Induction of immunity to feline caliciviral disease

Abstract

Six specific pathogen free cats were exposed by aerosol to a feline calicivirus of low virulence (F 9 virus). Homotypic (anti F 9) seroconversion occurred in all cats by postexposure day 14. The serum of one cat on postexposure day 14 and four of six cats on postexposure day 35 neutralized feline picornavirus isolate no. 255 (FPV 255), a virulent feline calicivirus. Homologous antiviral activity was detected before the appearance of heterologous (anti FPV 255) activity and always was present in higher titer. Protective immunity was evaluated on postexposure day 35 by aerosol challenge with FPV 255. The pyrexia, depression, dyspnea, oral ulcers, and severe pneumonia produced in two susceptible specific pathogen free cats by exposure to FPV 255 did not occur in the cats that had been infected previously with F 9 virus. The study demonstrates that heterotypic protective immunity to feline calicivirus disease can be induced by prior infection with feline calicivirus of low virulence.