PLGA nanoparticle-mediated delivery of tumor antigenic peptides elicits effective immune responses

Abstract

Wenxue Ma1, Mingshui Chen1, Sharmeela Kaushal1,2, Michele McElroy1,2, Yu Zhang3, Cengiz Ozkan3, Michael Bouvet1,2, Carol Kruse4, Douglas Grotjahn5, Thomas Ichim6, Boris Minev1,7,81Moores Cancer Center, University of California San Diego, 2Department of Surgery, University of California San Diego, 3Laboratory of Biomaterials and Nanotechnology, University of California Riverside, 4UCLA Division of Neurosurgery, Los Angeles, 5Chemistry Department, San Diego State University, San Diego, 6MediStem Inc. San Diego, 7UCSD Division of Neurosurgery, San Diego, 8Genelux Corporation, San Diego, CA, USA Abstract: The peptide vaccine clinical trials encountered limited success because of difficulties associated with stability and delivery, resulting in inefficient antigen presentation and low response rates in patients with cancer. The purpose of this study was to develop a novel delivery approach for tumor antigenic peptides in order to elicit enhanced immune responses using poly(DL-lactide-co-glycolide) nanoparticles (PLGA-NPs) encapsulating tumor antigenic peptides. PLGA-NPs were made using the double emulsion-solvent evaporation method. Artificial antigen-presenting cells were generated by human dendritic cells (DCs) loaded with PLGA-NPs encapsulating tumor antigenic peptide(s). The efficiency of the antigen presentation was measured by interferon-γ ELISpot assay (Vector Laboratories, Burlingame, CA). Antigen-specific cytotoxic T lymphocytes (CTLs) were generated and evaluated by CytoTox 96® Non-Radioactive Cytotoxicity Assay (Promega, Fitchburg, WI). The efficiency of the peptide delivery was compared between the methods of emulsification in incomplete Freund’s adjuvant and encapsulation in PLGA-NPs. Our results showed that most of the PLGA-NPs were from 150 nm to 500 nm in diameter, and were negatively charged at pH 7.4 with a mean zeta potential of -15.53 ± 0.71 mV; the PLGA-NPs could be colocalized in human DCs in 30 minutes of incubation. Human DCs loaded with PLGA-NPs encapsulating peptide induced significantly stronger CTL cytotoxicity than those pulsed with free peptide, while human DCs loaded with PLGA-NPs encapsulating a three-peptide cocktail induced a significantly greater CTL response than those encapsulating a two-peptide cocktail. Most importantly, the peptide dose encapsulated in PLGA-NPs was 63 times less than that emulsified in incomplete Freund’s adjuvant, but it induced a more powerful CTL response in vivo. These results demonstrate that the delivery of peptides encapsulated in PLGA-NPs is a promising approach to induce effective antitumor CTL responses in vivo.Keywords: peptide delivery, nanotechnology, dendritic cells, vaccination