The study could reveal more about HIV progression

The Positron Emission Tomography scan (PET) scan reveals areas where immune tissue is actively fighting HIV.

The research, published in the Lancet, indicates that different tissues are active depending on the length of infection.

US scientists say that one day, surgery or radiotherapy might tackle HIV.

However, this idea has been questioned by UK HIV experts, who say that the virus is likely to be present in too many places in the body to make localised therapies an option.

The researchers, from the Johns Hopkins University Bloomberg School of Hygiene and Public Health in Baltimore, looked at 12 people who had recently been diagnosed HIV positive.

Lymph tissue

They wanted to find out if signs of HIV were present in lymphatic tissue - immune tissue which is found in various locations around the body including the neck, armpits and the abdomen.

The lymphatic system is interconnected by vessels which allow the passage of immune cells and lymphatic fluid around the body.

Even if there is no sign of the virus in the blood, many suspect that it can hide within immune cells in these areas, ready to re-emerge if modern drug therapies lose their effectiveness.

The researchers injected the patients with "tracer" chemicals which can be detected by a PET scanner, and are taken up by active lymphatic tissues - thus showing on the scan which areas are active and which are not.

Big difference

They found there was a striking difference in the affected areas in patients with long-standing HIV infections, compared with those who had only been diagnosed a matter of weeks early.

In the recently infected patients, the activity was mainly confined to lymph "nodes" in the head and neck.

Those who had been infected for a little longer showed signs of lymphatic activity in "peripheral nodes" - further away from the head and neck.

Reactivation might not occur for months or years after removal of the active nodes - allowing extended interruptions of treatment Dr David Schwartz, Johns Hopkins University

Those infected the longest - including one person who had been HIV positive for a decade - had activity throughout the lymphatic system, including areas of tissue in the abdomen.

The researchers said that patients - even long-term patients - who had not progressed to develop Aids had small numbers of "persistently active" nodes, most of which were accessible for surgeons.

They believe that by targeting and destroying these either by surgery or via radiotherapy, the progress of the disease could be restricted.

Radiotherapy hope

Dr David Schwartz, one of the researchers, said: "The feasibility of excisional biopsy to study and remove 'foci' of persistent infection should be investigated.

"Although many systemic sites from which latent virus could reactivate would be left, reactivation might not occur for months or years after removal of the active nodes - allowing extended interruptions of treatment."

Doctors would like to minimise the use of powerful anti-HIV drugs to minimise the risk of the virus building resistance to them.

However, Julian Meldrum of Aidsmap, in the UK, said he did not believe radiotherapy or surgery were viable options for HIV patients.

"Although this idea has been discussed before, the areas of the immune system that are affected are widely spread and distributed around the body," he said.

"There are lots of unanswered questions about how HIV spreads around the body - evidence from humans in real life is hard to come by."