The inactive form of HIV that lingers in the body after successful treatment poses a far bigger threat than first thought, scientists have found.
American researchers have found that the hidden virus reservoir – made up of proviruses – may be 60 times larger than originally thought.
These proviruses continue to be a danger as they can continue to replicate HIV if a patient stops taking their treatment.
The study’s authors say the discovery, reported in the journal Cell, makes it harder to find a cure for HIV rather than just treatment.
Dr Robert Siliciano, the leader of the report, said: “It doesn’t mean that it’s hopeless, but it does mean we need to focus on getting an even clearer idea of the scope of the problem.”
Antiretroviral treatment affects active form of HIV, which hijacks the body’s T-cells to replicate itself, but it is unclear what the effects are on the dormant form.
Until this report, scientists have not had an accurate estimate for how big this reservoir of proviruses, which is important according to Dr Siliciano.
He said: “The field has struggled with what you even measure in people who are participating in eradication studies. How do you know how much virus is left?”
The new technique investigated proviruses that remained inactive despite a stimulation to infected T-cells in patients.
At first, scientists believed that they were inactive because of defects to the virus, but 12% of those still dormant possessed fully intact genomes.
These virus genomes were then artificially created in a laboratory, where it was found they could replicate without mutation.
The amount of dormant virus which could still replicate if activated shows that the reservoir is 60 times bigger than previous estimates, according to the report’s authors.
“This is a huge increase in the barrier to curing this disease,” said Dr Siliciano.
He added that only drugs that target those inactive viruses could lead to a complete cure or remission.
The study highlights one of the challenges researchers have in finding out more about HIV, according to Lisa Power, policy director at the Terrence Higgins Trust.
She said: “What is alarming is how many people believe a cure already exists. It doesn’t, and false hope may be leading people to take risks.
“Until a cure is found, we have to throw everything we’ve got behind HIV prevention. Using condoms, testing for HIV and getting treatment are our best weapons against the virus.”