Multi-component Polymeric System for Tumour Cell-Specific Gene Delivery Using a Universal Bungarotoxin Linker

A new universal tool for specific, non-covalent and non-destructive attachment of a recombinant antibody fragment to a polymer-modified adenovirus has been utilised to regulate the tropism of adenoviral gene delivery vector. We have prepared a multivalent reactive N-(2-hydroxypropyl)methacrylamide-based copolymer (PHPMA) bearing an alpha-bungarotoxin-binding peptide (BTXbp). The copolymer was used for covalent surface modification of adenoviral vectors (Ad). The alpha-bungarotoxin protein (BTX) has a nanomolar binding affinity for BTXbp, allowing non-covalent linkage of BTX fusion proteins. A single chain variable fragment of anti-PSMA antibody bearing BTX (scFv-BTX) binding to the prostate-specific membrane antigen (PSMA) was conjugated with the copolymer-coated adenovirus to enable specific infection of prostate cancer cells via PSMA receptors. As shown by ELISA, the copolymer-coated virus exhibited much reduced binding to anti-Ad antibodies. Infection of PC-3 and LNCaP prostate cancer cells was similar to 100-fold less efficient with copolymer-coated Ad than with un-modified Ad. Conjugation of scFv-BTX with Ad-PHPMA-BTXbp led to 5-10-fold restoration of infection in PSMA-positive LNCaP cells. In PSMA-negative PC-3 cells, the conjugation of scFv-BTX with Ad-PHPMA-BTXbp gave no enhancement of infection. We have shown that the presented Ad-PHPMA-BTXbp/scFv-BTX system can be used as a universal tool for a receptor-specific virotherapy.