Novel Virulence Properties of the Salmonella typhimurium Virulence-Associated Plasmid: Immune Suppression and Stimulation of Splenomegaly.

摘要

Mice infected subcutaneously with wild-type Salmonella typhimurium, SRll, developed a significant splenomegaly when compared with mice infected with an equal number of plasmid-cured strain. Further, the bacterial load in the spleen at 14 days after infection, measured as colony-forming units per gram tissue, was significantly higher in mice infected with the parent strain than in mice infected with the plasmid-cured strain. These data confirm the previously reported plasmid-associated ability of Salmonella to multiply within the spleen. In addition, lymph node cells (LNC) from mice infected with the parent strain had a significantly reduced ability to proliferate in response to concanavalin A. a T-cell mitogen, and to heat-killed S. typhimurium cells when compared with LNC isolated from mice infected with the plasmid-cured strain. Finally, reintroduction of a functional Tn5-tagged 90-kb plasmid into a plasmid-free strain restored its capacity to cause a marked splenomegaly and to suppress lymph node cell proliferation BALB/c mice. (JS)