Analysis of GBV-B core, HCV core and HCV core deletion mutants produced in BHK-21 cells. Proteins expressed at 16hrs post-transfection with SFV recombinant RNAs were separated, blotted onto PVDF membranes, and identified after incubation of the membrane with the C1856 anti-HCV core mouse monoclonal antibody (A) or with rabbit polyclonal anti-GBV-B core antibodies then with the C1856 antibody, for side-by-side comparison of the size of WT HCV and GBV-B core proteins (B). Molecular weight markers (M) are indicated on the left of the blots. Cells transfected with a recombinant SFV RNA encoding β-galactosidase (β-gal) were used as a negative control. In panel C, GBV-B core, WT C191 HCV core or HCV core del 3 and del 5 mutants were expressed in BHK-21 cells in the presence (+) or absence (−) of (Z-LL)2-ketone, an inhibitor of the signal peptide peptidase (SPP), and identified by immunobloting.