In fact, optimism ran so high at the international Aids conference in the US capital of Washington DC this week that some experts said the cure could be found in the next 10 years.

The renewed optimism followed presentations of the latest research into HIV, which causes Aids.

Findings of several studies have shown that the HI virus can be controlled and prevented from multiplying, and be completely eradicated in some cases, through various mechanisms.

These include gene therapy, beginning treatment soon after infection and stopping after a few years, and by waking up and killing dormant HIV-infected cells.

Gene therapy, which involves a stem cell transplant, has been proven to work.

In 2007, German resident ­Timothy Brown was cured after he received a stem cell bone marrow transplant from a donor who had a rare genetic mutation known as CCR5-Delta 32.

The mutation deletes the CCR5 receptors found around immune system cells, making it impossible for the HIV to enter and infect them as it needs the receptors as a gateway.

People who have this genetic disorder are resistant to HIV. Even if they are infected, the virus cannot multiply and ends up ­being flushed out of their systems.

Brown received stem cells from a donor with the CCR5 deficiency and today he has no trace of HIV.

With his colleagues, Professor Daniel Kuritzkes, head of the infectious diseases division at Brigham and Women’s Hospital in the US city of Boston, pursued a similar method three years ago on two HIV-positive patients who developed lymphoma, a cancer of the lymphatic system.

The study’s findings presented on Thursday by team member Jim Henrich showed that a stem cell transplant had the same effect on the two patients. They remain on ARV treatment, however, until they receive permission from US health authorities to stop.

“There are no traces of HIV in the patients. There were a few after the transplant but after several tests they remain undetectable,” Kuritzkes said.

However, he did say that the two patients are not yet considered cured “because they are still taking antiretroviral drugs which could be the reason why the HIV is not surfacing”.

“We believe that the continuous administration of effective ARV therapy after the transplant protected the donor cells from being infected. This then resulted in the donor cells eliminating the patient’s cells and replacing them,” he said.

While these findings were welcomed by HIV clinicians, policy makers and civil society, scientists still have to figure out how to make any new treatment safe and affordable.

“Gene therapy is not suitable for generalised use,” said Kuritzkes. “A person has a 15% chance of dying during or after chemotherapy and stem cell transplant. There is also the risk of infections and the cells not reacting well.”

Spanish virologist Professor Javier Martinez-Picado agreed: “This type of intervention is so complex and risky it would not be applicable on a large scale.”

He suggested that gene therapy be used as a base for expanding research on a cure for HIV.

“We have to consider the functional cure model that aims at the generation of effective host immunity to HIV in the absence of therapy that can eradicate HIV.”

The functional method involves studying a group of people who are able to control the HIV either spontaneously (called elite controllers) or after early and timeously ended treatment (the post-treatment controllers).

A study on a group of 15 people in France who became HIV-positive and started treatment early found they were able to successfully stop taking ARVs without the HIV resurfacing.

Charline Bacchus, lead researcher of the study at the French National Agency for Research on Aids and Viral Hepatitis, said: “Six years after interruption of treatment, patients treated early on in the post-infection period present a perfect ability to control the HIV infection.