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London - Aids researchers believe the time may have come to think the unthinkable: a growing body of expert opinion believes a cure for HIV infection is no longer a scientific impossibility but a realistic goal that scientists could reach in the very near future.
A scientist who shared a Nobel prize for the discovery of human immunodeficiency virus (HIV) has now added her voice to those who believe it is possible to cure a viral infection that until now has been considered life-long, chronic and, although treatable, ultimately incurable.
Françoise Barré-Sinoussi, who first reported the discovery of the Aids virus in 1983 with her colleague Luc Montagnier of the Pasteur Institute in Paris, is expected later today in Washington to say that talk of a cure for HIV should no longer be a taboo subject for Aids researchers.
She will cite the case of the “Berlin Patient”, an American gay man called Timothy Brown who received a bone marrow transplant in 2007 while a student in Germany. The transplant was undertaken to treat a type of blood cancer but in the process it also apparently cured Mr Brown of his HIV infection.
Five years after his transplant, he continues to be free of HIV despite having given up his anti-viral drugs. It is still not clear to scientists why Mr Brown has managed to shrug off his chronic HIV infection so effectively.
For decades, a cure for Aids has been little more than a pipe dream because of the ability of the virus to integrate itself within the genetic material of infected patients. Once installed within a patient's DNA, the Aids virus could “hide away” for years, even decades, from the body's immune defences.
As a result, scientists realised soon after HIV was discovered in the early 1980s that infected people would continue to be at risk of developing Aids throughout their life unless continuously treated with anti-viral drugs.
But Mr Brown's highly unusual case has given some scientists cause for optimism. In a comment article in this week's Nature, Professor Barré-Sinoussi and her colleague Professor Steven Deeks of the University of California, San Francisco, say that Mr Brown has been effectively cured of HIV - the first person in the world to fulfil the strict scientific definition of a cure.
“He has now been free of readily detectable virus in the absence of therapy for more than five years. In other words, he is cured. His experience suggests that HIV infection might one day be curable,” they say.
On Friday in Washington, Professor Barré-Sinoussi and Professor Deeks will take part in the launch of a global scientific strategy document for Aids and HIV prior to the 2012 International Aids Conference which begins next week. The document will place “cure research” centre stage, suggesting that instead of focusing almost exclusively on research into better anti-viral drugs and HIV vaccines, scientists should think about ways of curing patients outright, or at least to a point where progression to Aids becomes unlikely.
“It may not be necessary to completely eradicate the virus in the individual, however. In about 1 per cent of people infected with HIV, the virus is natural controlled, such that their risks of disease progression and transmission are minimal,” say Professor Barré-Sinoussi and Professor Deeks.
“Scientists have studied these 'elite controllers' in search of a path towards developing a vaccine. Elite controllers could also provide clues about how to control, if not eliminate, established infection,” they say.
Elite controllers include people who carry natural mutations in a gene called CCR5. About one in 100 people have such mutations, which prevent HIV from infecting the type of white blood cells where the virus is thought to lie dormant for many years.
Mr Brown's bone marrow donor was someone who was an elite controller. As a result of the transplant, Mr Brown's white blood cells - the T cells of the immune system - were repopulated by those of his donor, apparently making Mr Brown resistant to HIV.
However, not everyone is convinced that the procedure eliminated all of the HIV from Mr Brown's body. Alain Lafeuillade, head of infectious diseases at the General Hospital in Toulon, France, has questioned whether the word cure is applicable given that some scientists claim to have found low levels of HIV “viraemia” within Mr Brown's body.
“We cannot declare 'cured' a man who still has low levels of viraemia, low levels of anti-HIV antibodies not detectable by commercially available tests,” Dr Lafeuillade said.
Professor Deeks, who has followed Mr Brown's case for many years, meanwhile insists the patient has been effectively cured. “By any reasonable definition, Mr Brown is cured. He has been off drugs for over five years and has done well. If he has any virus left, which remains an unsettled question, it is clearly not of clinical relevance,” Professor Deeks said.
But even if Mr Brown does continue to defy scientific dogma, the method of his cure would never be appropriate for treating the millions of people in the world who are infected with HIV. A bone marrow transplant is not only expensive and difficult to undertake, it is extremely risky - Mr Brown suffers chronic neurological problems as a result of a second bone marrow transplant he had to receive to treat a relapse of his blood cancer.
Professors Barré-Sinoussi and Deeks accept that his case is only a starting point on the long journey towards a possible cure for HIV. “The barriers to curing HIV are real, and they may prove to be insurmountable,” they admit. -