Characterization of a highly virulent feline calicivirus and attenuation of this virus.

Feline calicivirus (FCV) is a common cause of upper respiratory and oral disease in cats. Highly virulent, systemic strains of FCV (vs FCV) have been recently described. These vs FCV isolates cause edema, cutaneous ulcers and high mortality in affected cats. This study reports a disease model with such a vs FCV isolate (FCV-33585). It also describes a full-length capsid gene sequence of this vs FCV isolate and the capsid sequence comparison of this strain with 35 other virulent and non-virulent FCV strains. In addition, sequence comparison of this strain with other 114 known sequences in the hyper-variable region of capsid gene was analyzed. Two amino acids were identified within the hyper-variable region as potentially unique signature for this vs FCV strain. This study also describes the attenuation of FCV-33585 by two methods: serial passaging at low temperature, and the generation of a temperature sensitive (ts) mutant by UV irridiation. Moreover, the potential use of attenuated vs FCV as vaccine was also explored. Monoclonal antibodies were also identified which could differentiate commonly used FCV vaccine strain from this vs strain (FCV-33585). And two monoclonal antibodies were found to react specifically the wild-type, not the attenuated FCV-33585.