IL-6-encoding tumor antigen generates potent cancer immunotherapy through antigen processing and anti-apoptotic pathways

A naked DNA vaccine delivered by gene gun into antigen-presenting cells (APCs) has emerged as an attractive strategy for antigen-specific cancer immunotherapy. However, APCs have a limited lifespan, hindering their long-term ability to prime antigen-specific T cells. Furthermore, the potency of DNA vaccines is limited by their inability to process and present antigens. Interleukin-6 (IL-6) could play a role in immunity and cell apoptosis. We explored how the DNA vaccine encodes IL-6 to a model tumor antigen, human papilloma virus type-16 (HPV-16) E7. Mice vaccinated with IL-6/E7 DNA exhibited dramatic increases in E7-specific T-cell immunities, anti-E7 antibody responses, and impressive anti-tumor effects against E7-expressing tumors. The in vitro results revealed that IL-6 enhances DNA vaccine potency through the major histocompatibility complex class I pathway via direct and cross-priming effects. In addition, the delivery of IL-6/E7 DNA prolonged the survival of transduced dendritic cells (DCs) in vivo. Our results indicated that the IL-6/E7 DNA vaccine combined the mechanisms of enhancing antigen processing and presentation with prolonging the survival of DCs. Using IL-6 represents an innovative approach to enhancing DNA vaccine potency and holds promise for cancer prevention and immunotherapy.