Dataset Information

Investigation of the immunogenicity of Zika glycan loop.

ABSTRACT:

Background

Zika virus (ZIKV) is a major human pathogen and member of the Flavivirus genus. Previous studies have identified neutralizing antibodies from Zika patients that bind to quaternary epitopes across neighboring envelope (E) proteins, called E dimer epitopes (EDE). An asparagine-linked glycan on the "glycan loop" (GL) of the ZIKV envelope protein protects the functionally important "fusion loop" on the opposite E subunit in the dimer, and EDE antibodies have been shown to bind to both of these loops. Human EDE antibodies have been divided into two subclasses based on how they bind to the glycan loop region: EDE1 antibodies do not require glycosylation for binding, while EDE2 antibodies strongly rely on the glycan for binding.

Methods

ZIKV GL was expressed on tobacco mosaic virus nanoparticles. Mice were immunized with GL or full-length monomeric E and the immune response was analyzed by testing the ability of sera and monoclonal antibodies to bind to GL and to neutralize ZIKV in in vitro cellular assay.

Results

We report here the existence of ZIKV moderately neutralizing antibodies that bind to E monomers through epitopes that include the glycan loop. We show that sera from human Zika patients contain antibodies capable of binding to the unglycosylated glycan loop in the absence of the rest of the envelope protein. Furthermore, mice were inoculated with recombinant E monomers and produced neutralizing antibodies that either recognize unglycosylated glycan loop or require glycan for their binding to monomeric E. We demonstrate that both types of antibodies neutralize ZIKV to some extent in a cellular virus neutralization assay.

Conclusions

Analogous to the existing EDE antibody nomenclature, we propose a new classification for antibodies that bind to E monomer epitopes (EME): EME1 and EME2 for those that do not require and those that do require glycan for binding to E, respectively.

SUBMITTER: Henderson EA

PROVIDER: S-EPMC7110905 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature

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Publications

Investigation of the immunogenicity of Zika glycan loop.

Henderson Elizabeth A EA Tam Christina C CC Cheng Luisa W LW Ngono Annie Elong AE Nguyen Anh-Viet AV Shresta Sujan S McGee Matt M Padgett Hal H Grill Laurence K LK Martchenko Shilman Mikhail M

Virology journal 20200331 1

<h4>Background</h4>Zika virus (ZIKV) is a major human pathogen and member of the Flavivirus genus. Previous studies have identified neutralizing antibodies from Zika patients that bind to quaternary epitopes across neighboring envelope (E) proteins, called E dimer epitopes (EDE). An asparagine-linked glycan on the "glycan loop" (GL) of the ZIKV envelope protein protects the functionally important "fusion loop" on the opposite E subunit in the dimer, and EDE antibodies have been shown to bind to ...[more]

PMID: 32234060

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Project description:The glycan loop of Zika virus (ZIKV) envelope protein (E) contains the glycosylation site and has been well documented to be important for viral pathogenesis and transmission. In the present study, we report that deletions in the E glycan loop, which were recorded in African ZIKV strains previously, have re-emerged in their contemporary Asian lineages. Here, we generated recombinant ZIKV containing specific deletions in the E glycan loop by reverse genetics. Extensive in vitro and in vivo characterization of these deletion mutants demonstrated an attenuated phenotype in an adult A129 mouse model and reduced oral infections in mosquitoes. Surprisingly, these glycan loop deletion mutants exhibited an enhanced neurovirulence phenotype, and resulted in a more severe microcephalic brain in neonatal mouse models. Crystal structures of the ZIKV E protein and a deletion mutant at 2.5 and 2.6 Å, respectively, revealed that deletion of the glycan loop induces encephalitic flavivirus-like conformational alterations, including the appearance of perforations on the surface and a clear change in the topology of the loops. Overall, our results demonstrate that the E glycan loop deletions represent neonatal mouse neurovirulence markers of ZIKV. IMPORTANCE Zika virus (ZIKV) has been identified as a cause of microcephaly and acquired evolutionary mutations since its discovery. Previously deletions in the E glycan loop were recorded in African ZIKV strains, which have re-emerged in the contemporary Asian lineages recently. The glycan loop deletion mutants are not glycosylated, which are attenuated in adult A129 mouse model and reduced oral infections in mosquitoes. More importantly, the glycan loop deletion mutants induce an encephalitic flavivirus-like conformational alteration in the E homodimer, resulting in a significant enhancement of neonatal mouse neurovirulence. This study underscores the critical role of glycan loop deletion mutants in ZIKV pathogenesis, highlighting a need for global virological surveillance for such ZIKV variants.

Project description:Background Although Zika virus (ZIKV) infection is typically self-limiting, other associated complications such as congenital birth defects and the Guillain-Barré syndrome are well described. There are no approved vaccines against ZIKV infection. Methods In this phase 1, open-label clinical trial, we evaluated the safety and immunogenicity of a synthetic, consensus DNA vaccine (GLS-5700) encoding the ZIKV premembrane and envelope proteins in two groups of 20 participants each. The participants received either 1 mg or 2 mg of vaccine intradermally, with each injection followed by electroporation (the use of a pulsed electric field to introduce the DNA sequence into cells) at baseline, 4 weeks, and 12 weeks. Results The median age of the participants was 38 years, and 60% were women; 78% were white, and 22% black; in addition, 30% were Hispanic. At the interim analysis at 14 weeks (i.e., after the third dose of vaccine), no serious adverse events were reported. Local reactions at the vaccination site (e.g., injection-site pain, redness, swelling, and itching) occurred in approximately 50% of the participants. After the third dose of vaccine, binding antibodies (as measured on enzyme-linked immunosorbent assay) were detected in all the participants, with geometric mean titers of 1642 and 2871 in recipients of 1 mg and 2 mg of vaccine, respectively. Neutralizing antibodies developed in 62% of the samples on Vero-cell assay. On neuronal-cell assay, there was 90% inhibition of ZIKV infection in 70% of the serum samples and 50% inhibition in 95% of the samples. The intraperitoneal injection of postvaccination serum protected 103 of 112 IFNAR knockout mice (bred with deletion of genes encoding interferon-α and interferon-β receptors) (92%) that were challenged with a lethal dose of ZIKV-PR209 strain; none of the mice receiving baseline serum survived the challenge. Survival was independent of the neutralization titer. Conclusions In this phase 1, open-label clinical trial, a DNA vaccine elicited anti-ZIKV immune responses. Further studies are needed to better evaluate the safety and efficacy of the vaccine. (Funded by GeneOne Life Science and others; ZIKA-001 ClinicalTrials.gov number, NCT02809443 .).

Dataset Information

Investigation of the immunogenicity of Zika glycan loop.

Background

Methods

Results

Conclusions

Publications

Investigation of the immunogenicity of Zika glycan loop.

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