Establishment of a disease model for Mycoplasma Ovipneumoniae infection in Hu sheep and its lung transcriptomic analysis.

The development of vaccines against Mycoplasma ovipneumoniae (MO) and the screening of novel therapeutic agents are hindered by the lack of a stable animal model for evaluation. Hu sheep, as a predominant breed in intensive farming systems, are highly susceptible to MO infection. Therefore, we established a MO infection model in Hu sheep to investigate the reasons for their susceptibility to MO. We collected tissue samples from the lung junction at the interface between diseased and healthy areas for pathological examination and transcriptomic analysis. Differentially expressed genes were screened and subjected to functional enrichment analysis, enabling an in-depth discussion of the mechanisms by which MO damages the lungs of Hu sheep. The study found that following infection with MO, Hu sheep exhibit a gradual rise in body temperature during the initial phase of infection. After several days of persistent fever, the temperature gradually returns to normal, while body weight shows a downward trend. Twenty-one days after infection with MO, hepatization of lung tissue was observed in the right apical lobe of the lung in Hu sheep. Histopathological sections from the lesion-control interface revealed thickened alveolar septa with extensive infiltration of red blood cells and inflammatory cells. Transcriptome sequencing identified 899 differentially expressed genes (|log2(Fold Change)| ≥ 1, padj≤ 0.05), comprising 535 upregulated genes and 364 downregulated genes. GO enrichment analysis indicates that the core functions of differentially expressed genes are concentrated in two biological processes: immune system processes and immune responses. KEGG enrichment analysis revealed that differentially expressed genes were significantly enriched across 28 distinct signaling pathways, identifying multiple key metabolic pathways associated with MO infection. These primarily encompassed the IL-17 signaling pathway, Toll-like receptor signaling pathway, NF-κB signaling pathway, TNF-α signaling pathway, and natural killer cell-mediated cytotoxicity pathways. We have additionally identified multiple genes associated with MO infection, including CCL19, CCL20, TNFSF11, CXCL8, CXCL11, CCR10, CSF3, IL2RA, CXCL1, CD40, BBOX1, and BPIFB1. These discoveries lay the groundwork for establishing MO infection models and investigating the mechanisms underlying sheep susceptibility.