A Safety, Tolerability and Immunogenicity Study of 2 Different Regimens of Tetravalent Ad26.Mos4.HIV Prime Followed by Boost With Tetravalent Ad26.Mos4.HIV Along With Either Clade C gp140 Plus Adjuvant OR With a Combination of Mosaic and Clade C gp140 Plus Adjuvant in Healthy HIV Uninfected Adults

This is a randomized (study medication assigned by chance), double-blind (neither physician
nor participant knows the treatment received), placebo-controlled (placebo is an inactive
substance that is compared with a drug to test whether the drug has a real effect in a
clinical trial), parallel-group (each treatment group will be treated at the same time),
multicenter (more than one clinical site) study in healthy human immunodeficiency virus
(HIV)-uninfected adults. The main study will be conducted in 3 phases: a 6-week screening
period; a 48-week vaccination period; and a follow-up period to the final main study visit at
Week 72. A Long-term Extension (LTE) phase (approximately 3 years after Week 72) will be
performed for participants randomized to Group 1 or Group 2, who receive all 4 vaccinations
and are negative for HIV infection at Week 72. The approximate duration of the study will be
approximately 78 weeks for participants not participating in the LTE phase and approximately
222 weeks for participants participating in the LTE phase. Participants safety will be
monitored throughout the study.

Inclusion Criteria:

- Participant must be healthy on the basis of medical history, physical examination, and
vital signs measurement performed at screening

- Participants are negative for human immunodeficiency virus (HIV) infection at
screening

- Participants are amenable to HIV-risk reduction counseling and committed to
maintaining behavior consistent with low risk of HIV exposure through the last
required protocol clinic visit

- All female participants of childbearing potential must have a negative serum
(beta-human chorionic gonadotropin [beta-hCG]) at the screening visit, and a negative
urine pregnancy test pre-dose on Day 1

- Participants are willing/able to adhere to the prohibitions and restrictions specified
in the protocol and study procedures

Exclusion Criteria:

- Has chronic hepatitis B (measured by hepatitis B surface antigen test) or active
hepatitis C (measured by hepatitis C virus [HCV] Ab test; if positive, HCV ribonucleic
acid [RNA] polymerase chain reaction (PCR) test will be used to confirm active versus
past HCV infection), active syphilis infection, chlamydia, gonorrhea, or trichomonas

- In the 12 months prior to randomization, participant has a history of newly acquired
herpes simplex virus type 2 (HSV-2), syphilis, gonorrhea, non-gonococcal urethritis,
chlamydia, pelvic inflammatory disease, trichomonas, mucopurulent cervicitis,
epididymitis, proctitis, lymphogranulomavenereum, chancroid, or hepatitis B

- Participant has had major surgery (eg, requiring general anesthesia) within the 4
weeks before screening, or will not have fully recovered from surgery, or has surgery
planned through the course of the study

- Participant has had a thyroidectomy or active thyroid disease requiring medication
during the last 12 months (not excluded: a stable thyroid supplementation)

- Current or past drug/alcohol use that investigator assesses poses any more than a
remotely increased risk of the ability of the participant to comply with the protocol
requirements

- Has been in receipt of any licensed vaccine within 14 days prior to the first dose of
study vaccine or placebo, plans to receive within 14 days after the first study
vaccination, or plans to receive within 14 days before or after the second, third or
fourth vaccination

- Is a recipient of a prophylactic or therapeutic HIV vaccine candidate at any time, or
a recipient of other experimental vaccine(s) within the last 12 months prior to the
Day 1 visit (Vaccination 1). For participants who received an experimental vaccine
(except HIV vaccine) more than 12 months prior to the Day 1 visit (Vaccination 1),
documentation of the identity of the experimental vaccine must be provided to the
sponsor, who will determine eligibility on a case-by-case basis