T cells recognizing tumor-specific neoantigens can mediate effective anti-tumor immunity and provide the rationale for personalized cancer vaccines (PCVs). Current approaches for PCVs include synthetic long peptides given with adjuvants or RNA vaccines. Such approaches induce de novo CD8 T cell responses in ~10% or less of predicted neoantigens. Here, we focused on how peptide based neoantigen vaccines could be altered to enhance the magnitude and breadth of CD8 T cells. A key finding was that particulate peptide antigens, unlike soluble peptide antigens, are more efficiently taken up by dendritic cells in draining lymphoid tissue for increasing CD8 T cell expansion. However, due to the broad range of neoantigen physicochemical properties, ensuring consistent particle vaccine formulations with neoantigen peptides is a major challenge. Therefore, we developed a new PCV platform based on charge-modified peptide-TLR-7/8 agonist conjugates that are chemically programmed for self-assembling into nanoparticles (“SNP-7/8a”) of a defined size (20–50 nm) irrespective of the underlying neoantigen peptide composition. Bioinformatics analysis of 72 million human genome-derived neoantigens shows that SNP-7/8a ensures consistent nanoparticle formation with neoantigens at extremes of charge and hydropathy. Vaccination of mice with SNP-7/8a using predicted neoantigens (n = 179) from three tumor models induced CD8 T cells in ~50% of those with high predicted MHC-I binding affinity (IEDB consensus score < 0.5). Moreover, therapeutic vaccination with SNP-7/8a enhanced tumor clearance in tumor models using neoantigens, self-antigens or viral antigens. Overall, the SNP-7/8a PCV is a universal approach for co-delivering peptide antigens and immune adjuvants in nanoparticles to enhance anticancer T cell immunity.
Citation Format: Geoffrey M. Lynn, Faezzah Baharom, Yaling Zhu, Vincent Coble, Andrei Ramirez-Valdez, Hide Yamane, Kennedy Tobin, Brennan Decker, Andrew Ishizuka, Robert Seder. Peptide-TLR-7/8 agonist conjugate vaccines chemically programmed for nanoparticle self-assembly to enhance the magnitude and breadth of anticancer neoantigen CD8 T cell immunity [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr IA29.