January 28, 2013
New Delivery System For DNA Vaccines Created
Lee Rannals for redOrbit.com — Your Universe Online
The vaccines could eventually not only overcome the safety risks of using viruses to vaccinate against diseases like HIV, but could also be more stable.
Scientists have been attempting to deliver DNA vaccines to human patients using techniques like electroporation. This method requires first injecting the DNA under the skin, then using electrodes to create an electric field that opens small pores in the membranes of cells in the skin. Unfortunately, this process can be a painful one.
“It's showing some promise but it's certainly not ideal and it's not something you could imagine in a global prophylactic vaccine setting, especially in resource-poor countries,” Darrell Irvine, an MIT professor of biological engineering and materials science and engineering, said in a statement.
The MIT researchers took a different approach to deliver DNA to the skin by creating a patch made of many layers of polymers embedded with the DNA vaccine. These films are implanted under the skin using microneedles that penetrate about half a millimeter into the skin.
Once the vaccine goes under the skin, the film degrades as they come in contact with water, releasing the vaccine over days or weeks.
Researchers are able to control how much DNA gets delivered by tuning the number of polymer layers. They can also control the rate of delivery by altering how hydrophobic the film is.
The film includes an adjuvant that consists of stands of RNA that resemble viral RNA, which provides inflammation and recruits immune cells to the area.
Michele Kutzler, an assistant professor at Drexel University College of Medicine, said other benefits of this new delivery system include targeting the wealth of immune cells in the skin, the use of a biodegradable delivery material, and the possibility of pain-free vaccine delivery.
“It´s an interesting approach that can be applied not just to delivery of DNA-based vaccine antigens, but other small molecules,” said Kutzler, who was not part of the research team.
The team found the immune response induced by the DNA-delivering film was as good as, or better than, that achieved with electroporation.
When testing whether the vaccine may provoke a response in primates, the team applied a film carrying DNA that codes for proteins from the simian form of HIV to macaque skin samples cultured in the lab.
“The hope is that that's an indication that this will translate to large animals and hopefully humans,” Irvine explained.
Now the team plans to perform further tests in non-human primates before using the delivery system in humans. The vaccine-delivering patch could potentially be used to deliver vaccines for many diseases, as the DNA sequence can be easily swapped out depending on the disease being targeted.
“If you're making a protein vaccine, every protein has its little quirks, and there are manufacturing issues that have to be solved to scale it up to humans. If you had a DNA platform, the DNA is going to behave the same no matter what antigen it´s encoding,” Irvine added.