A new type of skin patch being trialed on mice could one day replace needles as a method of vaccination.
Scientists have been studying needle free vaccine approaches for nearly two decades, but none of the technologies have so far lived up to the hype surrounding their launch. However, a new skin patch against the flu virus has elicited an appropriate immune response without side effects, when tested on mice.
The Centers for Disease Control and Prevention (CDC) in the United States estimates that the 2017-2018 flu season caused around 49 million illnesses, nearly 960,000 hospitalizations, and over 79,000 deaths in the country.
In publishing their findings the researchers acknowledged that previous attempts to deliver a flu vaccine using skin patches the relied on microneedle or electroporation, had proven difficult “to implement on a large scale for mass vaccination strategies.
In contrast to these techniques, the new patch uses a novel approach that mimics the process involved in the biology of atopic dermatitis, or eczema. In people with eczema, the skin barrier that normally prevents toxins and allergens from entering the body stops working properly and becomes permeable, or leaky.
The protein claudin-1 is essential for preventing leakiness of the skin barrier. People with eczema have low levels of claudin-1 compared with those without the skin condition. Exploiting this skin weakness, the researchers began experimenting on getting flu vaccine virus into the body through the skin.
The challenge lay in inducing leakiness in the skin for a length of time that lets in the vaccine virus but does not allow other materials to enter. Through a series of experiments with human skin cells, the team identified a peptide, or small protein, that can disrupt the skin barrier without causing toxic side effects. The peptide works by binding to and blocking claudin-1.
The researchers then created a skin patch containing the peptide and a recombinant flu vaccine and tested it in two ways on mice. In the first test, they applied the skin patch and then gave the mice a flu vaccine by injection. Their aim was to prime the immune system with the patch and then boost immunity with the flu shot.
In the second test, the team gave the mice the flu shot first and then applied the skin patch. Here, the aim was the other way around: prime the immune system with the flu shot and boost it with the skin patch.
The immune response to the patch in the first test was not significant. However, there was a robust immune response to the skin patch in the second test. Given that “humans are exposed to influenza as young as six months of age” and that as a consequence, most people’s immune systems are already primed to the virus, the second test best mimics a real world scenario.
These findings would suggest that the skin patch could serve as a delivery mechanism for the regular seasonal flu vaccine. Another notable result was that the researchers saw no side effects. They monitored the mice for three months and observed no physical changes in their skin, such as those that might arise from infections.
It will be some time before the skin patch is ready for human trials. The researchers need to run more animal studies to find out, for instance, how long the patch should remain on the skin for optimum results. The researchers believe that should the skin patch pass flu trials in humans, the technique could work for other vaccines that currently require needles.
While they are effective, needle based vaccines can cause people distress, and they require medical staff to deliver them. In addition, needles are biohazardous waste and require careful handling.
These barriers are particularly acute in less developed countries, which also happen to have the greatest need for vaccines. Delivery by means of a skin patch could be a quick and cheap way to vaccinate large numbers of people.
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