Last month, a team of scientists announced what could prove to be an enormous step forward in the fight against HIV.

Scientists at Scripps Research Institute said they had developed an artificial antibody that, once in the blood, grabbed hold of the virus and inactivated it. The molecule can eliminate HIV from infected monkeys and protect them from future infections.

But this treatment is not a vaccine, not in any ordinary sense. By delivering synthetic genes into the muscles of the monkeys, the scientists are essentially re-engineering the animals to resist disease. Researchers are testing this novel approach not just against HIV, but also Ebola, malaria, influenza and hepatitis.

“The sky’s the limit,” said Michael Farzan, an immunologist at Scripps and lead author of the new study.

Farzan and other scientists are increasingly hopeful that this technique may be able to provide long-term protection against diseases for which vaccines have failed. The first human trial based on this strategy — called immunoprophylaxis by gene transfer, or IGT — is underway, and several new ones are planned.

“It could revolutionize the way we immunize against public health threats in the future,” said Dr. Gary J. Nabel, the chief scientific officer of Sanofi, a pharmaceutical company that produces a wide range of vaccines.

Researchers still need to gauge IGT’s safety and effectiveness in humans. And the prospect of genetically engineering people to resist infectious diseases may raise concerns among patients.

“The reality is we are touching third rails, and so it’s going to take some explanation,” said Dr. David Baltimore, a Nobel Prize recipient and virologist at Caltech who is testing IGT against a number of diseases.

Conventional vaccines prompt the immune system to learn how to make antibodies by introducing it to weakened or dead pathogens. Our immune cells produce a range of antibodies, some of which can fight infections.

IGT is altogether different from traditional vaccination. It is instead a form of gene therapy. Scientists isolate the genes that produce powerful antibodies against certain diseases and then synthesize artificial versions. The genes are placed into viruses and injected into human tissue, usually muscle.

The viruses invade human cells with their DNA payloads, and the synthetic gene is incorporated into the recipient’s own DNA. If all goes well, the new genes instruct the cells to begin manufacturing antibodies.

Dr. Philip Johnson, a virologist at the University of Pennsylvania, had an idea: Why not try to give broadly neutralizing antibodies to everybody? At the time, he and other researchers were experimenting with gene therapy for disorders like hemophilia. The idea represented a radical new direction for gene therapy.

In 2009, Johnson and his colleagues announced that the approach worked. They sought to protect monkeys from SIV, a primate version of HIV, by using viruses to deliver genes to the monkeys’ muscles.

“We’re going around the immune system, rather than trying to stimulate the immune system,” Baltimore said. “So what we’re doing is pretty fundamentally different from vaccination, although the end result is pretty similar.”