|Agenda: The Latest Steps in the Search for a Cure for HIV
The Herald Scotland
By Sharon Lewin
April 17, 2018
The delivery of antiretroviral treatment to some 20 million people living with HIV across the world has been one of the most extraordinary global health achievements of the immediate past and present centuries. HIV/AIDS has been transformed from a death sentence only some 30 years ago into a chronic manageable disease. This has been a triumph for modern medicine, evidence-based research and community engagement which together have guided the successful delivery and implementation of HIV treatment, prevention and care.
At the same time, responding to HIV is like any other infectious disease – the general public would expect us scientists to be continually working on something approximating a cure. To date only one person, Timothy Brown, is known to have been cured of HIV infection. He was cured through a dangerous and expensive stem cell transplant from a donor known to be immune to HIV and the process was related to his treatment for acute myeloid leukaemia. It is not a viable route to cure other people, but it did prove a key point – curing HIV is possible.
The main reason why HIV can’t be cured at the moment is that HIV can persist inside a cell, even when viral replication is effectively controlled by antiretroviral therapy. The virus can hide in a cell forever during therapy and re-emerge rapidly, and at any time, once treatment is stopped.
We now know that initiating antiviral treatment early after infection has many benefits. Early treatment can reduce the amount of virus that goes into hiding, can preserve the immune system and also blocks transmission of the virus to others. But early treatment alone cannot prevent the virus from returning once treatment is stopped.
However, we have seen a handful of cases where early treatment with antiretroviral therapy has enabled an individual’s immune system to control the virus, without the need for lifelong treatment. Studies in these people have shown that two things are important to achieve control – low amounts of virus and a high-functioning immune system.
This approach of harnessing the immune system is similar to strategies now being used to treat some cancers. Indeed, there are multiple reasons behind why HIV cure and cancer research has now begun to converge at various points and synergies are being explored.
Both diseases face common barriers: the persistence of virus and certain types of cancer at very low levels that are not easily detected, exhaustion of the immune system and treatment resistance. Significantly too, we do not currently have the tools to properly measure the levels of HIV virus and cancers in the body.
The remarkable advances in immunotherapy to keep some cancers under control is likely to be important to control HIV. Some strategies include drugs that re-energise the immune system or giving an infusion of designer immune cells that can recognise the virus. Clinical trials of people with HIV and cancer are now receiving immunotherapy for their cancer, but these studies will also provide much-needed insights into how immunotherapy will affect the virus itself.
The immune system in people on ART can also be boosted through other drugs and vaccines. In a recent study in a monkey model, an approach like this seemed to work. In monkeys that received an activator of the immune system together with a vaccine, in the form of an antibody, the virus stayed under control in over half the animals once antiviral treatment was stopped. We now need to see if similar success can be achieved in human clinical trials.
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