Abstract
The envelope (E) protein is the major antigen of Japanese encephalitis virus (JEV) capable of inducing neutralizing antibodies. Thus, JEV E protein has been mainly chosen in the design of novel JEV vaccines. E protein contains three distinct domains (domains I, II, and III). The domain III (D3) contains several neutralizing epitopes and can be independently folded as a unique Ig-like conformational structure. One of the major goals in this thesis is to investigate the immunogenicity of the recombinant D3 protein produced in Escherichia coli. In addition, a full-length E protein of JEV was cloned into baculovirus vector and expressed functionally in cultured insect cells. The immunogenicity of the recombinant D3 protein coupled with FCA/FIA (freund’s complete adjuvant/freund’s incomplete adjuvant) immunized in ICR mice showed a 75% neutralizing titer at 1: 5 diluted sera (PRNT50 = 40). Immunization of the full-length recombinant E protein expressed in baculovirus/insect cell system coupled with FCA/FIA showed a 84% neutralizing titer at 1:5 diluted sera (PRNT50 = 80). Various formulations of liposome adjuvant coupled with the D3 recombinant protein were investigated for immunization studies. The cationic liposome adjuvant induced a 60% neutralizing titer at 1: diluted sera (PRNT50 = 10). After challenges, the survival rates for ICR mice immunized with the D3 recombinant protein coupled with cationic liposome were higher than that coupled with FCA/FIA and with anionic and neutral liposomes. These results can provide important information for further development of JEV recombinant protein vaccines and/or new adjuvant formations.