Current views on Zika virus vaccine development

Figures & data

Table 1. Zika virus vaccine candidates: results of preclinical studies.

Vaccine candidate	Vaccine characteristics	Animal model	Vaccination protocol	Results	Side effects	Refs.
ZIKV purified inactivated virus (PIV) vaccine	Derived from the Puerto Rico strain, produced in Vero cells, inactivated with formalin.	Balb/c mice	1 μg of PIV + alum, i.m. or s.c., single dose.	Induction of ZIKV-specific neutralizing antibodies (higher titer after i.m. route); complete protection against challenge by i.m. PIV vaccination	–	Larocca et al., Nature 2016 [5]
		Rhesus monkeys	5 μg of PIV + alum, s.c., two doses at weeks 0 and 4.	Induction of ZIKV-specific neutralizing antibodies and modest cellular immune responses, primarily to envelope (E). Complete protection against ZIKV challenge, without detectable virus in the blood and bodily fluids. Passive transfer of purified IgG in naive Balb/c mice and rhesus monkeys provided protection after ZIKV challenge. Correlates of protection were identified.	–	Abbink et al., Science 2016 [6]
ZIKV PIV vaccine	Derived from the MR 766 strain, produced in Vero cells, inactivated with formalin.	AG129 mice, Balb/c mice, New Zealand White rabbits	10 μg per dose of PIV + alum, i.m., two doses.	Complete protection of vaccinated AG129 mice against ZIKV challenge; induction of neutralizing antibodies, anamnestic response, and complete protection against challenge in Balb/c mice; protection of mice after passive immunization with immune rabbit sera.	–	Sumathy et al., Sci Rep 2017 [7]
Protein subunit vaccine	Purified ZIKV E ectodomain protein produced by using the Ad5.ZIKV-Efl vector.	C57BL/6 mice	20 μg per dose; two doses, i.d. by carboxymethyl cellulose microneedle arrays (MNA- ZIKV-Efl)	Induction of E-specific antibodies and neutralizing antibodies, but at lower titer than after vaccination with the adenoviral vector Ad5.ZIKV-Efl. Partial protection (50%) of pups born to immunized dams.	–	Kim et al., EBioMedicine 2016 [8]
ZIKV M-Env DNA plasmid vaccine	Based on Brazil BeH815744 strain, optimized for protein expression, encoding membrane (M) and E proteins	Balb/c mice, SJL mice, C57BL/6	50 μg of DNA; single dose or two doses, i.m.	Induction of E-specific antibodies, T-cell response, and dose-dependent neutralizing antibodies. Complete protection against challenge after a single dose of vaccine. Passive infusion of purified IgG by the i.v. route resulted in protection and correlates of protection identified. Depletion of CD8^+ and CD4^+ T-lymphocytes before challenge did not abrogate the protective efficacy.	–	Larocca et al., Nature 2016 [5]
		Rhesus monkeys	5 mg of DNA; two doses, i.m.	Induction of neutralizing antibodies after boost immunization and complete protection against challenge.	–	Abbink et al. Science 2016 [6]
ZIKV prM-Env DNA plasmid vaccines	Based on H/PF/2013 strain; chimeric ZIKV/JEV prM-E construct, with prM signal sequence (VRC5283) and also stem and E transmembrane regions (VRC5288) of JEV to improve secretion of virus-like subviral particles.	BALB/c mice, C57BL/6 mice	20 μg of DNA; single dose, i.m. electroporation	Induction of binding and neutralizing antibodies.	–	Dowd et al. Science 2016 [9]
		Rhesus monkeys	1 mg (VRC5283) or 4 mg (VRC5283, VRC5288), two doses at weeks 0 and 4; i.m. injection	Induction of binding and neutralizing antibodies after single and boost immunization. Complete protection against challenge after two doses of 4 mg or 1 mg of VRC5283 or 4 mg of VRC5288.
ZIKV prM-Env DNA plasmid vaccines (GLS-5700)	Based on ZIKV prM-E consensus sequence cloned into the pVax1 vector, with IgE leader peptide sequence, and without the N154-linked glycosylation site.	C57BL/6 mice; A129 mice	25 μg of DNA per dose, three or four doses, i.m. via electroporation	Induction of antigen-specific antibody and T-cell response; induction of neutralizing antibodies. Complete protection of A129 mice against challenge.	–	Muthumani et al. npj Vaccines 2016 [10]
		Rhesus monkeys	2.0 mg of DNA, two doses 4 weeks apart, i.d. via electroporation	Induction of antigen-specific antibody and T-cell response; induction of neutralizing antibodies. Passive transfer of anti-ZIKV immune sera from vaccinated monkeys protected A129 mice against challenge.	–
ZIKV VLP vaccine (TVXZO)	Based on codon-optimized sequences of ZIKV strain H/PF/2013; CprME and NS2B/NS3Pro sequences cloned into pcDNA3.4 plasmids and co-transfected in Expi293 cells. NS2B and protease domain of NS3 produced from a single transcription unit.	BALB/c mice	1 and 4 μg of total E protein of VLP vaccine + adjuvant (AddaVax, InVivoGen), a squalene-oil-in water nano-emulsion, two doses, i.m.	Induction of high titer, dose-dependent binding, and neutralizing antibodies. Serum from immunized mice (4 μg + adjuvant), diluted 1/500, did not enhance DENV-2 infection in vitro.	–	Boigard et al. PLoS Negl Trop Dis 2017 [11]
