• Safety (local and systemic reactogenicity signs and symptoms, laboratory measures, and adverse and serious experiences)
  
• immunogenicity (presence of HIV-specific immune response as measured by the interferon-gamma ELISpot, FACS Intracellular Cytokine Staining [ICS], neutralizing antibody, or HIV antigen-binding ELISA assays)
  
• social impacts (negative experiences or problems reported by the participants)
  

The development of a vaccine eliciting HIV-specific humoral and cellular immune responses is desirable for the prevention of HIV infection. This study will investigate a combination vaccine regimen consisting of priming with DNA followed by boosting with a recombinant envelope glycoprotein adjuvanted in MF59.

All participants will be followed for 15 months. Participants enrolled in Groups 1, 2, 3, and 4 will receive either the vaccine or placebo. Study visits will be completed at initial entry; five visits every 14 days for the first 2.5 months; and visits at Months 4, 4.5, 6, 6.5, 9, 9.5, 12, and 15. All participants will undergo physical exams, urine collection, and blood tests to assess safety, HIV infection, and immune responses to injections. Risk reduction/pregnancy prevention counseling will be given at every study visit. Participants will also be asked to complete questionnaires about outside testing and beliefs at certain visits.

There are two parts to this study. In Part A, participants will be sequentially assigned to one of three groups. Each group will receive injections of different amounts of either DNA vaccine or placebo at entry, Month 1, and Month 2. This is followed by identical injections of glycoprotein/adjuvant or placebo at Months 6 and 9. Group 1 will receive 250 mcg each of the gag and env DNA plasmid with microparticle vaccine; Group 2 will receive 500 mcg of each vaccine; Group 3 will receive 1000 mcg of each vaccine. Participants will be enrolled sequentially from low to high dose beginning with Group 1.

In Part B, Group 4 will begin the second part of the study simultaneously after safety review of all participants in Part A. Group 4 participants will receive identical injections of either DNA vaccine or placebo at entry and at Months 1, 2, 6, and 9.

Group 5 will begin enrollment after enrollment is completed for Groups 1, 2, 3, and 4. Group 5 participants will receive identical injections of either glycoprotein/adjuvant or placebo at study entry and at Months 3 and 9. There will be 11 study visits for Group 5 participants; they will occur at screening, study entry, and Months 0.5, 2, 3, 3.5, 6, 9, 9.5, 12, and 15. A physical exam and risk reduction/pregnancy prevention counseling will occur at all visits; participants will be asked at every visit about any adverse events they may have experienced. Blood and urine collection will occur at selected visits. Participants will be also asked to complete questionnaires about outside testing and beliefs at certain visits.