Current vaccine design aims to develop safer vaccines based on one or few selected antigens. RNA-based vaccines can be engineered to encode any antigen of interest and have the potential for rapid, inexpensive and scalable manufacturing and have an acceptable safety profile. Moreover, they enable in situ antigen expression, mimicking a real viral infection hence eliciting robust humoral and cellular-mediated immune responses. RNA vaccines therefore represent a versatile tool to fight infectious diseases and emerging pathogens effectively and rapidly. Furthermore, the antigen can be designed in a self-amplifying RNA (SAM) to enhance the immunogenicity and to reduce the therapeutic dose compared to conventional non-amplifying mRNA vaccines.RNAs can be encapsulated in delivery systems to protect them against degradation upon injection and to facilitate their delivery in host cells. Among them, lipid-based delivery systems and, more specifically, lipid nanoparticles (LNPs) are efficient non-viral delivery systems for RNA and SAM vaccines. Within this thesis, a panel of cationic LNPs (cLNPs), based on existing cationic lipids (e.g. DOTAP and DDA), was designed to deliver a SAM vaccine. The rabies virus was used as a model, as there is an established correlate of protection (neutralising antibodies) and there exist efficacious vaccines in the market (e.g. Rabipur) to be used as comparators. To this end, a SAM vaccine encoding the rabies virus glycoprotein (RVG), the only target for neutralising antibodies, was usedMicrofluidics-based methods for producing cLNPs of desired physicochemical properties were developed and optimal operating parameters (e.g. total flow rate and flow rate ratio) were established. Most promising SAM-cLNP candidates were chosen according to their physicochemical attributes, their ability to protect SAM from enzymatic degradation and their capacity to associate with cells and to induce antigen expression. These formulations were well retained at the injection site when administered intramuscularly or intradermally, while they were rapidly cleared following intranasal administration.On the other hand, SAM-cLNPs induced protective levels of anti-RVG antibodies following intramuscular injection in mice and RVG-specific polyfunctional T cell responses even with a dose as low as 0.15 Î¼g RVG-SAM. Remarkably, the immune responses elicited by SAM-cLNPs were comparable to Rabipur, a commercial vaccine based on an inactivated rabies virus, and a cationic nanoemulsion, a safe and well-established SAM delivery system which is currently being investigated in a phase I clinical trial in humans (as of September 2019). Intradermal administration of SAM-cLNPs resulted in similar humoral and cell-mediated immune responses, while significantly weaker immune responses were achieved when administered intranasally.
|Date of Award||28 Feb 2020|
- University Of Strathclyde
|Sponsors||EPSRC (Engineering and Physical Sciences Research Council) & University of Strathclyde|
|Supervisor||Yvonne Perrie (Supervisor) & Craig Roberts (Supervisor)|