(502b) Dendritic Cell-Derived Endogenous Virus-like Vesicles As Cancer Vaccines

The quest for enhancing the potency of cancer immunotherapies has led to the exploration of dendritic cell-derived extracellular vesicles (DEVs) based vaccines, which, however, are hampered by limited T cell stimulatory capacities in recent clinical trials. Addressing this challenge, we incorporated endogenous virus-like components into DEVs to boost their T cell engagement. Our approach aims to enhance the effectiveness of T cell mediated tumor targeting and eradication, utilizing engineered DEVs tailored to mimic viral attributes.

To achieve this goal, we genetically modified dendritic cells (DCs), introducing virus-like components to create engineered virus-like vesicles (eVLVs). We first analyzed their composition with mass spectrometry and tracked their enrichment in the spleen and direct interaction with T cells using in vivo and confocal imaging. Next, using the Ovalbumin (Ova) model antigen, we demonstrated that administration of eVLVs presented Ova to T cells and enhanced robust and balanced immune responses. RT-qPCR analysis showed elevated immune marker levels, and flow cytometry identified increased activation of both CD4+ helper and CD8+ cytotoxic T cells. Memory T cell formation, verified by ELiSpot assays for interferon-gamma (IFNg), highlighted the eVLV's capacity for inducing long-term immunological memory. IgG antibody levels in the eVLV group showed a dramatic 20-fold increase over the experimental control after four weekly doses.

To assess eVLV’s potential in cancer prevention, we generated a murine melanoma model by intradermally injecting B16-F10 melanoma cells into C57BL/6 mice. We monitored tumor growth via caliper measurements and computed tomography scans. Immune response evaluation employed flow cytometry to identify and quantify T cell subsets and other immune populations, ELISpot assays to measure IFNg secreting cells, and multiplex cytokine assays for systemic immune response profiling. The long-term efficacy and immune memory were tested by monitoring survival rates and performing a melanoma rechallenge in surviving mice. As a result, eVLV administration resulted in a 60% cure rate, with 67% of treated mice surviving more than 100 days post-melanoma rechallenge, markedly outperforming the control group, which had no survivors. This result emphasizes the potential of eVLVs for achieving lasting melanoma immunity and enhancing survival rates. Finally, our investigation into the molecular underpinnings of these effects uncovered a notable similarity between the eVLV surface proteins and retroviral envelope proteins, suggesting a new method for engaging T cell receptors.

In summary, our findings underscore the potential of utilizing endogenous virus-like properties of engineered DEVs to develop effective cancer vaccines. By harnessing the unique capabilities of eVLVs to recruit enveloping proteins and mimic viral engagement with immune cells, we present a new strategy for targeted cancer immunotherapy. This strategy also steers immunotherapy towards highly personalized treatments. Utilizing patient-derived donor DCs for vaccine production enhances personalization, ensuring vaccines are highly biocompatible and free from toxicity. This integration of biomedical engineering and immunology paves the way for tailored and targeted vaccines, offering a leap forward in the precision and safety of cancer immunotherapy.