The second ever case of cured human immunodeficiency virus (HIV) happened to 40-year-old Londoner Adam Castillejo, who has been 30 months HIV free since the beginning of March 2020. HIV was the last widespread global pandemic since coronavirus, beginning in 1981, infecting 75 million and killing 32 million.
HIV is a virus spreading through blood, breast milk, semen, pre seminal, rectal and vaginal fluids, most commonly transmitted through sex, sharing needles and perinatally. HIV attacks and destroys the infection fighting CD4 cells of the immune system, making it harder for the body to fight infections and certain HIV related cancers.
Antiretroviral therapy (ART) has significantly reduced the spread of HIV by preventing infected cells from multiplying. ART works in two ways: virological reduction, which reduces the viral load of HIV in the body to prevent progression, and by improving immunological function, which strengthens the immune system so it can fight off potential infection. This is the current ‘cure’ for HIV and enables sufferers to live normal lives with the disease and have families without passing HIV on. This treatment has significantly reduced the death toll of HIV, recorded in 2018 as 56% lower than its peak in 2004.
“Over a number of years the donor cells replaced the immune cells, essentially curing HIV as both patients stopped ART and were without the disease.”
However, the two men cured completely of HIV, Castillejo and Timothy Brown, known as the “Berlin Patient” after being cured in 2011, received a different treatment. Both patients underwent stem cell treatment for different cancer related issues. Stem cell transplants replaced the patient’s susceptible immune cells with ones that could resist infection, and therefore stopped the virus being able to replicate in their body. Usually, stem cell treatment is generated from the patient’s own stem cells, however, due to the damage caused by HIV to their own stem cells, external stem cells were used.
These external stem cells had a mutated copy of the CCR5 receptor, the cell which receives the virus, meaning the virus could not penetrate the cells in the body it would normally infect. Over a number of years the donor cells replaced the immune cells, essentially curing HIV as both patients stopped ART and were without the disease.
Although proven effective on these patients, stem cell therapy is an aggressive form of treatment used primarily to treat cancer and is a high risk procedure. The quality of life an average individual can get from ART is near normal, save having to take regular antibiotics and endure minor side effects. So although a cure has been found, there is not necessarily a demand for a different cure among HIV patients.
“Different strains are prevalent across the globe and ART has to be modified accordingly in order to combat the disease efficiently”
This is not to undermine the severity of the disease. In the African region, 61% of global HIV deaths occurred, where patients often lack resources. Different strains are prevalent across the globe and ART has to be modified accordingly in order to combat the disease efficiently.
Additionally, the mutated copy of the CCRS receptor was randomly generated and is almost impossible to replicate, so it may not be possible to harness for widespread use. As Mr Cahillejo outlines, “I was in the right place, probably at the right time, when it happened”.
Finally, the results of this cure have not been proven to be permanent. There is a risk that infected cells could replicate again and the HIV complications could return. Professor Sharon Lewin from the University of Melbourne, Australia states “only time will tell” if stem cell treatment can be seen as a permanent solution.
Roma Coombe
Featured image courtesy of Christoph Scholz via Flickr. Image license found here.
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