A vaccine designed to tackle multiple sclerois has passed initial safety tests, say Canadian scientists.
Protective myelin is stripped away by MS
It is hoped that the BHT-3009 jab might reduce the damaging immune system attacks which cause the disease.
Early checks were carried out on 30 patients at Montreal Neurological Institute, reported the journal Archives of Neurology.
A British expert said that the way was clear for bigger trials - perhaps showing real benefits to patients.
There is no cure for MS, which happens when the body's own defence system launches an attack on the tissue that surrounds nerve fibres, causing irreversible and worsening symptoms such as weakness and vision loss.
DNA vaccines are already used in healthy patients to protect against infectious diseases, but the latest idea is to give them to patients with an existing disease such as MS.
The Montreal researchers said they thought their study was the first time that a DNA vaccine had been given to someone with an "auto-immune" disease.
Animal experiments have suggested that it might be possible to tweak the body's immune system so that the unwanted self-harming response becomes smaller, slowing the progress of the disease.
The small-scale Montreal trial - using 30 MS patients - was designed to check that the vaccine would not cause any unexpected side-effects in advance of large-scale trials.
The scientists also checked to see if there was any evidence in the tiny number of patients who received the vaccine that it was having an effect on their disease.
They found some differences in MRI scans of the brains of vaccine patients, and blood tests revealed a lower number of immune system cells targeting the proteins in the nerve fibre sheath.
However, the trial was too small and too short to show whether, in the longer term, this might translate to a slowing of the illness or a reduction of symptoms.
The researchers wrote: "We have demonstrated in this first, to our knowledge, in-human trial of a DNA vaccine for auto-immune disease that the approach is safe and well tolerated."
Professor Christopher Linington, who researches the immunobiology of MS at the University of Aberdeen, said that the research was "exciting", and that to detect any evidence of benefits in such a small trial would have been "miraculous".
He said: "What this shows is that the DNA vaccine approach doesn't have any adverse consequences, but they will have to 'fine-tune' the vaccine further to see if it will offer any benefits to patients."
He said that larger studies into the vaccine would now follow.