Antonia Radaelli1, Carlo De Giuli Morghen2, Carlo Zanotto3, Francesca Paolini4. 1. Laboratory of Molecular Virology and Recombinant Vaccine Development, Department of Medical Biotechnologies and Translational Medicine, University of Milan, Via Vanvitelli 32, 20129, Milan, Italy. antonia.radaelli@unimi.it. 2. Catholic University "Our Lady of Good Counsel", Rr. Dritan Hoxha, 123, Tirana, Albania. 3. Laboratory of Molecular Virology and Recombinant Vaccine Development, Department of Medical Biotechnologies and Translational Medicine, University of Milan, Via Vanvitelli 32, 20129, Milan, Italy. 4. HPV-UNIT, Laboratory of Virology, Regina Elena National Cancer Institute, Via delle Messi d'Oro, 156, 00158, Rome, Italy.
Abstract
BACKGROUND: Zika virus (ZIKV) has been declared a public health emergency that requires development of an effective vaccine, as it might represent an international threat. METHODS: Here, two novel DNA-based (pVAXzenv) and fowlpox-based (FPzenv) recombinant putative vaccine candidates were constructed that contained the cPrME genes of ZIKV. The env gene inserted into the fowlpox vector was verified for correct transgene expression by Western blotting and by immunofluorescence in different cell lines. The production of virus-like particles as a result of env gene expression was also demonstrated by electron microscopy. BALB/c mice were immunosuppressed with dexamethasone and immunized following a prime-boost strategy in a heterologous protocol where pVAXzenv was followed by FPzenv, to evaluate the immunogenicity of the Env protein. The mice underwent a challenge with an epidemic ZIKV after the last boost. RESULTS: These data show that the ZIKV Env protein was correctly expressed in both normal human lung fibroblasts (MRC-5 cells) and green monkey kidney (Vero) cells infected with FPzenv, and that the transgene expression lasted for more than 2 weeks. After mucosal administration of FPzenv, the immunized mice showed specific and significantly higher humoral responses compared to the control mice. However, virus neutralizing antibodies were not detected using plaque reduction assays. CONCLUSIONS: Although BALB/c mice appear to be an adequate model for ZIKV infection, as it mimics the natural mild infection in human beings, inadequate immune suppression seemed to occur by dexamethasone and different immune suppression strategies should be applied before challenge to reveal any protection of the mice.
BACKGROUND: Zika virus (ZIKV) has been declared a public health emergency that requires development of an effective vaccine, as it might represent an international threat. METHODS: Here, two novel DNA-based (pVAXzenv) and fowlpox-based (FPzenv) recombinant putative vaccine candidates were constructed that contained the cPrME genes of ZIKV. The env gene inserted into the fowlpox vector was verified for correct transgene expression by Western blotting and by immunofluorescence in different cell lines. The production of virus-like particles as a result of env gene expression was also demonstrated by electron microscopy. BALB/c mice were immunosuppressed with dexamethasone and immunized following a prime-boost strategy in a heterologous protocol where pVAXzenv was followed by FPzenv, to evaluate the immunogenicity of the Env protein. The mice underwent a challenge with an epidemic ZIKV after the last boost. RESULTS: These data show that the ZIKV Env protein was correctly expressed in both normal human lung fibroblasts (MRC-5 cells) and green monkey kidney (Vero) cells infected with FPzenv, and that the transgene expression lasted for more than 2 weeks. After mucosal administration of FPzenv, the immunized mice showed specific and significantly higher humoral responses compared to the control mice. However, virus neutralizing antibodies were not detected using plaque reduction assays. CONCLUSIONS: Although BALB/c mice appear to be an adequate model for ZIKV infection, as it mimics the natural mild infection in human beings, inadequate immune suppression seemed to occur by dexamethasone and different immune suppression strategies should be applied before challenge to reveal any protection of the mice.
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