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Transcriptional response of turkey blood leukocytes challenged with Salmonella enterica serovar Typhimurium UK1

ABSTRACT: Salmonella is one of most common causes of bacterial foodborne disease and consumption of contaminated poultry products, including turkey, is one route of exposure. Minimizing colonization of commercial turkeys with Salmonella could reduce the incidence of Salmonella-associated human foodborne illness. Understanding host responses to these bacteria could lead to potential strategies to minimize colonization and thus food safety risk. In this study, we evaluated bacterial load and blood leukocyte transcriptomic responses of 3-week-old turkeys challenged with the Salmonella enterica serovar Typhimurium (S. Typhimurium) UK1 strain. Turkeys (n = 8/dose) were inoculated with 108 or 1010 colony forming units (CFU) of S. Typhimurium UK1 and fecal shedding and tissue colonization were measured across multiple days post inoculation (dpi). Fecal shedding was 1-2 log10 higher in the 1010 CFU group than the 108 CFU group, but both doses effectively colonized the crop, spleen, ileum, cecum, colon, bursa of Fabricius and cloaca without causing any overt clinical signs in either group of birds. Blood leukocytes were isolated from a subset of the birds (n =3-4/dpi) both pre-infection (0 dpi) and 2 dpi with 1010 CFU and their transcriptomic responses assayed by RNA-sequencing (RNA-seq). After 2 dpi, 647 genes had significant differential expression (DE), including large increases in expression of immune genes such as CCAH221, IL4I1, LYZ, IL13RA2, IL22RA2, and ACOD1. IL1B was predicted as a major regulator of DE in these leukocytes and this DE was predicted to activate cell migration, phagocytosis and proliferation, and to impact the STAT3 and toll-like receptor pathways. These data revealed genes and pathways by which turkey blood leukocytes responded to the pathogen and can provide potential targets for developing intervention strategies or diagnostic assays to mitigate S. Typhimurium in turkeys.

ORGANISM(S): Meleagris gallopavo

PROVIDER: GSE151896 | GEO | 2021/12/31

REPOSITORIES: GEO

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Project description:Consumption of contaminated poultry products is one of the main sources of human campylobacteriosis, of which Campylobacter jejuni subsp. jejuni (C. jejuni) and C. coli are responsible for approximately 98% of the cases. The ceca of commercial turkeys are the main anatomical site where Campylobacter asymptomatically colonizes. We have previously colonized the ceca of commercial turkey poults with C. jejuni, and demonstrated acute changes in cytokine gene expression in cecal tissue and histologically scored intestinal lesions at 2 days post-inoculation (dpi). The host-response of turkeys to C. coli colonization is unknown. Cecal tonsils (CT) are an important part of the gastrointestinal-associated lymphoid tissue that function to sample material passing in and out of the ceca and generating immune responses against intestinal pathogens. The CT immune response towards Campylobacter is unknown. In this study, we generated a C. coli kanamycin-resistant construct (CcK) for enumeration from cecal contents after experimental challenge. In vitro analysis of CcK demonstrated no changes in motility when compared to the parent isolate, but in vitro growth rates were significantly different than the parent strain. Poults were inoculated by oral gavage with CcK (5x10^7 cfu) or sterile-media (mock-colonized), and euthanized at 1 and 3 dpi. At both time points, CcK was recovered from cecal contents, but not from the mock-colonized group. As a marker of acute inflammation, serum alpha-1 acid glycoprotein was significantly elevated at 3 dpi in CcK inoculated poults compared to mock-infected samples. Significant histological lesions were detected in cecal and CT tissues of CcK colonized poults at 1 and 3 dpi, respectively. RNAseq analysis identified 250 differentially expressed genes (DEG) in CT from CcK colonized poults at 3 dpi, of which 194 were upregulated and 56 were downregulated. From the DEG, 9 significantly enriched biological pathways were identified, including platelet aggregation, response to oxidative stress and negative regulation of oxidative stress-induced intrinsic apoptotic signaling pathway. These data suggest that C. coli induced an acute inflammatory response in the intestinal tract of poults, and that platelet aggregation and oxidative stress in the CT may affect the turkey’s ability to resist Campylobacter colonization. Results from this study provide insight into host-response of the turkey CT to Campylobacter colonization. These findings will help to develop and test Campylobacter mitigation strategies to promote food safety in commercial turkeys.

Project description:A first generation Affymetrix GeneChipÂ® Porcine genome array was used to profile the gene expression in porcine mesenteric lymph nodes over a time course of infection with S. Typhimurium, including the acute (8 hours post inoculation (hpi), 24 hpi, 48 hpi) and chronic (21 days post-inoculation (dpi)) stages of infection. Our objectives were to 1) identify and examine the stereotypical gene expression response within host MLN to S. Typhimurium infection, 2) characterize global host responses by revealing the specific features of the hostâs innate immunity pathways, and 3) explore if and how S. Typhimurium may escape the host immune response and develop into a carrier state. Our study has attempted to investigate the features of host gene expression profiling during S. Typhimurium infection at the acute and chronic infection stages and to explore the mechanism by which S. Typhimurium can escape from the host immune response and develop a carrier state in the host. In conclusion, by using the Affymetrix porcine GeneChip, 848 differentially expressed genes were identified in porcine MLN during infection and several specific features of host response were revealed by gene cluster and pathway analysis. Our data are the first report to investigate global host responses to S. Typhimurium in porcine MLN, and this new study provides data applicable for studying enteric salmonellosis of pigs, as well as humans. Experiment Overall Design: Fifteen piglets from Salmonella spp.-free sows were weaned at 10 days (d) of age, shipped to the National Animal Disease Center, Ames, IA and raised in isolation facilities. To confirm that all piglets were free of Salmonella spp. prior to challenge, bacteriological cultures were performed on rectal swabs twice. Seven week old pigs were randomly divided into 2 groups, 3 non-infected pigs and 12 infected pigs. Three non-infected control pigs were necropsied 2 days prior to experimental infection. On day 0, pigs in the infected groups were intranasally challenged with 1 billion CFU of Salmonella enterica serovar Typhimurium. Three infected pigs were necropsied at 8 hours post-inoculation (hpi), 24 hpi, 48 hpi and 21 days post-inoculation (dpi). Tissue samples from the mesenteric lymph nodes (MLN) were collected and immediately frozen in liquid nitrogen for RNA isolation.

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Transcriptional response of turkey blood leukocytes challenged with Salmonella enterica serovar Typhimurium UK1

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