Figure 8

Model of PRRSV invasion and spread in porcine nasal mucosa. The porcine nasal mucosa consists of a ciliated pseudostratified columnar epithelium, an underlying basement membrane and the lamina propria[22]. Different mechanisms of invasion were observed between PRRSV strains LV and Lena. LV mainly infects CD163⁺Sn⁺ cells. The small number of Sn⁺ cells (5.2 cells/mm²) that are present within the epithelial cell layer does not allow LV to reach high levels of replication. Only 2.5 LV infected cells/mm² were observed at 72 hpi, all of them located in the lamina propria. 97% of the LV-infected cells had a phenotype of CD163⁺Sn⁺ (1.). Lena showed a wider cell tropism. This strain infects both CD163⁺Sn⁺ and CD163⁺Sn^- cells in order to migrate into the depth (2.). Lena was found to spread easily from one cell to another, forming after 48 hpi, clusters of mainly CD163⁺Sn^- infected cells within the epithelial cell layer and CD163⁺Sn⁺ in the lamina propria. These clusters expanded at 72 hpi and CD163^-Sn^- cells were detected at the periphery of them (3.).