CD8 Knockout Mice Are Protected from Challenge by Vaccination with WR201, a Live Attenuated Mutant ofBrucella melitensis

Abstract

CD8+ T cells have been reported to play an important role in defense againstB. abortusinfection in mouse models. In the present report, we use CD8 knockout mice to further elucidate the role of these cells in protection fromB. melitensisinfection. Mice were immunized orally by administration ofB. melitensisWR201, a purine auxotrophic attenuated vaccine strain, then challenged intranasally withB. melitensis16M. In some experiments, persistence of WR201 in the spleens of CD8 knockout mice was slightly longer than that in the spleens of normal mice. However, development of anti-LPS serum antibody, antigen-induced production ofγ-interferon (IFN-γ) by immune splenic lymphocytes, protection against intranasal challenge, and recovery of nonimmunized animals from intranasal challenge were similar between normal and knockout animals. Further, primaryBrucellainfection was not exacerbated in perforin knockout and Fas-deficient mice and these animals’ anti-Brucellaimmune responses were indistinguishable from those of normal mice. These results indicate that CD8+ T cells do not play an essential role as either cytotoxic cells or IFN-γproducers, yet they do participate in a specific immune response to immunization and challenge in this murine model ofB. melitensisinfection.