Lipid Nanoparticle Encapsulation Empowers Poly(I:C) to Activate Cytoplasmic RLRs and Thereby Increases Its Adjuvanticity

Small. 2024 Mar;20(10):e2306892. doi: 10.1002/smll.202306892. Epub 2023 Oct 22.

Abstract

Poly(I:C) is a synthetic analogue of dsRNA capable of activating both TLR3 and RLRs, such as MDA-5 and RIG-I, as pathogen recognition receptors. While poly(I:C) is known to provoke a robust type I IFN, type III IFN, and Th1 cytokine response, its therapeutic use as a vaccine adjuvant is limited due to its vulnerability to nucleases and poor uptake by immune cells. is encapsulated poly(I:C) into lipid nanoparticles (LNPs) containing an ionizable cationic lipid that can electrostatically interact with poly(I:C). LNP-formulated poly(I:C) triggered both lysosomal TLR3 and cytoplasmic RLRs, in vitro and in vivo, whereas poly(I:C) in an unformulated soluble form only triggered endosomal-localized TLR3. Administration of LNP-formulated poly(I:C) in mouse models led to efficient translocation to lymphoid tissue and concurrent innate immune activation following intramuscular (IM) administration, resulting in a significant increase in innate immune activation compared to unformulated soluble poly(I:C). When used as an adjuvant for recombinant full-length SARS-CoV-2 spike protein, LNP-formulated poly(I:C) elicited potent anti-spike antibody titers, surpassing those of unformulated soluble poly(I:C) by orders of magnitude and offered complete protection against a SARS-CoV-2 viral challenge in vivo, and serum from these mice are capable of significantly reducing viral infection in vitro.

Keywords: immunotherapy; innate immune receptors; lipid nanoparticles; vaccine adjuvants.

MeSH terms

  • Adjuvants, Immunologic / pharmacology
  • Animals
  • Humans
  • Liposomes*
  • Mice
  • Nanoparticles*
  • Poly I-C*
  • Spike Glycoprotein, Coronavirus*
  • Toll-Like Receptor 3* / genetics
  • Toll-Like Receptor 3* / metabolism

Substances

  • spike protein, SARS-CoV-2
  • Lipid Nanoparticles
  • Toll-Like Receptor 3
  • Poly I-C
  • Adjuvants, Immunologic
  • Liposomes
  • Spike Glycoprotein, Coronavirus