Researchers have developed an antibody that protects rhesus monkeys from infection by simian HIV (SHIV), a virus similar to HIV that causes an AIDS-like illness in the species.
For more than thirty years, enormous research effort has been directed toward finding a cure for AIDS, while simultaneous efforts have sought to develop a vaccine for HIV. Although these efforts have led to extraordinary progress in our understanding of the immune system and the nature of the disease, neither a cure nor an effective vaccine has been found.
While that work continues, neutralising antibodies may provide a way to substantially limit transmission of the virus.
Recent research shows that individuals with HIV can produce antibodies that neutralise the virus, and clinical trials are underway to determine whether such antibodies can control viral levels in HIV-positive individuals.
Using antibodies to prevent infection is the next step. Earlier studies in rhesus monkeys had shown that antibodies could provide short-lived protection, sometimes lasting as little as 8 weeks. For a prophylactic to be effective, it needs to last much longer.
To address this, researchers in the US introduced a single mutation into each of two antibodies that target and neutralise SHIV. These modifications enabled the antibodies to remain in the bloodstream longer. When the antibodies were administered to rhesus monkeys, both separately and in combination, they protected against SHIV infection significantly longer than the unmodified antibodies.
Remarkably, a single intravenous infusion of one of the modified antibodies was able to provide protection for up to 8 and a half months. However, the combination dose was the most important, because protection is needed not just against a single strain of HIV but also against genetically diverse or antibody-resistant HIV strains. Thus, a cocktail of antibodies is best.
The researchers found that a single injection of the combination dose conferred protection against SHIV for a median of 20 weeks. The paper’s authors note that this injection involved a much lower dose than the intravenous infusions, so there could be room for further improvement.
The findings suggest it may be possible to develop an effective biannual or annual regimen of injectable neutralising antibodies to protect against HIV infection.