Assessment of the Protective Efficacy of a Feline Calicivirus Inactivated Vaccine Using in Vivo FCV CH-JL2 Infection

Feline calicivirus (FCV), a highly contagious virus, is one of the major causes of upper respiratory infections in domestic cat populations and wild felines. It is a ubiquitous issue around the world, which constantly demands veterinary attention. Vaccination for FCV has generally been proposed as a cure for its infections. However, the high antigenic variability of this virus hinders the development of efficacious FCV vaccines. In this study, the experimental inactivated vaccine was developed with strain FCV CH-JL2 at 108.00 TCID50/mL, 1% binary ethylenimine (BEI) was utilized for inactivation at 37 & DEG;C for 48 h, then was mixed with aluminum hydroxide which was used as an adjuvant. Through regular observation and monitoring, it was confirmed that the kittens in each group had a good mental state and appetite after the vaccination, and their body temperature was normal. Compared with the control group, the antibody levels increased, and no adverse reactions were seen. Its effects were evaluated using the previously constructed animal infection model to measure clinical symptoms after vaccination and FCV challenging. All kittens were challenged with FCV CH-JL2 at 42 days of post vaccination (dpv). The clinical signs of body weight, body temperature, viral shedding, survival rates were monitored daily during 14 days of post challenge (dpc). It has been shown that serum IgG levels and neutralization titer were significantly higher than the commercial inactivated vaccine, and kittens manifested normal clinical signs, good mental status and appetite after vaccination and subsequent viral challenging, the protection rate is 100% (5/5). Collectively, these preliminary data indicate that inactivated vaccine can provide complete protection against infection caused by the challenge FCV CH-JL2 for kittens, and FCV CH-JL2 strain is a promising candidate for developing a safe and effective FCV vaccine in the future.