Charlie Sheen?s porn star ex Bree Olson has dismissed reports suggesting she?s HIV-positive as the actor prepares to address the same gossip in a candid TV chat on Tuesday. According to a press release Sheen will appear on ?Today,? when he will make a ?personal announcement?, but his ex-girlfriend has already made it clear that if the rumors are true, she has not contracted the virus. Meanwhile, sources tell ?Access Hollywood? that Sheen?s ex-wife Denise Richards has known about the actor?s alleged HIV diagnosis for years.