Analysis of the N-terminal polypeptide of the capsid precursor protein and the ORF3 product of feline calicivirus.

The N-terminal unique polypeptide region of the capsid precursor protein of feline calicivirus (FCV) and the protein encoded by ORF3 of FCV were expressed as fusion proteins with glutathione S-transferase to analyze the expressed products in FCV-infected cells. Immunoblot analysis using a serum from a cat experimentally infected with FCV indicated relatively high immunogenicity of the N-terminal polypeptide in FCV-infected cats, as compared with the ORF3 protein. Specific antisera were prepared by immunization to mice with the fused proteins and used in immunoblot analysis. A 14 kD product corresponding to the N-terminal polypeptide and a 10 kD polypeptide of the ORF3 product were identified in the FCV-infected cells but not detected in the purified particles. No neutralization activity against FCV was detected in these antisera. The proteins identified as polypeptides of 14 kD and 10 kD in this study may have functions as non-structural proteins.