FIG. 1.

Production of virus-like particles in tetKUNCprME-packaging BHK21 cells transfected with repPACβgal replicon RNA containing NS2A-I59N mutation after extended incubation. (A) Schematic representation of puromycin (PAC)-selectable and β-Gal-expressing KUN replicon constructs used for electroporation into tetKUNCprME-packaging BHK-21 cells. Heterologous gene inserts are gray, and the KUN nonstructural genes (as indicated) are colored white. NS2A-I59N mutation is shown by a broken line. (B) Detection of β-Gal expression in tetKUNCprME-packaging BHK-21 cells electroporated with KUN replicon RNAs (A) at 7 days posttransfection by using X-Gal staining after fixation with 4% formaldehyde. (C) Infectious VLP titers in culture fluids of tetKUNCprME-packaging BHK-21 cells electroporated with WT and NS2A-I59N mutant RNAs 3, 5, and 7 days postelectroporation. The titers were determined by infectivity assay on fresh VERO cells as described in Materials and Methods.