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HIV prevention trial tests virus-blocking antibody

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Holly Korschun

Despite years of research, there is no preventive vaccine against HIV. Now, a clinical trial sponsored by the National Institutes of Health will provide people with one of the things a vaccine is supposed to stimulate in the body -- antibodies that neutralize the virus – with the aim of preventing viral infection.

Both the Hope Clinic of the Emory Vaccine Center and the Ponce de Leon Center, part of Grady Health System, are participating in this study, which is called AMP, for antibody-mediated prevention.

In the United States and South America, the AMP study is aimed at HIV-negative men and transgender individuals who have sex with men. Researchers at 24 sites in Brazil, Peru and the United States plan to enroll 2,700 study volunteers. Another AMP study is planned to launch later this spring, enrolling 1,500 sexually active women at 15 sites in African countries.

Srilatha Edupuganti, MD, MPH, associate professor of medicine (infectious diseases) at Emory University School of Medicine, is co-chair of the AMP study in the Americas as well as overseeing the study at the Hope Clinic. Carlos del Rio, MD, professor of medicine (infectious diseases) at Emory University School of Medicine and chair of global health at Rollins School of Public Health, is directing the AMP study at the Ponce Center.

"New HIV infections have continued to increase in our most vulnerable populations in the United States, including African-American men who have sex with men," says Edupuganti. "The use of broadly neutralizing antibodies offers new hope to stem that tide as we have for other at-risk populations here and around the world."

The antibody being tested in the AMP study, called VRC01, was discovered in the blood of an HIV-infected person in 2010 by researchers at the National Institute of Allergy and Infectious Diseases. VRC01 prevents HIV from binding to a molecule on the surface of T cells, which the virus uses to get inside them. Laboratory studies have shown that the antibody stops up to 90 percent of HIV strains worldwide from infecting human cells.

“The AMP Studies could have a major impact on the future of HIV prevention and may be especially informative to HIV vaccine research,” says NIAID director Anthony Fauci, MD. “Many scientists believe that if a vaccine were developed that elicited broadly neutralizing antibodies in healthy people, it would protect them from HIV infection. The AMP Studies will test this hypothesis by directly giving people the VRC01 antibody.”

The AMP studies could also clarify what level of broadly neutralizing antibodies a vaccine or other long-acting HIV prevention method needs to achieve and maintain to provide sustained protection from the virus.

Volunteers will be assigned at random to receive two different doses of antibody or a saline placebo. Participants and researchers will not know who received which dose until the end of the study. Participants will receive ten infusions, once every eight weeks, with follow-up for 20 more weeks. The results of the trials are expected in 2022.

Volunteers will be tested for HIV infection every four weeks and after reporting possible exposure. Those who test positive for HIV will stop receiving infusions but will remain in the study for follow-up and referral.

All volunteers will receive the standard care for preventing HIV infection, including condoms and lubricant, behavioral counseling, and referral for post-exposure antiretroviral drugs, if exposure to HIV is suspected. Volunteers have the option of referral for pre-exposure prophylaxis (PrEP) medication; the AMP Studies have been designed so investigators will be able to discern a preventive effect from VRC01 even if some participants are taking PrEP.

The studies are being carried out through the national HIV Vaccine Trials Network and the HIV Prevention Trials Network.

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