Group I (30 volunteers): pseudovirion vaccine w/adjuvant or w/o adjuvant. Group II (30 volunteers): pseudovirion vaccine w/adjuvant or w/o adjuvant. Group III (18 volunteers): adjuvant (QS21 or alum) or saline placebo. NOTE: Group I will receive appropriate adjuvant or saline placebo at Month 3 without pseudovirion vaccine.