• Vaccine Name: Feline infectious peritonitis virus recombinant N proteins vaccine
• Target Pathogen: Feline infectious peritonitis virus
• Target Disease: Feline infectious peritonitis (FIP)
• Type: Recombinant vector vaccine
• Status: Research
• Host Species for Licensed Use: None
• Antigen: baculovirus-expressed N protein of the Type I FIPV strain KU-2 (Hohdatsu et al., 2003)
• N gene engineering:
  • Type: Recombinant protein preparation
  • Description: (Hohdatsu et al., 2003)
  • Detailed Gene Information: Click Here.
• Preparation: SF-9 cells cultured for 2 days were inoculated with the recombinant baculovirus. After absorption for 1 h, serum-free TC-100 medium was added to the cells and the cells were cultured at 27 °C. After culture for 96 h, the infected cells were recovered and washed with PBS. One milliliter of RSB buffer containing 0.2% NP-40 (0.01 M NaCl, 0.0015 M MgCl2, 0.01 M Tris–HCl, pH 7.4) was added to 1×107 cells and the cell suspension was kept at 4 °C for 30 min with occasional shaking. The cells were centrifuged at 800×g for 10 min. The precipitate was resuspended in PBS and used as recombinant N protein. Feline inactivated trivalent vaccine (Felidovac PCR; Intervet, The Netherlands), which is commercially available in Japan, was added to the recombinant N protein as an adjuvant. This feline inactivated trivalent vaccine contains 2% aluminum hydroxide gels and L80 as an adjuvant. (Hohdatsu et al., 2003)
• Immunization Route: subcutaneous injection
• Description: Cell lysate with baculovirus-expressed N protein of the Type I FIPV strain KU-2 recombinant vaccine was effective in preventing the progression of FIP without inducing antibody-dependent enhancement of FIPV infection in cats. (Hohdatsu et al., 2003)

Cat Response

• Vaccination Protocol: Eight SPF cats aged 6 months and eight SPF cats aged 7–9 months were used in the first and second experiments, respectively. In both experiments, four cats were subcutaneously vaccinated three times with 3-week intervals. The same vaccination/challenge experiment was repeated twice. (Hohdatsu et al., 2003)
• Immune Response: In all vaccinated cats, the ELISA value against N protein began to increase on Day 6 after the challenge and the antibody responded earlier than that in the control cats. The anti-challenge virus (strain 79-1146) neutralizing antibody production converted to positive on Day 12 after the challenge in the vaccination and control groups, showing no significant difference between the two groups. (Hohdatsu et al., 2003)
• Challenge Protocol: As a challenge control, four cats received a subcutaneous administration of the SF-9 cell-derive d antigen, which was prepared as the recombinant N protein described above, with the adjuvant. Four weeks after the third vaccination, all cats were challenged oronasally with 105 TCID50 FIPV strain 79-1146. (Hohdatsu et al., 2003)
• Efficacy: Combining the results of the first and second experiments, the survival rates were 75% (6/8) and 12.5% (1/8) for the immunized and control groups, respectively. These survival rates were analyzed using the X2-test, and there was a significant difference (P<0.05). (Hohdatsu et al., 2003)