Design of vaccine nanotechnology-based delivery systems : the effect of CpGODN TLR9 agonist-protein antigen conjugates anchored to liposomes

Student thesis: Doctoral Thesis

Abstract

The efficiency of CpG oligonucleotides as Toll like receptor (TLR) 9 agonist has been well established along the last few years. Although CpGODN has shown promising results as vaccine adjuvant in preclinical and clinical studies, its in vivo stability and potential systemic toxicity have generated concern for the use of CpGODN. In an effort to increase stability, localise action and reduce dosage, different strategies have been approached, such as conjugation of CpGODN with immunogenic agents or encapsulation/adsorption of CpGODN into/onto liposomes resulting in enhanced immunopotency compared to coadministration of free CpGODN and antigen. Despite the advances in the field, the effect of conjugation of TLR9 to antigen in combination with liposomes on the immunogenicity of protein-based vaccines has not been explored yet.In this present study, thiol-maleimide chemistry was utilised for the covalent ligation between protein antigen and CpGODN TLR9 agonist, which did not alter protein ’s ability to be recognised by specific antibodies or activation of receptor by TLR9 agonist. Thanks to its negative charge, protein conjugate was electrostatically bound to cationic liposomes composed of 1, 2-distearoyl-sn-glycero-3-phosphocholine (DSPC), cholesterol and dimethyldioctadecylammonium bromide (DDA). The designed system GBS67-CpGODN+L shared similar vesicle characteristics (size and charge) compared to free liposomes but exhibited different structure and morphology. Following immunisation through the intramuscular (i.m.) route, cationic liposomes-protein conjugate complex (GBS67-CpGODN+L) formed a vaccine depot at the injection site, which translated into notable increase of functional immune responses compared to the simple coadministration of GBS67, CpGODN and liposomes (GBS67+CpGODN+L). This effect seems due to increased total IgG level and specifically of IgG2a subtype, although no specific Th1/Th2-driven response was found.This work demonstrates that theconjugatio n of TLR9 agonist to GBS67 in conjunction with adsorption on cationic liposomes, can promote codelivery leading to the induction of a multifaceted immune response at low antigen and CpGODN doses. The findings of this study highlight the potential for harnessing the immunostimulatory properties of different adjuvants to develop more effective nanostructure-based vaccine platforms achieving therapeutic effect at lower doses.
Date of Award28 Feb 2020
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde
SupervisorYvonne Perrie (Supervisor) & Craig Roberts (Supervisor)

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