Study to Assess Adverse Events and How Intravenous (IV) or Subcutaneous (SC) ABBV-382 Moves Through the Body of Adult Participants With Human Immuno-Deficiency Virus (HIV-1)

Inclusion Criteria: * Body Mass Index (BMI) is \>= 18.0 to \<= 35.0 kg/m\^2 after rounding to the tenths decimal. * Must agree to use effective barrier protection during sexual activity for protection against Human Immunodeficiency Virus (HIV)-1 transmission through the last study visit. * Female participants of childbearing potential must give consent to abide by contraception requirements. * CD4+ count of \>= 350 cells/μL at screening and at least once during the 48 weeks prior to screening. * Negative screen for drugs of abuse and alcohol at screening. Participants with a positive marijuana screen may be included after evaluation by the investigator that the use would not interfere with adherence to study requirements, and that usage is not on a regular or chronic basis. * Laboratory values must meet the acceptable criteria. Part A participants must also have: * Positive test result for anti-HIV antibody at screening. * Plasma HIV-1 ribose nucleic acid (RNA) between 1,000 - 200,000 copies/mL at screening. * Must be naive to combination antiretroviral therapy (cART) or have been off of cART for \> 12 weeks or 5 half-lives of the drug (whichever is longer) prior to screening with documentation of at least one plasma HIV-1 RNA measurement greater than or equal to the lower limit of quantification (LLOQ) during the off cART period. * Willing to hold on initiation of cART throughout the screening period and until 4 weeks after dosing. Part B participants must also have: * Positive test result for anti-HIV antibody at screening. * Must have plasma HIV-1 RNA below the lower limit of quantification at screening and at least 24 weeks prior to screening. A single unconfirmed "blip" is allowed if preceded and followed by values below the lower limit of quantification. * Must be HIV-1 infected on cART for at least 48 weeks prior to screening and on current cART regimen for at least 12 weeks prior to screening. Exclusion Criteria: * Female participants who are pregnant, breastfeeding, or considering becoming pregnant during the study. * History or ongoing diagnosis of acquired immune deficiency syndrome (AIDS)-defining illness. * History of or active immunodeficiency (other than HIV). * Active autoimmune disease or history of autoimmune disease that has required systemic treatment. * Clinically significant medical disorders (other than HIV-1 infection) that might expose the participant to undue risk of harm, confound study outcomes, or prevent the participant from completing the study. * Active or suspected malignancy or history of malignancy (other than basal cell skin cancer or cervical carcinoma in situ) in the past 5 years. * History or evidence of active tuberculosis (TB) disease or untreated latent TB infection at screening. * No history of positive TB skin test or interferon gamma release assay (IGRA) or at screening which is considered clinically significant by the investigator. Participant with a history of a positive TB skin test or IGRA or at screening must have documentation of completion of a Centers for Disease Control and Prevention (CDC) recommended treatment course for latent TB. Any participant with suspicion for or diagnosis of active TB is excluded. * Known psychiatric or substance abuse disorders that would interfere with adherence to study requirements. * Currently enrolled in another interventional clinical study. * Received immunomodulatory or immunosuppressive (including intravenous \[IV\]/oral \[PO\] steroids at any dose, but excluding steroids that are inhaled or topical) therapy within 24 weeks prior to the first dose of study drug.