Non-canonical inflammasome activation mediates the adjuvanticity of nanoparticles

Area of Science:

• Immunology
• Nanotechnology
• Vaccine Development

Background:

• The non-canonical inflammasome sensor caspase-11 and gasdermin D (GSDMD) are crucial for inflammation and pyroptosis, a cell death mechanism that enhances cell-mediated immunity (CMI).
• Nanoparticulate vaccine adjuvants are designed to stimulate immune responses, but their precise mechanisms and optimal characteristics for inducing CMI are still being explored.

Purpose of the Study:

• To investigate the role of caspase-11 and GSDMD in nanoparticle-induced CMI.
• To determine the optimal nanoparticle characteristics for inducing robust CD8+ T cell and Th1 responses.
• To elucidate the molecular mechanisms underlying nanoparticle adjuvant activity, focusing on reactive oxygen species (ROS) and inflammasome activation.

Main Methods:

• Utilized mouse models to assess CD8+ and Th1 responses to nanoparticulate vaccine adjuvants.
• Investigated the impact of nanoparticle size on ROS production, GSDMD activation, and subsequent immune responses.
• Analyzed the distinct roles of IL-1 and IL-18 in mediating Th1 and CD8+ responses, respectively.
• Employed biodegradable poly-lactic co-glycolic acid (PLGA) nanoparticles to evaluate their potential as CMI-inducing adjuvants.

Main Results:

• Caspase-11 and GSDMD are essential for CD8+ and Th1 responses elicited by nanoparticulate adjuvants.
• Nanoparticle-induced ROS production is size-dependent, with 50- to 60-nm particles being optimal for ROS generation and CMI.
• Optimal nanoparticle size correlates with enhanced GSDMD activation, leading to robust Th1 and CD8+ immune responses.
• Demonstrated a functional division of labor between IL-1 (supporting Th1) and IL-18 (promoting CD8+ responses).
• Biodegradable PLGA nanoparticles of optimal size were confirmed as potent inducers of CMI.

Conclusions:

• Reactive oxygen species (ROS) and the non-canonical inflammasome pathway are critical mediators of polymeric nanoparticulate adjuvant function.
• Adjuvant size is a key design principle for developing effective vaccines that induce cell-mediated immunity.
• These findings provide a foundation for designing next-generation vaccines against cancer and intracellular pathogens by optimizing nanoparticle characteristics.