Quantitative evaluation of HIV-1 coreceptor use in the GHOST3 cell assay

The utility of the GHOST(3) cell assay has been evaluated for testing coreceptor use of primary human immunodeficiency virus type 1 (HIV-1) isolates. GHOST(3) cells were derived from the human osteosarcoma cell line, HOS, and have been engineered to stably express CD4 and one or another of the chemokine receptors CCR3, CCR5, CXCR4, Bonzo, or the orphan receptor BOB. The indicator cell line carries the HIV-2 long terminal repeat-driven green fluorescence protein (GFP) gene, which becomes activated upon infection with HIV or simian immunodeficiency virus. Viral entry is followed by Tat activation of transcription and GFP becomes expressed. Infected cells can be detected 2 or 3 days after infection by simple fluorescence microscopic observation. This simplicity is the main advantage of the GHOST(3) cell system and makes it particularly suitable for screening of a large number of isolates. In addition, the efficiency of coreceptor use can be accurately quantitated with flow cytometric analysis. Here, we evaluated the coreceptor use of 59 primary HIV-1 isolates of different subtypes.