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Research paper p. 870

DNA vaccines get under the skin

"Splash it all over" soon might be all that is required for vaccination if new research using naked DNA vaccines turns out to be transferable to humans. Most current vaccination approaches are of limited appeal and accessibility to patients, particularly those in developing countries, because they require the use of needles, injections, and skin-abrasive procedures. But Paul Khavari and his colleagues have discovered that DNA encoding a hepatitis B antigen can be applied directly to the skin of mice and still induce immune responses similar to those produced by intramuscular injection of a commercially available recombinant hepatitis B polypeptide vaccine.

Previously, it had been thought that successful topical delivery of a DNA vaccine required the use of physical abrasion or chemical dipilation of the skin. But Khavari and his collaborators now show that naked DNA encoding foreign genes induces immune responses in mice comparable to DNA delivered by injection or direct application to the skin using liposomes or packaging in a type of cold virus (adenovirus). When they used the naked DNA system to introduce hepatitis B antigen, they showed that the vaccine can induce both antibody and cellular immunity. Further analysis revealed that hepatitis B antigen DNA, at a certain threshold concentration, appears to be taken up by hair follicles rather than through the skin epidermis. What's more, vaccination failed to work in mice that lacked normal hair follicles. Khavari suggests that hair follicles of a certain age allow DNA to penetrate the skin's protective epidermal layer and express the antigen.

Contact (Author)
Dr. Paul A. Khavari
Stanford University School of Medicine
MSLS, P204 Stanford, CA 94305-5486
Tel: 650 725 5266 / 723 7944
Fax: 650 723 8762
Email: khavari@cmgm.stanford.edu

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