Clinical Trial to Evaluate the Safety and Immunogenicity of a Priming Regimen of 426c.Mod.Core-C4b Followed by HxB2.WT.Core-C4b Boosts, Both Adjuvanted With 3M-052 AF + Alum, in Adult Participants Without HIV and in Overall Good Health

Inclusion Criteria: 1. Demonstrates an understanding of the study and is able and willing to complete the informed consent process. 2. 18 to 55 years old, inclusive, on day of enrollment. 3. Available for clinic follow-up through the last clinic visit, willing to undergo leukapheresis, and willing to be contacted after the last study-product administration, including for potential participation in additional studies. 4. Agrees not to enroll in another study of an investigational agent during participation in the trial. If a potential participant is already enrolled in another clinical trial, approvals from the other trial sponsor and the HVTN 320 PSRT are required prior to enrollment into HVTN 320. 5. In good general health according to the clinical judgment of the site investigator. 6. Physical examination and laboratory results without clinically significant findings that would interfere with assessment of safety or reactogenicity in the clinical judgment of the site investigator. 7. Agrees to discuss their potential for HIV acquisition and agrees to prevention counseling. 8. Hemoglobin (Hgb): * ≥11.0 g/dL for AFAB volunteers * ≥13.0 g/dL for cisgender AMAB volunteers or for volunteers who have been on masculinizing hormone therapy for more than 6 consecutive months * ≥12.0 g/dL for AMAB volunteers who have been on feminizing hormone therapy for more than 6 consecutive months * For volunteers who have been on gender-affirming hormone therapy for less than 6 consecutive months, determine Hgb eligibility based on their sex assigned at birth. 9. White blood cell (WBC) count = 2,500 to 12,000/mm3 (WBC over 12,000/mm3 is not exclusionary if further evaluation shows general good health and if PSRT approval is granted). 10. Platelets = 125,000 to 550,000/mm3. 11. Alanine aminotransferase (ALT) \< 2.5 × upper limit of institutional reference range. 12. Serum creatinine ≤ 1.1 × upper limit of normal (ULN) based on the institutional normal range. 13. Corrected total serum calcium level of ≥ 8.5 mg/dL. "Corrected" includes measurement of serum albumin. 14. Systolic blood pressure of 90 to \< 140 mmHg and diastolic blood pressure of 50 to \< 90 mmHg at screening visit. The average blood pressure between the screening visit and the enrollment visit must be below 140 mmHg systolic and 90 mmHg diastolic. A single measurement ≥ 160 systolic mmHg or 100 mmHg diastolic during the current study evaluation is exclusionary. 15. Negative HIV test results by one of the following options: * US Food and Drug Administration (FDA)-approved enzyme immunoassay (EIA) * Chemiluminescent microparticle immunoassay (CMIA) * Two negative results on HIV rapid tests (one of which must be FDA-approved CMIA) 16. Negative for anti-hepatitis C virus (HCV) Abs (anti-HCV) or negative HCV nucleic acid test (NAT) if anti-HCV Abs are detected. 17. Negative for hepatitis B surface antigen (HBsAg). 18. For AFAB or intersex at birth volunteers who are capable of becoming pregnant (hereafter referred to as "persons of pregnancy potential"): * Must agree to use effective means of contraception from at least 21 days prior to enrollment through 8 weeks after their last scheduled vaccination timepoint. * Must have a negative beta human chorionic gonadotropin (β-HCG) pregnancy test (urine or serum) on day of enrollment. Note: Persons who are NOT of pregnancy potential due to total hysterectomy or bilateral oophorectomy (verified by medical records) or menopause (no menses for ≥1 year) are not required to undergo pregnancy testing. 19. AFAB or intersex at birth volunteers must agree to not seek pregnancy through alternative methods, such as oocyte retrieval, artificial insemination, or in vitro fertilization from at least 21 days prior to enrollment through 8 weeks after their last scheduled vaccination timepoint. Exclusion Criteria: 1. Volunteer who is breastfeeding/chestfeeding or pregnant. 2. Body mass index (BMI) ≥ 40. Enrollment of individuals with BMI ≥ 40, whom the site investigator assesses are in good health, may be considered by PSRT approval. 3. Diabetes mellitus (DM). Type 2 DM controlled with diet alone (and confirmed by HgbA1c ≤ 8% within the last 6 months) or a history of isolated gestational diabetes are not exclusionary. Enrollment of individuals with type 2 DM that is well controlled on hypoglycemic agent(s) may be considered by the PSRT on a case-by-case basis, provided that the HgbA1c is ≤ 8% within the last 6 months (sites may draw these at screening). 4. Previous or current recipient of an investigational HIV vaccine (previous placebo/control recipients are not excluded). 5. Receipt of non-HIV investigational vaccine(s) received within the last 1 year. Exceptions include vaccines that have subsequently undergone licensure or Emergency Use Authorization (EUA) by the FDA or World Health Organization (WHO) Emergency Use Listing (EUL), or if outside the US, by the national Regulatory Authority (RA) authorizing this clinical trial. 6. Congenital or acquired immunodeficiency, including systemic medication use likely to impair immune response to vaccine in the opinion of the site investigator, such as glucocorticoid use, ≥ prednisone 10 mg/day within 3 months prior to enrollment. 7. Blood products or immunoglobulin within 16 weeks prior to enrollment; receipt of immunoglobulin within 16 weeks prior to enrollment requires PSRT approval. 8. Previous receipt of VRC01 mAb or other CD4bs mAbs. 9. Receipt of any of the following within 4 weeks prior to enrollment: * Live replicating vaccine * Any mRNA-based vaccine with FDA licensure, FDA EUA, or WHO EUL * ACAM2000 vaccine \> 28 days prior with a vaccination scab still present. 10. Receipt of any vaccine that is not covered in exclusion criterion #9 within 14 days prior to enrollment. Please note this includes replication-incompetent vaccines such as the Jynneos vaccine for the prevention of mpox (formerly known as monkeypox) dis