Inclusion Criteria

Volunteers must have:

• Negative ELISA for HIV within 8 weeks prior to immunization.
• CD4 count greater than or equal to 400 cells/mm3.
• Normal history and physical examination. [Refer to Laboratory values for additional requirements.]

Exclusion Criteria

Co-existing Condition:

Volunteers with the following conditions or symptoms are excluded:

• Medical or psychiatric conditions or occupational responsibilities which preclude subject compliance with the protocol.
• Recent suicidal ideation or psychosis.
• Active syphilis. NOTE: If the serology is documented to be a false positive or due to a remote (greater than 6 months) treated infection, the volunteer is eligible.
• Active tuberculosis. NOTE: Volunteers with a positive PPD and a normal chest x-ray showing no evidence of TB and not requiring INH therapy are eligible.
• Positive for hepatitis B surface antigen.

Volunteers with the following prior conditions are excluded:

• History of immunodeficiency, chronic illness, or autoimmune disease.
• History of cancer unless there has been surgical excision followed by a sufficient observation period to give a reasonable assurance of cure.
• History of suicide attempts, recent suicidal ideation, or past or present psychosis.
• History of anaphylaxis or other serious adverse reactions to vaccines.
• History of serious allergic reaction to any substance requiring hospitalization or emergency medical care (e.g., Stevens-Johnson syndrome, bronchospasm, or hypotension).
• History of reaction to thimerosal.

Prior Medication:

Excluded:

• Live attenuated vaccine within 60 days of study. NOTE: Medically indicated subunit or killed vaccines (e.g., influenza, pneumococcal) are not exclusionary, but should be given at least 2 weeks away from HIV immunizations.
• Experimental agents within 30 days prior to study.
• HIV-1 vaccines or placebo as part of a previous HIV vaccine trial.

Prior Treatment:

Excluded:

• Blood products or immunoglobulin in the past 6 months.
• Experimental agents within 30 days prior to study.

Risk Behavior:

Excluded:

• Volunteers with an identifiable higher- or intermediate-risk sexual behavior for HIV infection (i.e., AVEG Risk Groups C or D ).
• History of intravenous drug use within 12 months prior to enrollment.