ALVAC-HIV vCP1452 Alone and Combined With MN rgp120

The purpose of this study is to test how the body's immune system responds to the vaccine ALVAC-HIV vCP1452 and to determine if the vaccine is safe when given alone and with MN rgp120. HIV infection and AIDS have no cure, in spite of recent advances in anti-HIV drugs. Many worldwide populations cannot afford the antiviral treatments for infected people. HIV vaccines offer hope for disease prevention. In this trial, 2 experimental HIV vaccines called ALVAC vCP1452 and MN rgp120 will be given to volunteers in Haiti, Brazil, Peru, and Trinidad and Tobago. The study will determine how volunteers' immune systems respond to the vaccines. (This protocol has been changed by adding new international sites.)