Fig. 4: Lineage-specific MERS-CoV spike proteins show no difference in host cell entry and DPP4 binding capacity.

a–c rhabdoviral particles harboring MERS-CoV spike proteins of the EMC isolate, lineage 3, lineage 4, and lineage 5, VSV-G (positive control), or eGFP (negative control) were inoculated onto TMPRSS2-expressing Calu-3, Caco-2, and TMRPSS2 negative Huh7 cells. Transduction efficiency was quantified at 18 h post transduction by measuring the activity of virus-encoded luciferase in cell lysates. Transduction mediated by EMC spike protein was set as 100%. The means of n = 3 individual experiments performed in biological quadruplicates are shown; error bars indicate SEMs. Statistical significance was analyzed by paired two-tailed Student´s t-tests. d 293 T cells untransfected or transfected to express MERS-CoV lineage-specific spike proteins or empty expression vector (pCG1) were detached and incubated with human Fc-tagged, soluble DPP4 (solDPP4-Fc), diluted 1:50, 1:200, and 1:1,000, and an Alexa Fluor 488-conjugated antihuman antibody before DPP4 binding was quantified by flow cytometry. For normalization, the binding of solDPP4-Fc (1:200) to EMC spike was set as 100%. For background subtraction of samples incubated with Alexa Fluor 488-conjugated antibodies only (control) was performed for each sample. EMC spike carrying the I529T SNP was included as an internal control, since this SNP has been previously shown to exhibit reduced DPP4 binding²¹. Shown are the normalized data of two independent experiments. Bars indicate mean and SEM. eGFP, enhanced green fluorescent protein; VSV-G, vesicular stomatitis virus glycoprotein; DPP4, dipeptidyl-peptidase 4.