Development of virus-like particles with inbuilt immunostimulatory properties as vaccine candidates

The development of virus-like particle (VLP) based vaccines for human papillomavirus, hepatitis B and hepatitis E viruses represented a breakthrough in vaccine development. However, for dengue and COVID-19, technical complications, such as an incomplete understanding of the requirements for protective immunity, but also limitations in processes to manufacture VLP vaccines for enveloped viruses to large scale, have hampered VLP vaccine development. Selecting the right adjuvant is also an important consideration to ensure that a VLP vaccine induces protective antibody and T cell responses. For diseases like COVID-19 and dengue fever caused by RNA viruses that exist as families of viral variants with the potential to escape vaccine-induced immunity, the development of more efficacious vaccines is also necessary. Here, we describe the development and characterisation of novel VLP vaccine candidates using SARS-CoV-2 and dengue virus (DENV), containing the major viral structural proteins, as protypes for a novel approach to produce VLP vaccines. The VLPs were characterised by Western immunoblot, enzyme immunoassay, electron and atomic force microscopy, and in vitro and in vivo immunogenicity studies. Microscopy techniques showed proteins self-assemble to form VLPs authentic to native viruses. The inclusion of the glycolipid adjuvant, α-galactosylceramide (α-GalCer) in the vaccine formulation led to high levels of natural killer T (NKT) cell stimulation in vitro, and strong antibody and memory CD8+ T cell responses in vivo, demonstrated with SARS-CoV-2, hepatitis C virus (HCV) and DEN VLPs. This study shows our unique vaccine formulation presents a promising, and much needed, new vaccine platform in the fight against infections caused by enveloped RNA viruses

Neuroimmune responses in viral infection

© 2020 Joon Keit LoiThe regulation of the immune responses is important in maintaining good health. Interactions between the nervous and immune systems are increasingly studied and widely appreciated to be influential in orchestrating immune responses. T cells express adrenergic receptors (AR) that enable them to respond to neurotransmitters produced by the sympathetic nervous system (SNS), noradrenaline (NA) and adrenaline, inducing downstream signalling and modulating cell functions, although whether this is stimulatory or inhibitory in T cell antiviral responses is unclear. In this thesis, I examine the effects of SNS in various models of viral infection through chemical sympathectomy and treatment with AR agonists. Modulation of sympathetic signals in systemic infections with LCMV had minor influences on T cell responses but resulted in increased viral loads. Notably, the infection results in a loss of tyrosine hydroxylase (TH) positive sympathetic fibres in the spleen as early as day 3 post infection and is reflected by decreased NA splenic NA. The immune response may play a role with interferon g partially contributing to the depletion. Additionally, this thesis also investigates the capability of long-lasting resident memory T cell (TRM) responses in the highly innervated, immune-privileged cornea. Using a model of herpes infection of the cornea, I showed that T cells are effectively recruited to the cornea with a small heterogenous population able to persist following cessation of immune responses. These cells express CD69 and CD103, canonical markers of tissue residency, to varying degrees. Persistence, but not recruitment, of these cells is dependent on antigen availability at the cornea. These memory cells are capable of responding to secondary encounters with antigen. Moreover, circulating memory cells are also able to infiltrate the immune-privileged cornea more efficiently following infection. Together, these results highlight the important nuances in the regulation of immune responses by the nervous system