Yersinia-induced apoptosis in vivo aids in the establishment of a systemic infection of mice.
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-alpha 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 alpha.
Monack
D M
DM
Department of Microbiology and Immunology, Stanford School of Medicine, Stanford University, Stanford, California 94305, USA. dmonack@leland.stanford.edu
Mecsas
J
J
Bouley
D
D
Falkow
S
S
D000818:Animals; D017209:Apoptosis; D005260:Female; D008221:Lymphoid Tissue / Q000382:microbiology* / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D009154:Mutation; D014774:Virulence / Q000235:genetics; D015007:Yersinia / Q000472:pathogenicity / Q000502:physiology*; D015009:Yersinia Infections / Q000473:pathology*