Effects of Adjuvants on the Immunogenicity and Efficacy of a Zika Virus Envelope Domain III Subunit Vaccine

Abstract

Zika virus (ZIKV), a mosquito-borne flavivirus, has attracted global attention due to its close association with congenital Zika syndrome and neurological diseases, and transmission through additional routes, such as sexual contact. Currently there are no vaccines approved for ZIKV, and thus, there is an urgent need to develop an effective and safe ZIKV vaccine. Domain III (DIII) of the ZIKV envelope (E) protein is an important vaccine target, and a vaccine developed using a mutant DIII of E (EDIII) protein protects adult and pregnant mice, and unborn offspring, against ZIKV infection. Here, we have used immunocompetent BALB/c mice treated with anti-interferon-α/β receptor 1 (Ifnar1) antibodies to investigate whether three adjuvants (aluminum (Alum), monophosphoryl lipid A (MPL), and MF59), either alone or in combination, could improve the efficacy of this EDIII subunit vaccine. Our data show that, although vaccine formulated with a single adjuvant induced a specific antibody and cellular immune response, and reduced viral load in mice challenged with ZIKV, the combination of Alum and MPL adjuvants led to a more robust and balanced immune response, stronger neutralizing activity against three recent ZIKV human strains, and greater protection against a high-dose ZIKV challenge. Particularly, the combination of Alum with MPL significantly reduced viral titers and viral RNA copy numbers in sera and tissues, including the male reproductive organs. Overall, this study has identified the combination of Alum and MPL as the most effective adjuvant for ZIKV EDIII subunit vaccines, and it has important implications for subunit vaccines against other enveloped viruses, including non-ZIKV flaviviruses.Vaccines 2019, 7, 161 2 of 16 with microcephaly, fetal demise, and other congenital disorders [4][5][6]. Thus, ZIKV has emerged as a global health threat and there is an urgent requirement for an effective vaccine to combat ZIKV-associated diseases.The ZIKV genome encodes a single polyprotein, which is processed into three structural proteins (capsid (C), precursor of membrane/membrane (prM/M), and envelope (E)) and seven non-structural proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5) [7][8][9]. The E protein has important roles in infection and pathogenesis, is involved in virus binding to target cells and membrane fusion, and also serves as an important vaccine target [7,8]. The E protein is a transmembrane protein and consists of three domains termed I, II, and III (DI-DIII), a fusion loop (FL), and a stalk region (S) [8]. The DI-DII region of ZIKV E protein is a target for cross-reactive antibodies with other flaviviruses, such as dengue virus (DENV) and West Nile virus (WNV), whereas the DIII domain induces ZIKV-specific antibodies [10][11][12], and therefore, is a key target for ZIKV vaccine development. ZIKV vaccine candidates under development include inactivated virus, live attenuated virus, DNA, mRNA, viral vectors, virus-like particles (VLPs), and viral proteins (or subunit vaccines) [13][14][15][16]. Although ma...

Conjugation of Hemoglobin and Mannan Markedly Improves the Immunogenicity of Domain III of the Zika Virus E Protein: Structural and Immunological Study

“…EDIII of ZIKV could elicit specific antibody titers to neutralize ZIKV . EDIII in the presence of the adjuvants (Alum, MPL, and MF59) showed high neutralizing activity against ZIKV and provided strong immune protection against ZIKV challenge . In our study, HM–EDIII-2 was expected to protect against ZIKV.…”

A vaccine inducing solely cytotoxic T lymphocytes fully prevents Zika virus infection and fetal damage

“…It took 2–3 weeks for the mice to be impregnated. After the female mice were impregnated (embryonic day [E]5–E7), they were injected with anti-IFNAR1 antibody (to make the mice susceptible to ZIKV by blocking IFNARs) ( Gorman et al, 2018 ; Morrison and Diamond, 2017 ; Wang et al, 2019 ). One day later, mice were challenged with a high dose of ZIKV (R103451, 2 × 10 5 plaque-forming unit [PFU]) and examined for morphological changes of uteri 6 days after.…”

In silico construction of a multiepitope Zika virus vaccine using immunoinformatics tools

“…Flaviviruses structural proteins, especially the Envelope protein, are the main targets for antibody production 33 , 34 . The ZIKV EDIII has been used in experimental subunit vaccines, and it was shown to induce neutralizing antibodies against different strains of ZIKV, as well as significant reduction of viral replication when used in combination with alum and Monophosphoryl lipid A (MPL) 35 . Conversely, ZIKV EDIII failed to induce satisfactory inhibition of viral replication in mice when given in the form of DNA, protein or when expressed by a chimpanzee adenovirus 36 , indicating that the choice of adjuvant, for instance, can impact the efficacy of the vaccine.…”

“…ZIKVac could also be used with aluminum, which is the most frequent adjuvant in licensed vaccines, showing a great safety record 74 , 75 . The combination of both adjuvants can lead to a more balanced Th1/Th2 response and resulted as the best adjuvant scheme when compared to either adjuvant alone or MF59 35 . Thus, we initially plan to express the proposed vaccine in eukaryotic cells and test it as a protein adjuvanted with alum and MPL in mice.…”