YopE specific CD8⁺ T cells provide protection against systemic and mucosal Yersinia pseudotuberculosis infection

Prior studies indicated that CD8⁺ T cells responding to a surrogate single antigen expressed by Y. pseudotuberculosis, ovalbumin, were insufficient to protect against yersiniosis. Herein we tested the hypothesis that CD8⁺ T cells reactive to the natural Yersinia antigen YopE would be more effective at providing mucosal protection. We first confirmed that immunization with the attenuated ksgA- strain of Y. pseudotuberculosis generated YopE-specific CD8⁺ T cells. These T cells were protective against challenge with virulent Listeria monocytogenes expressing secreted YopE. Mice immunized with an attenuated L. monocytogenes YopE+ strain generated large numbers of functional YopE-specific CD8⁺ T cells, and initially controlled a systemic challenge with virulent Y. pseudotuberculosis, yet eventually succumbed to yersiniosis. Mice vaccinated with a YopE peptide and cholera toxin vaccine generated robust T cell responses, providing protection to 60% of the mice challenged mucosally but failed to show complete protection against systemic infection with virulent Y. pseudotuberculosis. These studies demonstrate that vaccination with recombinant YopE vaccines can generate YopE-specific CD8⁺ T cells, that can provide significant mucosal protection but these cells are insufficient to provide sterilizing immunity against systemic Y. pseudotuberculosis infection. Our studies have implications for Yersinia vaccine development studies.