Innate immune mechanisms underlying the efficacy of a next-generation nanoparticle-based vaccine against opioid use disorders.

Since 1999, the opioid use disorder (OUD) and overdose epidemic has claimed millions of lives with ∼3 million people currently diagnosed with OUD and ∼ 100,000 fatal overdoses occurring annually. Curbing this public health crisis requires accelerating the translation of innovative, effective, and safe treatments. Our team is advancing vaccines against a variety of opioids as a preventative and therapeutic strategy against OUD and overdose. Previously, we reported that a hybrid lipid-polymer nanoparticle (hNP)-based vaccine targeting oxycodone demonstrated superior immunogenicity and efficacy in mice compared to an equivalent conjugate vaccine formulated in aluminum salts. Here, we extended our investigation of the hNP-based oxycodone vaccine to rats and applied the hNP platform to a lead vaccine targeting fentanyl and its analogs. Additionally, this study tested whether hNPs offer a suitable delivery system for vaccines adjuvanted with the toll-like receptor 7 and 8 (TLR7/8) agonist R848. This study assessed vaccine efficacy in blocking opioid-induced antinociception, respiratory/cardiovascular depression, and drug distribution to the brain. Innate immune responses to the anti-oxycodone nanovaccines were tested in murine macrophage and dendritic cell (DC) lines using cellular activation co-stimulatory/maturation markers. Cytokine profiles and immune cell activation in response to anti-fentanyl nanovaccines were assessed in human whole blood using multiplex cytokine assays paired with flow cytometry. Results demonstrate that hNP-formulated oxycodone vaccines exhibit improved efficacy in rats and superior activation of macrophage and DC compared to aluminum formulated conjugate vaccines. While the hNP-based fentanyl vaccine showed diminished efficacy relative to the unformulated vaccine in rats, adding R848 to the hNP formulation rescued its efficacy. These comprehensive immune profiling studies advance our understanding of OUD vaccines, providing a rational blueprint for next-generation vaccine design.