By Maggie Fox, Health and Science Editor

WASHINGTON, May 2 (Reuters) - A new type of treatment that trains immune system cells to better recognize the AIDS virus may help control the deadly and incurable infection, Australian researchers reported on Friday.

Tests on monkeys infected with a similar virus shows the treatment controlled the infection, although it does not cure it, and tests are already planned in people.

The treatment is called OPAL, for Overlapping Peptide-pulsed Autologous Cells, and would be categorized as an immunotherapy technique, or a so-called therapeutic vaccine, Stephen Kent of the University of Melbourne and colleagues said.

Writing in the Public Library of Science journal PLoS Pathogens, they said the treatment involves mixing a patient's own blood cells with tiny bits of protein from the virus.

These cells are then re-infused into the patient.

"Levels of virus in vaccinated monkeys were 10-fold lower than in controls, and this was durable for over one year after the initial vaccinations," they wrote.

"The immunotherapy resulted in fewer deaths from AIDS. We conclude this is a promising immunotherapy technique. Trials in HIV-infected humans of OPAL therapy are planned."

The AIDS virus infects more than 33 million people globally and has killed 25 million since it was identified in the 1980s.

While there is no cure and no vaccine, cocktails of drugs can control the virus. But they have side-effects, are expensive and eventually often stop working.

Kent's team took small bits of the virus called peptides and placed them in lab dishes with both whole blood and isolated immune system cells.

This helped train the cells to recognize the virus and attack it more effectively, they wrote in the paper, freely available at http://www.plospathogens.org/doi/ppat.1000055.

The macaque monkeys were infected with a related virus called SIV or simian immunodeficiency virus.

HIV is tricky to treat because it attacks the immune system. It specifically goes after immune cells called CD4 T cells, the very cells that are supposed to attack and kill viruses.

"Virus-specific CD4 T cells are typically very weak in HIV-infected humans or SIV-infected macaques; dramatic enhancement of these cells were induced by OPAL immunotherapy and this may underlie its efficacy," they wrote.

The treatment appears to work best if started right after someone becomes infected.

"Although it may be challenging to identify humans within three weeks of infection, this is when HIV-1 subjects typically present (show up at a doctors office) with acute infection," they wrote. (Editing by Todd Eastham)

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