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Japanese encephalitis virus structural and nonstructural proteins expressed in Escherichia coli induce protective immunity in mice

Tafuku, S;Miyata, T;Tadano, M;Mitsumata, R;Kawakami, H;Harakuni, T;Sewaki, T;Arakawa, T;

Ectodomain of Japanese encephalitis virus (JEV) E protein [domains I through III (D1-3), domains I and II (D1-2) and domain III (D3)] and the nonstructural protein 1 (NS1) were expressed in Escherichia coli, and administered to BALB/c mice via the intranasal (i.n.) route. The E protein, but not the NS1, induced JEV-specific serum IgG with virus-neutralization capacity in vitro. When mice were lethally challenged with JEV, i.n. immunization with D1-3, D1-2, D3, or a mouse brain-derived formalin-inactivated JE vaccine conferred complete protection, while an 80% protection rate was observed in the NS1 immunized mice. Cytokine analysis of the cervical lymph nodes of mice i.n. immunized with D1-3 or NS1 revealed antigen-specific IL-2 and IL-17 responses, but no IFN- T cell response, were observed. This study demonstrates for the first time the i.n. vaccine efficacy of the E. coli-expressed recombinant JEV proteins.