The primary focus of the Vaccine Research Center (VRC) at the NIH is to develop vaccines for HIV/AIDS. The main purpose of this study is to look in detail at the body s immune response to two experimental HIV vaccines currently in development at the VRC. One is known as the rAd5 vaccine and the other is known as the DNA vaccine. These vaccines are made with pieces of manufactured DNA. They do not contain live or killed HIV. It is impossible for study vaccines to give you HIV and they cannot cause you to give HIV to someone else. Both of these experimental vaccines have been given to people before in other research studies. They have not been approved for treating or preventing HIV infection.