Co-delivery of Dual Toll-Like Receptor Agonists and Antigen in Poly(Lactic-Co-Glycolic) Acid/Polyethylenimine Cationic Hybrid Nanoparticles Promote Efficient In Vivo Immune Responses

Abstract

Strategies to design delivery vehicles are critical in modern vaccine-adjuvant development. Nanoparticles (NPs) encapsulating antigen(s) and adjuvant(s) are promising vehicles to deliver antigen(s) and adjuvant(s) to antigen-presenting cells (APCs), allowing optimal immune responses against a specific pathogen. In this study, we developed a novel adjuvant delivery approach for induction of efficient in vivo immune responses. Polyethylenimine (PEI) was physically conjugated to poly(lactic-co-glycolic) acid (PLGA) to form PLGA/PEI NPs. This complex was encapsulated with resiquimod (R848) as toll-like receptor (TLR) 7/8 agonist, or monophosphoryl lipid A (MPLA) as TLR4 agonist and co-assembled with cytosine–phosphorothioate–guanine oligodeoxynucleotide (CpG ODN) as TLR9 agonist to form a tripartite formulation [two TLR agonists (inside and outside NPs) and PLGA/PEI NPs as delivery system]. The physicochemical characteristics, cytotoxicity and cellular uptake of these synthesized delivery vehicles were investigated. Cellular viability test revealed no pronounced cytotoxicity as well as increased cellular uptake compared to control groups in murine macrophage cells (J774 cell line). In the next step, PLGA (MPLA or R848)/PEI (CpG ODN) were co-delivered with ovalbumin (OVA) encapsulated into PLGA NPs to enhance the induction of immune responses. The immunogenicity properties of these co-delivery formulations were examined in vivo by evaluating the cytokine (IFN-γ, IL-4, and IL-1β) secretion and antibody (IgG1, IgG2a) production. Robust and efficient immune responses were achieved after in vivo administration of PLGA (MPLA or R848)/PEI (CpG ODN) co-delivered with OVA encapsulated in PLGA NPs in BALB/c mice. Our results demonstrate a rational design of using dual TLR agonists in a context-dependent manner for efficient nanoparticulate adjuvant-vaccine development.

Nanoparticle‐Based Nanomedicines to Promote Cancer Immunotherapy: Recent Advances and Future Directions

“…Considering that most pathogens need to stimulate multiple TLRs to upregulate pro‐inflammatory cytokines and chemokines, nanovectors are engineered to combine a few TLR agonists. For example, poly( d , l ‐lactic‐ co ‐glycolic acid) (PLGA)/polyethylenimine (PEI) polymeric nanoparticles codeliver R848 (TLR7/8 agonist), MPLA (TLR4 agonist), and CpG (TLR9 agonist) with OVA, exerting superior effects on promoting robust immune responses in comparison to a single bioadjuvant, which is consistent with other studies …”

IRAK1-mediated coincidence detection of microbial signals licenses inflammasome activation

“…Collaboration of multiple PRRs and their adaptors is required for an optimal host response to many pathogens (Delaloye et al, 2009;Ferwerda et al, 2007;Slater et al, 2010). In the context of vaccine-adjuvant development, it has also been shown that co-delivery of TLR agonists as adjuvants elicits an improved immune memory response (Ebrahimian et al, 2017;Pulendran and Ahmed, 2011). Thus, a cogent and effective immune response must involve concomitant engagement of multiple PRR pathways.…”

Biomaterials as Tools to Decode Immunity

“…Stimulator of interferon genes (STING), and nucleotide‐binding oligomerization domain (NOD)‐like receptors are additional PRRs that are present in the cell's cytoplasm and trigger the expression of the three activation signals . Triggering combinations of TLR pathways in APCs (or other synergistic immune pathways) is one developing area to improve understanding of the generation and regulation of a range of immune processes, both innate and adaptive . Another key function of APCs is the connection these cells have to adaptive immunity, which is the focus of the next section.…”

“…Along these lines, helper T cells adopt phenotypes optimized to combat specific classes of pathogens: T H 1 cells help clear intracellular pathogens like viruses and bacterium, while T H 2 cells help clear parasites and pathogens outside the cell. Ebrahimian et al developed a novel signal delivery method using a cationic polymer polyethylenimine (PEI) conjugated to poly(lactic‐ co ‐glycolide) (PLGA) NPs coencapsulating either a TLR7/8 agonist—resiquimod—or a TLR4 agonist—monophophoryl lipid A (MPLA) . These components were coassembled with a TLR9 agonist, CpG, to form NP formulations containing defined combinations of two TLR agonists.…”

“…In contrast, NPs coencapsulating TLR4 and TLR9 agonists stimulated greater T H 2‐associated cytokines—such as IL4, compared to the NPs coencapsulating TLR7/8 and TLR9 agonists. Thus, the NPs containing TLR4 and TLR9 favored T H 2 responses, while codelivery of TLR7/8 and TLR9 agonists favored a T H 1 response . Similar strategies have also been used to deliver coencapsulated ligands and antigens for generating pathogen clearing immune responses …”