Elvitegravir (EVG) Cerebrospinal Fluid (CSF) Pharmacokinetics in HIV-Infected Individuals

Inclusion Criteria: * Adult men or women aged 18-60 years. Able and willing to provide informed consent. * Presence of HIV-1 infection as documented by a licensed ELISA test kit and confirmed by Western blot or HIV RNA. * Track A (Currently taking E/C/F/TDF or E/C/F/TAF): Taking E/C/F/TDF or E/C/F/TAF for at least 3 months prior to screening and undetectable plasma HIV-1 RNA (≤ 40 copies/mL) * Track B (Currently not taking ART): Off ART for at least 3 months. Prior exposure to TDF and FTC will be allowed but subjects must not have primary genotypic drug resistance mutations to elvitegravir, tenofovir, or emtricitabine (see Exclusion Criteria) * Plasma HIV-1 RNA ≥ 5,000c/mL and CD4+ T-cell count ≥200cells/mm3. Exclusion Criteria: * Track B: Presence of primary drug resistance mutations for EVG, tenofovir, or emtricitabine. * Use of drugs of abuse or alcohol which would interfere with adherence or completion of this study. While on-study, subjects will be instructed not to consume alcohol for 48 hours prior to pharmacokinetic sampling days. * Pregnancy or breast-feeding. Women of childbearing potential must have a negative serum or urine pregnancy test within 14 days prior to study entry and day of entry. * Chronic, severe, or other medical conditions that, in the opinion of the investigator, would interfere with the subjects ability to participate in the protocol. * Use of prohibited protocol-specified drugs, prescription or over-the-counter, within 14 days prior to study entry. * Bleeding abnormality or other contraindication to lumbar puncture. * Moderate or severe cognitive impairment by history or based on Montreal Cognitive Assessment. * Hepatitis B surface antigen (HBsAg) positive (Positive anti-HBs antibody and negative HBsAg results are acceptable) * Hepatitis C antibody (HCV Ab) positive * Laboratory parameters documented within 21 days prior to study entry that would increase the risk for adverse events: 1. Hemoglobin \< 12.5 g/dL for men; \< 11.5 g/dL for women; 2. Platelet count \< 100,000 platelets/mm3; 3. AST (SGOT) or ALT (SGPT) \> 1.5 x the upper limit of normal (ULN); 4. Estimated GFR\<70 ml/min 5. Weight less than 50 kg