Fig. 4.

Screening of Vero/SARS-CoV cell-derived cell clones for virus particle production by RT-PCR. Total RNA extracts from Vero E6 cells that were mock-infected or acutely SARS-CoV-infected for 2 days as in Fig. 1, persistently SARS-CoV-infected (Vero/SARS-CoV) for 1 month (1 M), 2 M or 5 M, and five representative cell clones from Vero/SARS-CoV (#13, #18, #21, #34, and #12) either just after the cell cloning (0 M) or after being cultured for a subsequent 1 M, were reverse-transcribed, and then the cDNA fractions were used for single-round PCR (A). An aliquot (1/10) of the single-round PCR product was further subjected to second-round PCR (B).