This study will test the safety of and immune system response to a new HIV vaccine. The vaccine in this study is made from HIV DNA produced in a laboratory. Only part of the virus's DNA is used in the vaccine and the vaccine itself cannot cause HIV infection or AIDS. In addition to HIV DNA, the vaccine contains interleukin-2 (IL-2) DNA fused to a portion of immunoglobulin (Ig) DNA. IL-2 is a chemical that stimulates the immune system and may improve response to the vaccine.

Study hypothesis: The IL-2/Ig plasmid will be very well tolerated in humans.

Over 90% of the 40 million people infected with HIV live in developing countries and have little or no access to antiretroviral medications. The worldwide HIV/AIDS epidemic will only be controlled through development of a safe and effective vaccine that will prevent HIV infection. DNA vaccines are inexpensive to construct, readily produced in large quantities, and stable for long periods of time. The DNA vaccine in this study, VRC-HIVDNA009-00-VP (Gag-Pol-Nef-multiclade Env), uses multiple gene products to increase the breadth of the immune response across different HIV subtypes. The DNA plasmids in VRC-HIVDNA009-00-VP code for proteins from HIV subtypes A, B, and C, which together represent 90% of new HIV infections in the world.

The study vaccine is administered with an adjuvant. The adjuvant is a DNA plasmid encoding interleukin 2 (IL-2) fused to the Fc portion of IgG for enhanced stability. This IL-2/Ig adjuvant may augment the immune system's response to the vaccine.

Participants in this study will be randomly assigned to receive either the vaccine and adjuvant, the vaccine and placebo, the adjuvant and placebo, or placebo alone. All injections will be administered by needle-free injection in the upper arm. Participants will receive four does of vaccine: one at their first study visit and then at Months 1, 2, and 6. Participants will have a follow-up visit 2 days after each injection. Some participants may receive another injection at this follow-up visit. All study participants will be followed for 18 months and will have 16 to 20 study visits. Study visits will last 1/2 to 2 hours and will include blood and urine tests and a physical exam. Participants will also have six HIV tests over the course of the study.

Inclusion Criteria

• HIV negative
• Willing to receive HIV test results
• Good general health
• Acceptable methods of contraception for females of reproductive potential
• Hepatitis B surface antigen negative
• Anti-hepatitis C virus antibody (anti-HCV) negative or negative HCV PCR if anti-HCV is positive
• Normal thyroid stimulating hormone (TSH) level

Exclusion Criteria

• HIV vaccines or placebos in prior HIV vaccine trial
• Immunosuppressive medications within 168 days prior to first study vaccine administration
• Blood products within 120 days prior to first study vaccine administration
• Immunoglobulin within 60 days prior to first study vaccine administration
• Live attenuated vaccines within 30 days prior to first study vaccine administration
• Investigational research agents within 30 days prior to first study vaccine administration
• Subunit or killed vaccines within 14 days prior to first study vaccine administration
• Current tuberculosis prophylaxis or therapy
• Clinical depression with pharmacological treatment within the past 2 years
• Active syphilis
• Serious adverse reaction to vaccines. A person who had an adverse reaction to pertussis vaccine as a child is not excluded.
• Autoimmune disease or immunodeficiency
• Unstable asthma
• Type 1 or Type 2 Diabetes Mellitus
• Thyroid disease requiring treatment
• Serious angioedema within the past 3 years
• Uncontrolled hypertension
• Bleeding disorder
• Malignancy unless it has been surgically removed and, in the opinion of the investigator, is not likely to recur during the study period
• Seizure disorder requiring medication within the past 3 years
• Asplenia
• Mental illness that would interfere with compliance with the protocol
• Other conditions that, in the judgement of the investigator, would interfere with the study
• Pregnant or breast-feeding