Evaluation of Protective Efficacy of the Synthetic Peptide Vaccine Containing the T-Helper 1 Epitope with Cpg Oligodeoxynucleotide against Feline Infectious Peritonitis Virus Infection in Cats

Background Feline infectious peritonitis (FIP) is a feline coronavirus-induced fatal disease in domestic and wild cats. Cellular immunity is considered to play an important role in the prevention of FIP. Thus, induction of the cellular immune response is essential in vaccines against FIP virus (FIPV) infection. Methods We immunized cats with peptides containing T-helper (Th)1 epitopes derived from the nucleocapsid (N) protein of the type I FIPV KU-2 strain (NP 7 and NP 8 ) with feline CpG-oligodeoxynucleotides (fCpG-ODNs) as a vaccine adjuvant. Results Prevention against type II FIPV 79-1146 strain-induced FIP was slightly better in specific pathogen-free cats treated with NP 7 and NP 8 with fCpG-ODNs. However, immune tolerance was suggested to be induced by the high dose and frequency of NP 7 and NP 8 with fCpG-ODNs. Conclusions Further investigations on the combination and concentrations of the peptides and fCpG-ODNs, dose, frequency and route of administration are needed.