An experimental therapy has held back one man’s HIV infection for 10 months, doctors have reported.
He was one of 18 people in a small trial testing injections of “broadly neutralising antibodies” – the natural weapons of the immune system.
They delayed the resurgence of the virus in other participants by around two weeks.
The findings are being presented at the ninth International Aids Society Conference on HIV Science in Paris.
The human body is inefficient at making antibodies that neutralise HIV.
Only one in five people infected with the virus develops them – and even then it takes many years and high levels of uncontrolled virus.
But more than 200 broadly neutralising antibodies have been documented, which doctors hope could be useful for both preventing and treating HIV.
The trial in Thailand, led by the US Military HIV Research Program (MHRP), took people who were controlling their infection with their standard HIV medication.
Some were given no treatment and others had an infusion of the antibody – codenamed VRC01 – into their bloodstream.
Inevitably the virus came back in those getting no treatment. It took an average (median) of 14 days, at which point they were put back on antiretroviral therapy.
In those receiving the antibody it took 26 days.
Dr Jintanat Ananworanich, one of the MHRP scientists, said there was also the exceptional case.
She told the BBC News website: “[The patient] has been off treatment for around 10 months and has so far controlled the virus to very low levels.”
He had the antibody infusion every three weeks for six months.
The field is still at an incredibly early stage, but the results point to the potential of antibody-based therapies.
Dr Ananworanich added: “It suggests there’s some impact from the antibody, but how the antibody actually impacts the virus and the immune system – that’s an on-going investigation.
“I do think antibody therapy has potential because the antibody, in the future, could perhaps be given just two or three times a year.”