A medical breakthrough in HIV prevention could eventually lead to the development of an AIDS vaccine, due to a recent discovery by researchers at the Harvard-affiliated Dana-Farber Cancer Institute.

Scientists took an antibody from an HIV-positive man who had not shown any symptoms of AIDS even after a decade of having HIV and administered it to rhesus monkeys. They then injected the monkeys with a form of the human HIV virus that was mutated so it could spread in monkeys.

Although the virus in the monkeys was a different strain than the original human virus, the antibody still effectively prevented the onset of AIDS symptoms. Monkeys who were administered the antibody remained completely symptom-free, while monkeys without the antibody suffered all of the normal effects of the virus.

This finding is significant because one of the fundamental challenges in the development of an HIV vaccine is accounting for the millions of different strains of the highly-mutable HIV virus. Due to the variance, an effective and practical vaccine must target commonalities between the strains.

“The big problem with so many millions of HIV virus out there is there needs to be a way to target the common theme,” said Harvard Medical School Professor Ruth M. Ruprecht, senior author of the study. “This is a step in the direction of identifying targets for vaccines.”

In this study, researchers were able to discover a similarity between multiple strains of the virus by discerning what part of the virus was targeted by the antibody.

Medical School instructor Nagadenahalli B. Siddappa, one of the lead authors of the study, also stressed the importance of the antibody’s apparently universal protective qualities, noting the difficulty scientists often face when attempting to develop a preventative vaccine for a continually evolving virus.

“[Scientists] always see different viruses,” he said. “This could be very useful.”

While researchers said they were excited about this finding and its potential significance, they also stressed that there is still a long way to go before any type of preventative vaccine is actually ready for use on humans. An active immunization, which could be widely administered to the public, must allow antibodies to be produced on their own by the body.

“The next step is to see if we can focus active immunization on the portion of the [virus] that is conserved,” Ruprecht said. “At the same time, we are trying to find other regions that are conserved” between strains.

Ruprecht also explained that this antibody is not thought to be a cure, though she left the possibility open.

“This is a different clinical situation,” she said. “This is not about the cure.”

—Staff writer Mercer R. Cook can be reached at mcook@college.harvard.edu.