Multivalent display of envelope protein domain III with Mi3 nanoparticles induces protective immunity against lethal Zika virus infection in mice

Zika virus (ZIKV) infection is associated with severe neurological complications such as congenital microcephaly, yet no safe and effective vaccine is currently available. A critical challenge in ZIKV vaccine development arises from cross-reactive, non- or sub-neutralizing antibodies, which may enhance dengue virus (DENV) infection through antibody-dependent enhancement (ADE). Herein, we report a vaccine strategy utilizing Mi3 nanoparticles to display the envelope (E) protein domain III (EDIII) of ZIKV, which induces protective immunity against ZIKV infection in murine models. Compared to an EDIII subunit vaccine, the Mi3-EDIII nanoparticle vaccine elicited significantly higher antibody responses and stronger cell-mediated immune responses. In C57BL/6 mice, maternal immunization with Mi3-EDIII protected the neonates against ZIKV-caused symptoms, including body weight loss, neurological abnormalities, retardation of brain development, and mortality. In interferon-α/β receptor knockout (Ifnar1^-/-) C57BL/6 mice, Mi3-EDIII immunization conferred effective protection against lethal ZIKV challenge. Notably, unlike ZIKV convalescent sera, Mi3-EDIII immune sera did not enhance DENV infection in human chronic myelogenous leukemia K562 cells, suggesting the absence of ADE-prone antibody induction. Our results demonstrate that Mi3-EDIII is a promising vaccine candidate against ZIKV infection and warrants further development.