In a new approach, researchers are sidestepping the body's immune system to fight HIV by inserting a gene into muscle tissue to create protective antibodies. Already successful in mice, the technique has now worked in monkeys, which scientists turned to because of the similarity of simian immunodeficiency virus (SIV) to HIV.

"We used a leapfrog strategy, bypassing the natural immune system response that was the target of all previous HIV and SIV vaccine candidates," said study leader Dr. Philip R. Johnson of the Children's Hospital of Philadelphia. Over a decade, Johnson, Reed Clark of Nationwide Children's Hospital in Columbus, Ohio, and colleagues developed immunoadhesins - antibody-like proteins designed to attach to SIV and block it from infecting cells. The research was supported by the National Institute of Allergy and Infectious Diseases.

The team injected monkeys' muscles with modified adenovirus that carried immunoadhesin DNA, and then the muscles began producing the antibodies. One month later, nine vaccinated monkeys and six unvaccinated control monkeys were intravenously challenged with SIV. None of the vaccinated monkeys developed AIDS, though three showed signs of infection. A year later, they still had concentrations of the vaccine-generated antibodies in their blood. All six unvaccinated monkeys acquired infections, and four died.

Building upon this progress, Johnson is working with the International AIDS Vaccine Initiative toward human trials of a new HIV vaccine candidate.

The full study, "Vector-Mediated Gene Transfer Engenders Long-Lived Neutralizing Activity and Protection Against SIV Infection in Monkeys," was published online ahead of print in Nature Medicine (05.17.2009:doi:10.1038/nm.1967).