Shikimoyl-ligand decorated gold nanoparticles for use in ex vivo engineered dendritic cell based DNA vaccination.


Department of Applied Biology, CSIR-Indian Institute of Chemical Technology, Hyderabad 500 007, India. [Email] [Email]


Since mannose receptors (MRs) are expressed on the surfaces of dendritic cells (DCs), the most professional antigen presenting cells in our body, DNA vaccine carriers containing either covalently grafted mannosyl- or mannose-mimicking shikimoyl-ligands are being increasingly used in ex vivo DC-transfection based DNA vaccination. To this end, we have recently demonstrated that ex vivo immunization of mice with liposomes of shikimoylated cationic amphiphiles containing a 6-amino hexanoic acid spacer group in the head-group region in complexation with melanoma antigen (MART1) encoded DNA vaccine (pCMV-MART1) induces long lasting anti-melanoma immune responses (C. Voshavar, et al., J. Med. Chem., 2017, 60, 1605-1610). This finding prompted us to examine, in the present investigation, the efficacies of gold nanoparticles conjugated to the mannose-mimicking shikimoyl ligand (SL) via a 6-amino hexane thiol spacer (AuNPs-SL) for use in ex vivo DC-transfection based genetic immunization. Herein, we report on the design, synthesis, physico-chemical characterization and bioactivities of AuNPs-SL. Dynamic light scattering and transmission electron microscopy studies revealed the hydrodynamic diameters of theAuNPs-SL nanoconjugates to be within the range of 23-44 nm and their surface potentials within the range of 9-28 mV. MTT-assay showed the non-cytotoxic nature of AuNPs-SL and the findings in the electrophoretic gel retardation assays revealed strong DNA binding properties of the AuNPs-SL. Importantly, subcutaneous immunization of C57BL/6J mice with DCs ex vivo transfected with an electrostatic complex of AuNPs-SL & melanoma antigen (MART1) encoded DNA vaccine (p-CMV-MART1) induced a long lasting (100 days) anti-tumor immune response in immunized mice upon subsequent challenge with a lethal dose of melanoma. Notably, mice immunized with either autologous mbmDCs ex vivo pre-transfected with nanoplexes of shikimoylated AuNPs-SL & an irrelevant pCMV-SPORT-β-gal plasmid (without having encoded melanoma antigen) or untransfected DCs showed no lasting protection against subsequent tumor challenge. The presently described shikimoyl-decorated gold nanoparticles (AuNPs-SL) are expected to find future use in ex vivo DC-transfection based genetic immunization against cancer and other infectious diseases.