29 January 2013

DNA vaccine on a patch

Conventional vaccines contain inactivated viruses, after meeting with which the immune system acquires the ability to launch a targeted immune response when meeting with real enemies. However, when working with certain viruses, such as HIV, this approach may be too risky.

In recent years, many researchers have been considering DNA as a potential alternative to traditional vaccines. About 20 years ago, it was shown that DNA encoding viral proteins triggers a strong immune response in rodents, but so far these results have not been replicated in humans.

Specialists at the Massachusetts Institute of Technology have developed a promising new system for delivering DNA vaccines, which is a thin polymer film. If the effectiveness of this system is confirmed, it will not only solve safety problems, but also eliminate the need for syringes, as well as in special storage and transportation conditions.

Recently, scientists have achieved some success in using a technology known as electroporation to deliver DNA vaccines to the human body. This method involves the introduction of DNA under the skin and the subsequent impact on the injection zone by an electric field that opens pores in the membranes of skin cells through which DNA can penetrate inside. However, this process causes painful sensations and does not ensure the stability of the results.

The authors resorted to another approach, which consists in creating a patch consisting of many layers of a polymer film loaded with a DNA vaccine. This film is implanted into the skin using microneedles that penetrate no more than half a millimeter deep. This is enough to deliver DNA to the immune cells of the epidermis, but avoids the pain that occurs when the nerve endings of the deeper layer of the skin – the dermis are irritated. You can remove the patch in a few minutes.

Once inside the skin, the polymer comes into contact with the water contained in the extracellular space and degrades, releasing the vaccine within a few days or weeks. As the film dissolves, DNA strands intertwine with polymer fragments, which protects them from destruction and promotes penetration into cells.

The amount of DNA delivered to the body is regulated by changing the number of polymer layers. The delivery rate can also be changed by changing the hydrophobicity of the film.

The pure DNA introduced is destroyed before the immune system acquires the ability to develop an immune response. The gradual release of DNA gives the immune system more time, significantly increasing the effectiveness of vaccination.

The polymer film also contains an adjuvant compound that promotes the formation of an immune response. In this case, it is a chain of RNA, similar to viral RNA, which triggers an inflammatory process that attracts immune cells to the vaccine injection zone.

In experiments on mice, the developers demonstrated that the immune response induced by the polymer film releasing the DNA vaccine is not inferior or superior to the immune response achieved using the electroporation method.

In order to test the ability of the new vaccine to induce an immune response in primates, the researchers tested a polymer film containing DNA encoding proteins of the virus that causes immunodeficiency in macaques on laboratory-cultured skin samples of these animals. After applying the film, viral DNA was easily detected in skin samples, whereas DNA injected in the form of injections was destroyed very quickly.

Before the start of clinical trials, scientists plan to conduct experiments on great apes.
Article by Peter C. DeMuth et al. Polymer multilayer tattooing for enhanced DNA vaccination is published in the journal Nature Materials.

Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on MIT materials: A safer way to vaccinate.


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