Our previous study has demonstrated that porcine pulmonary microvascular endothelial cells (MVECs) are susceptible to highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV). The innate immune response of MVECs infected with HP-PRRSV would play important roles in controlling virus proliferation, resisting cellular injury, and preventing the virus from spreading to other tissues and organs. Type I interferon is one of the most effective antiviral cytokines in the innate immune response, and interferon-induced proteins with tetratricopeptide repeats (IFITs) are members of interferon-stimulated genes induced by viruses and other pathogens, which are crucial in inhibiting virus proliferation and regulating the innate immune response. However, their effects on HP-PRRSV-induced innate immunity in porcine pulmonary MVECs remain unclear. Here, the roles of IFITs in porcine pulmonary MVECs infected with the HP-PRRSV HN strain were investigated, and the effects of astragalus polysaccharides (APS), a widely used traditional Chinese herbal ingredient with the immunopotentiating effect, on them were studied. The results showed that more autophagosomes were observed in HP-PRRSV-infected MVECs, and the expression of IFN-α, IFIT3, and IFIT5 decreased or increased at different time points after infection. When silencing the genes of IFIT3 or IFIT5, the HP-PRRSV replication in MVECs was significantly increased. The expression of IFIT3 and IFIT5 could be upregulated by APS, whose inhibitory effects on the HP-PRRSV replication significantly declined when the genes of IFIT3 or IFIT5 were silenced. The results suggest that IFIT3 and IFIT5 play an important role in inhibiting the HP-PRRSV replication in porcine pulmonary MVECs, and APS suppress the multiplication of HP-PRRSV by upregulating their expression.

Previously, our study has demonstrated that porcine pulmonary microvascular endothelial cells (PPMVECs) were susceptible to highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) and produced a significant non-specific immune response to it. The significance of microvascular endothelial glycocalyx is increasingly attracting attention, and its rich carbohydrate components are not only important signaling molecules, but also remarkably influence the signaling of most proteins. Comprehending changes in the carbohydrate chains contributes to understanding cell functions. This study aimed to reveal the effects of HP-PRRSV infection on the surface carbohydrate chains of PPMVECs. PPMVECs were isolated and cultured in vitro and infected with HP-PRRSV HN and JXA1 strains. Scanning electron microscopy analysis indicated that at 48 h post-infection, some broken holes were in their cell membranes, and that the surface fibrous glycocalyx was obviously reduced or even disappeared. Lectin microarray analysis indicated that the fluorescence intensities of 8 and 7 lectin sites were significantly changed by the HP-PRRSV HN and JXA1 strains, respectively, among which there were 6 common lectin sites. The up-regulation of common lectins (RCA-I, LEL, and STL) and the down-regulation of common lectins (LCA, DSA, and PHA-E) were confirmed by lectin fluorescence staining and lectin flow cytometry, respectively. Together, the results show that the HP-PRRSV infection can induce the glycocalyx disruption of PPMVECs and their surface glycoprofiling changes, and that the poly-N-acetyllactosamine and complex N-glycan are the main up-regulated and down-regulated carbohydrate chains, respectively. Our findings may provide insights into revealing the pathogenesis of HP-PRRSV from the perspective of glycobiology.