Delivering electrical pulses along with an experimental AIDS vaccine elicited a better immune response in volunteers than administering the injection alone, researchers said Thursday at the AIDS Vaccine 2009 conference in Paris. Employing a technique called electroporation, US researchers used a device that looks like a pistol to inject a weakened DNA-based vaccine as well as three brief electric shocks.

"With a brief pulse of electricity, our cell membrane temporarily opens up and allows a lot more of the DNA to get inside," said Sandhya Vasan of the Aaron Diamond AIDS Research Center in New York. "The reason why DNA vaccines by themselves don't trigger a powerful immune response is because most of [the DNA] does not get inside our cells."

When injected alone, the vaccine produced an immune response in 25 percent of participants. When the same vaccine was injected in combination with electroporation, that rate increased, Vasan said.

"We improved the response rate, improved the duration of the response, and it also improved the breadth of the response," said Vasan. "There were four different genes of the virus, [and] for the highest dose, people were responding to three or even four of the genes."

Among 40 volunteers evenly divided into five groups, three of the groups received varying vaccine doses with electroporation; the fourth group was given a placebo plus electroporation; and the fifth was given a conventional injection but with the highest dose.

Those who got a traditional injection showed no immune response; three out of the eight participants given the lowest dose electroporally formed a response; and everyone given the highest dose with electroporation had a response.

"This is the first clinical trial of electroporation in healthy volunteers for a preventative vaccine," Vasan said. "It can be applied to many diseases, many vaccines, not just for HIV." Her group next plans to conduct a Phase II trial of a stronger DNA vaccine delivered with electroporation.