A single injection of HIV-targeting antibodies can protect monkeys from the simian version of the virus, SHIV, for nearly six months, reports a paper published online this week in Nature. The study provides a proof of concept for HIV-1 protection that could have a major impact on transmission of the virus in high-risk populations.
Antibodies from HIV-1-infected individuals have been shown to block infection in animals when transferred a day or two prior to a single high-dose virus challenge. However, the long-term efficacy of this passive immunization approach has not yet been examined.
Based on the idea that passive immunization against hepatitis A protected people for several months before an effective vaccine was available, Malcolm Martin and colleagues explored whether a single administration of a potent anti-HIV antibody could provide similar protection for extended periods of time. The authors simulated human transmission of HIV in a control group of nine macaques and determined that the median time to infection was 3 weeks. They then administered a single dose of three different antibodies to three groups of six animals and exposed them to weekly virus challenges. Virus acquisition was delayed in all groups that received antibodies, with the longest protection lasting 23 weeks. The duration of protection was directly related to the potency and half-life of the antibody. They also found that they could extend the half-life of the least potent antibody by introducing amino acid mutations.
The authors suggest that a combination of these antibodies could be used to improve their overall ability to block the transmission of resistant HIV-1 strains. However, more research is needed to establish whether this approach could represent a viable alternative to HIV-1 vaccination in humans.