Fellows’s training included consortium wide research training, bespoke personalised research training packages and operational training, entrepreneurial, management, presentations skills and ethics training. Each of the researchers had an individual, personalised research project joint supervised by a multi-disciplinary cross-sector team of at least two supervisors, one from GSKVACSRL and one from USTRATH. The research developed by the 4 ESRs can be summarised into two themes.
Knowledge-based modulation of antigens to improve immune responses
Our research considered the knowledge-based modulation of antigen structure. A structural vaccinology approach was adopted for the rational design of a self-assembling ferritin nanoparticle system displaying a chimeric protein antigen to stimulate broad and efficacious immunogenicity against the gram-negative diplococcus Neisseria meningitidis serogroup B (MenB). This chimeric antigen, incorporating epitopes from the NadA3 and PorA MenB antigens aimed to confer broader MenB strain coverage, whilst its incorporation into a self-assembling ferritin-based nanoparticle system presented the chimeric NadA3-PorA in a multicopy format on the ferritin surface, enhancing the immunogenicity. The NadA3-PorA-Ferritin epitope presentation was characterised by a range of structural and biochemical approaches, including cryo-electron microscopy. The immunogenicity of the NadA3-PorA-Ferritin was assessed in vivo, revealing that recombinant nanoparticle presentation of the NadA3-PorA enhanced the humoral responses raised against the subunit antigen.
We also considered enhancing the potency of antigens through conjugation of antigens with adjuvants. Although the well-known Toll like receptor 9 (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. Different strategies were employed to increase its stability, localise action and reduce dosage. These included conjugation of CpGODN with proteins or encapsulation/adsorption of CpGODN into/onto liposomes, and resulted in enhanced immunopotency compared to co-administration of free CpGODN and antigen. We designed a novel delivery system of CpGODN based on its conjugation to serve as anchor for liposomes. Thiol-maleimide chemistry was used to covalently ligate the Group B Streptococcus (GBS) GBS67 protein antigen with the CpGODN TLR9 agonist. Due to its negative charge, the protein conjugate readily electrostatically bound to cationic liposomes. Following intramuscular immunisation, the CpGODN-liposomes induced an increase in functional immune responses against GBS compared to the simple co-administration of GBS67, CpGODN and liposomes. This 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.
Developing delivery systems for self-amplifying RNA vaccines
Self -amplifying RNA (SAM) represents a versatile tool that can be used to develop potent vaccines, potentially able to elicit strong antigen-specific humoral and cellular-mediated immune responses to virtually any infectious disease. In order for these to be applied for clinical use, they require to be formulated with delivery systems. Therefore, we compared various cationic platforms including liposomes, lipid nanopartilces, solid lipid nanoparticles (SLNs), polymeric nanoparticles (NPs) and emulsions, to deliver a self-amplifying mRNA (SAM) vaccine. SAM encapsulating cationic polymeric nanoparticles and cationic liposomes induced the highest antigen expression in vitro and, from these, the cationic polymeric nanoparticles were the most potent in triggering humoral and cellular immunity among candidates in vivo. Given that lipid nanoparticles (LNPs), particularly those based on ionizable amino-lipids, are commonly adopted for sam-RNA delivery, we compared 6 commonly available cationic lipids, which have been broadly used in clinical investigations, as an alternative to ionizable lipids. All cationic LNP (cLNP) formulations promoting high association with cells in vitro and induced antigen expression. In vivo, the cLNPs were shown to be an efficient alternative to ionisable LNPs to deliver SAM vaccines.
