The recombinant
viruses were selected by two rounds of plaque purification on L2 cells
(11, 27). Recombinant virus genomes were amplified and sequenced in the
regions that were mutagenized, that is, from the 3 end of the spike gene into the
5 end of the EGFP coding region. Reverse transcriptase-mediated PCR (RTPCR)
amplification was carried out, using as templates cytoplasmic RNA extracted
from virus-infected L2 cells and the primers FIJ81 and RIJ84