Transcription analysis of the responses of porcine heart to Erysipelothrix rhusiopathiae

Abstract

Erysipelothrix rhusiopathiae (E. rhusiopathiae) is the causative agent of swine erysipelas. This microbe has caused great economic losses in China and in other countries. In this study, high-throughput cDNA microarray assays were employed to evaluate the host responses of porcine heart to E. rhusiopathiae and to gain additional insights into its pathogenesis. A total of 394 DE transcripts were detected in the active virulent E. rhusiopathiae infection group compared with the PBS group at 4 days post-infection. Moreover, 262 transcripts were upregulated and 132 transcripts were downregulated. Differentially expressed genes were involved in many vital functional classes, including inflammatory and immune responses, signal transduction, apoptosis, transport, protein phosphorylation and dephosphorylation, metabolic processes, chemotaxis, cell adhesion, and innate immune responses. Pathway analysis demonstrated that the most significant pathways were Chemokine signaling pathway, NF-kappa B signaling pathway, TLR pathway, CAMs, systemic lupus erythematosus, chemokine signaling pathway, Cytokine-cytokine receptor interaction, PI3K-Akt signaling pathway, Phagosome, HTLV-I infection, Measles, Rheumatoid arthritis and natural-killer-cell-mediated cytotoxicity. The reliability of our microarray data was verified by performing quantitative real-time PCR. This study is the first to document the response of piglet heart to E. rhusiopathiae infection. The observed gene expression profile could help screen potential host agents that can reduce the prevalence of E. rhusiopathiae. The profile might also provide insights into the underlying pathological changes that occur in pigs infected with E. rhusiopathiae.

Fig 1. Representative histopathological photomicrograph of heart lesions in pigs infected with E. rhusiopathiae strain SE38, G4T10 and control.

(A) Heart of a SE38-infected pig with endocarditis and neutrophil infiltration. (B) Thrombogenesis, myocardial necrosis, and inflammatory cell infiltration. (C) Heart of a G4T10-infected pig at 200 and 50μm. (D) PBS control at 200 and 50 μm.

Fig 2. Clustering and characterization of the differential expression of genes.

(A) SE38 group vs. PBS group. S95H_NS, S50H_NS and S96_H_NS belong to SE38 group; S32H_NS, S32H_2_NS and S71H_NS belong to PBS group. DE genes that showed clear functional annotation at 4 dpi between the SE38 and PBS groups were selected for cluster analysis as described in methods. At 4 dpi, a set of 262 genes were upregulated and the remaining 132 genes were downregulated. (B) G4T10 group vs. PBS group. S98H_NS, SR_1_H_NS and SR_2_H_NS belong to G4T10 group; S32H_NS, S32H_2_NS and S71H_NS belong to PBS group. Each row represents a separate gene and each column represents a separate piglet. Red indicates the increased gene expression levels; green denotes the decreased levels compared with normal samples.

Fig 3. STRING analysis of the relationship between DE genes.

(A) the DE genes in piglets infected ER were analyzed using STRING database. (B) the network of DE genes related to TLR4.