The recent epidemic of Zika virus (ZIKV) in the Americas was deemed a global public health emergency after an unexpected surge in congenital microcephaly cases suggested that the virus was teratogenic in pregnancy. ZIKV is a flavivirus, primarily transmitted to humans by the bite of infected mosquitoes. ZIKV can infect a variety of placental cells and is also highly neurotropic to target neural progenitor cells, astrocytes and neurons in all stages of development. The congenital ZIKV syndrome describes a severe pattern of placental and fetal brain injury associated with pregnancy infection including microcephaly, ventriculomegaly, and ocular injury. Although the epidemic is now in decline, outbreaks will recur and the US remains at risk for an epidemic. Thus, an enduring need remains to define the viral-host interactions that support ZIKV infection, replication, and maternal-fetal transmission, and to develop a clinically relevant animal model for studies of pathogenesis. Relevant animal models are essential to define the outcome of viral-host interaction within the progression of ZIKV infection and to evaluate the efficacy of vaccines and therapeutics to control ZIKV infection and emergence. We have developed a highly relevant nonhuman primate model of the congenital ZIKV syndrome (Macaca nemestrina, pigtail macaque) in addition to clinically relevant in vitro and ex vivo models of placental and neural stem cell infection. We have shown that ZIKV (1) mediates a broad blockade to the JAK-STAT pathway in infected cells to abrogate cytokine signaling mediated by STATs 1-6, to suppress interferon antiviral defenses; (2) infects trophoblast, myeloid, epithelial, and neural progenitor cells to impose a JAK-STAT blockade through the actions of viral nonstructural protein(s); (3) infects a variety of maternal and fetal tissues in our nonhuman primate model including the neural progenitor cells in the developing fetal brain, and (4) infection reprograms the STAT-dependent fetal brain transcriptome in vivo to alter developmental gene networks. In this resubmission, we present new preliminary data to reveal that ZIKV NS5 binding to HSP90 disrupts the essential interaction of Jak and Tyk2 kinases with HSP90 that otherwise promotes kinase folding and function. The ZIKV NS5-HSP90 interaction suppresses JAK-STAT signaling to abrogate interferon antiviral defenses, which also presents a blockade to cytokine-directed cell-fate decisions signaled via the JAK-STAT pathway that, in part, underlie ZIKV disease. Our central hypothesis is that acute ZIKV infection induces a broad blockade of JAK-STAT signaling involving multiple STATs to suppress antiviral defenses, which enhances vertical transmission and alters fetal brain development.
In Aim 1, we will determine how ZIKV mediates a broad JAK-STAT signaling suppression (STAT 1-6) in vitro and ex vivo to control innate immune defenses, viral trafficking and injury. A new feature of Aim 1 is that we will define the outcome of ZIKV NS5 binding to host cell HSP90, which we hypothesize will disrupt client Jak and Tyk2 kinase actions.
In Aim 2, we will determine how viral control of JAK-STAT impacts vertical transmission and pathogenesis of fetal brain injury in vivo in a nonhuman primate model of the congenital ZIKV syndrome.
The goal of our proposal is to investigate ZIKV blockade of JAK-STAT signaling as a mechanism for enhancing viral pathogenesis, vertical transmission and altering fetal neurodevelopment. These experiments are fundamental for understanding the pathogenesis of maternal-fetal transmission and fetal brain injury induced by ZIKV and will provide the necessary foundation for testing novel therapeutics and vaccines for fetal protection.