Figure 2.

Middle East respiratory syndrome coronavirus (MERS-CoV) efficiently infects CD4⁺ and CD8⁺ T cells and downregulates surface dipeptidyl peptidase 4 (DPP4) in the infected cells. A, T cells were infected with MERS-CoV and severe acute respiratory syndrome CoV (SARS-CoV) at 2 50% tissue culture infective doses (TCID₅₀) per cell. Cells were fixed at 24 hours after infection and immunolabeled for detection of expression of MERS-CoV NP or SARS-CoV NP. The shaded curve and the solid line represent virus NP expression from mock-infected and MERS/SARS-CoV–infected cells, respectively. B, T cells were infected with MERS-CoV at 2 TCID₅₀ per cell. Cells were fixed at 24 hours after infection and immunolabeled for detection of CD4 or CD8 and MERS-CoV NP expression. The shaded curve and the solid line represent NP expression from mock-infected and MERS-CoV–infected cells, respectively. C, Uninfected T cells were fixed and immunolabeled for detection of CD4 or CD8 and surface DPP4 expression. The shaded curve and the solid line represent isotype and DPP4-specific staining, respectively. D, T cells were infected with MERS-CoV at 2 TCID₅₀ per cell. Cells were fixed at 24 hours after infection and immunolabeled for detection of CD4 or CD8, DPP4, and MERS-CoV NP expression. Surface or total DPP4 was detected by labeling the cells with the DPP4 antibody before or after cell permeabilization, respectively. The shaded curve represents isotype staining of DPP4. The solid line and dotted line represent DPP4 staining from mock-infected and MERS-CoV–infected cells, respectively. The DPP4 mean fluorescence intensity (MFI) in infected cells was calculated on the basis of CD4⁺/MERS-CoV NP–expressing or CD8⁺/MERS-CoV NP–expressing double-positive T-cell data. The DPP4 MFI in mock-infected cells was calculated on the basis of CD4⁺ or CD8⁺ T-cell data. The summary panels at the right represent the average percentage of infected cells (A and B), MFI (C), or percentage of mock MFI (D) from 3 different donors. In all panels, bars and error bars represent means and standard deviations. Statistical analyses were performed using the Student t test. *P < .05.