After a stem cell transplant, a patient with HIV appears to be free of the virus.
Ravindra Gupta of the University of Cambridge was the physician who led the team that treated the patient. The blood cells of the patient’s bone marrow were destroyed and replaced with stem cells from a donor with HIV-resistant white blood cells. 16 months after the stem cell transplant, the patient stopped using antiretroviral drugs, and after 18 months of being antiretroviral drug-free, the patient shows no signs of the HIV virus.
Human Immunodeficiency Virus, or HIV, is a retrovirus that was first introduced to the human population between the years 1920 and 1940. It has 2 versions, HIV-1 and HIV-2, both of which evolved from non-human primates. In 2017, 36.9 million people across the globe were currently living with HIV or AIDS. 1.8 million of those people were children, and only 21.7 million people living with HIV were able to access antiretroviral therapy. This means a staggering 15.2 million people in 2017 were living with HIV and its consequent illnesses without treatment. It is considered an epidemic that has only been around, at least in humans, for about 100 years. The peak of the epidemic was in 1996, when AIDS was the leading cause of death in people of colour in the United States between the ages of 25 and 44. The most commonly affected group of individuals are male people of colour who have male to male sexual contact. HIV/AIDS is currently most prevalent in countries with majorly low- to middle-income.
The virus itself enters the body through injured skin, mucous membranes, infected needles, or it may be inherited from a parent. The virus infects and destroys the cells of the immune system, leaving those with the disease vulnerable to opportunistic infection from other viruses, bacteria, and even cancer. Once the immune system is taken advantage of and the individual with the disease is affected by an opportunistic infection, the disease progresses to Acquired Immune Deficiency Syndrome, or AIDS.
This patient who was treated not only had HIV, but also had a form of blood cancer that was not responding to chemotherapy. The donor who gave the stem cells to be transplanted in the patient’s bone marrow was specifically chosen because their CCR5 gene had two copies of a mutation. The CCR5 gene codes for a co-receptor on T cells and macrophages that allows the HIV virus to bind to the cells and enter them. If the virus enters a host cell, it is then able to metabolize and therefore proliferate, or in other words create more viruses which will infect more host cells. Having a mutation, or better yet two mutations, in the CCR5 gene means the T cells and macrophages are resistant to HIV because their co-receptors are not compatible with the virus. By replacing the patient’s white blood cells with stem cells with a mutated CCR5 gene, the white blood cells were able to proliferate and eventually overtake the patient’s original white blood cells. This means all of the T cells and macrophages were eventually replaced by those that are resistant to HIV. This phenomenon was tested in lab, with researchers trying to infect the newly created white blood cells with the HIV virus. They were unable to do so.
A similar experiment was done to Timothy Ray Brown, who had acute myeloid leukemia, in 2008, but his treatment was much more aggressive. In order to prepare for the transplant, he was given both chemotherapy and radiation therapy across his entire body. The recent patient was able to avoid radiation therapy. This is good news, as this treatment for HIV means a less aggressive preparation than was initially thought. However, this treatment is not suitable for those with HIV but not cancer. Bone marrow transplants are risky, invasive, and painful procedures that are unnecessary for HIV patients who respond well to antiretroviral drug treatment. For those with cancer who need a bone marrow transplant anyway, replacing the blood cells with stem cells from a donor with a mutated CCR5 gene is something that could kill 2 birds with 1 stone. Unfortunately, only 1% of people with European descent have a CCR5 gene mutated in 2 places.
Although the treatment will not be suitable for all HIV patients, this procedure is a major advancement in medical research. It cannot be certain that the patient is cured of HIV until quite some time has passed, but Timothy Ray Brown has been HIV free for over a decade, so there is a possibility. Luckily, the numbers of people affected by HIV have been steadily declining in recent years, and the numbers of people who have access to antiretroviral drug therapy have increased. Pregnant women with HIV are of particular interest to provide antiretroviral drug therapy to in order to keep them alive but also to reduce the risk of transmitting HIV to their children. More and more governments are working towards reducing the prevalence of HIV/AIDS, and awareness and information on HIV/AIDS is only spreading, so the outlook for an end to the epidemic and a possible cure to HIV/AIDS is promising.
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