This is a multicenter (more than 1 hospital or medical school team work on a study), randomized (the study drug is assigned by chance), parallel group (each group of participants will be treated at the same time), 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. All eligible participants will be randomly assigned to receive 1 of the 8 vaccine regimens. Participants will receive study vaccines (Ad26.Mos.HIV, MVA-Mosaic, gp140 DP, and placebo) 4 times as per assigned regimen. The study comprises a Screening Period (up to 4 weeks), a Vaccination Period (participants will be vaccinated at Baseline (Week 0), Week 12, Week 24 and Week 48), and a Follow-up Period (up to 48 weeks). A long-term follow-up period (approximately 2 years after Week 96) will continue for participants randomized to the regimen subsequently selected for future studies, based on analysis of Week 28 data. If Week 28 data are inconclusive, Week 52 data will be considered for regimen selection. If no clear decision can be made, the extended follow-up period could include participants from more than 1 group for assessing durability of immune responses. Participants' safety will be monitored throughout the study.