Figure 1.

X4 and R5-tropic viruses infect and have low replication in human primary astrocytes. A, Immunofluorescence analysis performed by confocal microscopy of cultures infected with HIV_92UG021 (X4), HIV_ADA (R5), or HIV_JR-CSF (R5). A representative set of pictures of astrocytes after 14 d of infection with HIV_ADA is shown stained for DAPI (nuclei labeling), GFAP (marker for astrocytes, red, Cy3), and p24 (an HIV-protein, green, FITC). The merge of these three colors (merge of the two cytoplasmic markers, p24 and GFAP, yellow plus nuclear staining) is also illustrated. Arrows denote the colocalization of p24 and GFAP staining demonstrating that HIV infects small numbers of astrocytes. Similar results were found using all three viral isolates. No staining of p24 was detected in uninfected cells (data not shown). Scale bar, 60 μm. B, Quantification of release of p24 into the medium of cultures of astrocytes, uninfected and HIV-infected, was performed by ELISA (n = 15) after 7, 14, 21, and 28 d after infection. No p24 was detected in uninfected cultures (data not shown). HIV_92UG021, HIV_ADA, or HIV_JR-CSF produced low levels of HIV replication (*p < 0.005; n = 15) compared with HIV-infected PBMCs with the same viral isolates (p24 = 1100 ± 150 pg/ml). HIV_92UG021 (X4) replicates more efficiently in astrocytes compared with HIV_ADA or HIV_JR-CSF (^#p < 0.005; n = 15).