Tumor & Cancer Immunology and Immunotherapy

Biography

Biography: Edyta Zyla

Abstract

The interaction of PD-L1 with T cell PD-1 receptor leads to the inactivation and death of T cells resulting in immunosuppression and undisturbed tumor development. We engineered Salmonella strain to deliver soluble PD-1 into tumor tissue. In principle, soluble PD-1 will compete with the PD-1 receptor on the T cell surface for binding to the PD-L1 ligand present on the surface of tumor cells and thus prevent T cell inactivation. The main goal of this work was to modify Salmonella therapeutic strain so it will be capable of efficiently secreting soluble PD-1 through the flagellar system. The flagellar system functions as a bacterial mobility motor but also serves as a secretory system for the extracellular elements of the flagellum. Special secretion signals direct certain proteins for flagellar channel-mediated secretion. To use the flagellar system for the secretion of recombinant proteins bacteria should be deprived of flagellin synthesis. To achieve this, we removed the fliC gene coding for flagellin monomer from the VNP20009 chromosome by homologous recombination and transformed the new strain with a plasmid coding for soluble PD-1 equipped with a suitable secretion signal. At present we are testing various secretion signals for optimal synthesis and secretion of PD-1 via the flagellar system. Interestingly, the characterization of the ΔfliC strain showed similarities characteristics to the parental one in terms of viability and growth kinetics. What is more, the mobility of the modified bacteria and the wild-type VNP20009 did not differ. However, the exposure of RAW264.7 cells to both Salmonella strains revealed that ΔfliC bacteria are less infective when compared to the parental strain. Nonetheless, in this case, the decreased cell infectivity might be beneficial as it will allow secreting PD-1 to the extracellular environment, where it may fulfill its anti-immunosuppressive task.