered some movement in their limbs after having their spinal cords injured.
This new approach shows the animal's own immune system can be recruited to produce antibodies against molecules in the spinal cord that prevent regeneration, said the team's leader, Dr. Sam David of McGill University. It's an important milestone in the field of spinal cord injury and promises to be an excellent direction for future work toward a cure, he added.
More basic research is required before the method can be tried on humans in a clinical setting, he cautioned.
But the vaccine approach shows for the first time that a non-invasive treatment can be part of the cure for spinal cord injuries, David said.
Spinal cord research took on a new focus in 1995, the same year actor Christopher Reeve was left a quadriplegic after falling from his horse during an equestrian event.
Since then, the former Superman actor - who remains paralyzed from the neck down and can breathe only with the aid of a respirator - has led the campaign for more money to fund spinal cord research. He remains convinced he will walk again.
In Canada, wheelchair athlete Rick Hansen has also worked tirelessly to promote spinal cord research as well as rehabilitation and education.
Researchers say that 85 per cent of what is known today about the brain and spinal cord has been learned within the last 10 years.
The significance of the Montreal find, David said, is that the treatment has resulted in far greater regeneration than any other so far. The team's results, published in the international science journal Neuron, are to be announced today at a Montreal news conference.
``What's exciting about this is that we have demonstrated in an animal model that it is feasible . . . to do this,'' David said.
``The novelty is recruiting the animal's immune system to produce the antibodies to block the inhibitors,'' he said. ``It now gives us another way of thinking about the problem of developing a cure.''
And it opens the door to developing a vaccine for people, he said.
Several inhibitors appear when a spinal cord is injured. The first was identified in the late 1980s in Switzerland. In 1994, David's group achieved a research milestone when it was able to identify a second. Once researchers know what they're dealing with, they can figure out a way of blocking the inhibitor's effects.
David's group is currently working on identifying other inhibitors.
Although the researchers can't say with certainty how many inhibitors are affected by the vaccine's action, they say they're confident it will be effective against more than one of the agents.
Unlike the peripheral nervous system, the central nervous system does not regenerate on its own after injury. Up until 20 years ago, it was taken for granted that nerves in the central nervous system could not be repaired.
In the early 1980s, Dr. Albert Aguayo, working out of McGill University, first proved that nerves in the spinal cord could be regenerated using a graft from the body's peripheral nervous system.
Researchers use various methods to stimulate regrowth, but the vaccine treatment is a new avenue of success, David noted.
In the experiment, adult mice were immunized for three weeks before their spinal cords were injured.
Fifty-five per cent of the treated mice showed regeneration of 30 to 75 per cent of neurons in the part of the brain that controls muscular activity, with nerve fibres regenerating long past the area of injury.
These animals also showed recovery of certain hind-limb motor functions, the study said.
With this vaccine, the animal's own immune system produced antibodies against the inhibiting molecules, which prompted the nerves to regenerate. Although these immunizations can cause diseases like multiple sclerosis, the scientists were able to prevent that. ``In a way we have tricked the immune system so that it now generates antibodies and at the same time doesn't produce an autoimmune disease,'' David said.
He said they are now treating mice at the time of injury - instead of in advance - and preliminary results are promising.
At the Society of Neuroscience meeting in October in Miami, this study was selected out of some 13,000 papers as one promising enough to present to the media.
The group has been searching for private funding to help speed the development of the vaccine and move it from the basic research level to clinical practice on humans.