A CpG-Ficoll Nanoparticle Adjuvant for Anthrax Protective Antigen Enhances Immunogenicity and Provides Single-Immunization Protection against Inhaled Anthrax in Monkeys

Abstract

Nanoparticulate delivery systems for vaccine adjuvants, designed to enhance targeting of secondary lymphoid organs and activation of APCs, have shown substantial promise for enhanced immunopotentiation. We investigated the adjuvant activity of synthetic oligonucleotides containing CpG-rich motifs (CpG-ODN) linked to the sucrose polymer Ficoll, forming soluble 50 nm particles (DV230-Ficoll), each containing over 100 molecules of the TLR9 ligand, DV230. DV230-Ficoll was evaluated as an adjuvant for a candidate vaccine for anthrax using a recombinant form of protective antigen (rPA) from Bacillus anthracis. A single immunization with rPA plus DV230-Ficoll induced 10-fold higher titers of toxin-neutralizing antibodies in cynomolgus monkeys at 2 weeks compared with animals immunized with equivalent amounts of monomeric DV230. Monkeys immunized either once or twice with rPA plus DV230-Ficoll were completely protected from challenge with 200 LD50 aerosolized anthrax spores. In mice, DV230-Ficoll was more potent than DV230 for the induction of innate immune responses at the injection site and draining lymph nodes. DV230-Ficoll was preferentially co-localized with rPA in key antigen-presenting cell populations and induced greater maturation marker expression (CD69 and CD86) on these cells and stronger germinal center B and T cell responses, relative to DV230. DV230-Ficoll was also preferentially retained at the injection site and draining lymph nodes and produced fewer systemic inflammatory responses. These findings support the development of DV230-Ficoll as an adjuvant platform, particularly for vaccines such as for anthrax, for which rapid induction of protective immunity and memory with a single injection is very important.

Toll‐like receptor 4 signalling regulates antibody response to adenoviral vector‐based vaccines by imprinting germinal centre quality

“…To undergo the functional changes, APCs need to acquire maturation signals and fully competent antigen‐presenting capacity. Based on the gating strategies illustrated by Kachura et al ., we examined the expression of activation marker CD69 and maturation marker CD86 (Fig. a–c, and see Supplementary material, Fig.…”

“…Spleens from immunized mice were harvested (5 × 10 7 cells/sample) and stored on ice in RPMI‐1640 medium (Gibco, Gaithersburg, MD) before preparation of a single‐cell suspension. Differential identification of cell subtypes was conducted, as described previously, with some modifications . For cell‐staining experiments, cells were blocked with anti‐CD16/anti‐CD32 (BioLegend) in PBS with 2% fetal bovine serum.…”

Optimization, Production, and Characterization of a CpG-Oligonucleotide-Ficoll Conjugate Nanoparticle Adjuvant for Enhanced Immunogenicity of Anthrax Protective Antigen

“…Further extensive evaluations concerning the biology and immunology of the DV230-Ficoll conjugate compared with free CpG-ODN were also conducted by our laboratory; including protection of monkeys treated with DV230-Ficoll + rPA from lethal exposure to anthrax spores. 15 …”

“…12 Accordingly, delivering CpG-ODN in a nanoparticulate form is an attractive approach both for enhancing CpG-ODN adjuvant activity and for reducing potential systemic toxicity effects 13,14 by increasing retention of the adjuvant at injection-site draining lymph nodes. 15 In recent years, a number of approaches combining CpG-ODN with nanoparticulate systems have been described. These include the IC31 peptide/CpG coacervate, 16 CpG covalently conjugated to polypropylene sulfide nanospheres, 17 cationic PLG and emulsion/CpG nanoparticles, CAPO4 nanoparticles, 18 CpG-loaded VLP, 19 and CpG-liposomes.…”

Advances and Opportunities in Nanoparticle‐ and Nanomaterial‐Based Vaccines against Bacterial Infections

“…Toward vaccination against microbial pathogens, nanoparticulate CpG has been explored by Kachura et al for preparing anthrax vaccine . The authors cross‐linked CpG ODN molecules to sucrose polymer Ficoll to engineer nanoparticles that have been previously characterized to augment IFN‐α production from human plasmacytoid dendritic cells (pDCs).…”