Original Article
Alginate-coated chitosan nanogels differentially modulate class-A and class-B CpG-ODN targeting of dendritic cells and intracellular delivery

https://doi.org/10.1016/j.nano.2014.06.003Get rights and content

Abstract

CpG-oligodeoxynucleotides (CpG-ODNs) interact with dendritic cells (DCs), but evidence is less clear for CpG-ODN admixed with or incorporated into vaccine delivery vehicles. We loaded alginate-coated chitosan-nanogels (Ng) with class-A or class-B CpG-ODN, and compared with the same CpG-ODNs free or admixed with empty Ng. Experiments were performed on both porcine and human blood DC subpopulations. Encapsulation of class-A CpG-ODN (loading into Ng) strongly reduced the CpG-ODN uptake and intracellular trafficking in the cytosol; this was associated with a marked deficiency in IFN-α induction. In contrast, encapsulation of class-B CpG-ODN increased its uptake and did not influence consistently intracellular trafficking into the nucleus. The choice of CpG-ODN class as adjuvant is thus critical in terms of how it will behave with nanoparticulate vaccine delivery vehicles. The latter can have distinctive modulatory influences on the CpG-ODN, which would require definition for different CpG-ODN and delivery vehicles prior to vaccine formulation.

From the Clinical Editor

This basic science study investigates the role of class-A and class-B CpG-oligodeoxynucleotides loaded into alginate-coated chitosan nanogels, demonstrating differential effects between the two classes as related to the use of these nanoformulations as vaccine delivery vehicles.

Graphical abstract

We loaded nanogels with class-A or class-B CpG-ODN, and compared with the same CpG-ODNs free or admixed with empty nanogels. Encapsulation of class-A CpG-ODN (loading into Ng) strongly reduced the CpG-ODN uptake and intracellular trafficking in the cytosol; this was associated with a marked deficiency in IFN-α induction. In contrast, encapsulation of class-B CpG-ODN increased its uptake and did not influence consistently intracellular trafficking into the nucleus. The choice of CpG-ODN class as adjuvant is thus critical in terms of how it will behave with nanoparticulate vaccine delivery vehicles.

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Section snippets

Core-shell nanogels

Empty nanogels Ng-[-] were prepared as described.22, 23 Class-A and class-B CpG-ODN containing Ng (Ng-[2216] and Ng-[2006]) were prepared: 50 μg of CpG-ODN-2216-FITC (class-A) or CpG-ODN-2006-FITC (class-B) (Invivogen, CA, USA) were resuspended in 50 μl 0.1% (w/v) sodium triphosphate pentabasic (TPP) (Sigma-Aldrich, Germany). This solution was added drop-wise to 450 μl 0.1% (w/v) chitosan (low viscosity, 95% deacetylation; Primex, Iceland), pH < 4, constant agitation. After 2 h at pH 4, these

Characterisation of empty and CpG-ODN loaded nanogels

Freshly produced empty Ng (Figure 1, Ng-[-]) exhibited a size of 959 ± 247 nm in water, and a zeta potential of − 31.5 ± 3.1 mV (Figure 1, A and B, red bars). Loading both classes of CpG-ODN into the Ng reduced the size, but did not significantly alter the zeta potential: Ng-[2216] gave 736 ± 55 nm, − 32.9 ± 1.2 mV; Ng-[2006] gave 710 ± 28 nm, − 32.8 ± 0.2 mV (Figure 1, A and B, red bars). When employing the experimental conditions for interaction with the DCs (ie., DMEM/1% porcine serum), all Ng formulations

Discussion

Inactivated vaccines often rely on formulation with adjuvants to enhance the activation and eventually maturation of the DCs critical for advancing immune defence development.1, 2, 31 Their efficacy is potentially enhanced by the advent of biodegradable delivery vehicles for increasing interaction with DCs.3, 4, 5, 6, 7 The CpG-ODN family has been widely investigated for adjuvant potential,8, 9, 10, 11, 12, 13 but the question remains on how they should be formulated with biodegradable

Acknowledgments

We thank Brigitte Herrmann for cell culture support; Pavlos Englezou for helpful discussions; Sylvie Python for cell sorting assistance; Res Michel for collecting porcine blood.

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    The work was funded by FP6 Project PANFLUVAC (044115) and Marie Curie IAPP Project Replixcel (251420).

    Disclosure: The authors declare no competing financial interests.

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