Formulation and testing of a liposomal-based vaccine for cancer and influenza

Vaccines are arguably the most important medical technology developed to date, and have provided dramatic reductions in disease morbidity and mortality over the last 200 years. Although vaccines have been undeniably successful, improvements in vector production, delivery and ease of use would be of great benefit. Historically, vaccine development has been based on the “three Is” paradigm of Louis Pasteur (isolate, inactivate, inject). However, an improved understanding of immunology, pathology and microbiology is now helping vaccine development adopt a more ‘rational design’ approach. This thesis builds on previous work in the development of a plug-and-play universal vaccination platform. Previously, this platform has been reported to evoke a rapid, high titre, isotype switched, epitope-specific antibody response against an epitope of the circumsporozoite protein from the malaria parasite. Here we describe repurposing the platform to vaccinate against ErbB-2 overexpressing tumours and H3N2 influenza viruses. Cancer is among the leading causes of morbidity and mortality today. ErbB-2 is a popular target for cancer treatment as it is localised to the cell surface and has raised expression in 15 - 30% of all breast cancers, as well as in some ovarian, renal, colon and lung cancers. Influenza is a common pathogen that annually infects 5 - 10% of adults and 20 - 30% of children worldwide. Despite influenza (flu) vaccines being available since the 1940s' they have had restricted success due to flu proteins being subject to a high rate of antigenic drift and shift. However, many groups have reported conserved regions of the viral proteins with low immunogenicity. If such low immunogenicity can be overcome then this would pave the way for a flu vaccine with long lasting efficacy. This thesis begins by first giving an overview of novel vaccination technologies before describing the formulation methods of the vaccine platform developed herein. The encapsulation efficiency of liposomal-vaccine particles after all purification steps was found to be approximately 0.1, 0.3, and 0.5% for the three formulation methods used. This low percentage is due to dilution factors in the purification steps and inherent poor passive loading efficiency of liposomes. The surface conjugation efficiency of the target peptide was demonstrated to increase from 0.4% in the first two formulation methods to 92.8% in the third method. The immunogenicity of this vaccination platform, after subcutaneous injection, is then demonstrated by the elicitation of a rapid (within 1 week) raised (10.5-fold, p<0.001) humoral immune response specific for the ErbB-2 peptide. This process is shown to be driven by non-cognate T helper cells specific for an ovalbumin peptide, OVA323-339. Lastly, to demonstrate the plug-and-play adaptability of the platform the formulation is repurposed to show raising of a class-switched, high-avidity, antibody response to a H3N2 influenza virus epitope, with titres reaching 98.7-fold higher than control groups (p<0.001) just one week after initial vaccination.

Keywords: vaccination
vaccine
influenza
cancer
Her2
ErbB2
hemagglutinin
HA
Advisor: Carlisle, R
Shenton, D