NOVEL APPROACHES TO MENINGOCOCCAL VACCINE DEVELOPMENT

Abstract

Antigen uptake and processing by professional antigen-presenting cells (APCs) plays an essential role in the adaptive immune response and subsequent activation of antigen-specific CD4+ and CD8+ T lymphocytes. Consequently, knowledge of antigen interaction with APCs to induce CD8+ and CD4+ T-cell responses is useful in the rational design of peptide-based vaccines. Virus-like particles (VLPs) are non-infectious, self-assembled viral structural proteins that are inherently immunogenic and have been used as scaffolds to display heterologous antigens. Hepatitis B core antigen (HBcAg or HBc) is a widely studied VLP with proven safety and effectiveness as an antigen display platform. Neisseria meningitidis is a Gram-negative bacterium and a causative agent of life-threatening invasive meningococcal disease known to be associated with high morbidity and mortality. There have been effective vaccines for serotypes A, C, W135 and Y produced using their capsular polysaccharides (CPS) but with limited impact against serogroup B (MenB). This study examined the incorporation of meningococcal antigens into HBc. One such antigen fusion HBc-NadA, was used for further studies of binding and uptake into THP-1-derived dendritic cells and macrophages. Comparison was made with native NadA (not coupled to HBc), native HBc and heat denatured NadA. THP-1-derived DCs effectively internalised NadA but failed to internalise HBc or HBc-NadA. THP-1-derived macrophages effectively internalised HBc, HBc-NadA, and NadA. Both HBc and HBc-NadA were internalised through clathrin-mediated endocytosis, macropinocytosis and caveolae-mediated endocytosis. NadA and thermally-denatured NadA (NadA-D) were internalized through clathrin-independent pathways (macropinocytosis and caveolae-mediated endocytosis). HBc-NadA and HBc stimulated M1 macrophage polarization, characteristic of a Th1-skewed response, based on surface marker stimulation (CD80, CD40 and HLA-DR) and IFN-γ, TNF and IL-2 production. NadA alone, by contrast, stimulated M2 macrophage polarisation, characteristic of a Th2-skewed response. The pattern of surface marker stimulation and cytokine production of HBc-NadA was similar to that of HBc. Collectively, these results demonstrate that the uptake and processing of an HBc-fusion displaying a meningococcal antigen (HBc-NadA) is more characteristic of the native VLP (HBc) and distinct from that of the antigen alone (NadA). These findings have generated insights that could assist rational vaccine design using HBc to display bacterial antigens.

Date of Award	31 Dec 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Jeremy Derrick (Supervisor) & Kevin Couper (Supervisor)