FIG. 2.
Use of chemokine coreceptors in a cell-to-cell fusion assay. (A) The env genes from isolates HIV-1BORI and HIV-1BORI-15 were PCR amplified and cloned in an expression vector as described in the text. Fusion assays were then performed with QT6 cells transiently expressing several chemokine coreceptors as previously described (13). Note that the CCR3 construct (CCR3P) was designed to increase surface expression. In this assay, cell-to-cell fusion results in expression of the luciferase gene, which is monitored by chemiluminescence (relative light units). Three HIV-1BORI-15 envelope clones [BORI-15 (4C), BORI-15 (5C), and BORI-15 (7A)] and one HIV-1BORI envelope clone [BORI (11A)] were used. Envelopes from HIV-1JRFL and HIV-1YU-2, two viruses obtained directly from the brain, were used as controls for expression of CCR3. The envelope genes from brain isolates DS-br and RC-br were amplified and cloned as described in the text, and a fusion assay was performed as described previously (13). The envelope from the dualtropic isolate HIV-189.6 was used as a control for expression of CCR3. These experiments are representative of two to three assays performed with these envelopes.