2.8 Immunogenicity of PRV isolate
As the representative PRV isolate, NY isolate was inoculated into ST cells. The cell culture suspension was inactivated by incubating with moderate formalin (Sigma-Aldrich) at 37℃ for 24 h, and then emulsified with Freund’s complete adjuvant and Freund’s incomplete adjuvant, respectively. 60 six-week-old healthy BALB/c female mice were randomly divided into four groups of 15 mice each. Mice in Group 1 were injected with 0.5 mL of NY isolate containing Freund’s complete adjuvant in 1th week, followed by injecting with equal volume of emulsifier with Freund’s incomplete adjuvant in 3thweek, and finally with the inactivated virus in 5thweek. Groups 2-4 were injected with 0.5 mL the Bartha-K61, Hubei 98 and DMEM in 1th, 3th and 5th respectively. At the 32th day after the final injection, blood samples were collected from 5 mice of each group for serum neutralization assay, and the remaining mice of each group were challenged with PRV NY isolate. Serum neutralizing antibodies against PRV were detected as described previously (Zheng et al., 2020).