Conjugation of an antibody Fv fragment to a virus coat protein: cell-specific targeting of recombinant polyoma-virus-like particles

The development of cell-type-specific delivery systems is highly desirable for gene-therapeutic applications. Current virus-based vector systems show broad cell specificity, which results in the need to restrict the natural t ropism of these viral systems. Here we demonstrate that tumour-cell-specifi c virus-like particles can be functionally assembled in vitro from recombin ant viral coat protein expressed in Escherichia coli. The insertion of a ne gatively charged peptide in the HI loop of polyoma VP1 interferes with the binding of VP1 to the natural recognition site on mammalian cells and also serves as an adapter for the coupling of antibody fragments that contain co mplementary charged fusion peptides. A recombinant antibody fragment of the tumour-specific anti-(Lewis Y) antibody B3 could be coupled to the mutant VP1 by engineered polyionic peptides and an additional disulphide bond. Wit h this system an entirely recombinant cell-specific delivery system assembl ed in vitro could be generated that transfers genes preferentially to cells presenting the tumour-specific antigen on the cell surface.