Proof-of-Concept Study Shows HIV Antibodies Shield Animals

Scientists have found that three different HIV antibodies can prevent monkeys from getting infected with a virus similar to HIV. The study, published in Science Translational Medicine, could help design a vaccine for humans.

What are HIV antibodies?

HIV antibodies are proteins that can recognize and bind to parts of the HIV virus, preventing it from infecting cells. Some HIV antibodies can neutralize many strains of HIV, and are called broadly neutralizing antibodies. These antibodies are rare and hard to induce by vaccination.

How did the study work?

The researchers, led by the Vaccine Research Center (VRC) at the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, tested three HIV antibodies that target a site on an HIV surface protein called the fusion peptide. The fusion peptide helps the virus fuse with and enter cells.

The researchers isolated one of the antibodies, called VRC34.01, from a person living with HIV who donated blood samples for research. They also isolated two antibodies, called DFPH-a.15 and DF1W-a.01, from rhesus macaques—a species of monkey with immune systems like humans’—who previously had received a vaccine regimen designed to generate fusion peptide-directed antibodies.

The researchers gave each monkey a single intravenous infusion of one type of antibody or a placebo, and then exposed them to a virus called simian-HIV (SHIV), which is a combination of HIV and a monkey virus. SHIV can infect and cause disease in monkeys, and is used as an animal model for testing HIV vaccines and treatments.

What did the study find?

The study found that all three antibodies protected monkeys from SHIV infection, compared to the placebo group. None of the monkeys that received VRC34.01 at a high dose (10 mg/kg) or DFPH-a.15 at any dose acquired SHIV. Only one out of four monkeys that received VRC34.01 at a low dose (2.5 mg/kg) or DF1W-a.01 at any dose acquired SHIV.

The researchers also measured the concentration of antibodies in the blood of the monkeys over time, and found that it declined gradually. They estimated that the half-life of VRC34.01 was about 10 days, while the half-life of DFPH-a.15 and DF1W-a.01 was about 20 days.

Why is this study important?

This study is important because it shows that fusion peptide-directed antibodies can protect animals from SHIV infection in a proof-of-concept study. This means that the fusion peptide is a promising target for human vaccine design, and that these antibodies could be used as potential candidates for passive immunization or antibody therapy.

Passive immunization is when antibodies are given directly to a person to prevent or treat an infection, rather than stimulating their own immune system to produce them. Antibody therapy is when antibodies are used to treat an existing infection or disease.

The researchers plan to further investigate the mechanisms of protection by these antibodies, and to test them in combination with other broadly neutralizing antibodies against different strains of SHIV.

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