Figure. 2.

The outcome of plaque assay

Vero 81 cells (in 12-well plates, 100% confluent) are infected with mock virus or serial-diluted MERS-CoV in 0.2 mL serum-free DMEM, 37°C, 1 h. The plates are gently shaken every 15 min. After incubation, mock or virus-containing medium are removed, and 0.5 mL/well 0.6% agarose in DMEM are added into each well. After agarose solidifies, 0.5 mL/well 2% FBS-DMEM is added to overlay the gel. 3 days later, the media are removed, and the plates are fixed with 10% formalin, RT, 15 min. After fixation, the formalin and the gel are carefully removed and the plaques (arrows) are visualized by 0.1% Crystal violet staining, RT, 5 min.