Adenovirus vector-based vaccine	Rhesus adenovirus serotype 52 (RhAd52) vector expressing prM-Env	Rhesus monkeys	10^11 vp, single dose, i.m.	Induction of neutralizing antibodies, E-specific cellular immune responses, and complete protection against challenge.	–	Abbink et al. Science 2016 [6]
Adenovirus vector-based vaccine	Adenoviral-based Zika vaccines encoding condon-optimized extracellular portion of E fused to the T4 fibritin foldon trimerization domain (Ad5.ZIKV-Efl)	C57BL/6 mice	10^11 vp per dose, two doses, s.c.	Induction of neutralizing antibodies. Complete protection against challenge of pups born to immunized dams.	–	Kim et al. EBioMedicine 2016 [8]
Nucleoside-modified mRNA vaccine	Lipid-nanoparticle-encapsulated nucleoside-modified mRNA (mRNA-LNP) encoding prM-E of the H/PF/2013 ZIKV strain and the signal peptide from MHC class II.	C57BL/6 mice, BALB/c mice	30 μg of RNA-LNP, single dose, i.d. injection.	Induction of E-protein-specific CD4+ T-cell responses and IgG, induction of neutralizing antibodies. Complete protection against challenge.	No local side effects	Pardi et al. Nature 2017 [13]
		Rhesus monkeys	600, 200, and 50 μg of RNA-LNP, single dose, i.d. injection.	Induction of E-protein-specific IgG and neutralizing antibodies, without significant differences between doses. Complete protection against challenge with 50 and 200 μg doses; low-level viral in one out of five monkeys vaccinated with 600 μg dose).	None
Nucleoside-modified mRNA vaccine	mRNA-LNP encoding prM-E from a Micronesia 2007 ZIKV strain; optimized 3ʹ and 5ʹ UTR and signal sequence from human IgE.	AG129 mice; C57BL/6 wild-type mice treated with a blocking anti-ifnar1 antibody the day before challenge.	2 or 10 μg of RNA-LNP, two doses, i.m.	Induction of neutralizing antibodies. Complete protection against challenge.	–	Richner et al. Cell 2017 [14]
Nucleoside-modified mRNA vaccine	mRNA-LNP encoding variant ZIKV prM-E with mutations destroying the conserved fusion-loop epitope in the E protein; optimized 3ʹ and 5ʹ UTR and leader sequence from JEV.	BALB/c mice	2 or 10 μg of RNA-LNP, two doses, i.m.	Induction of neutralizing antibodies. JEVsig-prM-E LNPs induced stronger inhibitory responses than IgEsig-prM-E and mutant JEVsig-prM-E-FL. Complete protection against challenge after vaccination with 2 or 10 μg doses of JEVsig-prM-E LNPs; breakthrough viremia in some animals receiving the other vaccines. FL-mutant vaccines diminished induction of cross-reactive enhancing antibodies and were associated with lower morbidity and mortality in a mouse model of dengue antibody enhancement.	–	Richner et al. Cell 2017 [14]
Nanoparticle-replicon-based vaccine	prM-E of Asian lineage ZIKV isolate Z1106033 encoded as a single ORF into an VEEV-based RNA replicon vector. RNA replicon formulated with a modified dendrimer nanomaterial to form MDNP vaccines.	C57BL/6 mice	40 μg of RNA, two doses, i.m. injection	Induction of ZIKV E protein-specific IgG antibodies and CD8+ T-cell response.		Chahal et al. Sci Rep 2017 [12]
Live-attenuated ZIKV vaccine	Live-attenuated vaccine containing a 10-nt deletion in the 3ʹ UTR of ZIKV genome (Cambodian strain FSS13025).	A129 mice	10 to 10^4 IFU, single dose, s.c.	Increased sensitivity of mutated virus to interferon inhibition. Induction of E-protein-specific IgG and neutralizing antibodies, without significant differences between doses. Induction of T-cell response. Complete protection against challenge. Noninfectious to A. Aegypti mosquitoes.	Low viremia, no organ infection, no damage of testes. No death of newborn CD-1 mice after intracranial injection.	Shan et al. Nat Med 2017 [15]
Recombinant vesicular stomatitis virus (rVSV) vaccines	Replication-competent wild-type rVSV and attenuated rVSVm with mutated matrix protein, carrying ZIKV prM-E or E only.	BALB/c mice; C57BL/6 mice	2 × 10^6 to 1 × 10^8 PFU, two doses, i.v.	Induction of E-specific antibodies, CTLs, and neutralizing antibodies; higher titers with vaccines carrying prM-E than E. Partial protection against challenge of pups born to dams immunized with the VSVm-ZprME vaccine.	No overt malaise or general adverse effects after high doses of vaccine.	Betancourt et al. J Immunol 2017 [16]
Chimeric vaccine	Chimeric DENV-2 with ZIKV prM-E.	A129 mice	10^4 PFU, single dose, i.p.	Induction of neutralizing antibodies. Complete protection against challenge.	Low viremia, no death in A129 mice.	Xie et al. MBio 2017 [17]

