(209f) Design of Nanoparticle Cancer Vaccines for Co-Delivery of MHC Class I and II Epitopes to Improve Anti-Tumor Immune Responses

Nanoparticle-based cancer vaccines offer promising advantages for enhancing treatment outcomes, including the simultaneous delivery of antigens and adjuvants, protection from degradation, and preferential uptake by dendritic cells. While traditional vaccination strategies predominantly focus on stimulating CD8 T cells through major histocompatibility complex (MHC) Class I recognition, recent research highlights the significance of CD4 T cells (recognizing MHC Class II peptides) in fostering effective anti-tumor immune responses.

Our study investigates whether a nanoparticle vaccine carrying an MHC Class II peptide can induce a T helper type-1 (Th1) response in a Th2-biased BALB/c mice, with the goal of improving anti-tumor immunity by incorporating both Class I and Class II peptides on a single nanoparticle. In this study, we started by conjugating an MHC Class II peptide (CT-II) and an adjuvant (CpG) to the self-assembling E2 nanoparticle (CpG-(CT-II)-E2), yielding a ~30 nm nanoparticle, which is optimal for dendritic cell uptake and lymph node drainage. This nanoparticle design presents an attractive vehicle for vaccine delivery for the CT26 colon carcinoma model.

In this study, BALB/c mice were immunized with CpG-(CT-II)-E2, and we evaluated the antigen-specific IFN-g response. CpG-(CT-II)-E2 immunized mice exhibited significant increases in antigen-specific IFN-g producing cells compared to PBS-treated mice, indicating nanoparticles delivering an MHC Class II peptide can be processed and trigger a Th1 immune response even in Th2-biased mice. These findings suggest that co-delivering Class I and Class II peptides could further enhance a robust antigen-specific immune response. Moreover, previous studies reported higher IFN-g production per CD8 T cell when both CD4 and CD8 T cells recognize the same dendritic cells. Based on this, we hypothesized that displaying both Class I and Class II peptides on the same nanoparticle could increase anti-tumor responses compared to peptides delivered on separate nanoparticles. To test this hypothesis, we either co-conjugated Class I and Class II peptides to the same nanoparticles or separately conjugated them to different nanoparticles, resulting in ~30 nm nanoparticles capable of delivering both types of peptides along with the adjuvant. While the differences in cell population among the vaccination groups were not clear, the IFN-g ELISpot assay demonstrated that co-delivering both Class I and Class II peptides on the same nanoparticles elicited significantly higher IFN-g response compared to delivering them on different nanoparticles. Other cytokines produced by splenocytes after peptide stimulation are currently being investigated. Overall, our study suggests the importance of incorporating class II peptides into nanoparticle-based cancer vaccines, even in the Th2-biased BALB/c mice, to enhance anti-tumor immune responses.