Marc Franke, a 54-year-old from western Germany, was dealt his first blow in 2008, when he learned he had HIV — a diagnosis that "ripped his world apart," he said.

"I had always used protection, but apparently one time I didn't and it got me," he told DW in his home in the German region of North Rhine Westphalia. Thankfully, HIV isn't the death sentence it used to be. After decades of medical progress, patients receiving antiretroviral therapy (ART) have the same life expectancy as those without the infection.

But, three years later, when Franke was only 42, he started feeling sick again. He thought he'd come down with pneumonia. But, days after checking into the hospital, he was dealt his second blow: a diagnosis of acute myeloid leukemia at an abnormally young age — people are typically diagnosed around age 69.

Meeting Ingo

His hospital stay in 2011 proved life-changing, and not just because it was then that Franke found out he had leukemia. It also marked his first meeting with his future husband, Ingo, a schoolteacher from Dusseldorf.

"We chatted online, and he came to visit," Franke said. "He didn't care about the HIV. He didn't care about the problem with my blood. He didn't care about my sickness. He cared about me as a human being."

Franke said the prospect of a future relationship with Ingo — the "power of love," as he called it — kept him going that winter, despite his double diagnosis.

"I had to look good when Ingo came to visit," said Franke. "The doctors were saying, with the HIV and the chemotherapy for leukemia, 'Marc, you must be feeling horrible.' But I wasn't. I knew I wanted to live with him and that's what got me through it all."

Relapse brings hope

After undergoing chemotherapy, Franke went into remission, but relapsed just one year later, in August 2012. The leukemia started spreading aggressively in his body, leaving him with few options for treatment. The only possibility left was a stem cell transplant, an invasive procedure only recommended to some patients with certain types of deadly cancers — like leukemia — that haven't responded to chemotherapy.

The doctors were keen to try the treatment on Franke. They knew of other cases when transplants of this sort — using stem cell donations from people with a specific genetic mutation that means they lack what is called the "CCR5-Delta 32 receptor" — had "healed" HIV patients, and wanted to see if the same could work for him.

Timothy Ray Brown, who was known as the "Berlin patient", was the first person to be healed of HIV using this method. His cure was announced in 2008. Adam Castillejo, the "London patient," became the second. His cure was announced in 2019. Two others are considered "possibly" cured of the virus.

People with the CCR5-Delta mutation are essentially immune to HIV, because the virus has to dock onto the CCR5 receptor in order to live in the body. Without the receptor, the virus cannot survive.

The doctors started looking for a donor. 

Fortunately, they were able to locate one with the mutation quickly —  former flight attendant Anja Prause, also from the west German region North Rhine Westphalia.  The transplant using Prause's bone marrow took place on Valentine's Day in February 2013, and would cure Franke of HIV. But it would be years until either of them would find out it had worked.

Stem cell transplants not a scalable treatment

Stem cell transplants for leukemia patients like Franke work like this: First, intensive chemotherapy essentially wipes out the patient's old immune system.

Then doctors facilitate the stem cell transplant, inserting the donor's cells into the patient's bloodstream. If everything goes right, these cells will find the patient's bone marrow and start producing new, altered blood cells.

It's a high-risk procedure that ends in death up to 15% of the time, doctors say. Because this treatment can only ethically be offered to patients like Franke who need a stem cell transplant in order to survive, cancer-free HIV patients aren't eligible.

"The people are at very high risk of infections, of bleeding and so on and so on," said Björn Jensen, Franke's doctor. "And this is why people die from this procedure and this is why you can't just use it for, you know, diseases that are not deadly. Even if they would be willing to take that risk, it's just unethical from a physician's point of view to take a risk of killing somebody with 15% probability when you have combination antiretroviral therapy."

How important is a cure?

With the seeming ubiquity of antiretroviral therapies in the developed world — which, if taken daily, can render a person's HIV more or less void — one may wonder whether an HIV cure is even worth it at this point.

Interviews with HIV-positive patients show it is.

"I've been living with HIV for the past 15 years," Patrick McGregor, an HIV patient from South Africa, told DW. "Finding a cure will be imperative for us to prevent unnecessary death for our brothers and sisters because HIV still kills a lot of people, particularly in our country, and in my province in South Africa. Many of my comrades that I know have defaulted on treatment and then they end up dying."

Studies show that, globally, 25% of people with HIV aren't taking ART medications because they don't have access to them. This doesn't include the many who merely forget to take their pills, which can cause complications.

Genetic modification a possible solution

So if stem cell transplants won't ever offer a scalable cure, what will? Doctors are looking at other ways to cure HIV through the modification of patients' CCR5 receptors, proteins on the surfaces of white blood cells, through genetic modification — without wiping out their entire immune system.

Monique Nijhuis, who researches HIV cures at the AI System headquarters in Utrecht in the Netherlands, which oversees patients who have undergone procedures like Franke's, said scientists have already successfully facilitated what it takes to "cure" HIV in lab settings.

"I can very easily cure cells infected with HIV using these different techniques," she told DW. "The thing is that we have to translate this to an individual with HIV in a way that is not harming the individual with HIV."

Although genetic modification isn't as risky as stem cell transplants, in order to offer the therapy at a population level, scientists need to make sure that the "scissors" involved in the therapy only cut out the intended receptor, CCR5, and nothing else, Nijhuis said.

"I'm not really 100% sure whether these scissors that we have trained so much in the lab to recognize CCR5 are not by mistake are also recognizing something else," she said. "Because that would be harmful if those scissors would go and go and react against CCR2 or any other chemokine receptor."

More research has to be done to ensure the scissors only cut out the one specific reactor, CCR5, and not reactors essential to people's health. There are research institutes currently doing this work, like Tulane University in the US state of Louisiana, as well as US-based company American Gene Technologies, which is about to publish phase one clinical trials on human beings.

Franke meets his donor

Two years after Franke received the stem cell transplant, he met Prause. The contact between the two started with a letter from Prause, who'd been informed by doctors that everything had gone well with Franke.

"Hello, you," she wrote. "I guess with us being pretty much a bullseye in genetic terms, I think I can use the informal pronoun ‘du' here. We're almost family. From what I've been able to hear, you are doing better. It will, of course, be a long way to full recovery. But I am overjoyed that you have successfully taken on my transplanted cells. My thoughts are with you often. I close my eyes for a short moment and hope to hear from you soon that you are okay. With love from all my heart."

A few years later, in 2018, Franke discontinued his use of antiretroviral therapy for HIV under medical supervision. He continued testing for the virus twice a week — he still tests now, but only once every two months.

"When people call Dr. Jensen a healer, he's still very careful with the term 'cure,'" said Franke. "But when he writes an article in Nature Medicine about how I've been cured of HIV, I think that's all the proof I need."

Edited by: Jane Paulick

This story was adapted from a DW Science Unscripted podcast published July 13. To hear from Marc Franke and others featured in this story, click here: