A Phase 1 Study to Evaluate the Safety and Immunogenicity of eOD-GT8 60mer mRNA Vaccine (mRNA-1644) and Core-g28v2 60mer mRNA Vaccine (mRNA-1644v2-Core)

Inclusion Criteria:

1. Healthy adults as assessed by a medical history, physical examination, and laboratory
tests who are at least 18 years at the time of screening and less than 51 years at the
time of first IP administration;

2. Willing to comply with the requirements of the protocol and be available for follow-up
for the planned duration of the study;

3. In the opinion of the Principal Investigator (PI) or designee and based on Assessment
of (informed consent) Understanding (AOU) results, has understood the information
provided and potential impact and/or risks linked to IP administration and
participation in the study; written informed consent will be obtained from the
participant before any study-related procedures are performed;

4. Willing to undergo HIV testing, risk reduction counseling, and receive HIV test
results;

5. All women of reproductive potential who are engaging in sexual activity that could
lead to pregnancy must commit to use an effective method of contraception for at least
2 weeks prior to the first IP administration and continue until 4 months following the
last IP administration. Effective contraception includes:

- Condoms (male or female) with or without spermicide

- Diaphragm or cervical cap with spermicide

- Intrauterine device

- Hormonal contraception, including contraceptive implant or injectable

- Oral contraception

- Successful vasectomy in the male partner (considered successful if a woman
reports that a male partner has documentation of azoospermia by microscopy [1
year ago], or a vasectomy more than 2 years ago with no resultant pregnancy
despite sexual activity post vasectomy)

- Not of reproductive potential, such as having undergone hysterectomy, bilateral
oophorectomy or tubal ligation, postmenopausal (≥45 years of age with amenorrhea
for at least 2 years, or any age with amenorrhea for at least 6 months and a
serum follicle stimulating hormone (FSH) level > 40 IU/L), surgically sterile
Note: More restrictive measures may be required by the study sites.

6. All participants born female who are not heterosexually active at screening must agree
to utilize an effective method of contraception if they become heterosexually active
as outlined above;

7. All participants born female who are of reproductive potential must be willing to
undergo urine pregnancy tests at time points indicated in the Schedule of Activities
(SOA);

8. All sexually active participants born male, regardless of reproductive potential, must
be willing to use an effective method of contraception (such as consistent condom use)
from the day of the first IP administration until at least 4 months after the last IP
administration;

9. Willing to forgo donations of blood, or any other tissues during the study and, for
those who test HIV-positive due to IP-induced antibodies, until the anti-HIV antibody
titers become undetectable.

Exclusion Criteria:

1. Positive test for HIV-1 or HIV-2;

2. Any clinically relevant abnormality on history or examination, including history of
immunodeficiency or autoimmune disease; use of systemic corticosteroids (the use of
topical or inhaled steroids is permitted), immunosuppressive, anticancer,
antituberculosis, or other medications considered significant by the Investigator
within the previous 6 months; Note: The following exceptions are permitted and will
not exclude study participation: use of corticosteroid nasal spray for rhinitis,
topical corticosteroids for an acute uncomplicated dermatitis, or a short course
(duration of 10 days or less or a single injection) of corticosteroid for a
non-chronic condition (based on Investigator's clinical judgment) at least 2 weeks
prior to enrolment in this study.

3. Any clinically significant acute or chronic medical condition that is considered
progressive or in the opinion of the Investigator makes the participant unsuitable for
participation in the study; Note: All chronic conditions must be considered stable,
there can be no significant change of medications within the previous 2 months, and
for diabetics HgbA1c must be <10%.

4. History of substance abuse or alcohol abuse;

5. Reported behavior that puts the participant at risk for HIV infection within 6 months
prior to screening, as defined by:

- Unprotected sexual intercourse with a known HIV-infected person, a partner known
to be at high risk for HIV infection, or a casual partner (ie, no continuing
established relationship)

- Engaged in sex work

- Frequent excessive daily alcohol use or frequent binge drinking, or any other use
of illicit drugs

- History of newly acquired syphilis, gonorrhea, non-gonococcal urethritis, herpes
simplex virus-2, chlamydia, pelvic inflammatory disease, trichomonas,
mucopurulent cervicitis, epididymitis, proctitis, lymphogranuloma venereum,
chancroid, or hepatitis B-or hepatitis C;

