A clinical trial of a DNA 'reverse' vaccine designed to combat type-1 diabetes, has delivered initially promising results, scientists say.
The trail led by Stanford University School of Medicine researchers suggests that the vaccine may selectively counter the errant immune response that causes the disease.
In the study, levels of a blood-borne proxy of insulin production were maintained - and in some cases increased - over the course of the 12-week dosing regimen.
This indicates that those getting the vaccine may have suffered less ongoing destruction of beta cells, which produce and secrete the peptide hormone insulin after a meal, than those given placebo injections.
Also, blood levels of a specific group of immune cells that inappropriately home in on and destroy a protein found only on beta cells appeared to have been selectively depleted in patients receiving the vaccine.
No adverse effects, serious or otherwise, that could be attributed to the vaccine were observed.
"We're very excited by these results, which suggest that the immunologist's dream of shutting down just a single subset of dysfunctional immune cells without wrecking the whole immune system may be attainable," said Lawrence Steinman, professor of pediatrics and of neurology and neurological sciences at Stanford.
"This vaccine is a new concept. It's shutting off a specific immune response, rather than turning on specific immune responses as conventional vaccines for, say, influenza or polio aim to do," Steinman said.
To date, no DNA vaccine has ever been approved for human use, and any likely application is several years off. The vaccine's observed beneficial effects began to drop off a few weeks after the 12-week vaccine-dosing schedule was discontinued, the study reported.
"This is the first demonstration of a DNA vaccine targeting type-1 diabetes in humans," said Richard Insel, chief scientific officer of JDRF, formerly known as the Juvenile Diabetes Research Foundation.
Using an approach developed at Stanford by Steinman and his colleagues, the investigators tweaked a piece of DNA containing the proinsulin gene in a way that, they predicted, would cause a special class of immune cells ingesting the vaccine to deliver an anti-inflammatory signal to CD8 cells targeting proinsulin - and to those cells alone.
The study was published in Science Translational Medicine.
