Abstract 1959: Surface modifications and drug-loading affect immunogenicity of targeted nanoparticles

Abstract

Abstract Introduction: Targeted nanoparticles offer great promise for developing new cancer imaging and targeted therapy approaches. For future clinical translation, one of the major concerns is that repeated administrations of the targeted nanoparticles may induce a strong immune response to the targeting ligands. The production of a high titer of neutralizing antibodies will block the receptor-binding site and reduce efficiency of targeted delivery of the nanoparticles. Methods: We have examined the titers of targeting ligand-specific antibodies in the blood and the antibody producing B lymphocytes in the spleen of Balb/c mice, bearing mouse 4T1 mammary tumors, following injections of magnetic iron oxide nanoparticles (IONPs) conjugated with targeting ligands derived from mice or humans. Results: We found that conjugation of targeting ligands onto IONPs increases immunogenicity of the ligand and results in a higher antibody titer compared to free targeting ligand injected mice. Furthermore, targeting ligands from different species, such as a human single chain antibody to epidermal growth factor receptor (scFvEGFR), induce a much higher level of the antibody in the mice compared to the mice that received a recombinant receptor binding domain of the mouse urokinase plasminogen activator (uPA), which targets uPA receptor. Surface coating of polyethylene glycol (PEG) reduces nonspecific uptake of the nanoparticles by macrophages in the liver and spleen. However, we found higher antibody titers in the mice that received PEG-coated targeting IONPs compared to the mice received targeting IONPs without PEG. We further elucidated the mechanism of the enhanced antibody response and found that although PEG-coated IONPs avoided uptake by mouse macrophages, they efficiently enter into mouse dendritic cells. High levels of the PEG-coated IONPs and longer circulation time in the blood allow uptake of more IONPs in the antigen-presenting dendritic cells, thereby stimulating antibody production. However, for targeted therapy using nanoparticles carrying chemotherapy drugs, the antibody response may not be significant since we found that the antibody response was significantly inhibited in mice that received the targeted nanoparticles carrying a chemotherapy drug, doxorubicin. Results of ELISPOT assay of the spleen cells from the mice that received systemic delivery of the targeted nanoparticles with or without doxorubicin revealed that the nanoparticles carrying the drug were able to selectively eliminate ligand-specific, antibody-producing B lymphocytes in the spleen, with no overall decrease in the total number of antibody producing cells. Results of our study provide important information for the development of targeted nanoparticle drug carriers for effective treatment of human cancer. Our study further supports the feasibility of translation of targeted theranostic nanoparticles for clinic applications. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1959. doi:1538-7445.AM2012-1959