*2.7. Flow Cytometry Assay*

A549-Dual™ cells were grown on six-well plates at 5 × 10<sup>5</sup> cells per well and infected at a multiplicity of infection (MOI) of 1. Infected cells were harvested and fixed with 3.7% formaldehyde in PBS for 20 min, permeabilized with 0.1% Triton X-100 in PBS for 4 min and then blocked with PBS-BSA for 10 min. Cells were stained with anti-E mAb 4G2 (1:1000) for 1 h. Antigen staining was visualized with goa<sup>t</sup> anti-mouse Alexa Fluor 488 IgG (1:1000) for 20 min. Cells were subjected to a flow cytometric analysis using a CytoFLEX flow cytometer (Beckman Coulter, Brea, CA, USA). The percentage of positive cells was determined using FlowJo software (version 10, Tree Star, Inc., Ashland, OR, USA).
