The transcriptional response to Salmonella infection in swine

The porcine response to infection with Salmonella is the result of differential expression of host-specific genes. To characterize these alterations in gene expression, functional genomic analyses were performed on swine tissues following experimental inoculation of the pigs with Salmonella enterica serovars Choleraesuis and Typhimurium. Suppression subtractive hybridization and quantitative real-time RT-PCR revealed that the transcriptional profiles of the porcine response to the swine-adapted strain (Choleraesuis) and the non-host-adapted strain (Typhimurium) exhibit unique differences

Analysis of Porcine Transcriptional Response to Salmonella enterica serovar Choleraesuis suggests novel targets of NFkappaB are activated in the Mesenteric Lymph Node

<p>Abstract</p> <p>Background</p> <p>Specific knowledge of the molecular pathways controlling host-pathogen interactions can increase our understanding of immune response biology as well as provide targets for drug development and genetic improvement of disease resistance. Toward this end, we have characterized the porcine transcriptional response to <it>Salmonella enterica </it>serovar Choleraesuis (<it>S</it>. Choleraesuis), a <it>Salmonella </it>serovar that predominately colonizes swine, yet can cause serious infections in human patients. Affymetrix technology was used to screen for differentially expressed genes in pig mesenteric lymph nodes (MLN) responding to infection with <it>S</it>. Choleraesuis at acute (8 hours (h), 24 h and 48 h post-inoculation (pi)) and chronic stages (21 days (d) pi).</p> <p>Results</p> <p>Analysis of variance with false discovery rate control identified 1,853 genes with significant changes in expression level (<it>p</it>-value < 0.01, <it>q</it>-value < 0.26, and fold change (FC) > 2) during infection as compared to un-inoculated control pigs. Down-regulation of translation-related genes at 8 hpi and 24 hpi implied that <it>S</it>. Choleraesuis repressed host protein translation. Genes involved in the Th1, innate immune/inflammation response and apoptosis pathways were induced significantly. However, antigen presentation/dendritic cell (DC) function pathways were not affected significantly during infection. A strong NF<it>κ</it>B-dependent response was observed, as 58 known NF<it>κ</it>B target genes were induced at 8, 24 and/or 48 hpi. Quantitative-PCR analyses confirmed the microarray data for 21 of 22 genes tested. Based on expression patterns, these target genes can be classified as an "Early" group (induced at either 8 or 24 hpi) and a "Late" group (induced only at 48 hpi). Cytokine activity or chemokine activity were enriched within the Early group genes GO annotations, while the Late group was predominantly composed of signal transduction and cell metabolism annotated genes. Regulatory motif analysis of the human orthologous promoters for both Early and Late genes revealed that 241 gene promoters were predicted to contain NF<it>κ</it>B binding sites, and that of these, 51 Early and 145 Late genes were previously not known to be NF<it>κ</it>B targets.</p> <p>Conclusion</p> <p>Our study provides novel genome-wide transcriptional profiling data on the porcine response to <it>S</it>. Choleraesuis and expands the understanding of NF<it>κ</it>B signaling in response to <it>Salmonella </it>infection. Comparison of the magnitude and timing of porcine MLN transcriptional response to different <it>Salmonella </it>serovars, <it>S</it>. Choleraesuis and <it>S</it>. Typhimurium, clearly showed a larger but later transcriptional response to <it>S</it>. Choleraesuis. Both microarray and QPCR data provided evidence of a strong NF<it>κ</it>B-dependent host transcriptional response during <it>S</it>. Choleraesuis infection. Our data indicate that a lack of strong DC-mediated antigen presentation in the MLN may cause <it>S</it>. Choleraesuis infected pigs to develop a systemic infection, and our analysis predicts nearly 200 novel NF<it>κ</it>B target genes which may be applicable across mammalian species.</p

Distinct Peripheral Blood RNA Responses to Salmonella in Pigs Differing in Salmonella Shedding Levels: Intersection of IFNG, TLR and miRNA Pathways

