SARS-CoV-2 Is More Efficient than HCoV-NL63 in Infecting a Small Subpopulation of ACE2+ Human Respiratory Epithelial Cells.

Human coronavirus (HCoV)-NL63 is an important contributor to upper and lower respiratory tract infections, mainly in children, while severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the etiological agent of COVID-19, can cause lower respiratory tract infections, and more severe, respiratory and systemic disease, which leads to fatal consequences in many cases. Using microscopy, immunohistochemistry (IHC), virus-binding assay, reverse transcriptase qPCR (RT-qPCR) assay, and flow cytometry, we compared the characteristics of the susceptibility, replication dynamics, and morphogenesis of HCoV-NL63 and SARS-CoV-2 in monolayer cultures of primary human respiratory epithelial cells (HRECs). Less than 10% HRECs expressed ACE2, and SARS-CoV-2 seemed much more efficient than HCoV-NL63 at infecting the very small proportion of HRECs expressing the ACE2 receptors. Furthermore, SARS-CoV-2 replicated more efficiently than HCoV-NL63 in HREC, which correlates with the cumulative evidence of the differences in their transmissibility.

Downregulation of miR-671-5p promotes IL-10 mRNA increase in porcine moDCs stimulated with the probiotic BB12.

BACKGROUND: Previous work showed that the microRNA (miRNA) miR-671-5p was upregulated in monocyte-derived dendritic cells (moDCs) stimulated with Bifidobacterium animalis subsp. lactis BB12 (BB12) with no increase in IL-10 after six hours of stimulation. In this work, we performed an in silico prediction of genes targeted by miR-671-5p and which are the terms and pathways involved with it. Also, miR-671-5p was transiently downregulated to assess its effect on IL-10 regulation. METHODS AND RESULTS: First, we performed a Gene Ontology enrichment analysis to predict immune response terms and pathways involved with miR-671-5p. Some of the terms and pathways found were related to the immune response promoted by the probiotic, as the terms "negative regulation of the inflammatory response to an antigenic stimulus" and "cancer" were highlighted. Then, to assess the role of miR-671-5p in IL-10 regulation, moDCs were derived from porcine peripheral blood and later transfected with miR-671-5p antisense oligonucleotide (ASO). Flow cytometry was employed to evaluate the transfection efficiency. Then, the moDCs were stimulated with BB12, and the expression of IL-10 was assessed by RT-qPCR and ELISA. An increase in IL-10 transcript in miR-671-5p-ASO-transfected moDCs stimulated with BB12 was observed compared with moDCs stimulated with BB12 but not transfected. These results suggest the participation of miR-671-5p as a negative regulator of IL-10. CONCLUSION: These findings suggest that miR-671-5p participates in the downregulation of IL-10, as previously predicted in silico by our work group. miR-671-5p could play an essential role in the immunomodulation promoted by the probiotic BB12.