Understanding Zika Virus Stability and Developing a Chimeric Vaccine through Functional Analysis

Abstract

Compared with other flaviviruses, Zika virus (ZIKV) is uniquely associated with congenital diseases in pregnant women. One recent study reported that (i) ZIKV has higher thermostability than dengue virus (DENV [a flavivirus closely related to ZIKV]), which might contribute to the disease outcome; (ii) the higher thermostability of ZIKV could arise from an extended loop structure in domain III of the viral envelope (E) protein and an extra hydrogen-bond interaction between E molecules (V. A. Kostyuchenko, E. X. Y. Lim, S. Zhang, G. Fibriansah, T.-S. Ng, J. S. G. Ooi, J. Shi, and S.-M. Lok, Nature 533:425–428, 2016, https://doi.org/10.1038/nature17994). Here we report the functional analysis of the structural information in the context of complete ZIKV and DENV-2 virions. Swapping the prM-E genes between ZIKV and DENV-2 switched the thermostability of the chimeric viruses, identifying the prM-E proteins as the major determinants for virion thermostability. Shortening the extended loop of the E protein by 1 amino acid was lethal for ZIKV assembly/release. Mutations (Q350I and T351V) that abolished the extra hydrogen-bond interaction between the E proteins did not reduce ZIKV thermostability, indicating that the extra interaction does not increase the thermostability. Interestingly, mutant T351V was attenuated in A129 mice defective in type I interferon receptors, even though the virus retained the wild-type thermostability. Furthermore, we found that a chimeric ZIKV with the DENV-2 prM-E and a chimeric DENV-2 with the ZIKV prM-E were highly attenuated in A129 mice; these chimeric viruses were highly immunogenic and protective against DENV-2 and ZIKV challenge, respectively. These results indicate the potential of these chimeric viruses for vaccine development.

Functional Analysis of Glycosylation of Zika Virus Envelope Protein

“…Day 6-cultured DCs were infected with ZIKV at an MOI of 1. At day 1, 3, and 4 p.i., culture fluids were measured for infectious virus using plaque assays on Vero cells (Xie et al, 2017). The infected cells were extracted for total intracellular RNA using Trizol (Invitrogen).…”

Zika in the Americas, year 2: What have we learned? What gaps remain? A report from the Global Virus Network

“…Among these candidates, subunit and inactivated vaccines have shown efficacy in both mice and NHPs, and several of these candidates have already advanced to phase 1-II clinical evaluation in humans (Barouch et al, 2017). Chimeric virus and live-attenuated vaccines have shown murine efficacy (Xie et al, 2017; Shan, 2017), but their efficacies in NHPs remains to be reported. These promising preclinical results are not surprising because similar approaches have been successful for development for other flavivirus vaccines.…”

“…To support the feasibility of this approach, Xie et al recently reported a chimeric DENV-2 containing the ZIKV prM-E genes that fully protected against WT ZIKV challenge in the A129 mouse model; reciprocally, a chimeric ZIKV containing the DENV-2 prM-E genes completely protected WT DENV-2 challenge (Xie et al, 2017). Along the same lines, Stephen Whitehead and colleagues are currently developing such chimeric vaccines using the 3′UTR deletion DENV vaccine backbones (personal communications).…”

p38MAPK plays a critical role in induction of a pro-inflammatory phenotype of retinal Müller cells following Zika virus infection

“…Studies using neural progenitor cells (NPCs) and mice further show that ZIKV may disrupt the development of and induce the death in NPCs, which leads to microcephaly (Dang et al, 2016; Li et al, 2016). Currently, little is known about ZIKV pathogenesis and there is no approved antiviral therapy or licensed human vaccines, though several groups have identified potential antiviral targets or candidate vaccines in experimental models (Abbink et al, 2016; Barrows et al, 2016; Richner et al, 2017; Xie et al, 2017; Xu et al, 2016). …”