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J. Exp. Med.,
Volume 188, Number 11, December 7, 1998 2127-2137
By

From the * Department of Microbiology and Immunology and the Pathogenic Yersinia cause a systemic infection in mice that is dependent on the presence of a
large plasmid encoding a number of secreted virulence proteins called Yops. We previously
demonstrated that a plasmid-encoded Yop, YopJ, was essential for inducing apoptosis in cultured macrophages. Here we report that YopJ is a virulence factor in mice and is important for
the establishment of a systemic infection. The oral LD50 for a yopJ mutant Yersinia pseudotuberculosis increases 64-fold compared with wild-type. Although the yopJ mutant strain is able to
reach the spleen of infected mice, the mutant strain seldom reaches the same high bacterial load
that is seen with wild-type Yersinia strain and begins to be cleared from infected spleens on day
4 after infection. Furthermore, when in competition with wild-type Yersinia in a mixed infection, the yopJ mutant strain is deficient for spread from the Peyer's patches to other lymphoid
tissue. We also show that wild-type Yersinia induces apoptosis in vivo of Mac-1+ cells from infected mesenteric lymph nodes or spleens, as measured by quantitative flow cytometry of
TUNEL (Tdt-mediated dUTP-biotin nick-end labeling)-positive cells. The levels of Mac-1+,
TUNEL+ cells from tissue infected with the yopJ mutant strain were equivalent to the levels
detected in cells from uninfected tissue. YopJ is necessary for the suppression of TNF-
Department of Comparative
Medicine, Stanford School of Medicine, Stanford University, Stanford, California 94305
production seen in macrophages infected with wild-type Yersinia, based on previous in vitro studies (Palmer, L.E., S. Hobbie, J.E. Galan, and J.B. Bliska. 1998. Mol. Microbiol. 27:953-965). We
conclude here that YopJ plays a role in the establishment of a systemic infection by inducing
apoptosis and that this is consistent with the ability to suppress the production of the proinflammatory cytokine tumor necrosis factor
.
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