A Phase I, Observer-Blind, Placebo-Controlled Study of the Chiron Vaccine HIV p24/MF59 Administered to Healthy HIV-Seronegative Adults

Inclusion Criteria Volunteers must have: * Good health as determined by medical history, physical examination, and clinical judgment. * Negative serology for HIV infection as determined by licensed HIV ELISA test performed within 6 weeks prior to first immunization. * In vitro Epstein-Barr virus-immortalized cell line from peripheral blood can be established (required for selected Part B volunteers only). Exclusion Criteria Co-existing Condition: Volunteers with the following symptoms or conditions are excluded: * Significant acute systemic infection. * Occupational or other responsibilities that would prevent completion of participation in the study. * Any condition that might interfere with the evaluation of the study objectives. Volunteers with the following prior conditions are excluded: * History of immunodeficiency, autoimmune disease, or any serious chronic illness. * Evidence of psychiatric or medical history or substance abuse that would adversely affect the volunteer's ability to participate in the trial. * History of anaphylaxis or other serious adverse reactions to vaccines or vaccine components. 1\. Immunosuppressive medications. * Live, attenuated vaccine within 60 days of study entry. NOTE: * Medically indicated subunit or killed vaccines (e.g., influenza or pneumococcal) are not exclusionary but should be given at least 4 weeks before or after HIV immunizations to avoid potential confusion of adverse reactions. * Experimental agents within 30 days of study entry. * HIV vaccine or MF59 adjuvant. Blood products or immunoglobulins in the past 3 months. Engaging in high-risk behavior within 6 months of study entry, i.e.: * injection drug use, sexual intercourse without a condom with 4 or more partners or with known iv drug user or HIV+ partner, or newly acquired sexually-transmitted disease.