FIG. 5.

Differentiation between cloned virus and parental JX/CHA/97 strain. An EcoRV restriction site was introduced in the full-length cDNA clone of JX/CHA/97 to allow discrimination between cloned virus (tagged with the EcoRV site) and parental virus (lacking an EcoRV site). RNA was extracted from the viral suspension of rabbits inoculated with either the cloned virus or the parental JX/CHA/97 isolate (lane A), and a 443-bp fragment was amplified by RT-PCR as described in Materials and Methods (lane B). The amplicons were digested with EcoRV and analyzed on a 2.0% agarose gel. The presence of an EcoRV restriction site resulted in fragments of 263 bp and 180 bp. As expected, the restriction site was found in the cloned virus but not in the parental JX/CHA/97 virus isolate. Molecular size markers (in base pairs) are noted at the right of blots.