Inclusion Criteria

Subjects are:

• Normal, healthy adults (by history and physical examination) who fully comprehend the purpose and details of the study.

Exclusion Criteria

Co-existing Condition:

Subjects with the following conditions or symptoms are excluded:

• Positive syphilis serology (such as VDRL) unless positive test is due to a documented clinical event that occurred and was treated 5 or more years prior to enrollment.
• Circulating hepatitis B antigenemia.

Subjects with the following prior conditions are excluded:

• History of immunodeficiency, chronic illness, or autoimmune disease.
• Evidence of depression or under treatment for psychiatric problems during the past year.

Prior Medication:

Excluded:

• Immunosuppressive medications.

Prior Treatment:

Excluded:

• Blood transfusions or cryoprecipitates within the past 6 months.

Identifiable high-risk behavior for HIV infection, including:

• history of intravenous drug use; syphilis, gonorrhea, or any other sexually transmitted diseases (including chlamydia or pelvic inflammatory disease) in the last 6 months; more than two sexual partners, or sexual contact with a high-risk partner, in the preceding 6 months.