<qa>  What is the first commercially available integrase inhibitor?The purpose of this study is to characterize the way the first commercially available integrase inhibitor, raltegravir, a new class of antiretrovirals that is used to treat HIV, is distributed into the rectal mucosal tissue. This information will generate important information regarding the drugs penetration into lymphoid tissues that are rapidly depleted in HIV infection. Subsequently strategies to prevent the sexual transmission of HIV and for treating HIV-infected individuals will be designed. 