Transcriptomic analysis of the response to bacterial pathogens has been reported for several species, yet few studies have investigated the transcriptional differences in whole blood in subjects that differ in their disease response phenotypes. Salmonella species infect many vertebrate species, and pigs colonized with Salmonella enterica serovar Typhimurium (ST) are usually asymptomatic, making detection of these Salmonella-carrier pigs difficult. The variable fecal shedding of Salmonella is an important cause of foodborne illness and zoonotic disease. To investigate gene pathways and biomarkers associated with the variance in Salmonella shedding following experimental inoculation, we initiated the first analysis of the whole blood transcriptional response induced by Salmonella. A population of pigs (n = 40) was inoculated with ST and peripheral blood and fecal Salmonella counts were collected between 2 and 20 days post-inoculation (dpi). Two groups of pigs with either low shedding (LS) or persistent shedding (PS) phenotypes were identified. Global transcriptional changes in response to ST inoculation were identified by Affymetrix Genechip® analysis of peripheral blood RNA at day 0 and 2 dpi. ST inoculation triggered substantial gene expression changes in the pigs and there was differential expression of many genes between LS and PS pigs. Analysis of the differential profiles of gene expression within and between PS and LS phenotypic classes identified distinct regulatory pathways mediated by IFN-γ, TNF, NF-κB, or one of several miRNAs. We confirmed the activation of two regulatory factors, SPI1 and CEBPB, and demonstrated that expression of miR-155 was decreased specifically in the PS animals. These data provide insight into specific pathways associated with extremes in Salmonella fecal shedding that can be targeted for further exploration on why some animals develop a carrier state. This knowledge can also be used to develop rational manipulations of genetics, pharmaceuticals, nutrition or husbandry methods to decrease Salmonella colonization, shedding and spread

Distinct Peripheral Blood RNA Responses to \u3ci\u3eSalmonella\u3c/i\u3e in Pigs Differing in \u3ci\u3eSalmonella\u3c/i\u3e Shedding Levels: Intersection of IFNG, TLR and miRNA Pathways

Transcriptomic analysis of the response to bacterial pathogens has been reported for several species, yet few studies have investigated the transcriptional differences in whole blood in subjects that differ in their disease response phenotypes. Salmonella species infect many vertebrate species, and pigs colonized with Salmonella enterica serovar Typhimurium (ST) are usually asymptomatic, making detection of these Salmonella-carrier pigs difficult. The variable fecal shedding of Salmonella is an important cause of foodborne illness and zoonotic disease. To investigate gene pathways and biomarkers associated with the variance in Salmonella shedding following experimental inoculation, we initiated the first analysis of the whole blood transcriptional response induced by Salmonella. A population of pigs (n = 40) was inoculated with ST and peripheral blood and fecal Salmonella counts were collected between 2 and 20 days post-inoculation (dpi). Two groups of pigs with either low shedding (LS) or persistent shedding (PS) phenotypes were identified. Global transcriptional changes in response to ST inoculation were identified by Affymetrix GenechipR analysis of peripheral blood RNA at day 0 and 2 dpi. ST inoculation triggered substantial gene expression changes in the pigs and there was differential expression of many genes between LS and PS pigs. Analysis of the differential profiles of gene expression within and between PS and LS phenotypic classes identified distinct regulatory pathways mediated by IFN-y, TNF, NF-kB, or one of several miRNAs. We confirmed the activation of two regulatory factors, SPI1 and CEBPB, and demonstrated that expression of miR-155 was decreased specifically in the PS animals. These data provide insight into specific pathways associated with extremes in Salmonella fecal shedding that can be targeted for further exploration on why some animals develop a carrier state. This knowledge can also be used to develop rational manipulations of genetics, pharmaceuticals, nutrition or husbandry methods to decrease Salmonella colonization, shedding and spread