Tattooing is a more effective way of administering DNA vaccines than direct injection into muscle tissue, according to new research by German and Czech scientists.

In DNA vaccination, a gene from a pathogen is injected directly into the host, which then produces the corresponding pathogen protein inside its own cells. This triggers a response from the
host’s immune system. Advantages of DNA vaccination include the fact that the vectors can be constructed quickly, and rapid and large scale vaccine production is much cheaper than for
traditional vaccines. These vaccines are also temperature stable; in contrast many traditional vaccines require cold storage and have a limited lifetime.

In this latest piece of research, the scientists compared tattoo delivery with intramuscular injection, both with and without the use of additional adjuvants, which are designed to boost the
immune response of the vaccine. Their results are published in the journal Genetic Vaccines and Therapy.

The tattoo method gave a much stronger antibody and cellular response than intramuscular injection. Three doses of DNA vaccine delivered via tattooing elicited antibody levels 16 times higher
than three intramuscular injections with adjuvant. The scientists also found that while adjuvants boosted the immune response for intramuscular vaccinations, they had no effect on DNA
vaccinations.

The process of tattooing causes a wound and sufficient inflammation to ‘prime’ the immune system. Furthermore, it covers a larger area of the skin than an injection, allowing the DNA vaccine to
get into more cells. The researchers speculate that these factors could contribute to the efficacy of tattooing as a vaccine delivery method.

‘Vaccination with naked DNA has been hampered by its low efficiency,’ commented Martin Müller of the German Cancer Research Centre (DKFZ), who led the research. ‘Delivery of DNA via
tattooing could be a way for a more widespread commercial application of DNA vaccines.’

While acknowledging that tattooing may not be acceptable for everyone – the procedure is rather painful – the scientists believe it could have applications for the routine vaccine of livestock,
or for delivering therapeutic (as opposed to preventive) vaccines in people. ‘Nevertheless, DNA vaccination via tattoo seems to be the method of choice if faster and stronger immune responses
have to be achieved,’ the researchers conclude.

Advantages of the tattoo method include the low cost of the tattooing device and a standardised method for the application. On the down side, the researchers cite the strain on the animals and
a ‘somewhat cumbersome application procedure’.

Tattooing is already in use in some medical research applications where it is used to deliver materials to the skin, for example for scar treatments. It is also used to study the processes
involved in cosmetic tattooing, or to deliver DNA for prospective gene therapy of skin disorders.

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