Targeting the Zika virus envelope domains I and III as a recombinant vaccine protects mice from lethal challenge

Zika virus (ZIKV) vaccine candidates developed through Phase I clinical trials are based on the full-length envelope glycoprotein (E), which presents both desirable and undesirable antigenic determinants. Among the latter, the conserved fusion loop epitope (FLE) within domain II is a major target for flavivirus cross-reactive and poorly neutralizing responses. To eliminate unwanted FLE targeting, we redesigned ZIKV E using a reverse vaccinology approach, excising domain II and allowing domains I and III (DI-DIII) to fold into an independent subunit harboring key neutralizing epitopes. Ifnar1^-/- mice vaccinated with ZIKV DI-DIII elicited high ZIKV neutralizing antibodies and were protected from weight loss and death. In addition, sera from DI-DIII vaccinated mice demonstrated a reduced capacity to enhance DENV 1-4 infection in vitro, compared to mice vaccinated with full-length E. This study identifies DI-DIII as a promising immunogen, focusing antibody responses to protective epitopes on ZIKV and minimizing the elicitation of unwanted responses.