A vaccine that would inhibit the onset of Type I diabetes -- insulin dependent diabetes -- could be on the horizon for those at high risk of developing the disease, researchers at North Carolina at Chapel Hill said Wednesday.
"Our study indicates that a vaccine could be applied to intervene for high-risk
people to block the auto-immune process to prevent the onset of Type 1
diabetes," said Dr. Roland Tisch, of the Chapel Hill Medical School. A report of the research appears
in the Feb. 1 issue of the Journal of Immunology.
Type I diabetes, also known as juvenile diabetes, results from an auto-immune
response -- the body destroys the cells needed to produce insulin. It's mostly
diagnosed in adolescents but can be found in young adults as well. Type II
diabetes is found mostly in older adults who produce less insulin and is
considered a metabolic disease.
The North Carolina researchers used plasmid DNA that would inhibit development
of insulin-dependent diabetes. Plasmid DNA is circular genetic material obtained
from bacteria and therefore plentiful. "Plasmid DNA functions as a scaffold that
genes of interest are inserted," Tisch explained. "In the past, our group and
others could manipulate the damaging auto-immune response in various animal
models for Type I diabetes but not in ways that would be readily feasible
Tisch used the genetic vaccine to re-establish the natural balance between two
kinds of immune cells -- Th1 cells and Th2 cells. When misbehaving, and
researchers still don't know why, the former attack the critical
insulin-producing islet beta cells. When Th2 cells fail to do their job, Th1
cells eventually lead to Type I diabetes.
"Our approach was relatively simple," Tisch said. "The vaccines allowed us to
selectively suppress the body's auto-immune response while leaving the remainder
of the immune response intact."
Tisch and his colleagues engineered their vaccines to express two different
proteins -- one that activated T cells that recognize islet beta cells and
another that boosted those T cells to develop into Th2 cells needed to hold Th1
cells in check.
"One of the appealing features of plasmid DNA vaccines is that the DNA persists
for long periods," Tisch said. "We gave our mice three injections in three
weeks, and the majority of the animals have remained diabetes-free for more than
a year -- mice have a lifespan of about two years." Ideally, human patients
might require injection of plasmid DNA vaccines only every year or two,
according to Tisch.
"The study clearly demonstrates that only a few injections of the genetic
vaccine could prevent the onset of insulin-dependent diabetes," Dr. Alex
Rabinovitch, of the University of Alberta, in Canada, told UPI. "This research
advance is important because the type of vaccine developed in human subjects at
high-risk for Type I diabetes."
Those considered at high-risk for diabetes are those who have a first-degree
relative with Type I diabetes, test positive for certain antibodies and test
positive for poor insulin response to glucose.