A safer way to vaccinate

Vaccines usually consist of inactivated viruses that prompt the immune system to remember the invader and launch a strong defence if it later encounters the real thing. However, this approach can be too risky with certain viruses, including HIV.

In recent years, many scientists have been exploring DNA as a potential alternative vaccine. About 20 years ago, DNA coding for viral proteins was found to induce strong immune responses in rodents, but so far, tests in humans have failed to duplicate that success.

In a paper appearing in the 27 January online issue of Nature Materials, MIT researchers describe a new type of vaccine-delivery film that holds promise for improving the effectiveness of DNA vaccines. If such vaccines could be successfully delivered to humans, they could overcome not only the safety risks of using viruses to vaccinate against diseases such as HIV, but they would also be more stable, making it possible to ship and store them at room temperature.

This type of vaccine delivery would also eliminate the need to inject vaccines by syringe, says Darrell Irvine, an MIT professor of biological engineering and materials science and engineering. ''You just apply the patch for a few minutes, take it off and it leaves behind these thin polymer films embedded in the skin,'' he says.

Irvine and Paula Hammond, the David H. Koch Professor in Engineering, are the senior authors of the Nature Materials paper. Both are members of MIT's David H. Koch Institute for Integrative Cancer Research. The lead author of the paper is Peter DeMuth, a graduate student in biological engineering.

Gradual vaccine delivery
Scientists have had some recent success delivering DNA vaccines to human patients using a technique called 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, allowing DNA to get inside. However, the process can be painful and give varying results, Irvine says.