- Three or more sexual partners

6. If female, pregnant or planning a pregnancy during the period of enrolment until 4
months after the last IP administration; or lactating;

7. Bleeding disorder that was diagnosed by a physician (eg, factor deficiency,
coagulopathy, or platelet disorder that requires special precautions) Note: A
participant who states that he or she has easy bruising or bleeding, but does not have
a formal diagnosis and has IM vaccinations and blood draws without any adverse
experience is eligible;

8. Infectious disease diagnosis: chronic hepatitis B-infection (HBsAg-positive), current
hepatitis C infection (HCV Ab-positive and HCV RNA positive), or active syphilis
(screening and confirmatory tests);

9. History of splenectomy;

10. Any of the following abnormal laboratory parameters listed below at screening:

Hematology

- Hemoglobin ≤10.5 g/dl or ≤6.5 mmol/L in females; ≤11.0 g/dl or ≤6.8 mmol/L in
males

- Absolute Neutrophil Count (ANC) ≤1,000/mm3 or ≤1.0 × 109 cells/L

- Absolute Lymphocyte Count (ALC) ≤650/mm3 or ≤0.65 × 109 cells/L

- Platelets ≤125,000 cells/mm3 or ≤125 × 109 cells/L Chemistry

- Creatinine ≥1.1 × upper limit of normal (ULN)

- AST ≥1.25 × ULN

- ALT ≥1.25 × ULN Urinalysis

Clinically significant abnormal dipstick confirmed by microscopy:

• Protein = 1 + or more Blood = 2 + or more (not due to menses) or >10 RBCs per high
power field. If Urinalysis is the only exclusion criteria that is met, consider repeat
urinalysis to confirm

11. Receipt of live attenuated vaccine within the previous 30 days or planned receipt
within 30 days after IP administration; or receipt of other vaccine (including all
authorized or approved COVID-19 vaccinations) within the previous 14 days or planned
receipt within 14 days after IP administration. (Exception is live attenuated
influenza vaccine within 14 days); Note 1: COVID-19 vaccinations: Participants should
not have received any COVID-19 vaccinations in the 14 days before or 14 days after IP
administration.

Note 2: COVID-19 immunoprophylaxis will be permitted prior to and/or during the study
provided the agent has received either Emergency Use Approval from FDA, Conditional
Marketing Authorization from EMA, or granted licensure from a country's regulatory
agency.

12. Receipt of blood transfusion or blood-derived products within the previous 3 months;

13. Participation in another clinical study of an IP currently, within the previous 3
months or expected participation during this study; Note: Concurrent participation in
an observational study not requiring blood or tissue sample collection is not an
exclusion;

14. Prior receipt of any investigational HIV vaccine candidate or HIV monoclonal antibody;
Note: Receipt of placebo in a previous monoclonal antibody including HIV monoclonal
antibody study will not exclude a participant from participation if documentation is
available and the Medical Monitor gives approval.

15. History of significant local or systemic reactogenicity to vaccines (eg, anaphylaxis,
respiratory difficulties, angioedema, injection site necrosis, or ulceration); (This
includes individuals with history of anaphylaxis and/or severe hypersensitivity
reaction to mRNA vaccines or its excipients)

16. Psychiatric condition that compromises the safety of the participant and precludes
compliance with the protocol. Specifically excluded are persons with psychoses within
the past 3 years, ongoing risk for suicide, or history of suicide attempt or gesture
within the past 3 years;

17. Seizure disorder: A participant who has had a seizure in the last 3 years is excluded.
(Not excluded: a participant with a history of seizures who has neither required
medications nor had a seizure for 3 years);

18. History of malignancy in the past 5 years (prior to screening) or ongoing malignancy
(a history of completely excised malignancy that is considered cured is not an
exclusion);

19. Active, serious infections as assessed by the Investigator requiring antibiotic,
antiviral or antifungal therapy within 30 days prior to enrolment;

20. Body mass index (BMI) ≥35;

21. Body weight <110 pounds (50 kg);

22. Prior daily use of NSAID/aspirin that cannot be held for 5 days prior to the
leukapheresis procedure (if applicable at the study site);

23. If, in the opinion of the PI, it is not in the best interest of the participant to
participate in the study.