Salmonella-induced cell death is not required for enteritis in calves.
Salmonella enterica serovar Typhimurium causes cell death in bovine monocyte-derived and murine macrophages in vitro by a sipB-dependent mechanism. During this process, SipB binds and activates caspase-1, which in turn activates the proinflammatory cytokine interleukin-1beta through cleavage. We used bovine ileal ligated loops to address the role of serovar Typhimurium-induced cell death in induction of fluid accumulation and inflammation in this diarrhea model. Twelve perinatal calves had 6- to 9-cm loops prepared in the terminal ileum. They were divided into three groups: one group received an intralumen injection of Luria-Bertani broth as a control in 12 loops. The other two groups (four calves each) were inoculated with 0.75 x 10(9) CFU of either wild-type serovar Typhimurium (strain IR715) or a sopB mutant per loop in 12 loops. Hematoxylin and eosin-stained sections were scored for inflammation, and terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL)-positive cells were detected in situ. Fluid accumulation began at 3 h postinfection (PI). Inflammation was detected in all infected loops at 1 h PI. The area of TUNEL-labeled cells in the wild-type infected loops was significantly higher than that of the controls at 12 h PI, when a severe inflammatory response and tissue damage had already developed. The sopB mutant induced the same amount of TUNEL-positive cells as the wild type, but it was attenuated for induction of fluid secretion and inflammation. Our results indicate that serovar Typhimurium-induced cell death is not required to trigger an early inflammatory response and fluid accumulation in the ileum.
Santos
R L
RL
Department of Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, Texas 77843, USA.
Tsolis
R M
RM
Zhang
S
S
Ficht
T A
TA
Bäumler
A J
AJ
Adams
L G
LG
D000818:Animals; D017209:Apoptosis / Q000276:immunology*; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology; D002417:Cattle; D003967:Diarrhea / Q000276:immunology*; D004195:Disease Models, Animal; D004751:Enteritis / Q000276:immunology*; D008297:Male; D016296:Mutagenesis; D012480:Salmonella Infections / Q000276:immunology*; D012486:Salmonella typhimurium / Q000276:immunology*
D001426:Bacterial Proteins; C060972:SopB protein, Bacteria; C489224:SopB protein, Salmonella