The purpose of this study is to determine whether treatment with Raltegravir further decreases HIV viral replication in HAART-suppressed, HIV-infected patients, potentially improving immune response to antiretroviral therapy.

Inclusion Criteria:

• Stable antiretroviral therapy for at least 12 months
• Screening CD4+ T cell count < 350 cells/mm3
• All available CD4+ T cell counts in the last year and at screening < 350 cells/mm3
• Screening plasma HIV RNA levels below level of detection (< 50 copies RNA/mL using Roche Amplicor or < 75 copies/mL using Bayer bDNA or < 40 copies/mL using Abbott RT-PCR), and all available determinations in past 12 months also below level of detection (isolated single values > 75 but < 1000 copies/mL will be allowed if they were preceded and followed by undetectable viral load determinations).
• >90% adherence to therapy within the preceding 30 days, as determined by self-report
• Both male and female adult (at least 18 years old) subjects are eligible. Females of childbearing potential must have a negative serum pregnancy test at screening and agree to use a double-barrier method of contraception throughout the study period.

Exclusion Criteria:

• Patients who are intending to modify antiretroviral therapy in the next 24 weeks for any reason
• Serious illness requiring hospitalization or parental antibiotics within preceding 3 months
• **Any vaccination 2 weeks prior to baseline (day 0) visit and throughout the study period
• Concurrent treatment with immunomodulatory drugs, or exposure to any immunomodulatory drug in past 16 weeks
• Concurrent treatment with phenobarbital, phenytoin, or rifampin.
• Screening absolute neutrophil count <1,000 cells/mm3, platelet count <70,000 cells/mm3, hemoglobin < 8 mg/dL, estimated creatinine clearance <40 mL/minute
• Pregnant or breastfeeding women

24 weeks