Inclusion Criteria

Subjects must have:

• Negative ELISA and Western blot for HIV-1 within 6 weeks prior to immunization.
• Normal history and physical exam.
• History of smallpox vaccination at least 5 years prior to study entry (Part I) OR no prior smallpox vaccination (Part II).
• Absolute CD4 count >= 400 cells/mm3.
• Normal urinalysis.

NOTE:

• No more than 10 percent of volunteers in both Parts I and II may be over 50 years of age.

Exclusion Criteria

Co-existing Condition:

Subjects with the following symptoms or conditions are excluded:

• Positive hepatitis B surface antigen.
• Medical or psychiatric condition (such as recent suicidal ideation or present psychosis) that precludes compliance.
• Occupational responsibilities that preclude compliance.
• Active syphilis. NOTE: Subjects with serology documented to be a false positive or due to a remote (> 6 months) treated infection are eligible.
• Active tuberculosis. NOTE: Subjects with a positive PPD and a normal chest x-ray showing no evidence of TB and not requiring isoniazid therapy are eligible.
• Eczema.
• Household contact with persons meeting any of the following criteria:
• pregnancy, less than 12 months of age, eczema, immunodeficiency disease, or use of immunosuppressive medications.

Subjects with the following prior conditions are excluded:

• History of immunodeficiency, chronic illness, autoimmune disease, or use of immunosuppressive medications.
• History of anaphylaxis or other serious adverse reactions to vaccines.
• Eczema within the past year.
• History of serious allergic reaction to any substance, requiring hospitalization or emergent medical care (e.g., Steven-Johnson syndrome, bronchospasm, or hypotension).
• Prior psychiatric condition (such as history of suicide attempts or past psychosis) that precludes compliance.
• History of cancer unless there has been surgical excision that is considered to have achieved cure.

Prior Medication:

Excluded:

• Prior HIV vaccines.
• Live attenuated vaccines within the past 60 days. NOTE: Medically indicated subunit or killed vaccines (e.g., influenza, pneumococcal) do not exclude but should be administered at least 2 weeks prior to HIV immunizations.
• Experimental agents within the past 30 days.

Prior Treatment:

Excluded:

• Receipt of blood products or immunoglobulins within the past 6 months. It is STRONGLY RECOMMENDED that any activity that might expose subject to HIV (unprotected sex or needle sharing) be avoided.