Subjects from both groups will be admitted to the NIH Clinical Center overnight for the first 24 hours following vaccination with rAd5. On the rAd5 vaccination day, peripheral blood samples will be collected for serum, plasma and peripheral blood mononuclear cells at seven target time points in the first 24 hours as follows: pre-injection and post-injection hours 1, 3, 6, 12, 18 and 24; then days 3, 5, 7, 14 and 28 post-rAd5 vaccine. Mucosal sampling will occur on day 14 after rAd5 vaccine. This will include buccal mucosa, rectal secretions, cervical secretions (from women) and semen samples (from men). There will be a blood collection to assess innate immunity following the 3rd DNA vaccination in Group 2 with blood draws at pre-injection and at post-injection hours 1, 3, 6 and 18.