Detection of Antibodies to Tat in the CSF of individuals infected with HIV: (A) Relative Light Units of an ELISA for anti-Tat antibodies detected in spinal fluid of HIV-infected individuals without dementia (HIV-Normal) (MSK 0) (n=15; 86.7%>mean+1SD), with HIV-associated neurocognitive disorder (HAND) (MSK≥0.5) (n=37; 83.8%>mean+1SD), HIV negative controls (n=5), and neuro-inflammatory controls (n=8). Anti-Tat levels in spinal fluid of the HIV-Normal group were significantly higher than in HIV-HAND (p<0.05). Antibody level was significantly higher in HIV-infected individuals without dementia than the HIV negative individuals (p<0.01) and the neuro-inflammatory control individuals (p<0.001). CSF anti-Tat levels are higher in individuals with higher serum and CSF viral loads and lower CD4 cell counts. (B) In the CSF of individuals with HIV (n=51), anti-Tat levels are significantly higher in the group with serum viral load >400 copies/ml (p<0.01). (C) In the CSF of individuals with HIV (n=47), anti-Tat levels are significantly higher in the group with CSF viral load >400 copies/ml (p<0.01). (D) In the CSF of individuals with HIV (n=51), anti-Tat levels are significantly higher in the group with CD4 cell level <250 cells/μl (p<0.05). In all panels, the points in the figure represent individual patient data and lines represent the mean. Statistical analysis was by ANOVA with Newman-Keuls post-test for (A) and by unpaired t-test for (B, C, D).