Arm A - Group I: 5 immunizations with Tat (7.5 microg) at weeks 0, 4, 8, 12, 16; Arm A - Group II: 5 immunizations with Tat (30 microg) at weeks 0, 4, 8, 12, 16; Arm B - Group I: 3 immunizations with Tat (7.5 microg) at weeks 0, 4, 8; Arm B - Group II: 3 immunizations with Tat (30 microg) at weeks 0, 4, 8.