Development of technologies for a toxoplasma gondii vaccine

  • Dalia Ahmed Kalef Al-Taie

Student thesis: Doctoral Thesis

Abstract

Studies were undertaken to test the utility of Surface Antigen 1 (SAG1), a surface glycoprotein and Cyclophilin 18 (TgCyc18) a chemokine mimic specific for CCR5 as a vaccine in a murine model of T. gondii infection. SAG1 has been shown to provide some protection against infection in previous studies. As Cyc18 induces, IL-12 when it binds to CCR5 it could act as an adjuvant to drive Th1 and CD8+ T cell development. As SAG1 is known to undergo post-translational modification, initial experiments focused on development of a novel eukaryotic expression system. The system as envisaged would utilise heterologous expression of filamentous L. mexicana secreted acid phosphatases fused to the proteins of interest in Leishmania tarentolae. It was anticipated that these filaments would facilitate purification. Plasmids were constructed and transfected into L. tarentolae. Recombinant parasites were found to express and secrete the fusion protein into the media. The identities of proteins were confirmed by immunoblot, immunofluorescence, ELISA, and mass spectrometry. Levels of secreted proteins were too low for vaccination studies. DNA vaccination was used as an alternative approach.TgSAG1 and TgCyc18 genes were cloned into the eukaryotic expression vector (pVAX-1). pVAX-Cyc18 induced IL-12 in murine bone marrow-derived dendritic cells. The inclusion of TgCyc18 gene in the vaccine augmented Th1 cell activation in BALB/c mice as their splenocytes produced significantly greater levels of IFN-ɣ, TNF-α, IL-2 and IgG2a compared with mice vaccinated with SAG1 alone. These mice also had reduced weight loss compared with mice vaccinated with SAG1 alone. Addition of SAG4 and SAG4.2 genes to this vaccine cocktail conferred significant protection following oral challenge with T. gondii cysts as measured by the reduction of mortality rate and reduced body weight loss. These results demonstrate that TgCyc18 has potential as adjuvant in multicomponent vaccines where a Th1 response is required.
Date of Award1 Oct 2019
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SupervisorCraig Roberts (Supervisor) & Martin Wiese (Supervisor)

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