Oral Immunization of Common Carp with a Liposome Vaccine Fusing Koi Herpesvirus Antigen

Abstract

In this study, we made liposome vaccines in which formalin-inactivated koi herpesvirus (KHV) was entrapped within the liposomal membrane compartment for oral vaccination in common carp Cyprinus carpio. In vaccination experiments, two fish groups (mean body weight, 30 g) received the liposome vaccine (protein concentration of 20 μg/mL using an isolate of NKC03 from Nara Prefecture or an isolate of IKC03 from Ibaraki Prefecture) at a dose of 20 μL/fish/day for 3 days. Neutralization titers of vaccinated fish sera were significantly higher than control at 22 days after last vaccination. In addition, 22 days after last vaccination, the fish were challenged with NKC03 at 10^2.3 TCID₅₀/100 μL/fish or IKC03 at 10^2.2 TCID₅₀/100 μL/fish by dropping the inoculum onto their gills, and resulted RPS was 74.4% and 65.0%, respectively. These results proved the efficacy of oral vaccination with the KHV liposome vaccine against KHV infection in carp.