Fig 1: Human metapneumovirus (hMPV) infection inhibits C/EBPa expression, which is critical for cathelicidin antimicriobial peptide (CAMP) expression in human macrophages. (A,B) Monocyte-derived macrophages (MDMs) were mock-infected (N.I.), infected with hMPV (hMPV) or inoculated with UV-inactivated hMPV (UV-hMPV) for 24 h. C/EBPa mRNA (CEBPA) expression (A) and protein expression (p42) (B) was assessed by quantitative real-time PCR (qRT-PCR) and immunoblotting. (C–E) MDMs were transfected with siRNA targeting C/EBPa (siCEBPA) or scrambled control siRNA (siControl) for 72 h before vehicle or 1,25(OH)2D3 treatment. mRNA expression of C/EBPa (CEBPA) (C) and CAMP (D) was assessed by qRT-PCR. C/EBPa (p42) and CAMP (hCAP-18) protein expression was assessed by immunoblotting (E). Error bars represent SD for triplicates. **p < 0.01, ***p < 0.001. Data are representative of at least three independent experiments from different donors. Full-length blots are presented in Figure S1 in Supplementary Material.