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Session 97 Poster Session Neuropathogenesis Session Time: 4:30-6:30 pm Room 4E-F

734-W. Intracellular HIV-1 p24 Expression in Cerebrospinal Fluid T Cells by Flow Cytometry J. Neuenburg*1,2, M. Warmerdam1, A. Nilsson2, R. W. Price2, and R. M. Grant1 1Gladstone Inst. of Virology and Immunology, San Francisco, CA and 2Univ. of California, San Francisco Background: While high cerebrospinal fluid (CSF) viral load correlates with increased CSF white blood count (WBC), it is not known whether CSF WBCs produce HIV-1. Methods: In order to evaluate individual T cells, we analyzed lymphocytes derived from paired CSF/blood samples by 4-color flow cytometry using surface- and intracellular-antibody staining. Infected T cells were identified using the surface markers CD3+, CD4+ or CD4-, CD14-, and the intracellular marker anti-p24-antibody after permeabilizing cells with Tween20. While CD4 surface marker was also analyzed, it was not required because some infected cells clearly did not express CD4, presumably because of receptor down-regulation. We verified this with PBMC's in culture and PCR identifying HIV gag transcripts in anti-p24+/CD3+/CD14- cells that were not expressing CD4. Results: We evaluated 45 paired CSF/blood samples, 3 CSF samples only, and 2 blood samples only from 20 different subjects. 8 subjects were followed longitudinally, of which 2 were undergoing structured treatment interruption and 2 were initiating therapy. Analysis of CSF and blood of 2 HIV-1-uninfected subjects indicated that false-positive p24 staining of CD3+, CD14- cells did not exceed 0.2% but that anti-p24 antibody nonspecifically stained monocytes and granulocytes, thereby precluding further analysis of viral expression in these cell types. HIV p24 expression was detected in CSF cells at a median of 0.82% (range 0.2 - 2.7%). The percentage of T cells expressing HIV-1 in the blood was lower than in CSF (p<0.001), with a median of 0.33% (range 0.2% - 1.5%). The percentage of p24 expressing CSF T-cells decreased in 2 of 2 subjects with good plasma viral load response after initiating therapy. Conclusions: The percentages of T cells expressing viral protein are relatively low in both the blood and CSF of chronically infected persons, but are detectable in the specific range of this flow cytometric assay. The higher percentage of virus-producing T cells inside the CSF compartment may reflect higher levels of T-cell activation observed among CSF cells.

©2002 9th Conference on Retroviruses and Opportunistic Infections