Inclusion Criteria

Volunteers may be eligible for this study if they:

• Are 20 to 60 years old.
• Are HIV-negative.
• Have used intravenous drugs in the previous 12 months.
• Are available and commit to 3 years of follow-up.
• Have a Thai National ID or its equivalent such as government official ID or state enterprise ID.
• Are able to understand the study and pass a test showing they understand it, and give written informed consent.

Exclusion Criteria

Volunteers will not be eligible for this study if they:

• Have a serious disease or condition, or history of a serious disease or condition such as lymphoma, that would interfere with the study.
• Are HIV-positive.
• Have ever received an experimental HIV-1 vaccine.
• Have had or expect to have any treatments or medications that interfere with the immune system (e.g., long-term use of systemic steroids, chemotherapy, or radiation).
• Have received a vaccine or immunoglobulin within 2 weeks of receiving the first study injection, or other vaccines within 4 weeks of the first study injection.
• Have received immunoglobulins for a long time.
• Have received non-licensed, research agents within 4 weeks of the first study injection.
• Expect to miss study visits or plan to move within 36 months.
• Are pregnant or breast-feeding or plan to become pregnant during the 36-month study period.
• Are women who have sex with men and do not plan to use effective birth control.