Abstract
In this study we were interested in identification of new markers of chicken response to Salmonella Enteritidis infection. To reach this aim, gene expression in the spleens of naive chickens and those intravenously infected with S. Enteritidis with or without previous oral vaccination was determined by 454 pyrosequencing of splenic mRNA/cDNA. Forty genes with increased expression at the level of transcription were identified. The most inducible genes encoded avidin (AVD), extracellular fatty acid binding protein (EXFABP), immune responsive gene 1 (IRG1), chemokine ah221 (AH221), trappin-6-like protein (TRAP6) and serum amyloid A (SAA). Using cDNA from sorted splenic B-lymphocytes, macrophages, CD4, CD8 and γδ T-lymphocytes, we found that the above mentioned genes were preferentially expressed in macrophages. AVD, EXFABP, IRG1, AH221, TRAP6 and SAA were induced also in the cecum of chickens orally infected with S. Enteritidis on day 1 of life or day 42 of life. Unusual results were obtained for the immunoglobulin encoding transcripts. Prior to the infection, transcripts coding for the constant parts of IgM, IgY, IgA and Ig light chain were detected in B-lymphocytes. However, after the infection, immunoglobulin encoding transcripts were expressed also by T-lymphocytes and macrophages. Expression of AVD, EXFABP, IRG1, AH221, TRAP6, SAA and all immunoglobulin genes can be therefore used for the characterization of the course of S. Enteritidis infection in chickens.
Highlights
Except for the infection with S. enterica serovars Gallinarum or Pullorum, chicken infection with the other remaining S. enterica serovars is usually not associated with any obvious clinical signs
The chicken response to intravenous infection with S. enterica is characterized by splenomegaly associated with macrophage and heterophil infiltration and Th1 and Th17 cytokine signaling, similar to the response in the cecum after oral infection [4,5]
Enteritidis and chickens some of these transcripts were described as responsive to Salmonella in other experimental animals [12] or were characterized as LPS inducible or as belonging among acute phase proteins. This is true mainly for genes coding for serum amyloid A, avidin, immune responsive gene 1 or extracellular fatty acid binding protein [8,13,14,15,16,17]
Summary
Except for the infection with S. enterica serovars Gallinarum or Pullorum, chicken infection with the other remaining S. enterica serovars is usually not associated with any obvious clinical signs. Despite the absence of gross clinical signs, chickens respond to oral infection by an inflammatory response associated with heterophil and monocyte/macrophage infiltration into the cecal mucosa. The scope of this response is age dependent and is more obvious in chickens up to 2 weeks of age than in adult birds [1]. The chicken response to intravenous infection with S. enterica is characterized by splenomegaly associated with macrophage and heterophil infiltration and Th1 and Th17 cytokine signaling, similar to the response in the cecum after oral infection [4,5]
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