Figure 4.

Immunization with S RBD-HBD 2 reinforces local mucosal Ab responses, downregulates ER-stress-associated genes, and prevents lung damage in hDPP4-Tg mice following MERS-CoV infection. (A) Representative H&E-stained lung sections from control and immunized hDPP4-Tg mice after MERS-CoV infection. H&E-stained lung sections were analyzed for inflammation by light microscopy. Control group represented distorted lung morphologies, including wider and thicker alveolar septa with perivascular and peribronchial cuffing. Immunized groups exhibited less alveolar thickening and fewer inflammatory infiltrations. Regions of inflammatory cell infiltration around vasculature, bronchiole, and proximal alveoli were noted by arrowheads. Scale bars = 100 µm. (B) Expression levels of SIgA-associated Igα chain, J chain, and pIgR in the lungs of hDPP4-Tg mice. Total RNA was extracted from the lung of hDPP4-Tg mice five days after infection with MERS-CoV and was used to assess the expression of mucosal IgA response-related genes by qRT-PCR. Reactions were performed in duplicate. Data are presented as means ± SD (n = 2). * p < 0.05 and ** p < 0.01. (C) Effect of S RBD immunization with or without HBD 2 on the expression of ER-stress-associated genes in the lungs of MERS-CoV infected hDPP4-Tg mice. Total RNA was extracted from the lungs of control and immunized mice five days after MERS-CoV infection and was used to assess the relative expression levels of ER-stress-associated genes by qRT-PCR. Reactions were performed in duplicate, and β-actin was used as the internal control for normalization. Fold changes relative to the non-treated controls are shown. Data are presented as means ± SD (n = 2). * p < 0.05, ** p < 0.01, and *** p < 0.001.