Safety, Tolerability and Immunogenicity Study of 2 Dose Levels of Trimeric Glycoprotein140 (gp140) in Healthy Adult Volunteers

This is a single-center, randomized (the study drug is assigned by chance), placebo-controlled (study in which the experimental treatment or procedure is compared to a pretend treatment with no drug in it to test if the drug has a real effect), and double-blind (neither physician nor participant knows the treatment that the participant receives) study. The study comprises a Screening Period (up to 4 weeks), a Vaccination Period (participants will be vaccinated on Days 1 and 29), and a Follow-up Period (up to 48 weeks). All eligible participants will be randomly assigned to 1 of the 2 sequential cohorts (low dose cohort and high dose cohort). Participants in low dose cohort will receive 1 of the following treatments: low dose (50 microgram \[mcg\]) gp140 drug product (DP), low dose gp140 DP with adjuvant (aluminum phosphate), placebo matched to low dose DP; and participants in high dose cohort will receive 1 of the following treatments: high dose (250 mcg) gp140 DP, high dose gp140 DP with adjuvant, and placebo matched to high dose DP. There will be an interim safety review of safety/tolerability from low-dose cohort before the high-dose cohort receives study treatment. Total study duration will be 56 weeks per participant. Participants' safety will be monitored throughout the study.