Addition of Partial Envelope Domain II into Envelope Domain III of Dengue Virus Antigen Potentiates the Induction of Virus-Neutralizing Antibodies and Induces Protective Immunity.

Dengue virus (DENV) comprises four serotypes in the family Flaviviridae and is a causative agent of dengue-related diseases, including dengue fever. Dengue fever is generally a self-limited febrile illness. However, secondary infection of patients with a suboptimal antibody (Ab) response provokes life-threatening severe dengue hemorrhagic fever or dengue shock syndrome. To develop a potent candidate subunit vaccine against DENV infection, we developed the EDII-cEDIII antigen, which contains partial envelope domain II (EDII) including the fusion loop and BC loop epitopes together with consensus envelope domain III (cEDIII) of all four serotypes of DENV. We purified Ab from mice after immunization with EDII-cEDIII or cEDIII and compared their virus neutralization and Ab-dependent enhancement of DENV infection. Anti-EDII-cEDIII Ab showed stronger neutralizing activity and lower Ab-dependent peak enhancement of DENV infection compared with anti-cEDIII Ab. Following injection of Ab-treated DENV into AG129 mice, anti-EDII-cEDIII Ab ameliorated DENV infection in tissues with primary and secondary infection more effectively than anti-cEDIII Ab. In addition, anti-EDII-cEDIII Ab protected against DENV1, 2, and 4 challenge. We conclude that EDII-cEDIII induces neutralizing and protective Abs, and thus, shows promise as a candidate subunit vaccine for DENV infection.