Using a DNA vaccine could one day be as easy as applying a temporary tattoo, according to U.S. research published in Nature Materials.
DNA vaccines in animals trigger robust immune responses, but these aren't always replicated in humans, and as a consequence, there is still no DNA vaccine that is commercially available, despite a couple of decades of research. Another challenge is getting the DNA into the cell. Although techniques such as electroporation have improved delivery, this still involves a shot, and the sensation can be unpleasant or even painful.
The researchers, including a team from MIT, have created a patch of microneedles half a millimeter long, coated with multilayers of vaccine-loaded polymer film. The idea is that the patch is placed on the skin for a few minutes and then peeled off, leaving a "tattoo" of thin polymer films painlessly embedded in the skin. The polymers break down and release the vaccine DNA, with an RNA adjuvant that boosts the immune response, into the epidermis, which is populated with immune cells. The DNA tangles with the polymer as it breaks down, helping it get inside the cells.
In animal studies the DNA vaccine lasted between days and weeks, depending on the number of layers and the makeup of the polymer. In mice, the vaccine tattoo triggered immune responses against HIV similar to those of a vaccine delivered using electroporation. In cultured skin samples from nonhuman primates, the patch triggered gene expression 140-fold higher than that of a transdermal injection and enhanced the production of memory T cells. The next step is to carry out tests in nonhuman primates and then in humans.
As well as successfully triggering an immune response and avoiding shots, these multilayered tattoos could be more stable than other formulations of DNA vaccine, allowing storage at room temperature. Their stability, size and weight could mean that they could be posted or couriered out quickly to areas of need in epidemics and pandemics without worrying about refrigeration. Their simplicity also means that they could be self-administered or administered by people with little specialist training.