Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: 3/7/2005
Publication Date: 6/5/2005
Citation: Uthe, J.J., Royaee, A.R., Lunney, J.K., Stabel, T.J., Zhao, S., Tuggle, C.K., Bearson, S.M. 2005. Differences in the swine response to infection with Salmonella enterica serovars Choleraesuis and Typhimurium [abstract]. American Society for Microbiology. p. 614.
Technical Abstract: Salmonella spp have a large number of specific hosts, including birds, reptiles and mammals. To investigate the host specificity of Salmonella enterica serovar Choleraesuis (swine-adapted) and Salmonella enterica serovar Typhimurium (generalist), real-time RT-PCR was performed. The transcriptional profile of various immune genes was analyzed using RNA extracted from the mesenteric lymph nodes (MLN) of eight-week-old pigs after experimental infection over a three-week period, from acute to chronic stages of infection. Unique differences were observed between the porcine responses to the two Salmonella strains: in general, S. Choleraesuis induced a more intense and extended up-regulation of porcine immune gene expression whereas S. Typhimurium triggered both a transient up-regulation (IFNG, SOCS1, STAT1) as well as a significant down-regulation in gene expression of many host immune factors (IL1B, IL4, IL6, TLR4, CSF2). These findings correlate with the clinical signs of infection, as S. Choleraesuis causes a more severe infection than S. Typhimurium in swine. To further investigate the differences in host gene expression in response to infection with the two Salmonella strains, a direct comparison using Suppression Subtractive Hybridization (SSH) was performed on the MLN samples at 24 hr post-infection (acute infection). Forward and reverse SSH was performed using pooled mRNA samples from three S. Choleraesuis-infected pigs and three S. Typhimurium-infected pigs. Differential screening by DNA blot hybridization was performed on 384 cDNA clones. DNA sequence was determined for 40 cDNA clones identified as induced in the S. Choleraesuis-infected pigs (compared to the S. Typhimurium-infected pigs) and 45 cDNA clones induced in the S. Typhimurium-infected pigs. Real-time RT-PCR confirmed the SSH results on select immune-related genes (CXCL10, TXNIP, HSP105). These investigations suggest that S. Typhimurium may down-regulate the porcine immune response, thereby potentially evading the host's immune system and progressing into a carrier state in the animal.