The ultimate goal would allow patients to stop taking AIDS drugs, knocking a hole in a $12 billion-a-year market dominated by Californian drugmaker Gilead and the likes of Pfizer, GlaxoSmithKline and Merck.
It’s unlikely to happen anytime soon, but Brown’s case has opened the door to new ideas. “What it proved was that if you make someone’s cells resistant to HIV…then all the last bits of HIV, that hang around for a long time in patients on treatment, did in fact decay and disappear,” says Lewin.
Now scientists working on mimicking the effect of the Berlin patient’s transplant have had some success. One experimental technique uses gene therapy to take out certain cells, make them resistant to HIV and then put them back into patients in the hope they will survive and spread.
At an HIV conference in Boston earlier this year, American researchers presented data on six patients who had large numbers of white blood cells known as CD4 cells removed, manipulated to knock out the existing CCR5 gene, and then replaced.
“It works like scissors and cuts a piece of genetic information out of the DNA, and then closes the gap,” says Huetter. “Then every cell arising from this mother cell has this same mutation.”
Early results showed the mutated cells managed to survive inside the bodies of the patients at low levels, remaining present for more than three months in five. “This was a proof of concept,” says Lewin. Another potential avenue is a small group of patients known as “elite controllers”, who despite being infected with HIV are able to keep it under control simply with their own immune systems. Researchers hope these patients could one day be the clue to developing a successful HIV/AIDS vaccine or functional cure.
Scientists are also exploring ways to “wake up” HIV cells and kill them. As discovered in the late 1990s, HIV has a way of getting deep into the immune system itself - into what are known as resting memory T-cells - and going to sleep there. Hidden away, it effectively avoids drugs and the body’s own immune response.
“Once it goes to sleep in a cell it can stay there forever, which is really the main reason why we can’t cure HIV with current drugs,” says Lewin. Her team in Melbourne and another group in the United States are about to start the first human trials using a drug called SAHA or vorinostat, made by Merck and currently used in cancer treatment, which has shown promise in being able to wake up dormant HIV.