Zika virus (ZIKV) is an RNA virus belonging to the flavivirus genus of the Flaviviridae family, and is mainly transmitted by mosquitoes. Over the past several years, large ZIKV outbreaks have occurred in the Pacific regions and the Americas, with millions of people infected.

Clinical studies have revealed associations between ZIKV infection and neurological diseases such as microcephaly and Guillain-Barré syndrome. ZIKV is now posing a serious threat. However, no commercial vaccine is available to prevent ZIKV infection.

Recently, a joint research team led by Drs. HUANG Zhong and JIN Xia at the Institut Pasteur of Shanghai (IPS) of Chinese Academy of Sciences (CAS) completed preclinical studies of recombinant protein-based candidate Zika vaccines. The study was published in Antiviral Research.

To develop recombinant vaccines for ZIKV, the researchers produced different forms of ZIKV envelope protein (E) in the Drosophila S2 insect cell expression system, and subsequently evaluated their immunogenicity and protective efficacy in mice.

The results showed that the N-terminal approximately 80% region (designated as E80) and the domain III (designated as EDIII) of ZIKV E protein could be efficiently produced as secreted proteins in the S2 cell expression system. Both E80 and EDIII elicited antigen-specific neutralizing antibody and T-cell responses in mice.

Importantly, passive transfer of either anti-E80 or anti-EDIII sera protected recipient mice against lethal ZIKV challenge.

It is worth noting that, at the same dose, EDIII induced higher neutralizing antibody titers than did E80, and the resulting anti-EDIII sera appeared to confer better protection against experimental ZIKV infection compared to the anti-E80 sera.

These data indicated that the S2 cell-produced EDIII represents an elite recombinant Zika vaccine candidate worthy of further preclinical development and clinical testing.

This work was supported by grants from the National Major R&D Program of China, CAS, and the EU Horizon 2020 program.