A gp160 vaccine developed from the IIIB strain of HIV-1 has been found to be safe and immunogenic in healthy adults. Since the MN strain of HIV-1 is representative of a larger proportion of HIV-1 isolates in the United States than is the IIIB strain, evaluation of a gp160 vaccine derived from the MN strain is important.

Volunteers are randomized to receive 200 mcg MN rgp160 or placebo at months 0, 1, and 6 or at months 0, 2, and 8. For each immunization schedule, ten volunteers receive vaccine and two volunteers receive placebo. Per amendment, volunteers receive a fourth immunization of 800 or 200 mcg (or placebo) at 9 or 11 months after the third injection (i.e., at month 17) and are followed for 6 months afterward.

Inclusion Criteria

Subjects must have:

• Normal history and physical exam.
• Negative test for HIV by ELISA within 6 weeks prior to immunization.
• CD4 count >= 400 cells/mm3.
• Normal urine dipstick with esterase and nitrate.
• No history of immunodeficiency, chronic illness, autoimmune disease, or use of immunosuppresssive medications.

Exclusion Criteria

Co-existing Condition:

Subjects with the following conditions are excluded:

• Positive for hepatitis B surface antigen.
• Medical or psychiatric condition or occupational responsibilities that preclude compliance.
• Active syphilis (NOTE: If serology is documented to be a false positive or due to a remote (> 6 months) infection, subject is eligible).
• Active tuberculosis (NOTE: Subjects with a positive PPD and normal x-ray showing no evidence of TB and who do not require INH therapy are eligible).

Subjects with the following prior conditions are excluded:

• History of anaphylaxis or other serious adverse reactions to vaccines.

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:

• Blood products or immunoglobulin within the past 6 months.

Higher risk behavior for HIV infection as determined by screening questionnaire, including:

• History of injection drug use within 12 months prior to study entry.
• Higher or intermediate risk sexual behavior.