Abstract B11: Control of in vivo spatiotemporal dynamics of antigen and adjuvant by a delivery system CHP nanogel markedly improves the immunogenicity and antitumor efficacy of long peptide cancer vaccine.

Abstract

Abstract When subcutaneously administered to mice, soluble agonists of Toll-like receptors (TLRs) such as CpG oligo DNA and poly-I:C RNA activate antigen-presenting cells in the draining lymph node (DLN) within 24 hours. It suggests that vaccine antigen also should exist in the DLN at this phase, to maximize combinatorial effect of vaccine and adjuvant. Using CHP nanogel, a delivery system consisting of polysaccharide-based nanoparticle with an ability to modify in vivo distribution of cargo, we studied a relation among the spatiotemporal dynamics of antigen and adjuvant, immunogenicity and anti-tumor potency. We prepared around 40 amino acids of synthetic long peptides containing both CD8+ and CD4+ T cell epitopes for mouse T cells, derived from tumor antigen such as human MAGE-A4 or a mutated form of mouse ERK2. Each long peptide was complexed with CHP nanogel, and subcutaneously administered to BALB/c mice as vaccine. Long peptide admixed with incomplete Fruend's adjuvant (IFA) that is known to have a depot effect at the injection site was also tested for comparison. Induction of the peptide-specific CD8+ and CD4+ T cell responses was then measured, and in the absence of adjuvant, it was marginal in the mice with either long peptide/CHP nanogel or long peptide/IFA. However, when the vaccines were co-administered with TLR agonists, T cell response was enhanced, and it was remarkably more prominent in the mice with long peptide/CHP nanogel than those with long peptide/IFA. The employment of CHP nanogel also augmented the inhibitory effect of long peptide vaccine on in vivo growth of tumors expressing specific antigen. We then evaluated the capability of CHP nanogel and IFA to transport long peptide to the DLN after subcutaneous injection. Incorporation of the fluorescently labeled long peptide into antigen-presenting cells in the DLN was analyzed using flow cytometry. As a result, when complexed with CHP nanogel, long peptide was promptly incorporated to a significant proportion (approx. 10 to 55%) of CD11c+ dendritic cells and CD11b+ macrophages in the DLN, at the phase similar to when soluble agonists of TLRs act on the DLN, while the long peptides with IFA were not. A tracking analysis of the long peptide/CHP nanogel injected to the back of mice at the different sites but draining to same lymph node suggested a cell-independent mechanism underlying the CHP nanogel-mediated rapid antigen transportation to the DLN. Consistently, the modifications of CHP nanogel (e.g. cationic or larger particle size) that were expected to cause its retention at the injection site, resulted in the reduced incorporation of cargo long peptide to the DLN and decrease in the CD8+ T cell response even in the presence of adjuvant. These results indicate that appropriate control of the in vivo spatiotemporal dynamics of antigen and adjuvant is highly important to optimize the immunogenicity and efficacy of cancer vaccines, and our CHP nanogel is an ideal delivery system for such purpose. Citation Format: Daisuke Muraoka, Naozumi Harada, Tae Hayashi, Shin-ichi Sawada, Kazunari Akiyoshi, Hiroshi Shiku. Control of in vivo spatiotemporal dynamics of antigen and adjuvant by a delivery system CHP nanogel markedly improves the immunogenicity and antitumor efficacy of long peptide cancer vaccine. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology: Multidisciplinary Science Driving Basic and Clinical Advances; Dec 2-5, 2012; Miami, FL. Philadelphia (PA): AACR; Cancer Res 2013;73(1 Suppl):Abstract nr B11.