Sequence analysis of feline caliciviruses isolated from the oral cavity of clinically normal domestic cats (Felis catus) in Florida.

Four isolates (7.3 per cent) of feline calicivirus (FCV), from oropharyngeal swabs taken from 55 unvaccinated apparently healthy cats, were identified by electron microscopy and reverse transcription-polymerase chain reaction (RT-PCR). A 671-bp fragment, comprising part of region B, all of regions C, D, and E and part of region F of the FCV capsid protein gene, was amplified from each isolate by RT-PCR and cloned for sequence analysis. Amino acid sequence comparison of these regions revealed significant sequence divergence from the F9 vaccine strain within regions C, E, and F. The hypervariable region E of the four Florida isolates and the NADC isolate contained three fewer amino acids than the commonly used F9 vaccine strain. This work provides support to the idea that currently circulating FCV strains may differ substantially from presently used vaccine strains.