A critical role for phospholipase C in protective immunity conferred by listeriolysin O-deficient Listeria monocytogenes

Attenuated recombinant Listeria monocytogenes (Lm) strains are a promising class of vaccine vectors that trigger protective antigen-specific CD8 T cells. Listeriolysin O (LLO) is an important Lm virulence determinant allowing the bacterium to escape from the endocytic vacuole into the cell cytoplasm in phagocytic cells. However in non-phagocytic cells, Lm phospholipase C can also mediate cytoplasmic entry. The ability of LLO-deficient Lm to confer long-term protection to infection is uncertain. Herein, we demonstrate that LLO-deficient Lm mutants can prime protective immunity to subsequent Lm infection and that Lm phospholipase C is required for protective immunity conferred by LLO-deficient Lm.