Scientists take step towards HIV cure Adam Cresswell, Health editor 30jun07
SCIENTISTS have discovered how to strip the embedded genetic code of HIV out of infected human cells - a breakthrough that could lead to treatments, or even a cure. a.. Adam Cresswell: Light at the end of the tunnel? In a move that has stunned HIV experts, German scientists reported yesterday that they had engineered an enzyme that attacked the DNA of the HIV virus, and cut it out of the infected cell. Until now, HIV research had focused on improving ways to stop infection spreading, thereby postponing the onset of AIDS, when opportunistic infections overwhelm the body's damaged immune system. Other areas of research, more hypothetically, are seeking a vaccine to prevent infections taking hold in the first place. Rooting out established infections had been thought of as next to impossible. The results, reported in the journal Science, make clear that because the experiments were conducted in a test tube, the finding is still a long way from being translated into an effective treatment. Australian experts have described the findings as exciting and, in an accompanying editorial, Alan Engelman, of Harvard University's Dana-Farber Cancer Institute, said the results changed the outlook for HIV research. "A customised enzyme that effectively excises integrated HIV-1 from infected cells in vitro might one day help to eradicate (the) virus from AIDS patients," he wrote. An estimated 15,310 people were living with HIV or AIDS, the condition it causes, in Australia at the end of 2005. Forty million people are thought to be infected worldwide. Sharon Lewin, president of the Australasian Society for HIV Medicine and director of infectious diseases at The Alfred hospital in Melbourne, said the finding was "very exciting" and "a very major discovery". "It's the beginning of a new avenue that we might have towards a cure, but any cure is still a long way off," Professor Lewin said. Steve Wesselingh, an HIV physician and director of Melbourne's Burnet Institute, said it was an important step as eradication had been considered practically impossible. "There's a huge number of cells that have integrated viral DNA, including brain cells," Professor Wesselingh said. "You have to design something that can find all the viral DNA and remove it all -- all you have to do is leave one copy, and it reactivates." Cutting HIV out of infected cells had been dismissed as a distant dream because the virus is so good at hiding itself. As a retrovirus, HIV splices itself into the host cell's DNA -- meaning it is inextricably linked to the person it has infected. The infected cell can remain in a latent state, when it is all but undetectable by the body's defence mechanisms, or it can become active. When activated, the infected cell turns into a factory for making more viral copies, killing the cell in the process. The new copies go out to infect other cells. What makes HIV so pernicious is that it targets the immune cells that co-ordinate the body's fight against invaders. While existing anti-retroviral drugs are effective at stopping the virus from replicating, they cannot root out the viral DNA, meaning that replication takes off again if patients try coming off the medications. In the German experiments, the enzyme recognised sections of infected cell DNA as belonging to HIV, and cut it out. The enzyme, Tre recombinase, eliminated the virus from the infected cells in about three months. The researchers were optimistic about their ability to design extra enzymes that would target other parts of the virus's DNA. Additional reporting: AFP http://www.theaustralian.news.com.au/printpage/0,5942,21992355,00.html
