• To characterize intrathecal viral replication during chronic untreated HIV-1 infection, and to assess how intrathecal viral replication relates to stage of HIV-1 disease. [ Time Frame: end of study ] [ Designated as safety issue: No ]
  
• To measure intrathecal and systemic cellular immune responses against HIV-1 and to assess how these responses relate to intrathecal viral replication. [ Time Frame: end of study ] [ Designated as safety issue: No ]
  
• To correlate intrathecal viral replication and anti-HIV CTL responses with the degree of glial activation/proliferation and neuronal dropout in the brain. [ Time Frame: end of study ] [ Designated as safety issue: No ]
  

HIV-infected subjects who are at least 18 years of age, with no ART in the previous 3 months, and with plasma HIV-1 RNA >20,000 copies/mL. Individuals with past ART experience must have the ability to construct an ART regimen predicted to completely suppress plasma HIV-1 RNA, based on results of viral susceptibility testing that is done as a routine part of clinical practice.

Inclusion Criteria:

• (All subjects in Groups A1, A2 and B):
• At least 18 years of age.
• No more than one month of ART in the past.
• No ART in the previous 3 months.
• Platelet count >100,000 cells/mm3 on most recent determination within 60 days prior to first study lumbar puncture.
• Normal prothrombin time (PT) and partial thromboplastin time (PTT) on most recent determination within 60 days prior to first study lumbar puncture.
• Among individuals with past ART experience, the ability to construct an ART regimen predicted to completely suppress plasma HIV-1 RNA, based on results of viral susceptibility testing that is done as a routine part of clinical practice.
• Plasma HIV-1 RNA >20,000 copies/mL.
• Additional Inclusion Criteria for Groups A1 and A2.
• Group A1:
• CD4+ T cell count >200 cells/mm3.
• CSF HIV-1 RNA >2,000 copies/mL on screening lumbar puncture.
• No history of significant allergy to beta lactam antibiotics, including penicillins and cephalosporins.
• No history of allergy to vancomycin.
• Group A2:
• CD4+ T cell count <200 cells/mm3.
• CSF HIV-1 RNA >2,000 copies/mL on screening lumbar puncture.
• No history of significant allergy to beta lactam antibiotics, including penicillins and cephalosporins.
• No history of allergy to vancomycin.

Exclusion Criteria:

• Evidence of CNS opportunistic infections or space occupying lesion.
• History of significant CNS disorder unrelated to HIV infection such as trauma, congenital malformations or genetic disorders.
• History of seizures.
• As determined by the investigator, a significant active or previous history of cardiovascular, renal, liver, hematologic, neurologic, gastrointestinal, psychiatric, or endocrine disease(s) that would interfere with study participation.
• Evidence or suspicion of vascular or Alzheimer's type dementias.
• Evidence or suspicion of Parkinson's disease.
• History of allergy to lidocaine.
• Implanted metal objects that make MRI contraindicated. This may require consultation with colleagues in the Vanderbilt Dept. of Radiology.
• Women who are pregnant or breastfeeding.
• Women with a positive pregnancy test on enrollment or prior to study drug administration.
• Women of childbearing potential (WOCBP) who are unwilling or unable to use an adequate method of contraception to avoid pregnancy throughout the study in such a manner that the risk of pregnancy is minimized.
• Prisoners or subjects who are compulsorily detained (involuntarily incarcerated) for treatment of either a psychiatric or physical (e.g., infectious disease) illness must not be enrolled into this study.