Engineering a Tp0751-based Vaccine Scaffold: Applying Iterative Protein Design to Optimize Antigen Presentation




Thompson, Lexie

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Treponema pallidum subspecies pallidum is the causative organism of syphilis, a widespread sexually transmitted infection and re-emerging public health threat. The continued resurgence of syphilis, despite the discovery of effective penicillin treatment, highlights the need for preventative and affordable syphilis control. Previous efforts to develop a protective vaccine candidate have been hindered due to the limited discovery of protective antigens and the paucity of outer membrane proteins on the bacterial surface. A majority of the currently identified vaccine candidates are integral outer membrane proteins that, due to their highly insoluble nature, cannot be recombinantly produced in a properly folded and soluble state. Our focus is expressing the immunogenic epitopes from these large integral membrane proteins in a more sophisticated expression platform, allowing us to bypass the expression of these full-length proteins. Our designs focus on using Tp0751, a T. pallidum adhesin protein, as a scaffold on which to build our recombinant vaccine candidate. These studies aimed to engraft epitopes from a select few of these integral outer membrane proteins into the flexible loop and termini regions of Tp0751 to yield a stable and soluble candidate capable of recapitulating the immune response raised against each separate protein. Here we have successfully shown that not only is Tp0751 amenable to this engineering with up to four separate epitope engraftments, but that a lead chimeric candidate offers partial protection in a rabbit model. Altogether, the body of work summarized in this thesis highlights the success of Tp0751 as a vaccine platform and opens new avenues for future recombinant vaccine production.



Biochemistry, Protein Engineering, Syphilis, Tp0751