The purpose of this study is to see whether an HIV vaccine, ALVAC vCP205, is safe and can prevent HIV infection. The vCP205 vaccine will be tested with another vaccine, gp160MN/LAI-2.

This study consists of 2 parts:

Part A: Dose-escalation protocol using oligomeric gp160MN/LAI-2. Part B: Placebo-controlled, randomized, double-blind (within arm) study of vCP205 priming with gp160MN/LAI-2 boosting.

Volunteers are followed for at least 1 year.

Inclusion Criteria

Volunteers may be eligible for this study if they:

• Are HIV-negative.
• Are in good health.
• Are between ages 18 and 55.
• Are available for at least 1 year.
• Are a resident of the United States of America.
• Agree to practice sexual abstinence or use birth control.

Exclusion Criteria

Volunteers will not be eligible for this study if they:

• Have ever been given an HIV vaccine or certain other vaccines. (However, rabies vaccines are allowed.)
• Participate in activities that place them at high-risk for HIV infection, such as injection drug use or unprotected sex with someone who has HIV infection.
• Have certain psychiatric, medical, or substance abuse problems.
• Are allergic to eggs or other vaccines.
• Are an employee at a participating site and have access to study information.
• Are taking certain medications.
• Have received blood transfusions within 3 months before entering this study.
• Are pregnant or breast-feeding.