The last of us: A fungi based dendritic cell vaccine

Introduction: Glioblastoma Multiforme (GBM) is the most common primary malignant brain tumor with a median survival of 15 months. The current standard of care has not changed in the past 20 years and currently there is no FDA-approved immunotherapy.

Our lab has previously developed a subcutaneous autologous tumor vaccine utilizing the following combined components: irradiated (IR) tumor cells with phagocytosis-stimulating ligands (Mannan-BAM), toll-like receptor (TLR) agonists, and immunostimulant anti-CD40 antibody (collectively abbreviated as MBTA). This regime allowed recognition of tumors resulting in a coordinated innate and adaptive immune response in both prophylactic and therapeutic studies with colon carcinoma, and breast tumor mouse models. The aim of our study was to generate a dendritic cell (DC) vaccine utilizing this strategy.

Methods: To assess if MBTA anchored GBM cells could mature DCs in-vitro, we co-cultured them with bone-marrow DCs (BMDCs) from mice for 24 hours. Analysis was performed via flow cytometry and ELISA to confirm maturation markers and DC polarization. To assess if MBTA DCs could protect against tumor metastasis, we utilized a melanoma (B16) prophylactic model. To asses if MBTA DCs could protect against a primary tumor, we utilized a GBM (SB28) therapeutic model.

Results: We found robust up-regulation of co-stimulatory molecules CD40, CD80 and CD86 and preferential upregulation of MHCI in the MBTA group with ELISA analysis demonstrating MBTA DCs significantly upregulated Type 1 cytokines (TNFa and IL-6) and limited regulatory cytokine (IL-10) secretion.

Mice vaccinated with MBTA DCs had a significant decrease in lung metastasis compared to controls, with lung immunohistochemistry demonstrating robust perivascular lymphocytic infiltration. In our preliminary GBM experiments we found equivalent efficacy to tumor-lysate loaded dendritic cells, with brain immunohistochemistry demonstrating robust M2 macrophage infiltration.

Conclusion : Collectively our results demonstrate that MBTA is an effective strategy to mature and load tumor antigens onto DCs ex-vivo. It has efficacy as a DC vaccine to prevent melanoma metastasis. Further, work is needed to demonstrate it's efficacy in GBM models in combination with other therapeutics.