Capsid protein gene variation among feline calicivirus isolates

We amplified the capsid protein gene fragments of 30 Japanese isolates of f eline calicivirus (FCV), including the C, D, and E regions, by reverse tran scription-polymerase chain reaction (RT-PCR), followed by direct sequencing . Alignment of the predicted amino acid sequences, together with other publ ished sequences from the isolates obtained in other countries, demonstrated a marked heterogeneity among the isolates, confirming the current definiti on of hypervariable regions within the capsid protein; these regions give r ise to the antigenic variations seen in FCV isolates. Phylogenetic analysis of the nucleotide sequences could not identify significant geographically or temporally separated clusters of FCV isolates, supporting the theory of a single genotype.