Rapid Expression of Chemokines and Proinflammatory Cytokines in Newly Hatched Chickens Infected withSalmonella entericaSerovar Typhimurium

Poultry meat and eggs contaminated withSalmonella entericaserovar Enteritidis orSalmonella entericaserovar Typhimurium are common sources of acute gastroenteritis in humans. However, the exact nature of the immune mechanisms protective againstSalmonellainfection in chickens has not been characterized at the molecular level. In the present study, bacterial colonization, development of pathological lesions, and proinflammatory cytokine and chemokine gene expression were investigated in the liver, spleen, jejunum, ileum, and cecal tonsils in newly hatched chickens 6, 12, 24, and 48 h after oral infection withSalmonellaserovar Typhimurium. Very high bacterial counts were found in the ileum and cecal contents throughout the experiment, whereasSalmonellastarted to appear in the liver only from 24 h postinfection. Large numbers of heterophils, equivalent to neutrophils in mammals, and inflammatory edema could be seen in the lamina propria of the intestinal villi and in the liver. Interleukin 8 (IL-8), K60 (a CXC chemokine), macrophage inflammatory protein 1 β, and IL-1β levels were significantly upregulated in the intestinal tissues and in the livers of the infected birds. However, the spleens of the infected birds show little or no change in the expression levels of these cytokines and chemokines. Increased expression of the proinflammatory cytokines and chemokines (up to several hundred-fold) correlated with the presence of inflammatory signs in those tissues. This is the first description of in vivo expression of chemokines and proinflammatory cytokines in response to oral infection withSalmonellain newly hatched chickens.