Anti-CD20 single chain variable antibody fragment-apolipoprotein A-I chimera containing nanodisks promote targeted bioactive agent delivery to CD20-positive lymphomas

A fusion protein comprising an alpha-CD20 single chain variable fragment (scFv) antibody, a spacer peptide, and human apolipoprotein (apo) A-I was constructed and expressed in Escherichia coli. The lipid interaction properties intrinsic to apoA-I as well as the antigen recognition properties of the scFv were retained by the chimera. scFv center dot apoA-I was formulated into nanoscale reconstituted high-density lipoprotein particles (termed nanodisks; ND) and incubated with cultured cells. alpha-CD20 scFv center dot apoA-I ND bound to CD20-positive non-Hodgkins lymphoma (NHL) cells (Ramos and Granta) but not to CD20-negative T lymphocytes (i.e., Jurkat). Binding to NHL cells was partially inhibited by pre-incubation with rituximab, a monoclonal antibody directed against CD20. Confocal fluorescence microscopy analysis of Granta cells following incubation with alpha-CD20 scFv center dot apoA-I ND formulated with the intrinsically fluorescent hydrophobic polyphenol, curcumin, revealed alpha-CD20 scFv center dot apoA-I localizes to the cell surface, while curcumin off-loads and gains entry to the cell. Compared to control incubations, viability of cultured NHL cells was decreased upon incubation with alpha-CD20 scFv center dot apoA-I ND harboring curcumin. Thus, formulation of curcumin ND with alpha-CD20 scFv center dot apoA-I as the scaffold component confers cell targeting and enhanced bioactive agent delivery, providing a strategy to minimize toxicity associated with chemotherapeutic agents.