The development of a synthetic self-adjuvanting cancer vaccine
Publication Date
December 12, 2023
Creator
Abstract
Cancer testis antigens (CTA) have demonstrated high immunogenicity towards multiple cancer types, and due to their restricted expression profile, they warrant further attention as potential vaccine candidates. Covalently attaching an adjuvant to an antigen is an effective strategy to induce a strong, targeted immune response. This thesis describes a robust synthetic method to palmitoylate CTA peptides with a dipalmitoyl- S-glyceryl cysteine residue (Pam2Cys). These adjuvants, known to effectively enhance the severity of an immune response, were covalently linked to the chosen CTA sequences to develop a self-adjuvanting, targeted cancer vaccine.
Liposomes can provide adjuvant activity either by enhancing antigen delivery or by activating innate immune responses. To examine this, a CTA antigen bearing an N-terminal Cys was conjugated covalently to the outer envelope of liposome particles via conjugation to a lipid carrying an appropriate electrophilic headgroup. The palmitoylated CTA sequences with native Pam2Cys were also inserted into the lipid bilayer of the liposomes via the palmityl 'tails' and these strategies of adjuvant and antigen incorporation into the particle formulation compared. The immune responses generated by the self-adjuvanting CTA peptide vaccine constructs, self-adjuvanting CTA peptides formulated into liposomal vaccine formulations, and the liposomes carrying the conjugated peptide antigens onto outer envelope of the nanoparticles were examined in vivo using healthy mouse models.
Chapter 1 gives an introduction on the human immune system and how it acts against foreigner antigens, leading to vaccine development. This chapter also discusses the CTA peptides and several types of adjuvants including Pam2Cys and liposomes. Previously reported syntheses of palmitoylated peptides are discussed. Chapter 2 describes our efforts towards the preparation of the lipid building block (Pam2Cys) and studies towards the conjugation of this component to the CTA peptides. Chapter 3 discusses the synthesis of CTA peptides that carry the Pam2Cys adjuvant. The adjuvant was covalently linked to the selected CTA sequences successfully to develop a self-adjuvanting peptide-based vaccine using two of the synthetic methods discussed in Chapter 2. Two CTA sequences were selected for this project. A fragment of the CTA, NY-ESO-1157-165, that has been shown to produce a strong anticancer immune response and the BAGE418-39 peptide, an under-explored melanoma antigen. Further engineering of the peptide antigens to include a solubility tag was also undertaken. The adjuvant was conjugated to these versions of the CTA to produce vaccine constructs with higher aqueous solubility. Chapter 4 describes the successful formulation of liposomes decorated with the BAGE418-39 antigen via reaction with a maleimide linker. The chapter initially describes the synthesis of a maleimide-containing lipid formulation of this compound into liposomes. This is followed by the successful optimisation of Cys- BAGE418-39 conjugation, resulting in a BAGE4Cys-maleimide-liposome formulation. Also, a second formulation that incorporates the native Pam2Cys linked to the BAGE418-39 was formulated for comparison. Chapter 5 describes the biological evaluation of the vaccines described in the previous chapters: Pam2Cys-SK4-NY-ESO-1157-165, BAGE418-39 antigen, BAGE4Cys-Mal-lipo formulation, Pam2Cys-SK4-BAGE418-39, and formulated Pam2Cys-SK4-BAGE418-39 liposome by readout of T-cell response using ELISpot assay. The results showed an immunogenic response was elicited by the Pam2Cys-SK4-NY-ESO-1157-165 conjugate; however, it was not strong enough to be taken to cancer models. The data also shows that the BAGE418-39 sequence is immunogenic, however, the immune response of the BAGE4Cys-maleimide-liposome formulation is not effective. Unfortunately, both of the last two vaccine candidates; Pam2Cys-SK4-BAGE418-39 administered alone and formulated into liposomes, were toxic to the model which led to sacrifice of the animals within the first 24 hrs, thus, study was stopped.
Item Type
ethesis
Thesis Type
PhD
Supervisors
Subjects (LC)
Associated Schools / Departments
School of Chemistry
eprints ID
76484
UoN Repository URI
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