HIV is a retrovirus – a virus which inserts a copy of its own genetic material into a cell’s DNA, thus changing the cells own DNA. The cell actually treats the virus as a part of it and the virus tricks the cell into replicating itself to form new copies of the virus, which then go on to infect cells. HIV invades a specific white blood cell, called a CD4 Helper Cell or T Cell, which helps the body fight off infection and disease. After the virus infects once CD4 cells it goes on to infect more. The continual replication process in a single cell eventually destroys it, which in time causes a ripple effect and a slow decline of these disease fighting cells in the body.
Antiretrovirals were developed as a method of keeping the virus at bay, i.e. to stop the virus from invading further cells, but to date there has been no cure for HIV. However, following a stem cell transplant, three HIV-positive patients have seen radical changes to their HIV status without the use of antiretrovirals. The first patient in Berlin received a stem cell transplant for treatment of an aggressive blood cancer in 2008, to this day he has been free of the HIV virus. A second patient in London who received a stem cell transplant to help treat Hodgkin’s lymphoma has remained free of the HIV virus for the past 18 months. Most recently a patient who received a stem cell transplant to treat leukaemia, now only has trace amounts of the virus in his body.
When looking further into these cases, one thing was common across the transplants. The stem cells were received from donors who carry a very specific genetic mutation, found in the CCR5 Gene. This mutation affects the virus’s ability to latch on to CD4 helper cells. With no mutation the gene creates a molecule which helps the virus attach and invade the cell; with this mutation the creation of this molecule is inhibited which means HIV can’t attach and invade the white blood cells and spread the virus.
The three patients who are now free of the HIV virus all received stem cell transplants from donors who have the CCR5 mutation. “Once settled into their new hosts, blood stem cells activated and essentially repopulated the entire blood system – immune cells included – with the HIV-resistant super-cells.” Scientists have tried to recreate this process in an attempt to cure HIV patients, but it has not been successful as there are other factors which lead to being virus free and more research needs to be done before any conclusions on this type of treatment can be made.
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