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7th June 2016
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Shot in the arm for HIV

Anthony King, 7 June 2016

An antibody to reduce the spread of HIV infection could be made available in areas where HIV-1 is endemic, say the authors of a new US study. It would not be a vaccine, but could drive down transmission to new patients.

The HIV-1 antibody comes from special HIV patients, so-called ‘elite neutralisers,’ who make up just 1 to 2% of all HIV infected individuals and generate potent anti-viral antibodies against HIV viruses. Labs around the world have collected these broadly neutralising HIV-1 antibodies and generated monoclonal antibodies.

The new study, by the US National Institute of Allergy and Infectious Diseases (NIAID), found that 2 HIV-1 antibodies (3BNC117 and 10-1074) protected macaque monkeys exposed weekly to the virus for almost six months. The researchers tested these two antibodies and one other (VRC01) by injecting them into macaques subjected to low-dose virus challenges each week. Animals without the antibodies became infected after between two and six challenges with the virus. A single injection of HIV-1 antibodies prevented the viruses from gaining a foothold in monkeys for up to 23 weekly challenges (Nature, doi:10.1038/nature17677).

In addition, the researchers reengineered the weaker HIV-1 antibody, VRC01, which showed lower activity and protected for a shorter period of time. The new version [VRC01-LS] stayed in circulation longer, increasing its lifetime from eight to 14.5 weeks. 

‘Right now there are no vaccines against HIV and we may never have a vaccine against HIV. This [prophylactic use of an antibody] is a possible alternative, preventive approach,’ says senior author Malcolm Martin, chief of the Laboratory of Molecular Biology at NIAID. ‘It is similar to what we used before we had a Hep A vaccine.’

The ultimate plan is to deliver a protective mix of antibodies to people living in area where HIV-1 is endemic. It is far more common and virulent than HIV-2.

‘If you look at the transmission rate, just with the antibodies we tested, it took approximately five times longer to infect an animal that was given an antibody, compared with controls. That could translate into reducing transition up to five-fold,’ says Martin. ‘That would be pretty impressive in a place like sub-Saharan Africa, where instead of 100,000 cases a year, you might have 20,000.’

The shot could be given like a flu jab each year, with the mix reformulated to maximise protection. Martin says the antibodies might offer protection for four or six months. It’s thought they compete with or tweak the docking machinery with which HIV-1 attaches to human immune cells.

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