Genetic diversity among historical and contemporary clinical isolates of felid herpesvirus 1
2016-09-05T03:26:27Z (GMT)
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<p>This study used next generation
sequencing to compare the genomes of contemporary Australian clinical isolates
of FHV-1, vaccine isolates and historical clinical isolates, including isolates
that predated the introduction of live attenuated vaccines into Australia.
Analysis of the genome sequences aimed to assess the level of genetic
diversity, identify potential genetic markers that could influence the <i>in vivo</i> phenotype of the isolates and
examine the sequences for evidence of recombination. </p>
<p>The full genome sequences of 26
isolates of FHV-1 were determined, including two vaccine isolates and 24 clinical
isolates that were collected over a period of approximately 40 years. Analysis
of the genome sequences revealed a remarkably low level of diversity (0.0 - 0.01%)
between the isolates. No potential genetic determinants of virulence were
identified, but unique single nucleotide polymorphisms (SNPs) in the UL28 and
UL44 genes were detected in the vaccine isolates that were not present in the clinical
isolates. No evidence of FHV-1 recombination was detected using multiple
methods of recombination detection, even though many of the isolates originated
from cats housed in a shelter environment where high infective pressures were likely
to exist. Evidence of displacement of dominant FHV-1 isolates with other
(genetically distinct) FHV-1 isolates over time was observed amongst the
isolates obtained from the shelter-housed animals. </p>
<p><b>Conclusions:
</b>The results show that FHV-1 genomes are highly conserved. The
lack of recombination detected in the FHV-1 genomes suggests that the risk of
attenuated vaccines recombining to generate virulent field viruses is lower
than has been suggested for some other herpesviruses. The SNPs detected only in
the vaccine isolates offer the potential to develop PCR-based methods of
differentiating vaccine and clinical isolates of FHV-1 in order to facilitate
future epidemiological studies.</p>
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