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DNA sequences between 0 and 98.8 genome map units (m.u.) from canine parvovirus
(CPV) and feline panleukopenia virus (FPV) were cloned into plasmid vectors to
form infectious molecular clones. Those plasmids were transfected into
permissive cells and viruses recovered were shown to contain intact genomes,
having regenerated the complete viral 5' ends up to 100 m.u. The viruses derived
from the plasmids were compared to the original viruses, and shown to be
indistinguishable in antigenic type, hemagglutination (HA) type and host range.
The plasmid origin of the viruses was shown by preparing recombinant clones
between CPV and FPV, and demonstrating the recombinant nature of the resulting
viruses by restriction mapping and by sequencing viral DNA across the
recombination sites. The sequences of our wild-type isolates CPV-d and FPV-b
were completed, revealing 50 nucleotide sequence differences, of which 16
determined coding changes--5 in NS-1,2 in NS-2, and 9 in VP-2 protein. The
sequences of the 5' ends (95.3-100 m.u.) of both viruses were also determined.
Analysis of recombinant viruses mapped both CPV- and FPV-specific antigenic
epitopes, the pH dependence of HA, and sequences affecting canine host range of
the viruses within the VP-1 and VP-2 structural protein genes. Most of the
specific changes were shown to be either on, or within one amino acid of, the
surface of the virus capsid, indicating that the exposed surface of the
parvovirus capsid plays an important role in determining a number of virus
functions. The specific epitopes were affected by differences in a raised area
on the capsid ("threefold spike"), while the pH dependence of HA difference was
adjacent to a depression in the surface of the capsid at the twofold axis of
symmetry.
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