Detection of MERS-CoV S and HIV-1 p24 protein expression in the packaged MERS-CoV pseudovirus and DPP4 protein expression in target cells by Western blot. (A) Detection of p24 and MERS-CoV S in pseudotyped MERS-CoV. Anti-p24 (1:50) and MERS-CoV S-specific polyclonal antibodies (1:200) were used for the test. (B-C) Detection of DPP4 expression in different cell lines. Goat anti-DPP4 (1 μg/ml) was used for the test, and anti-β-actin monoclonal antibodies (1:5,000, Sigma) were applied as the internal control.