In vivo characterization of the physicochemical properties of polymer-linked TLR agonists that enhance vaccine immunogenicity

Abstract

The efficacy of vaccine adjuvants such as Toll-like receptor agonists (TLRa) can be improved through formulation and delivery approaches. Here, we attached small molecule TLR-7/8a to polymer scaffolds (polymer-TLR-7/8a) and evaluated how varying physicochemical properties of the TLR-7/8a and polymer carrier influenced the location, magnitude and duration of innate immune activation in vivo. Particle formation by polymer-TLR-7/8a was critical for restricting adjuvant distribution and prolonging activity in draining lymph nodes. The improved pharmacokinetic profile by particulate polymer-TLR-7/8a was also associated with reduced morbidity and enhanced vaccine immunogenicity for inducing antibodies and T cell immunity. We extended these findings to the development of a modular platform in which protein antigens are site-specifically linked to temperature-responsive polymer-TLR-7/8a adjuvants that self-assemble into immunogenic particles at physiologic temperatures in vivo. Our findings provide a chemical and structural basis for optimizing adjuvant design to elicit broad-based antibody and T cell responses with protein antigens.

Beyond antigens and adjuvants: formulating future vaccines

“…Chemical conjugation of adjuvant compounds to protein antigens ensures delivery to the same endocytic compartment, and this approach has been shown to enhance both humoral and cellular immunity in preclinical mouse and NHP models (65)(66)(67). Notably, these studies revealed that aggregation of antigen-danger signal conjugates to form particulates was critical to their in vivo efficacy, results which motivated recent studies that demonstrated how polymer-conjugated TLR agonists show both enhanced efficacy and safety when engineered to aggregate into a particulate form (68). The incorporation of antigen or danger signals into particulate vehicles can also be achieved by conjugation of these components to the surface of nanoparticles (69), entrapment within lipid vesicles or capsules (70), or encapsulation within polymer particles (47) or VLPs (60).…”

Cutting Edge: A Dual TLR2 and TLR7 Ligand Induces Highly Potent Humoral and Cell-Mediated Immune Responses

“…1E). This effect may be explained by the fact that PamadiFectin contains a lipidic moiety, leading to the formation of 50-nm particles, which in turn may limit dissemination and enhance uptake by APCs, thereby avoiding excessive inflammation as recently described for a TLR7 agonist (25). PamadiFectin enhances the avidity of Abs generated in vivo against HIV-1 p24 Endpoint titer ELISAs were performed in duplicate using nonreducing (PBS) and reducing (8 M urea) washes after sample addition to evaluate the avidity of Abs generated in vivo against HIV-1 p24.…”

pH-degradable imidazoquinoline-ligated nanogels for lymph node-focused immune activation

“…Nevertheless, the procedures applied to entrap TLR agonists inside polymeric carriers are often highly complex and yield ill-defined systems that suffer from burst releases of the TLR agonist (19) following in vivo application. Covalent ligation of TLR agonists to polymeric nanoparticles might provide chemically better-defined alternatives to physical (co)encapsulation systems, as recently nicely highlighted by the Seder laboratory (20).…”

“…Nevertheless, the procedures applied to entrap TLR agonists inside polymeric carriers are often highly complex and yield ill-defined systems that suffer from burst releases of the TLR agonist (19) following in vivo application. Covalent ligation of TLR agonists to polymeric nanoparticles might provide chemically better-defined alternatives to physical (co)encapsulation systems, as recently nicely highlighted by the Seder laboratory (20).Here, we report on the design of self-assembled, pH-degradable TLR7/8 agonist-ligated nanogels that efficiently restrict the innate immune-activating properties of the molecular adjuvant to the injection site and its DLN. Degradable polymer nanogels were prepared by self-assembly of amphiphilic block copolymers composed of a hydrophilic, PEG-like polymer block based on methoxy triethylene glycol methacrylate (mTEGMA) and a hydrophobic polymer block based on pentafluorophenyl methacrylate (PFPMA) (21).…”