The stem cell transplantation as part of a cancer treatment, although the HI virus disappeared, but German researchers urge caution: As HIV therapy is good stem cell transplantation.

Nobody wants to talk about “healing,” but even so, the news that for the second time an HIV patient is virus-free after a stem cell transplant made headlines worldwide.

Scientists had reported on Tuesday that in a previously HIV-positive patients 18 months after a special stem cell transplantation virus no longer be detected. The male lymphoma of a lymphoma, Hodgin’s lymphoma, had transplanted stem cells from a bone marrow donor that is resistant to HIV infection due to a rare genetic modification. After this stem cell treatment, the “London patient” no longer shows symptoms of HIV infection.

Genetic specificity of the stem cell donor

The decisive factor is the stem cell donor, in which the HI virus can not infect an immune cell, since a gene mutation on the surface of immune cells used by most HI viruses receptor, the CCR5 receptor, is defective and thus functionless. The HIV virus uses this receptor as a type of portal of entry for the infection of immune cells. Without the functioning co-receptor, this path is denied him.

There had been a similar case 12 years ago. The “Berliner Patient” Timothy Ray Brown is considered since 2008 as the first and only healed of HIV infection man. The London doctors treated the patient described now on the same principle as the Berlin colleagues at the Charité.

The fact that there is now a second case was received enthusiastically in the professional world: “Repeatability is a decisive criterion of scientific evidence,” said the director of the Department of Virology at Heidelberg University Hospital, Hans-Georg Kräusslich . According to the president of the German Society of Infectious Diseases (DGI), Gerd Fätkenheuer , the second case shows that the cure of the Berlin patient was not a singular event, but in principle repeatable. It boosted scientists looking for ways to cure those infected with HIV and could limit the number of treatment strategies.

German scientists urge caution

“This is an encouraging sign, but no proof of cure,” said the Heidelberg virologist Hans-Georg Kräusslich. For example, a baby had no detectable amount of virus in the USA for a total of 27 months after the therapy, after which the virus had recurred.

Gero Hüter, who had treated the “Berlin patient” Brown at the Berlin Charité in 2008, pointed out that some patients who had received the same treatment in the meantime had died early of complications or relapses of their cancers.

Myanmar AIDS patients medication (picture-alliance / dpa / L. Bo Bo)

Antiretroviral therapy (ART) with drugs remains the only HIV treatment option so far

In the future, stem cell transplantation will not be an option for curing HIV infection. A stem cell therapy is a massive intervention that “would not be acceptable in view of a generally well-tolerated and long-term effective antiviral therapy, if it were not indicated for other medical reasons,” said Kräusslich. In both cases, patients had received this stem cell therapy because of their cancer rather than their HIV disease.

Worldwide, millions of HIV patients will be treated with antiretroviral therapy (ART), but this does not release them from the AIDS virus. Lifelong use of drugs that control the virus is currently the only way to treat HIV.

Lengthy and delicate search for HIV therapy

Which methods are successful in the treatment of HIV in the end, is still largely unclear. The focus of science is the functionless CCR5 receptor on the surface of immune cells. For the development of HIV therapies, the genome of cells in HIV patients could be changed to the variant that causes resistance. For example, it is attempted  to destroy the gene for the CCR5 receptor with the gene scissors CRISPR / Casc9 in the patient’s own stem cells in order to allow non- infectible immune cells to be permanently produced from the person’s stem cells.

HIV Laboratory Screening Science (picture-alliance / dpa / G. Bally)

The focus is on the functionless CCR5 receptor on the surface of immune cells

This – ethically controversial – approach was also pursued by the Chinese researcher He Jiankui , who changed the genome of embryos by means of genome manipulation. He caused a storm of indignation with this experiment at the end of last year, and the Chinese leadership has drastically tightened the rules for all genetic research in China.

Almost 37 million people worldwide are infected with the HIV virus, but only 59 percent of them receive antiretroviral therapy. Every year, around one million HIV patients die from diseases related to the virus. And meanwhile, a new, drug-resistant HIV virus is causing increasing concern among experts.

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