Researchers say a new antibody treatment is 100 percent effective in clearing HIV from baby rhesus monkeys.

Scientists have found a way to eliminate a version of HIV in baby monkeys immediately after infection, according to a study published this week in the journal Nature Medicine.

If successful in humans, the treatment could join a suite of therapies used to prevent women that are HIV-positive from passing the virus on to their children.

The researchers, based at the Oregon National Primate Research Center, injected 1-month-old rhesus monkeys with HIV-battling antibodies shortly after exposing to them to a genetically engineered combination of HIV and its simian analogue, SIV.

Within two days, the monkeys’ viral loads were much lower than those in the control group that received no antibodies. Within two weeks, the monkeys were virus-free.

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The immune system responds to viruses and other germs by producing antibodies. These are the proteins that tag the invaders and help destroy them.

However, the antibodies the body makes in response to an HIV infection aren’t powerful enough, or develop quickly enough, to beat the disease.

In some people with HIV, however, the body begins to produce effective antibodies after several years, although by then the virus has already taken hold.

Scientists have isolated several versions of these broadly neutralizing antibodies from patients with HIV and mass-produced them in the lab. These are the antibodies that the Oregon scientists used to treat the newborn monkeys.

“Antibodies are 100 percent effective if you have them in advance of the virus,” Nancy Haigwood, Ph.D., the primate center’s director and a senior author of the study, told Healthline.

Indeed, the experiment was 100 percent successful in clearing the virus from the young monkeys, even in tissues where the virus is known to lurk.

Scientists have isolated the killer antibodies and learned how to clone them only within the past decade. So far, they have shown potential as a treatment or even as a vaccine in animal models. They have also been tested in humans.

Last year, a team based at Rockefeller University in New York administered antibody therapy to adults that were HIV-positive. In many of these patients the antibodies reduced the viral loads dramatically.

What’s new and exciting about this study, said Rowena Johnston, Ph.D., vice president and director of research at the Foundation for AIDS Research, or amfAR, is that the antibodies were shown to eliminate the virus after it had taken hold in the body.

“We’re looking forward to researchers building on that principle that HIV infection can in fact be cleared,” she told Healthline.

However, she isn’t sure where this potential new treatment would fit among the other options available to treat pregnant women with HIV and their babies.

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About 1.5 million women with HIV were pregnant in 2014, according to UNICEF. The majority of these women live in sub-Saharan Africa.

Without medical intervention, there is a 15 to 45 percent chance that their babies will also acquire the virus.

To reduce that risk, women are encouraged to have a cesarean delivery, avoid breastfeeding, and take antiretroviral drugs.

These methods work well where women have access to healthcare. In fact, Cuba announced last year that mother-child transmission of HIV has been eliminated in that country. The U.S. is approaching that goal.

Johnston added that in the study, researchers knew exactly when the monkeys were exposed to the virus and were able to give them treatment right away. This model is somewhat at odds with reality.

“When a human infant is born with HIV you don’t know the time of infection with that level of specificity,” she said.

A baby can be infected during the third trimester of pregnancy or during birth.

Antiretroviral drugs can be given throughout a woman’s pregnancy to reduce the risk to her baby, she said. Plus, the drugs are less expensive than antibodies.

However, these drugs must be taken daily in order to be effective and to prevent the virus from becoming drug resistant. In contrast, antibodies could be engineered so that patients would only need one injection every six months, Haigwood said.

The monkeys in her study were still virus-free when the experiment ended at six months, even though the last dose of antibodies had been given just 10 days after infection.

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Haigwood said what surprised her most about the results was the speed at which the virus established itself in the young monkeys.

Previous wisdom held that it takes several days after exposure for HIV to set up shop in the body. However, her team found that the HIV/SIV hybrid had already begun to replicate and spread in the young monkeys within a single day.

That discovery is likely due to newly available, highly sensitive detection methods that Haigwood’s team used to look for the virus in the animals’ tissue.

“So to me the implications are that early intervention is extremely important because the virus is getting going much faster than we had assumed,” she said.

The antibodies seemed to be a good match for the virus. They, too, spread through the body faster than Haigwood had anticipated.

Haigwood and Johnston agree that antibody therapy has huge potential for fighting HIV, dependent on the outcome of future trials on safety and efficacy in humans.

Safety trials in babies are currently under way in South Africa and in the United States. After that, there’s still the matter of getting the ingredients and dosage right, Haigwood said.

“We need to figure out a way to make antibodies better at killing infected cells now that we know they can do it,” she explained.