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1 .This is Scientific American 60-Second Science. I'm Cynthia Graber. Got a minute?
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2 .They were thought to have great promise in the fight to stop the spread of AIDS.
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3 .Indeed, vaginal microbicides did a fine job killing HIV in the lab.
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4 .But they failed to work in clinical trials.
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5 .Now, researchers think they have identified the culprit: semen.
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6 .In previous studies, scientists had looked at the HIV virus on cells protected by microbicides.
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7 .But the latest tests evaluated microbicides in the more real-world situation where semen is present.
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8 .And semen stopped the microbicides from working.
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9 .Probably because semen contains protein fragments that help HIV to attach to cell surfaces and infect cells.
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10 .The research is in the journal Science Translational Medicine.
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11 .There's good news, though, a drug not currently used as a microbicide did seem to offer protection.
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12 .It's an antiretroviral called Maraviroc.
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13 .Conventional microbicides target the virus itself.
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14 .But Maraviroc binds to receptors on host cells.
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15 .That action forms a barrier that prevents the HIV virus from attaching to the cell.
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16 .Maraviroc is currently approved as an HIV drug, and is being considered as a microbicide to try to stop infection in the first place.
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17 .The research is a reminder that, in drug testing, context is crucial.
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18 .Thanks for the minute, for Scientific American 60-Second Science. I'm Cynthia Graber.
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