Zika virus (ZIKV) is a re-emerging flavivirus which has caused minor, sporadic outbreaks ever since the first identification of a human Zika case in the 1950s. However, during 2015-2016, Zika infections caused a significant outbreak in the Americas with millions of people either suspected or confirmed to be infected with the virus including children born with neurological complications sparking worldwide media attention. Although the global incidences of ZIKV have declined significantly since 2017, WHO has evidenced limited surveillance in 89 countries and territories with mosquito-borne Zika infections which makes ZIKV poised to cause another explosive outbreak and further highlights the importance of continuing vaccine development efforts.
DNA vaccines are clinically effective, inexpensive, easy to construct and thermostable making them an ideal platform to target ZIKV in endemic regions. Consequently, we pioneered a proprietary DNA vaccine encoding codon-optimised non-structural protein 1 (NS1) of ZIKV and the tissue plasminogen activator (pVAX-tpaNS1) to facilitate secretion of NS1 and obviate issues associated with antibody-dependent enhancement of infection which could result from antibodies elicited against the structural proteins of ZIKV. We have previously shown that, following intradermal delivery via needle and syringe, the vaccine elicited rapid control of ZIKV challenge in a T-cell dependent manner in immunocompetent mice. In the conference presentation, we will provide evidence that intradermal delivery of pVAX-tpaNS1 using Vaxxas’s proprietary high-density microarray patch (HD-MAP) not only elicited protection in mice, but compared to needle and syringe vaccination also elicited higher NS1-specific IgG responses and higher and broader T helper cell and cytotoxic T cell responses in vivo. This study is likely the first study to demonstrate this effect in vivo in the context of DNA vaccination against flaviviruses using a microprojection skin delivery device and delineates a distinctive advantage of the HD-MAP technology to deliver nucleic acid vaccines.