The treated monkeys, which had suffered paralysis in one hand, regained 80 per cent of the movement they had lost.
Up to 12 months of further study is needed to confirm these results and, in particular, to see if there are any serious side effects.
“This is one more step on a very long road,” cautioned Eric Rouiller, professor of neurophysiology at Fribourg University.
“If we can get this confirmation in primates, this will be an important step.”
In Switzerland alone, 2,200 people have spinal cord injuries and about 180 new cases are registered every year.
The latest experiments follow 15 years of pioneering work by neuroscientist Martin Schwab at the University of Zurich.
For centuries, doctors considered that a damaged spinal cord could not be repaired.
Then in 1988, Schwab identified a substance in the Central Nervous System, which prevents the brain and spinal cord from repairing themselves after an injury.
Dubbed Nogo because of its inhibiting effect, the gene produces a protein, which prevents damaged nerves from re-growing after they are cut.
His team subsequently developed an Antibody that neutralises the blocking protein and allows the nerves to reconnect.
Researchers partially cut the spinal cords of rats, paralysing the animals, then gave them the antibody.
The nerves re-grew and the animals resumed normal activities such as grabbing food pellets and climbing a rope.
In this new study, the monkeys were trained to open drawers that were held with a spring, extract raisins from slits in a board using their thumb and index finger, or catch food that they were thrown.
After their spinal cords had been partially cut, the animals were unable to use one of their hands.
Treatment with the antibodies restored a high degree of manual dexterity.
“In the monkeys which have these Nogo antibodies, we find a recovery of hand function to a really amazing degree,” Schwab told swissinfo. “It’s about 80 per cent of the original function that comes back.”
“They open drawers. They pull out raisins quickly with high precision. They catch food almost like a normal monkey.”
Their performance was in marked contrast to that of untreated animals.
Wary of raising hopes in human patients, the scientists point out that this recovery was achieved in monkeys whose spinal cord had only been partially severed.
Moreover, studies in rats have shown that the scientists have to begin treatment within two days for it to be effective.
“A major spinal cord injury creates a large destruction zone,” said Schwab. “I sometimes compare it to a bomb which goes off in a computer centre and a full repair back to completely normal is probably not even something for the distant future.”
Schwab says the realistic hope would be to help Paraplegic patients achieve some movement – probably with crutches or handrails – as well as restore bladder control.
“These are functions which are relatively crude and do not require an enormous number of nerve fibres and there we see very good recovery in the animal models,” said Schwab.
Scientists believe that a multi-therapy approach involving a Nogo blocker, an agent to boost nerve growth, and some kind of cell transplant will eventually be available for treatment of severe paralysis.
In the United States, paralysed rats have been able to walk again after researchers transplanted stem cells into their spinal cords.
swissinfo, Vincent Landon