A cure for HIV: ‘One of the hardest goals in science’

WEB DESK: Curing HIV will be harder than curing cancer. Apart from a few ‘miracle’ cases, antiretrovirals only suppress HIV, they don’t kill it. But new research is promising.

HIV is “like a time bomb,” said James Riley, a microbiologist at University of Pennsylvania, US. Even now — decades after the virus was identified — and with antiretroviral drugs allowing us to suppress it before it develops into AIDS, 40 million people still live with the condition. Scientists are still trying to find a cure for HIV.

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Because, “unless people get PrEP (pre-exposure prophylaxis) therapy every day, HIV will go off and restart the infection again,” said Riley.

Scott Kitchen, an expert in infectious diseases at University of California Los Angeles, US, described antiretroviral HIV drugs as a “miracle” of modern medicine, but said they were still not a cure for infection.

Finding a cure is proving to be very challenging for researchers. Riley said finding a cure for HIV is “one of the hardest goals in science.”

“We’ll beat solid cancers [cancers with tumours] because we have a good handle on what the problem is and how to solve it. But with HIV, we haven’t got a solution to the problem yet,” he said.

The problem: HIV hides in the human genome

An HIV infection is so difficult to cure because the virus is incredibly effective at hiding in our cells.

When HIV infects our bodies, it integrates itself into our genetic material and hides in the genomes of our cells in a dormant, inactive state.

It is then activated when our cells turn DNA into proteins — a process called transcription and translation — and it’s one that we need for life. HIV piggybacks this process. And our cells inadvertently replicate the virus.

The problem is that there’s nothing to distinguish the cells which harbor HIV from those that don’t, so there are no reliable ways to eradicate HIV from the body — if you can’t see the target, you can’t hit it.

Antiretroviral drugs like PrEP do suppress the virus to undetectable levels, but the virus still remains embedded and hidden in the human genome.

Haven’t people already been cured of HIV?

Seven people are confirmed to have been cured of HIV with a stem cell therapy used to replace all the immune cells in their bodies.

“Everyone who has, to date, been cured of HIV received a bone marrow transplant to treat a cancer [leukemia or lymphoma] while concurrently infected with HIV,” said Kitchen.

But this form of stem cell therapy is unsuitable as a cure for HIV in most people. Bone marrow transplants are a difficult procedure, with a high risk of death. They are only attempted in people undergoing late-stage cancer treatment.

“Outside of the high costs, these procedures, because they carry considerable risk to the patient, need to be performed in a major hospital or medical center. This limits their [use] in many settings where HIV is of high prevalence,” said Kitchen.

Kitchen is currently researching a new type of stem cell therapy as a cure for HIV. It uses modified blood stem cells to kill HIV-infected cells once they mature in the body.

“In essence, this is a ‘genetic vaccination‘ that could allow the body to naturally form cells that eradicate HIV,” he said.

While still in the early stages of research, Kitchen said their approach would avoid the need for chemotherapy or finding a stem cell donor.

Could T-cell therapies (TCRs) cure HIV?

Other researchers are pegging their hopes of a cure on T-cell therapies (TCRs), which do not require a stem cell transplant.

T-cells are a type of immune cell. They detect proteins made inside cells, as though they were viral proteins or toxic chemicals, then kill the cell to eradicate the threat.

If a cell is infected with HIV, it will contain markers of the HIV, but they are very difficult to detect by normal T cells.

“[TCRs] work by designing [specialized] T cells to hunt for markers of HIV in a cell, then kill the cell,” said Riley.

It’s like introducing a pack of hunting dogs into the system who’ve been primed with the scent of a fox.

TCRs are being tested in several clinical trials, with an emphasis on proving their safety. It’s too early to say whether they are effective or not.

Riley said he’s not pessimistic about finding a HIV cure, but conceded the goal was like getting to the moon.

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“Was going to the moon hard? Yes. But we got there. And we invented new technologies because of trying to get to the moon. That’s what I think curing HIV is like. Our efforts will spill over into how we cure other diseases,” he said.