FIG. 8.

Marker mutations are present in virus derived from the infectious construct. Cultures of ST cells were infected with wild-type (WT) TGEV or plaque-purified icTGEV isolates derived from the infectious construct. Intracellular RNA was isolated, and RT-PCR was performed using primer pairs that asymmetrically flank each of the unique BglI-BstXI junctions inserted into the infectious construct. (A) Wild-type TGEV. (B) icTGEV-1 (passage 1). (C) icTGEV-3 (passage 3). In panel C, a larger ∼1.6-kb wild-type TGEV amplicon spanning the B1-B2 junction was also treated with BstXI as a control (the amplicon was derived from primer pairs located between nucleotides 9730 and 9750 and 11342 and 11362 in the TGEV sequence [3]). Arrows indicate cleaved DNA intermediates.