Can we cure HIV?
Article by C Foster, S Fidler October 2018
The simple answer is no, not yet, however we can control HIV extremely well with antiretroviral (ART) medicine. Antiretroviral medicines work by blocking the virus from growing. In doing so they stop the virus killing CD4 (white fighter) cells and allow the body’s immune system to recover. When the virus is completely blocked (known as undetectable viral load), this means there are hardly any new HIV virus particles being produced, but there are still a very small number of cells that have virus inside their DNA- Reservoir cells- that are invisible to the immune system and are not affected by the medicines. It is because of these reservoir cells that as soon as ART is stopped HIV will start to grow again and it is these cells that are preventing us curing HIV completely with the drugs we currently have available to us.
There are two main types of HIV cure: the first is the standard cure that means there is NO virus found in any part of the body or cells even when ART has been stopped. This is called a sterilising cure. So far there is one man in the world who has been cured of HIV like this; Timothy Brown (also called the Berlin Patient). He had HIV and was successfully on ART for many years but then developed cancer of his lymph glands. As part of his cancer treatment many years ago he had chemotherapy, total body irradiation and two bone marrow transplants; the second transplant after his cancer came back. It is now 10 years since he finished his cancer treatment and stopped ART. It appears that it has not been possible to identify ANY cells that are infected with HIV, even reservoir cells, suggesting that he has been cured of the infection. Whilst the complicated treatment for Timothy Brown was necessary to treat the cancer it is not the sort of treatment that could be suitable for everyone living with HIV. Bone marrow transplants alone have a 20% risk of death and require you to take lifelong medication afterwards to keep the transplant working – more pills, more times a day than you would take for HIV treatment. The case is an important concept showing that HIV COULD be cured, an idea that was not previously thought possible.
The other type of cure for HIV is called a “functional cure or HIV remission” This means that after stopping ART, although it is still possible to detect extremely small amounts of HIV viral protein in cells of the HIV reservoir using very sensitive research tests, there is no live HIV virus. This is important because it means there is no killing of CD4 white cells and no growing virus which means HIV cannot be passed onto sexual partners or from a mother to her baby.
There have been a few cases reported of infants and young children who have remained off ART but with no live virus in the blood for several years, which is very unusual. The Mississipi Baby was born to a mother who was not on antiretroviral therapy and therefore there was a high chance she could pass HIV onto her baby at birth. (If your viral load is undetectable when you have a baby the risk of passing HIV to your baby is less than 1 in a 100). The baby was started on antiretroviral therapy at 30 hours of age to try and prevent HIV infection. Early blood tests suggested the baby was infected and so stayed on treatment. When the baby was about 18 months the mother stopped the baby’s treatment and very surprisingly the baby’s viral load stayed undetectable. Research tests on the baby showed extremely low levels of HIV protein but no live virus a few years after stopping ART, although in the end the virus did come back in this child. Similarly there have been 2 cases (one in France and one in South Africa) reported of teenagers who have been born with HIV, took ART for several years and then stopped medicines but no live virus has returned. These cases are very rare but can help scientists learn a lot about HIV. Almost all people who stop ART the virus comes back in the blood within 4 weeks.
There has been some more recent encouraging developments looking at new treatments in addition to ART that may work to remove some of the HIV reservoir cells, that are being tested in clinical research (experimental) to see if they can reduce the number of HIV reservoir cells even more than ART alone. These include proteins called Broadly Neutralising antibodies, which seem to remove HIV reservoir cells, as well as certain types of special treatment vaccines that can help the immune fighter cells to reduce the number of reservoir cells. There is a lot of research starting that will combine these different new treatments with ART to see if we can end up with HIV remission.
At the moment the best advice is to start ART when you find out you are infected with HIV. Stay on your HIV medicines to keep your viral load undetectable and stay well while scientists work out what additional treatments may work better to control the virus and how best to do this. If you are interested in this area of research look at the CHERUB Collaboration website for more information on studies in the UK. At the moment we do not recommend anyone stops their ART since the research suggests that apart from very rare cases, virus will come back, and this will probably happen quite quickly.