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Kick, kill, contain – researchers examine three possible steps in a cure for HIV
Gus Cairns, 2013-07-03 07:00:00

The  7th International AIDS Society Conference on HIV Pathogenesis, Treatment and Prevention (IAS 2013) in Kuala Lumpur featured a special two-day symposium on progress towards a cure for HIV and also featured a number of presentations on possible approaches towards a cure in the main body of the conference.

Both the symposium and the conference heard about a number of cases of 'functional cure' or 'remission' from HIV replication in people who had started antiretroviral therapy (ART) soon after infection, including a German case that can now be added to the 'Mississippi baby' case and 14 members of the French VISCONTI cohort. These individuals manage to maintain an undetectable viral load after coming off ART and it is becoming clear that there may be other early-treated patients who might be able to come off their medication too.

The majority of people who did not start ART till later, however, are unlikely to achieve control of their HIV without more help. The problem is that unless HIV is suppressed early, it integrates into the genetic material of some of the long-lived central memory cells in the immune system. As long as people are on ART, HIV is prevented from replicating but as soon as it is stopped, these cells – only one in a million of which may contain HIV genes – start producing HIV again, it reappears in the blood, and more cells are infected.

Several different approaches are being tried to halt ongoing infection, but the one that has received the most attention has been the so-called 'kick and kill' approach.

Initially, gene-stimulating drugs are given that 'kick' the normally quiescent central memory cells into becoming activated and producing some HIV. As long as this remains suppressed at controllable levels with ART, the hope is that by becoming activated, the cells turn into 'effector' cells with short lives and the so-called reservoir of long-term infected cells is drained.

It is possible that, if the reservoir is sufficiently emptied, the body's own immune surveillance could keep HIV suppressed in the very few left. However, one study where HIV reappeared in someone with fewer than two-in-a-billion HIV infected reservoir cells casts doubt on this.

There may need to be further stages where drugs are given that actively target and kill off the activated reservoir cells, driving their number down still further, and then an immune therapy might be given that magnifies the body's natural immune response to HIV and contains the activation of the tiny number of HIV-infected cells that remain.