Researchers are hoping they are one step closer to a HIV vaccine – using HIV. At the 6th International AIDS Society Conference on HIV Pathogens, Treatment, and Prevention in Rome, researchers with the Maryland-based VirxSys Corporation announced the findings of their VRX1273 vaccine.

The vaccine is a genetically altered version of SIV, the version of HIV found in non-human primates. Over the course of six months, five infected monkeys were injected with the vaccine three times, while five others were given a placebo vaccine. After 18 months, it was found that 40% of the vaccinated monkeys had very low to undetectable amounts of virus in their bodies.

“We are well on the path to a functional cure, at least in monkeys,” says Laurent Humeau, VirxSys vice president of research and development.

“Although this pre-clinical study is modest in terms of size, it is highly unusual to see near non-detectable levels of the virus not only circulating in the blood, but also in the reservoirs where HIV is known to replicate,” said Joep Lange, M.D., Ph.D., professor of medicine at the Academic Medical Center, University of Amsterdam, and head of the Amsterdam Institute of Global Health and Development.

In the monkeys, the vaccine’s effect was sustained two years after the initial vaccination, without the need for any booster shots.

Other researchers have created similar type therapeutic vaccines. In May, Dr. Louis Picker of the Oregon Health and Science University’s Vaccine and Gene Therapy Institute announced a vaccine successful in preventing monkeys from acquiring SIV. Like the VirxSys vaccine, this was a genetically altered virus. In this case, the altered virus was CMV, from the herpes family.

But making the leap from monkeys to humans is a big step. Therapeutic vaccines "have looked really good in monkeys – but monkeys are not people and SIV is not HIV," said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Disease. "Really good concepts in primates have been duds in people.”

Unlike many antiretroviral drugs on the market, a therapeutic vaccine such as VRX1273 has the potential to be a cost effective way of dealing with HIV. Unlike drugs that are taken for the entire course of a patient's lifetime, this vaccine has the potential to administered just several times, possibly only once, over the course of a patient's life.

Humeau believes that he and his team are headed in the right direction and hope to start clinical trials in humans as soon as 18 months with approval from the U.S. Food and Drug Administration.