Designing a plague vaccine utilizing α-gal modified antigens (52.6)

Abstract Background: F1-V from Yersinia pestis has been shown to be a protective antigen against disease. We modified the F1-V antigen with α-galactose residues and immunized α galactosyl transferase (α-GT) KO mice in order to mimic the same defect in humans that results in circulating antibodies against α-gal epitopes enhancing immune responsiveness. Aim: To demonstrate that α-gal modified F1-V induces a more robust immune response than unmodified F1-V. Methods: α-GT KO mice were injected subcutaneously with different doses of α-gal-F1-V or F1-V. All mice were boosted with F1-V at 36 dpi and necropsied on day 40 in order to evaluate in vitro recall response of lymphocytes and to measure anti-F1-V antibody titers. Results: Mean IgG titer values were 50,000 and 10,000 for mice immunized with the α-gal-F1-V or F1-V, respectively. The relative avidity of the antibody response was also higher for the α-gal-F1-V immunized mice. Moreover, lymphocytes from α-gal-F1-V immunized mice demonstrated enhanced proliferation in response to F1-V compared to cells from F1-V immunized mice. Conclusions: α-gal modified F1-V increases both the avidity and amount of anti-F1-V produced following vaccination. As a functional assay, α-gal-F1-V antisera efficiently opsonized Y. pestis, facilitated phagocytosis by human monocytes and prevented Y. pestis-induced monocyte cytotoxicity.