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The porcine reproductive and respiratory syndrome virus (PRRSV), especially the highly pathogenic strains, can cause serious acute lung injury (ALI), characterized by extensive hemorrhage, inflammatory cells and serous fluid infiltration in the lung vascular system. Meanwhile, the pulmonary microvascular endothelial cells (PMVECs) are essential for forming the air–blood barrier and keeping the water–salt balance to prevent leakage of circulating nutrients, solutes, and fluid into the underlying tissues. As well, they tightly regulate the influx of immune cells. To determine the possible relationship between the PMVECs' function changes and lung vascular permeability during PRRSV infection, the PMVECs were co-cultured with HP-PRRSV-inoculated primary pulmonary alveolar macrophages (PAMs) in transwell model, and then the RNA sequencing (RNA-seq) and comprehensive bioinformatics analysis were carried out to characterize the dynamic transcriptome landscapes of PMVECs. In total, 16,489 annotated genes were identified, with 275 upregulated and 270 downregulated differentially expressed genes (DEGs) were characterized at both 18 and 24 h post PRRSV inoculation. The GO terms and KEGG pathways analysis indicated that the immune response, metabolic pathways, cell death, cytokine–cytokine receptor interaction, viral responses, and apoptotic process are significantly regulated upon co-culture with PRRSV-infected PAMs. Moreover, according to the TERR and dextran flux assay results, dysregulation of TJ proteins, including CLDN1, CLDN4, CLDN8, and OCLN, is further confirmed to correlate with the increased permeability of PMVECs. These transcriptome profiles and DEGs will provide valuable clues for further exploring the roles of PMVECs in PRRSV-induced ALI in the future. [ABSTRACT FROM AUTHOR]

Porcine reproductive and respiratory syndrome virus (PRRSV) is economically important and characterized by its extensive variation. The codon usage patterns and their influence on viral evolution and host adaptation among different PRRSV strains remain largely unknown. Here, the codon usage of ORF5 genes from lineages 1, 3, 5, and 8, and MLV strains of type 2 PRRSV in China was analyzed. A compositional property analysis of ORF5 genes revealed that nucleotide C is most frequently used at the third position of codons, accompanied by rich GC3s. The effective number of codon (ENC) and codon pair bias (CPB) values indicate that all ORF5 genes have low codon bias and the differences in CPB scores among four lineages are almost not significant. When compared with host codon usage patterns, lineage 1 strains show higher CAI and SiD values, with a high similarity to pig, which might relate to its predominant epidemic propensity in the field. The CAI, RCDI, and SiD values of ORF5 genes from different passages of MLV JXA1R indicate no relation between attenuation and CPB or codon adaptation decrease during serial passage on non-host cells. These findings provide a novel way of understanding the PRRSV's evolution, related to viral survival, host adaptation, and virulence. [ABSTRACT FROM AUTHOR]