An HIV patient is in remission after a unique stem cell transplant. Why it could be a path to a cure

A German HIV patient who is in remission following a stem cell transplant from a donor with genes that are partially resistant to the disease is giving researchers new hope that more people could benefit from the treatment.

The first step in a stem cell transplant for people with cancer involves wiping out a patient's immune cells with chemotherapy. When patients also have HIV, these cells can be replaced with transplanted stem cells from rare individuals carrying genes that essentially make them immune to the virus that causes AIDS. Only a handful of people around the world are eligible for this procedure because they must have both HIV and cancer.

According to a study presented by Christian Gaebler of Charité — Berlin University's medical school — the German HIV patient was treated for acute myeloid leukemia with a stem cell transplant in 2015. He stopped taking antiretroviral drugs in 2018 and the virus remains in remission. He's one of just seven people who went into remission from HIV between 2007 and 2023. 

In most of these cases, the stem cell donors naturally inherited two copies of the gene called CCR5 delta 32, which confers resistance to HIV. The German patient is the first case where the stem cell donor inherited just one copy of the CCR5 delta 32 gene, according to Gaebler and his co-authors. The research is not yet peer reviewed.

Researchers hope Thursday's virtual announcement at the 25th International AIDS conference in Munich, Germany, could open the door to treatment being offered to more people and have promising implications for future HIV cure strategies.

"Hope is, to me, that a cure is possible, and that's what these cases demonstrate," Sharon Lewin, president of the International AIDS Society (IAS), told reporters. 

But the reality, she noted, is that it's rare.

Come September, the German HIV patient will have been in remission for six years, according to Gaebler, a length of time that gives the researchers confidence in what they're seeing.

"A healthy person has many wishes, a sick person only one," the anonymous patient said in a statement from IAS on Thursday. 

Dr. Marina Klein, a professor of medicine based at Montreal's McGill University, said the man's case could inform how new treatments are developed.

"This case shows that you don't actually need 100 per cent of your cells to be completely resistant," said Klein, who was not involved in the study. 

Research suggests that about 1 per cent of Caucasians were measured to have two copies of the resistance gene, while about 20 per cent have one copy. According to experts who study HIV, in individuals with one copy of the gene, the virus progresses slowly if they don't receive antiretroviral treatment, while those with two copies seem to be able to hold the virus at bay altogether. 

Lewin, the IAS president, says the German patient's experience "suggests that we can broaden the donor pool for these kinds of cases." 

Researchers also hope it could have promising implications for future, more scalable HIV cure strategies.