Recent results of the Antibody Mediated Prevention, or AMP, trials are an “important proof of concept” that showed the feasibility of blocking HIV with bimonthly infusions of broadly neutralizing monoclonal antibodies. The Laboratory of Infectious Disease Prevention at the New York Blood Center/Project ACHIEVE was one of multiple NIAID-funded HVTN study sites involved in the pivotal, proof-of-concept AMP studies.
The results come from two AMP trials that opened in 2016 and enrolled 4,623 volunteers on four continents. Led by Dr. Hong Van Tieu, Project ACHIEVE at the New York Blood Center enrolled 74 participants in the trial in New York City. The study was designed to evaluate whether a single broadly neutralizing antibody, known as VRC01, could be safely delivered by intravenous infusion and to provide detailed information on how well it blocked infection by multiple strains of HIV.
The trials found that this antibody completely blocked about 30% of HIV strains circulating in the communities where the infusions were tested, but it was not potent enough to block the other 70% of strains, and therefore by itself is not an effective candidate for HIV prevention.
For years, HIV vaccine researchers have been stymied by the ability of HIV to outmaneuver a range of antibodies that our immune system normally uses to control invading viruses. The AMP trials were designed to test whether infusions of a broadly neutralizing antibody, one that HIV could not readily evade through mutation, could block new infections. The VRC01 antibody was originally discovered in the blood of a patient living with HIV, and manufactured in the laboratory as a so-called monoclonal antibody.
Susceptibility to VRC01 of the HIV strain to which a person was exposed was the key determinant of how well the antibody worked to prevent HIV infection. The results show that more than one single bnAb is needed to prevent HIV acquisition. Similar to antiretroviral medications to treat HIV infection, combination monoclonal antibody cocktails need to be developed to offer effective protection against the diverse population of HIV strains that circulate in these communities. There are still more than 1.7 million new cases per year of HIV globally; more than 75 million people have acquired HIV and more than 32 million people have died from AIDS-related illnesses since the pandemic began. The need for a safe and effective preventive HIV vaccine and other HIV prevention technologies is as urgent as ever.