Single-cell landscape of piglet lung response with Actinobacillus pleuropneumoniae
Actinobacillus pleuropneumoniae can cause lethal porcine infectious pleuropneumonia, resulting in substantial economic losses for the pig industry. The lung is the main target organ of A. pleuropneumoniae. However, the lung-specific immune responses against the pathogen remain unclear. In this study, single-cell RNA sequencing analysis of the transcriptome of the piglet lung with or without A. pleuropneumoniae infection identified 18 subpopulations with different phenotypes. Monocytes, neutrophils, and plasmacytoid dendritic cells (pDC) were enriched in the lung post-infection and played anti-infection roles by promoting the expression of interferon-induced factors (such as IL-18) and inflammatory response-associated genes. A. pleuropneumoniae reduced the number of macrophages by inhibiting monocyte differentiation into interstitial macrophages (IM) and alveolar macrophages (AM) and triggering AM endogenous apoptosis. Additionally, A. pleuropneumoniae lowered the amount of various T cell subsets and induced CD8A+ ?d T exhaustion and apoptosis. Furthermore, we identified dramatically augmented pathological fibroblast-¬like cells contributing to rapidly developing pulmonary fibrosis, whereas epithelial cells were significantly decreased, and included those with features of epithelial-mesenchymal transition differentiated into fibroblasts through the signaling of TGFB1 and HIF1A. Cell-to-cell communication analysis further revealed that the interaction between the EMT-epithelial, vascular endothelial, pDC, and fibroblast subsets, except for COL3A1 fibroblasts, were enhanced, mainly via CD74/(COPA or MIF) receptor ligands after infection, whereas COL3A1 fibroblasts interacted via EGFR/MIF and EGFR/TGFB1 pairs. In summary, our study is the first time to systematically analyze the cell response of piglet lung under the status of physiology and A. pleuropneumoniae infection, deepening the understanding of the molecular basis of pathogenesis, and providing a wealth of resources for the prevention and treatment of A. pleuropneumoniae and other fibrotic lung diseases. Overall design: Single-cell RNA sequencing (10X Genomics) was used to profile the transcriptomes signatures of lung tissue from three Actinobacillus pleuropneumoniae-infected and three healthy pigs.