Impacts of Salmonella enteritidis infection on liver transcriptome in broilers.

Salmonella enterica serovar enteritidis is an enteric bacterium that can contaminate chicken eggs and meat, resulting in production losses and consumer illness. To provide insight into the systemic metabolic effects of S. enteritidis infection, liver samples were harvested 10-days postinfection from broiler hens. Hepatic global gene expression levels were assessed using a chicken 44K Agilent microarray. Forty-four genes were differentially expressed at a significance level of q value < 0.05. One hundred eighty-three genes were differentially expressed at a suggestive significance level of q value < 0.1. A predominance of downregulation existed among significantly differentially expressed genes. Cell cycle and metabolism networks were created from the differentially expressed genes. Mitochondria-mediated apoptosis, electron transport, peptidase activity, vein constriction, cell differentiation, IL-2 signaling, Jak-Stat signaling, B-cell receptor signaling, GDP/GTP exchange, and protein recycling were among the functions of the differentially expressed genes that were down-regulated in response to S. enteritidis. The effects of S. enteritidis infection on the liver transcriptome profiles of broilers reflect a predominance of downregulation of genes with cell cycle and metabolic functions. The most pronounced response was the downregulation of genes that function in metabolic pathways, inflammation, and mitochondria-mediated apoptosis. These results provide insight into important systemic metabolic mechanisms that are active in the chicken liver in response to S. enteritidis infection at 10-days postinfection.

Deep sequencing-based transcriptome analysis of chicken spleen in response to avian pathogenic Escherichia coli (APEC) infection.

Avian pathogenic Escherichia coli (APEC) leads to economic losses in poultry production and is also a threat to human health. The goal of this study was to characterize the chicken spleen transcriptome and to identify candidate genes for response and resistance to APEC infection using Solexa sequencing. We obtained 14422935, 14104324, and 14954692 Solexa read pairs for non-challenged (NC), challenged-mild pathology (MD), and challenged-severe pathology (SV), respectively. A total of 148197 contigs and 98461 unigenes were assembled, of which 134949 contigs and 91890 unigenes match the chicken genome. In total, 12272 annotated unigenes take part in biological processes (11664), cellular components (11927), and molecular functions (11963). Summing three specific contrasts, 13650 significantly differentially expressed unigenes were found in NC Vs. MD (6844), NC Vs. SV (7764), and MD Vs. SV (2320). Some unigenes (e.g. CD148, CD45 and LCK) were involved in crucial pathways, such as the T cell receptor (TCR) signaling pathway and microbial metabolism in diverse environments. This study facilitates understanding of the genetic architecture of the chicken spleen transcriptome, and has identified candidate genes for host response to APEC infection.

Strong concordance between transcriptomic patterns of spleen and peripheral blood leukocytes in response to avian pathogenic Escherichia coli infection.

Avian pathogenic Escherichia coli (APEC) causes morbidity in chickens and exhibits zoonotic potential. Understanding host transcriptional responses to infection aids the understanding of protective mechanisms and serves to inform future colibacillosis control strategies. Transcriptomes of spleen and peripheral blood leukocytes (PBLs) of the same individual birds in response to APEC infection were compared to identify common response patterns and connecting pathways. More than 100 genes in three contrasts examining pathology and infection status were significantly differentially expressed in both tissues and similarly regulated. Tissue-specific differences in catalytic activity, however, appear between birds with mild and severe pathology responses. Early expression differences, between birds with severe pathology and uninfected controls, in the mitogen-activated protein kinase pathway in PBLs precede spleen responses in the p53 and cytokine-cytokine receptor pathways. Tissue bianalysis is useful in identifying genes and pathways important to the response to APEC, whose role might otherwise be underestimated in importance.

Leukocyte transcriptome from chickens infected with avian pathogenic Escherichia coli identifies pathways associated with resistance.

Avian pathogenic Escherichia coli (APEC) causes colibacillosis, which is responsible for morbidity and mortality in chickens. Gene expression patterns have previously been demonstrated to differ between chicken populations that are resistant vs. susceptible to bacterial infection, but little is currently known about gene expression response to APEC. Increased understanding of gene expression patterns associated with resistance will facilitate genetic selection to increase resistance to APEC. Male broiler chicks were vaccinated at 2 weeks of age and challenged with APEC at 4 weeks of age. Peripheral blood leukocytes were collected at 1 and 5 day post-infection. Lesions on the liver, pericardium, and air sacs were used to assign a mild or severe pathology status to non-vaccinated, challenged chicks. Ten treatment groups were therefore generated with a priori factors of vaccination, challenge, day post-infection, and the a posteriori factor of pathology status. Global transcriptomic response was evaluated using the Agilent 44K chicken microarray. APEC infection resulted in more up-regulation than down-regulation of differentially expressed genes. Immune response and metabolic processes were enriched with differentially expressed genes. Although vaccination significantly reduced lesions in challenged bird, there was no detectable effect of vaccination on gene expression. This study investigated the transcriptomic differences in host responses associated with mild vs. severe pathology, in addition to the effects of vaccination and challenge, thus revealing genes and networks associated with response to APEC and providing a foundation for future studies on, and genetic selection for, genetic resistance to APEC.

Spleen transcriptome response to infection with avian pathogenic Escherichia coli in broiler chickens.

BACKGROUND: Avian pathogenic Escherichia coli (APEC) is detrimental to poultry health and its zoonotic potential is a food safety concern. Regulation of antimicrobials in food-production animals has put greater focus on enhancing host resistance to bacterial infections through genetics. To better define effective mechanism of host resistance, global gene expression in the spleen of chickens, harvested at two times post-infection (PI) with APEC, was measured using microarray technology, in a design that will enable investigation of effects of vaccination, challenge, and pathology level. RESULTS: There were 1,101 genes significantly differentially expressed between severely infected and non-infected groups on day 1 PI and 1,723 on day 5 PI. Very little difference was seen between mildly infected and non-infected groups on either time point. Between birds exhibiting mild and severe pathology, there were 2 significantly differentially expressed genes on day 1 PI and 799 on day 5 PI. Groups with greater pathology had more genes with increased expression than decreased expression levels. Several predominate immune pathways, Toll-like receptor, Jak-STAT, and cytokine signaling, were represented between challenged and non-challenged groups. Vaccination had, surprisingly, no detectible effect on gene expression, although it significantly protected the birds from observable gross lesions. Functional characterization of significantly expressed genes revealed unique gene ontology classifications during each time point, with many unique to a particular treatment or class contrast. CONCLUSIONS: More severe pathology caused by APEC infection was associated with a high level of gene expression differences and increase in gene expression levels. Many of the significantly differentially expressed genes were unique to a particular treatment, pathology level or time point. The present study not only investigates the transcriptomic regulations of APEC infection, but also the degree of pathology associated with that infection. This study will allow for greater discovery into host mechanisms for disease resistance, providing targets for marker assisted selection and advanced drug development.