Just a little prick, or not

Work is now gathering pace on the possibilities of administering vaccines topically, so no more needles much to the relief of those of us putting up to some degree with trypanophobia (a fear of needles).

Topically administering a vaccine simply involves stretching the skin before the vaccine is applied to it. Our skin is a vital barrier to protect against pathogens, and works in concert with our immune system. If, for example, you gently scratch yourself receptors are activated that give a boost to our immune defences.

To see if stretching the skin has similar effects to injection, researchers at King’s College London applied a suction device to human and mice skin samples to increase the skin’s tension to about 6 Newtons, about four times its normal tension. Under a microscope, fluorescently labelled molecules demonstrated that when the skin is stretched as such the skin’s collagen fibres rearranged and hair follicles opened to increase skin permeability and allow the molecules through. The skin stayed in this state for some 15 minutes after stretching. The stretching also triggered stromal cells that give structural support to the skin, resulting in a mild inflammatory response to stimulate the immune system.

Tests in mice showed that stretching the skin raised the number of immune cells in that skin part, along with changes to the activity of genes that encode immune system signalling molecules called cytokines. A further experiment involving injecting an H1N1 vaccine then applying a lotion to the stretched skin showed a similar immune response in both cases. This raised the propitious prospect of getting a nanoparticle inside the body simply by stretching the skin.

The effect of the topical vaccine was also strong with or without an adjuvant, these being molecules used in vaccines to trigger the immune system that some people are allergic to.

It is now envisaged that people could administer topical vaccines themselves at home by first applying a small suction device to the skin. This would be non-invasive with no blood or breaking of the skin.

But questions do remain, such as the depths that can be reached with this form of treatment and with what accuracy you can administer a particular target dose. More work also has to be done because people have a thicker outer skin layer than mice, but the prospects are indeed encouraging.