We wanted to test our hypothesis that the gp33 epitope
would also be disrupted in most of the viral genomes recovered
from nonfluorescent plaques from the brains of protected animals.
Thus, we analyzed the portions of the genomes encoding
the ORF4a/gp33/EGFP fusion proteins from viruses isolated
from both fluorescent and nonfluorescent plaques and from
both protected and unprotected animals.
RT-PCR was carried
out to amplify a fragment encoding ORF4a/gp33/EGFP, using
primers representing sequences at the 3end of the spike gene
and the 5 end of ORF5 (FIJ81 and RIJ84, respectively [Table
1]);
the genomes of viruses isolated from the nonfluorescent
plaques contained deletions of various sizes; sequencing of
these amplified fragments, (using the same primers) demonstrated
deletions encompassing part or all of the EGFP coding
region.