ZIKV: Zika virus; VLP: virus-like particle; LNP: lipid nanoparticle; JEV: Japanese encephalitis virus; i.m.: intramuscular; s.c.: subcutaneous; i.d.: intradermal; i.v.: intravenous; MHC: major histocompatibility complex; UTR: untranslated region; FL: fusion loop; ORF: open reading frame; VEEV: Venezuelan equine encephalitis virus; MDNP: modified dendrimer nanoparticle; IFU: infectious focus units; DENV: dengue virus; CTLs: cytotoxic T lymphocytes.

Table 2. Zika virus vaccine candidates: ongoing clinical trials.

Vaccine candidate	Phase	Trial design	Sponsor; ClinicalTrials.gov identifier
Zika virus purified inactivated vaccine with alum adjuvant	Phase I, double-blinded, randomized, placebo-controlled (or YF vaccine control).	Healthy flavivirus-naive and flavivirus-primed subjects. Two vaccinations 28 days apart with 5 µg i.m.	Walter Reed Army Institute of Research (WRAIR); National Institute of Allergy and Infectious Diseases (NIAID); NCT02963909
	Phase I, randomized, double-blinded, placebo-controlled, dose de-escalation.	Safety, reactogenicity, and immunogenicity; healthy male and nonpregnant female adult subjects in a flavivirus-endemic area (Ponce, Puerto Rico). Ages 21–49 years; two vaccinations 28 days apart with 5 or 2.5 µg i.m.	NIAID; NCT03008122
	Phase 1, randomized, double-blinded, placebo-controlled.	Safety and immunogenicity of an accelerated vaccination schedule in healthy adults; one to two vaccinations with 5 µg i.m., four different schedules. Ages 18–50 years.	Kathryn Stephenson, Beth Israel Deaconess Medical Center; WRAIR; NIAID; NCT02937233
	Phase 1, double-blinded, placebo-controlled, dose de-escalation.	Safety and immunogenicity in flavivirus-naive adults; two vaccinations with 1.25, 2.5, and 5 µg, i.m.; ages 18–49 years.	NIAID; NCT02952833
DNA vaccine (VRC-ZKADNA085-00-VP): plasmid-encoding WT prM-E from ZIKV H/PF/2013 strain	Phase I, randomized.	Safety and immunogenicity in healthy adults; ages 18–35 years; two to three vaccinations of 4 mg i.m., administered through high-pressure device.	NIAID; NCT02840487
DNA vaccine (VRC-ZKADNA090-00-VP): plasmid-encoding WT prM-E from ZIKV H/PF/2013 strain	Phase I, randomized.	Safety and immunogenicity in healthy adults; ages 18–50 years; three vaccinations with 4 mg i.m., administered via needle and syringe or needle-free injector, PharmaJet.	NIAID; NCT02996461
	Phase II/IIB, randomized, multicenter, placebo-controlled.	Safety, immunogenicity, and efficacy in healthy adults and adolescents; ages 15–35 years; three vaccinations of 4 or 8 mg i.m.	NIAID; The EMMES Corporation; Leidos Biomedical Research, Inc.; FHI 360; PPD; NCT03110770
DNA vaccine (GLS-5700): plasmid encoding for ZIKV prM-E.	Phase I, open-label, dose-ranging.	Safety, tolerability, and immunogenicity in dengue virus-naive adults; i.d. followed by electroporation; ages 18–65 years.	GeneOne Life Science, Inc. (Seoul, South Korea); Inovio Pharmaceuticals; NCT02809443
	Phase I, double-blinded, placebo-controlled.	Safety, tolerability, and immunogenicity in dengue virus-seropositive adults; i.d. followed by electroporation; ages 18–65 years; 2 mg DNA/dose.	GeneOne Life Science, Inc.; Inovio Pharmaceuticals; NCT02887482
mRNA encoding for ZIKV antigenic proteins (mRNA-1325)	Phase I/II, randomized, placebo-controlled, dose-ranging.	Safety, tolerability, and immunogenicity in healthy adult subjects in non-endemic Zika region. Ages 18–49 years; i.m.	Moderna Therapeutics (Cambridge, MA, USA); NCT03014089
Live-attenuated recombinant Zika vaccine based on measles vaccine as vector platform (MV-Zika vaccine).	Phase I, double-blinded, randomized, placebo-controlled, dose-finding trial.	Immunogenicity, safety, and tolerability in healthy volunteers; ages 18–55 years. High dose, single shot; high dose, two vaccinations; and low dose, two vaccinations.	Themis Bioscience GmbH (Vienna, Austria); Medical University of Vienna, Austria; NCT02996890

YF: Yellow fever; i.m.: intramuscular; i.d.: intradermal.

Figure 1. Schematic representation of ZIKV genome structure and of the different ZIKV vaccines that have been developed and evaluated in preclinical studies.

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