ATLANTA -- AIDS researchers at Yerkes Regional Primate Research Center have created a DNA vaccine that protects monkeys against a formidable challenge HIV virus. Achieving protection with this vaccine, made with harmless components from a SHIV -- a blend of parts from HIV and SIV (simian or monkey immunodeficiency virus) -- marks a significant and promising step toward the development of an effective AIDS vaccine. The study results are reported in the May issue of Nature Medicine by Dr. Harriet Robinson, Chief of Microbiology and Immunology at Yerkes Primate Center.
In a three-year study, Dr. Robinson compared combinations of three different vaccine approaches and two different delivery methods for administering them. The most effective vaccination involved two steps: first "priming" the immune system with a DNA vaccine, which consisted of genes taken from a SHIV. The genes express specific SHIV proteins that help the body produce an initial immune response. This was followed 46 and 66 weeks later with "booster" immunizations with the same SHIV DNA inserted into a pox virus. The pox virus deftly invades the host's cells, expressing very high levels of the useful SHIV proteins. However, once in the cells, the virus itself does not replicate. Thus it poses no risk of unwanted dissemination in the vaccinated individual.
Dr. Robinson also tested two different ways of introducing the DNA vaccine. Innoculation through the skin (intradermal) proved more effective in containing viral challenges than did administration with a "gene gun," which bombards cells with DNA-coated gold beads.
Dr. Robinson's vaccine was successful in containing the virus over a
62-week period, during which a series of three SHIV challenge infections were
administered. The containment was remarkably effective, preventing detectable
levels of virus in blood at all times post-challenge -- in contrast to
unvaccinated animals, which had viral loads of up to one billion.
Contact: Kate Egan
Emory University Health Sciences Center