Stable transfection of provirus of human immunodeficiency virus into a murine packaging cell line

In order to generate HIV (murine leukemia virus (MuLV)) pseudotypes, HIV genome was transfected into the ecotropic murine packaging cell line (GP+E86) and four of the nine transfected clones were extensively characterized. One clone (801), harbouring a full copy of integrated HIV sequences, exhibited a detectable level of intracellular HIV p24 antigen expression. Northern blot analysis revealed that clone 801 expressed all three classes of HIV mRNAs. Multispliced 2 kb mRNAs were detected in another clone (8.14). Two other clones (1.31 and 1.32) also exhibited a complete HIV provirus, but did not show any viral expression, as evaluated by Northern blot analysis or HIV p24 ELISA. Reverse transcription-polymerase chain reaction (RT-PCR) experiments revealed the presence of full length genomic RNA in four transfected clones, which were extensively characterized. A co-cultivation of clone 801 with human CD4' cells resulted in syncytia formation. By electron microscopy, mature HIV particles were observed after co-cultivation of uninfected C8166 cells with 801 cells. These results demonstrated that the murine clone was stably transfected with the complete HIV genome and was capable of shuttling infectious HIV to human cells. Clone 801 was co-cultivated with murine NIH-3T3 fibroblasts. In several experiments, HIV infection of NIH-3T3 cells was revealed by PCR technique. Thus, 801 cells appear to produce low levels of HIV (MuLV) pseudotypes capable of transferring the HIV genome into mouse cells.