Multi-enveloping of particulated antigens with biopolymers and immunostimulant polynucleotides

The main objective of this work is to study the possibility of enveloping particulated antigens using biomaterials and polynucleotides with immunostimulant properties, and to assess the value of this potential adjuvant strategy. The nanoparticulate structure (22 nm) of the recombinant Hepatitis B surface antigen (rHBsAg) has inspired us to use it as a substrate in the design of multi-enveloped nanoparticles. Our approach relies on the adsorption of polymers and immunostimulants by electrostatic interactions. Considering the negative charge of the rHBsAg, as a first layer we adsorbed the cationic polymers protamine (PR) and polyarginine (PARG). Subsequently, these nanostructures were enveloped using the anionic polymers dextran sulfate (DS) and alginate (ALG), and the immunostimulant polynucleotide poly (I:C) (pIC). The resulting multi-enveloped nanoparticles (HB:PR; HB:PR:DS; HB:PARG:ALG; HB:PARG:pIC) presented very small sizes (<50 nm) and were shown to be internalized by macrophages. With regard to the capacity of these new nanocompositions to elicit immune responses, the results observed following either intranasal or intramuscular administration indicated that despite the modest IgG titers, the IgG1/IgG2a ratio was more balanced that the one observed for the alum-adsorbed antigen. Overall, this work highlights the possibility to protect antigens and modify their presentation using a simple layer-by-layer approach.

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