Inclusion Criteria:

• Participants must meet all of the following criteria to be eligible for this study:
• 1. Aged \>=18 years.
• 2. People with HIV-1 documented using US Food and Drug Administration-approved screening and confirmatory or supplemental assays in Centers for Disease Control and Prevention (CDC)-recommended testing strategies.
• 3. Established medical care outside NIH.
• 4. Able to provide informed consent.
• 5. Willing to allow samples to be stored for future research.
• 6. Willing to allow genetic testing.
• 7. Undergoing cART using recommended, alternative, or other regimens as defined by Guidelines for the Use of Antiretroviral Agents in Adults and Adolescents with HIV.
• 8. Viral RNA \<40 copies/mL plasma by conventional assay for at least 3 years (blips \[transient increases within 6 weeks\] of \<200 copies/mL are allowable when succeeding viral levels return to \<40 copies/mL on subsequent testing).
• 9. CD4 cell count \>=350 cells/microliter.
• 10. Willing to interrupt ART for up to 90 days.
• 11. Willing to use a barrier method of contraception, such as condoms or dental dams, when engaging in sexual activity, or remain abstinent during ATI and after re-initiating ART until viral re-suppression is achieved, to prevent pregnancy and transmission of HIV.

Exclusion Criteria:

• Participants who meet any of the following criteria will be excluded from this study:
• 1. Active intercurrent illness or infection, including fever \>38 degrees Celsius.
• 2. Known history of initiating ART during the first year of infection with HIV. Participants will be considered to have initiated ART within 1 year of infection as defined by documented screening/confirmatory seroconversion (positive testing within one year of non-reactive HIV enzyme-linked immunosorbent assay).
• 3. Pregnant.
• 4. Breastfeeding.
• 5. Currently undergoing therapy with drugs that, in the judgment of the investigators, may interfere with biodistribution of FDG, including prednisolone, valproate carbamazepine, phenytoin, phenobarbital, and catecholamines.
• 6. Undergoing ART that is incompatible with an ATI.
• 7. Has undergone PET/CT within the last 6 months.
• 8. History of poorly controlled diabetes that, in the judgement of the investigators, would prevent completion of PET/CT scan.
• 9. Vaccination within the previous 4 weeks.
• 10. History of ATI within the past 1 year.
• 11. Has comorbid illness for which, in the judgment of the investigators, an ATI will represent elevated risk.
• 12. Active opportunistic infection as defined by the Guidelines for the Prevention and Treatment of Opportunistic Infections in Adults and Adolescents with HIV.
• 13. Significant active substance abuse or psychiatric illness that may, in the judgment of the investigator, interfere with study visits or procedures.
• 14. Allergy to planned anesthetic agents that are expected to be used. For local anesthetics, this is lidocaine. For sedation, this is midazolam and fentanyl.
• 15. Currently undergoing chronic systemic steroid therapy (corticosteroid nasal spray or inhaler and topical steroid use are acceptable).
• 16. Contraindication to use of IV contrast.
• 17. History of developing keloids.
• 18. Renal impairment: HIV-related kidney disease or estimated glomerular filtration rate (eGFR) CKD-EPI equation \<60 mL/min/1.73 m\^2. For individuals undergoing therapy with cobicistat or integrase strand inhibitors, GFR may be estimated using cystatin C or creatinine.
• 19. Active or chronic hepatitis B virus infection, with detectable hepatitis B surface antigen, hepatitis B virus DNA, or both.
• 20. Active hepatitis C virus infection, with detectable virus RNA.
• 21. History of HIV-associated dementia or progressive multifocal leukoencephalopathy.
• 22. Documented ARV drug resistance that, in the judgment of the investigator, would pose a risk of virologic failure should additional mutations develop during the study.
• 23. History of cardiovascular event or at high risk of an event (eg, atherosclerotic cardiovascular disease score \>20%) (https://tools.acc.org/ascvd-risk-estimatorplus/#!/calculate/estimate/).
• 24. History of AIDS-defining illness according to CDC criteria within the past 3 years.
• 25. Hepatic impairment: alanine transaminase \>2.5 X the upper limit of normal or documented history of cirrhosis.
• 26. Any condition that, in the judgment of the investigator, contraindicates participation in this study.