Design of a novel vaccine nanotechnology-based delivery system comprising CpGODN-protein conjugate anchored to liposomes

Abstract

Although the well-known Toll like receptor (TLR9) agonist CpGODN has shown promising results as vaccine adjuvant in preclinical and clinical studies, its in vivo stability and potential systemic toxicity remain a concern. In an effort to circumvent these issues, different strategies have been employed to increase its stability, localise action and reduce dosage. These include conjugation of CpGODN with proteins or encapsulation/adsorption of CpGODN into/onto liposomes and have resulted in enhanced immunopotency compared to co-administration of free CpGODN and antigen. Here, we designed a novel delivery system of CpGODN based on its conjugation to serve as anchor for liposomes. Thiolmaleimide chemistry was utilised to covalently ligate the Group B Streptococcus (GBS) GBS67 protein antigen with the CpGODN TLR9 agonist. This treatment did not alter protein's ability to be recognised by specific antibodies or the CpGODN to function as a TLR9 agonist. Due to its negative charge, the protein conjugate readily electrostatically bound cationic liposomes composed of 1, 2-distearoyl-snglycero-3-phosphocholine (DSPC), cholesterol and dimethyldioctadecylammonium bromide (DDA).The novel cationic liposomes-protein conjugate complex (GBS67-CpGODN+L) shared similar vesicle characteristics (size and charge) compared to free liposomes but exhibited different structure and morphology. Following intramuscular immunisation, GBS67-CpGODN+L formed a vaccine depot at the injection site and induced a remarkable increase of functional immune responses against GBS compared to the simple co-administration of GBS67, CpGODN and liposomes. This work demonstrates that the conjugation of CpGODN to GBS67 in conjunction with adsorption on cationic liposomes, can promote co-delivery leading to the induction of a multifaceted immune response at low antigen and CpGODN doses. Our findings highlight the potential for harnessing the immunostimulatory properties of different adjuvants to develop more effective nanostructure-based vaccine platforms.

Delivery of self-amplifying mRNA vaccines by cationic lipid nanoparticles: The impact of cationic lipid selection

“…Within our studies, we demonstrate that cLNPs and iLNPs formed depots at the injection site, with DDA-based systems remaining longer at the injection site. No detectable signal was observed in organs during the course of the experiment, as have previously shown with similar DDA formulations [22].The retention of liposomal DNA vaccines (composed of PC, DOPE and DOTAP) at the injection site has also been previously shown using radiolabelled trackers [48]. In vivo gene expression at the injection site after administration with LNPs containing SAM encoding luciferase has also been shown with high levels bioluminescence at day 3, which peaked at day 7, and decreased to background by day 63 [4].…”

Recent Progress in Bioconjugation Strategies for Liposome-Mediated Drug Delivery

“…Peptides can be conjugated to the liposome surface by way of various covalent linkages, including maleimide-thiol bonds, peptide bonds, sulfanyl bonds, disulfide bonds, and phosphatidyletanolamine-linker bonds [109]. Additionally, larger peptides, proteins, and enzymes can be attached to the liposome surface to provide a desired functionalization [110,111].…”

Stable anchoring of bacteria-based protein nanoparticles for surface enhanced cell guidance

“…GFP IB-like pNPs produced by E. coli and L. lactis were covalently attached to maleimide-terminated SAMs through their cysteine aminoacids by means of a Michael addition interfacial reaction using the mCP technique, as recently shown for other nano-objects. [46][47][48] More specifically, the exposed thiol groups of the cysteine residues of GFP at the surface of the pNPs reacted with the maleimide groups of the SAM forming covalent bonds, thus providing a more stable binding in comparison with a simple physisorption procedure (Fig. 1).…”