A genetically-modified form of HIV has helped save the life of 7-year-old Emily Whitehead, a patient at the Children's Hospital of Philadelphia. After nearly two years of braving the killer leukaemia, the little girl is now able to go back to school.

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Emily had been battling leukaemia with chemotherapy for almost two years. She suffered from two relapses within the period. U.S. doctors said the young girl was losing the battle against the aggressive disease when they started the experimental treatment in February this year.

HIV was modified such that it would lose the harmful properties that cause AIDS. With the modified HIV, doctors have boosted Emily's own immune system.

Emily was one of a dozen people who have received the treatment. Three adults remain in remission, and two of them have been cancer-free for more than two years now, reports Telegraph's Nick Allen. The treatment failed to work in two adults.

Speaking to news.com.au, Paediatric oncologist Stephan Grupp, who looked after Emily, said the young girl was never at risk of acquiring AIDS in the process of the treatment.

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"The way we get the new gene into the T cells (immune cells) is by using a virus. This virus was developed from the HIV, however all of the parts of the HIV that can cause disease are removed [such that it is] impossible to catch HIV or any other infection. What's left is the property of the HIV virus that allows it to put new genes into cells," Dr Grupp said.

The treatment was no less difficult than chemotherapy for Emily. She had gone to the intensive care unit in the process. But it may be all worth the extreme difficulty. The doctors said it is too soon to tell whether Emily is now cancer-free, but test results seemed promising. If all works well, Emily will have a supercharged immune system against a recurrence of the cancer.

"She has no leukaemia in her body for any test that we can do - even the most sensitive tests," Mr Grupp told ABC news. "We need to see that the remission goes on for a couple of years before we think about whether she is cured or not. It is too soon to say."

The treatment costs about $20,000 for each patient. It worked well with Emily, but the results in others show more studies have to be made. It is hoped that with further research, the modified HIV treatment could replace the more risky bone marrow transplants as leukaemia treatment.

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