 This study will comprise two parts Parts A and B. Part A will last 9 months and Part B, 15 months. Part A will consist of 48 participants enrolled in 4 groups. Group 1 participants will be randomly assigned to receive the gag DNA vaccine or placebo. Participants in Groups 2, 3, and 4 will be randomly assigned to receive the gag DNA vaccine and either 100 mcg, 500 mcg, or 1,500 mcg IL-12 DNA or placebo. Vaccinations for Groups 1 through 4 will be given intramuscularly and will occur at study entry and at Months 1 and 3. 